European Journal of Medicinal Chemistry 123 (2016) 596e630 Contents lists available at ScienceDirect European Journal of Medicinal Chemistry journal homepage: http://www.elsevier.com/locate/ejmech Review article Synthetic strategy with representation on mechanistic pathway for the therapeutic applications of dihydroquinazolinones K. Hemalatha, G. Madhumitha* Chemistry of Heterocycles & Natural Product Research Laboratory, Department of Chemistry, School of Advanced Sciences, VIT University, Vellore, Tamil Nadu 632014, India a r t i c l e i n f o a b s t r a c t Article history: Received 18 May 2016 Received in revised form 1 August 2016 Accepted 1 August 2016 Available online 3 August 2016 Dihydroquinazolinones is an important core structure reported with a wide variety of pharmacological activities. They are capable of undergoing various transformations because of its reactivity towards various reagents. The synthetic strategies for the functionalization and derivatization of the nucleus were explained. The diversified pharmacological actions of this moiety were illustrated through various biochemical pathways. The structural-activity relationship study of dihydroquinazolinones anticipated the relationship between the various substituents and its role in the pharmacological action. The main objective of this review is to summarize the importance of dihydroquinazolinones in the field of chemical biology. © 2016 Elsevier Masson SAS. All rights reserved. Keywords: Dihydroquinazolinones Synthetic strategy Functionalization Pharmacological action Biochemical pathway Contents 1. 2. 3. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 Synthesis and therapeutic applications of dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 2.1. M1/M4 mAchR agonist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 2.2. MPO inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 2.3. Antibacterial activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 2.4. IRAP inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 2.5. Antimalarial activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601 2.6. Chorismate mutase inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602 2.7. Cyclooxygenase inhibitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604 2.8. Antitumor agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606 2.9. 5-HT2c receptor agonist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607 2.10. Melanoma inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 2.11. T-type calcium channel antagonist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 2.12. IMPDH inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 2.13. Sodium/calcium exchange inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610 2.14. PDE7 inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613 2.15. p38 MAPK inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 615 2.16. CDK5 inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617 2.17. RyR agonist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618 2.18. Non-nucleoside reverse transcriptase inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618 2.19. Aldosterone synthase inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 Miscellaneous synthesis and applications of dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 * Corresponding author. E-mail addresses: [email protected], (G. Madhumitha). [email protected] http://dx.doi.org/10.1016/j.ejmech.2016.08.001 0223-5234/© 2016 Elsevier Masson SAS. All rights reserved. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 4. 597 3.1. Synthesis of 2, 3-dihydroquinazolin-4(1H)-ones from N-heterocyclic carbenes of indazole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 3.2. Copper oxide nanoparticle mediated synthesis of dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 3.3. Y(OTf)3 mediated synthesis of dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 3.4. Boric acid mediated synthesis of dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622 3.5. Visible light mediated synthesis of dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 3.6. Importance of 7-fluoro-2, 2-dimethyl-2, 3-dihydroquinazolin-4(1H)one . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625 3.7. Bromination of 2, 3-dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627 3.8. Suzuki Miyaura coupling of 2, 3-dihydroquinazolinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627 1. Introduction Medicinal chemistry is an interdisciplinary area which links both organic chemistry and biology [1]. The compounds isolated from the natural resources [2,3] and by the synthesis [4e6] were identified with numerous applications in various fields. In some cases, the extracts from the natural resources were used as such and the active components present in it either induce chemical reaction [7e9] or biological response [10e16]. Nitrogen-rich heterocycles are present ubiquitously in natural products, pharmaceutical drugs and agrichemicals [17]. Among the various heterocycles [18e22], quinazolinones [23e25] are of prime importance because of its ease in synthetic feasibility from less expensive chemicals [26]. Quinazolinones can be synthesized from a wide variety of starting materials and also widely distributed in natural sources [27,28]. The reviews concentrating on the synthetic and isolated quinazolinones are maintained up to date [29,30]. The quinazolinones can also exist in the form of 2, 3dihydroquinazolinones [31] and 3, 4-dihydroquinazolinones [32] derivatives. The dihydroquinazolinones were found incorporated in the marketed drugs and in the drugs undergoing clinical trial (Fig. 1). Evodiamine [33] is an alkaloid isolated from the fruits of Evodia rutaecarpa. It acts as a fat burner by increasing the number of serotonin transporters in the brain and enhancing the serotonin reuptake. Quinethazone [34], fenquizone and metolazone are thiazide-like diuretics [35] and they are used to treat hypertension. BIBN 4096 BS [36] is an antagonist of CGRP and it is used for migraine headaches. DPC083, DPC961, and DPC963 are NNRTIs and they act as a synergistic agent in the treatment of HIV-1 patient [37]. Due to the tremendous increase in the number of research outputs related to quinazolinone nucleus, the separate collections of dihydroquinazolinones will be an efficient tool to assess the properties of the nucleus. Recently enantioselective synthesis of dihydroquinazolinone based anti-HIV agents were reviewed [38]. The main scope of this review is to elaborate the synthetic scheme and the various reagents utilized in the functionalization pathway of dihydroquinazolinones. The review also explains the diverse pharmacological actions mechanistically portrayed through the different biochemical pathways. 2. Synthesis and therapeutic applications of dihydroquinazolinones 2.1. M1/M4 mAchR agonist The mAchR subtypes M1 and M4 can regulate the cognitive deficits and psychosis disorders and thereby its stimulation can improve the symptoms of schizophrenia. The markedly available Fig. 1. Drug moieties containing dihydroquinazolinones. 598 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 M1 and M4 mAchR agonist, xanomeline produces unwanted gastrointestinal stress because of its action through the M3 receptor (Fig. 2) [39]. The importance of the M1 and M4 mAchR agonistic activity was identified and the SAR study was performed for the series of dihydroquinazolinone derivatives [40]. Based on the high throughput screening, a hit compound 1 with weak M4 mAchR agonist was selected as a potential compound. Through the earlier reports, the pharmacophore N-carbethoxy-piperidine moiety was thought to be essential for the M4 mAchR agonistic activity. The change of the benzyl group of 1 by N-carbethoxy-piperidine moiety 2 activated the M2 agonist activity along with M1 and M4 mAchR agonist activity. The removal of the methylene group 3 potentiated the activity towards all the (M1, M2, M3, M4, M5) receptors. Therefore, the importance of the methylene group in increasing the selectivity towards the receptor subtype was identified. The replacement of piperidine as a linker to the various cyclic amine linkers affected the M1 and M4 mAchR agonistic activity without receptor subtype selectivity. The increase and decrease in the agonist activity of the M1 and M4 mAchR were resulted for the Rsubstituted 4 pyrrolidine linker and the S-substituted 5 pyrrolidine linker respectively. The presence of azetidine 6 lin ker also potentiated the activity. The M4-mAChR partial agonistic activity was obtained through the replacement of N-carbethoxy piperidine by N-carbethoxy tropane 9 moiety. This highly active compound was tested for its pharmacokinetic profile. This compound is less affected by liver enzymes, high cell permeability, effective brain/ blood penetration and good affinity for G-protein coupled receptors. The in vivo pharmacological profile resulted in the reversal of METH-induced hyperlocomotion in rats and produced a potent antipsychotic effect than the standard drug xanomeline. Finally, the active compound was synthesized from sodium triacetoxyborohydride mediated reduction reaction between the readily available starting material, (S)-3-(pyrrolidin-3-yl)-3, 4-dihydroquinazolin2(1H)-one 7 and ethyl 3-formyl-8-azabicyclo [3.2.1] octane-8carboxylate 8 (Scheme 1). 2.2. MPO inhibitor MPO is an enzyme from heme peroxidase superfamily. MPO acts a catalyst in the production of endogenous oxidant, hypochlorous acid (Fig. 3) [41]. Hypochlorous acid also causes oxidative damage to the host tissue. Endothelial-derived NO was utilized by MPO and thereby reducing its bioavailability. Reduction in NO bioavailability impairs its vasodilating and anti-inflammatory property [42]. Li et al. [43] designed three series of compounds (12, 16 and 18) and they were tested for their activity against MPO inhibition. The synthesis of compound series 12 was carried out from the reaction of isatoic anhydride 10 with various substituted alkyl amines and carbon disulfide (Scheme 2). Another series of compounds 16 were obtained from the reaction between benzamine 13 and thiophosgene 14 followed by reflux with alkyl hydrazine. The treatment of thiocyanate 15 with hydrazine and chlorocarbonyl reagent resulted in the formation of another series of compounds 18. The SAR study concluded that halogen in 6th position and free amino group in the 3rd position of quinazolinone were stringent for the activity. Either change in the position of halogen/alteration of the substituent in the place of halogen decreased the potency. Also, the replacement of hydrogen in the amine group by other substituents weakened the potency. An aromatic ring attached to NeN linkage of compound 16, 18 was more active than the aliphatic chain containing compounds. The water solubility of the compound was increased by introducing the methylene piperidinyl group 19. In short, thioxo-dihydroquinazolinone derivatives were proved to be effective inhibitors of MPO and can be utilized in the treatment of inflammation-related neurodegenerative diseases and atherosclerosis. These compounds act reversibly and do not trap the enzyme which showed its superiority over the existing inhibitors. 2.3. Antibacterial activity Ma et al. [44] reported the synthesis of 2-substituted-3-(phenylamino)-dihydroquinazolin-4(1H)-ones through cascade reaction from isatoic anhydride 20 and phenyl hydrazine 21 (Scheme 3). The reaction was carried out using different acid catalyst and the most efficient catalyst was found to be bentonite. Water was found to be the best solvent and the reaction was carried out in the presence of ultrasonic irradiation. Optimizing the amount of catalyst concluded that the change in the concentration (1e7 mol %) displayed no significant change in the yield. However reduction in the concentration of bentonite (0.5 mol %) decreased the Fig. 2. Mechanism of action of M1/M4 muscarinic acetylcholine receptor agonist. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 599 Scheme 1. Synthesis of dihydroquinazolinones as an M1/M4 mAChRs agonist. Fig. 3. Mechanism of action of myeloperoxidase inhibitor. percentage yield. These optimized reaction conditions were utilized in the synthesis of various 2-substituted-3-(phenylamino)dihydroquinazolin-4(1H)-ones 22. The derivatives of dihydroquinazolin-4(1H)-ones with electron-donating substituents resulted in good yields when compared to the electronwithdrawing substituents. The in vitro antibacterial activity against the gram-negative bacteria Escherichia coli (E. coli) was carried out for all the synthesized derivatives. The antibacterial potency of the highly active compounds of dihydroquinazolin4(1H)-ones was supported through the docking studies with the biotin carboxylase enzyme. Biotin carboxylase (E. coli) is an important enzyme involved in the fatty acid biosynthesis [45]. This pathway is utilized by the bacteria for the membrane biogenesis. Enzymes involved in this pathway were proved to be a valuable target for the antibacterial drug discovery [46]. This enzyme requires three substrates: ATP, BCCP and CO2 and they are converted into ADP, phosphate and carboxybiotin-carboxyl-carrier protein (Fig. 4). The active compounds displayed hydrogen bonding interactions with the amino acid residues such as Leu204, Lys159, and Gly166 of biotin carboxylase enzyme. 2.4. IRAP inhibitor The spiro-oxindole containing dihydroquinazolinones were synthesized from 5-bromo-1-methyl isatin 23, isatoic anhydride 20 and substituted aniline (Scheme 4) [47]. The time taken for the conventional synthesis can be reduced from 2 h to 10 min by carrying out the reaction under MW irradiation. The reaction carried out in the borosilicate glass reactor by MW batch synthesis end up with the unreacted starting material along with unidentified 600 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 2. Synthesis of thioxo-dihydroquinazolinone derivatives. Scheme 3. Synthesis of 2-substituted-3-(phenylamino)-dihydroquinazolin-4(1H)-ones. byproducts. The flow rate of 1 mL/min and the temperature of 200 C were optimized to get an isolated yield of 40% for the reaction mixture collected after 5 min. The flow rate of 0.5 mL/min and the temperature of 120 C were utilized in the SiC glass reactor with the CF of MW irradiation to obtain an isolated yield of 55%. The experimentation was carried out in borosilicate reactor using the same reaction condition and the yield was only 8%. The SiC glass reactor was advantageous over the borosilicate glass reactor in terms of low temperature, less complex reaction mixture and thereby it leads to the easy way of purification. Both in the batch synthesis and CF, there is an existence of 5-bromo-1-methyl isatin in the reaction mixture. The reaction proceeded to completion by increasing the equivalence of p-toluidine. Increasing the equivalence of p-toluidine 24 lead to substantial increase in the yield of spiro-oxindole dihydroquinazolinones 25. The reaction mixture containing 1 equivalence of 5-bromo-1-methyl isatin, 1.5 equivalence of isatoic anhydride and p-toluidine with the flow rate maintained at 0.5 mL/min at a temperature of 160 C resulted in the completion of the reaction with the highest yield (82%). The other derivatives of dihydroquinazolinones were synthesized using the optimized conditions of MW-SiC-CF method. The aliphatic amines were not utilized in the reaction because of the drawback of protonation. IRAP is a transmembrane protein and it belongs to the family of aminopeptidases. It is also known as an AT4 receptor, a binding site for the peptide angiotensin IV. Angiotensin IV is the metabolite obtained from the biologically active peptide fragment, angiotensin II. The role of angiotensin IV is to enhance the memory and learning. Therefore, IRAP based inhibitors are useful for improving cognition and develop an effective treatment for dementia (Fig. 5) [48,49]. The IRAP inhibitory activity of spirooxindole dihydroquinazolinones concluded that the 5th position bromine atom is essential for the activity. The absence of bromine K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 601 Fig. 4. The role of biotin carboxylase in E. coli fatty acid biosynthesis. Scheme 4. Synthesis of spiro-oxindole containing dihydroquinazolinones. atom decreased the activity whereas the changes in the position of the bromine atom lead to the inactive compound. In order to carry out the SAR study, spiro-oxindole dihydroquinazolinones were subjected to Suzuki Miyaura coupling reaction. The MW batch synthesis was carried out using this optimized reaction condition. The result concluded that 1 equivalence of halide 25, 2 equivalence of boronic acid 26, 1.5 equivalence of DBU, 2 mol% PdCl2(dppf), acetonitrile with 2% water was appropriate to carry out the reaction. Using this optimized condition, the coupling reaction was carried out in the borosilicate reactor using CF mode. The reactants got consumed at the flow rate of 0.5 mL/min at 220 C with an isolated yield of 71%. Because of the inactive nature of Suzuki Miyaura product 27 towards the IRAP inhibition further optimization on the reaction methodology was not carried out. 2.5. Antimalarial activity Malaria is one of the deadliest diseases and the treatment mainly relies on the chemotherapy [50e52]. Even though there are potential drugs for malaria, the treatments are no longer effective due to the evolution of resistance. The present scenario is to focus primarily on the complicated life cycle of the parasite [53] (Fig. 6) and develop molecules that reduce the mortality rate effectively. Derbyshire et al. reported the effectiveness of various compounds that acts as an inhibitor against both the liver and blood stage of malaria [54]. The malarial drugs act through different mechanism because of the difference in the transcriptomic and proteomic data of the liver and blood stage parasites. Preliminary high-throughput phenotypic blood stage malarial screening identified compounds of different chemotype which showed more than 80% inhibition against the malarial parasites. The compounds on further screening identified hit with inhibition against blood stage parasites. These selected libraries of compounds were tested for its effectiveness against liver stage parasites in infected human hepatoma HepG2 cells. The results explored that most of the compounds were not effective against liver stage parasites. This difference in activity was assumed to be either due to the process such as hemozoin formation or because of the metabolic instability of the compounds towards the liver cell. Among the hits, 32 compounds were active against the liver stage parasites and 22 compounds displayed EC50 value less than 10 mM. The potential hit containing dihydroquinazolinone 28 (EC50 ¼ 1.4 mM) were further subjected to SAR analysis (Fig. 7). The modification in the 2nd position of dihydroquinazolinone using bulky ring system revealed no change in activity. This confirmed that the binding site residues are not sterically hindered. The alteration of substituents on the phenyl ring of 602 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Fig. 5. Mechanism of action of IRAP inhibitor as cognitive enhancers. Fig. 6. The life cycle of the malarial parasite and the site of action of dihydroquinazolinones. the compound 28 changed the activity. The elimination of liver stage activity was reported in the ortho substituents whereas the para and meta substituents were well tolerated. Variation in the 3rd position of compound 28 indicated that 3-dialkyl aminoethyl group was essential for activity, whereas the compounds with other group were less potent. The presence of 3-dialkyl aminoethyl group was found to be lethal for the blood stage parasite. Any factor which increases the liver stage activity correspondingly increased the blood stage activity. Through the SAR study, the compound 29 was found to be an ideal candidate for both liver and blood stage malaria parasites. 2.6. Chorismate mutase inhibitor Fig. 7. Quinazolinones for blood and liver-stage malarial parasites. CM is an important enzyme that catalyzes the isomeric conversion of chorismate to prephenate (Fig. 8) [55]. This is the key reaction involved in the biosynthesis of aromatic amino acids essential for the survival of microorganisms and plants. CM is the only naturally occurring enzyme catalyzing pericyclic reaction. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 603 Fig. 8. The role of chorismate mutase in amino acid synthesis. Scheme 5. Synthesis of spiro 2, 3-dihydro-quinazolin-4(1H)-ones. Since this pathway is not present in the mammals, it can be used a selective pathway for the treatment of tuberculosis [56]. Rambabu et al. synthesized the series of spiro 2, 3-dihydro-quinazolin-4(1H)ones 30 using Amberlyst-15 as a catalyst and ultrasound irradiation in the presence of oxygen (Scheme 5). The standard CM inhibitor, 4(3, 5-dimethoxyphenethylamino)3-nitro-5-sulfamoylbenzoic acid displayed IC50 value less than 10 mM. Among the synthesized series, compound 31 and 32 were reported with 30e35% of CM inhibition Fig. 9. Mechanism of action of anti-inflammatory agents. 604 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 6. Synthesis of 2, 3-diaryl 2, 3-dihydro-1H-quinazolin-4-ones. Scheme 7. Synthesis of 3-aryl-2-substituted 1, 2- dihydroquinazolin-4(3H)-one metal complexes. when compared to the other derivative. Because of very few reports on CM inhibition and increasing resistance to antitubercular therapy, these derivatives are of pharmaceutically important [57]. 2.7. Cyclooxygenase inhibitors The reactions involving the conversion of arachidonic acid to Fig. 10. The effect of an antitumor agent on the cell cycle. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 605 Scheme 8. Synthesis of isoxazoline/oxazoline and dihydroquinazolinone derivatives. (i)Benzamide, p-toluene sulfonic acid monohydrate, DMA; (ii) Br(CH2)nBr, K2CO3, DMF. prostaglandins were catalyzed by the COX enzyme. There are two isoforms of COX referred to as COX-1 and COX-2. The COX-1 is a constitutive enzyme and it is involved in the various physiological processes for maintaining the homeostasis. The COX-2 is induced in case of the inflammatory condition and it is the target for the selective NSAIDS (Fig. 9). The drugs selective for the COX-2 enzyme can be designed on the basis of difference in the amino acid sequence of both the enzymes [58]. Manivannan et al. designed the molecule by applying the analog based pharmacophore design. The quinazolinone nucleus was selected from the two well known natural products, rutaecarpine, and tryptanthrin. The diaryl and the methyl sulfonyl pharmacophore were chosen from the selective COX-2 inhibitors, celecoxib, and rofecoxib. The designed compounds were categorized into methyl sulfanyl and methyl sulfonylcontaining series. The various substituted anilines 33 were condensed with 4-thiomethyl benzaldehyde 34 to yield 4methylsulfanyl-benzylidene)-phenyl-amine 35. The oxidation of 4-methylsulfanyl-benzylidene)-phenyl-amine 35 into (4-methyl sulfonyl-benzylidene)-phenyl-amine 37 was carried out in the presence of oxone medium. The intermediate azomethines 35 & 37 were microwave irradiated with isatoic anhydride resulted in the formation of 2, 3-diaryl 2, 3-dihydro-1H-quinazolin-4-ones 36 & 38 (Scheme 6). The compounds were screened for in vitro antiinflammatory activity using ovine cyclooxygenase enzyme. The compound 40 was less active to inactive towards COX-1 enzyme whereas highly active towards the COX-2 enzyme inhibition. The in vivo anti-inflammatory activity of the compounds was evaluated by carrageenan-induced rat paw edema method. The compounds which showed positive results in the in vitro assay were correlated with the in vivo methodology. Among the active series except 39, all the other compounds belong to methyl sulfonyl series and they are selective towards the COX-2 enzyme [59]. Hoonur et al. evaluated the analgesic and anti-inflammatory activity of the 3-aryl-2-substituted 1, 2- dihydroquinazolin-4(3H)one derivatives and its various transition metal complexes. The dihydroquinazolin-4(3H)-one ligand 43 was prepared by the condensation of o-aminobenzoylhydrazine 41 with 2acetylpyridine 42 and followed by the treatment with benzaldehyde. The transition metal complexes 44 were obtained by refluxing the ligand with the transition metal (II) chloride (Cu, Zn, Mn, Ni, Co and Cd) in ethanol (Scheme 7). The analgesic activity was evaluated by acetic acid induced writhing method. The induction of acetic acid generated the visceral type of pain and produced stretching of hind limbs and bending of trunks. The antiinflammatory activity was carried out by the carrageenaninduced rat paw edema method. The copper complex displayed significant analgesic and anti-inflammatory activity than the ligand and other metal complexes. The effectiveness of the metal complex may be due to the metal chelation which increased the lipophilic character [60]. 606 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 9. Synthesis of dihydroquinazolinones containing anticancer activity. 2.8. Antitumor agents Microtubules are the principle component of cytoskeleton and function in the separation of chromosomes during mitosis. The two closely related polypeptides a-tubulin and b-tubulin are polymerized to form the microtubules. Microtubules play a major role in mitosis and the drugs which inhibit microtubule polymerization (Fig. 10) are useful in the cancer chemotherapy [61]. The hybrid molecules that inhibit microtubule polymerization were synthesized through the formation of ether linkage between the hydroxyl group of 3, 5-diaryl isoxazoline/3, 5-diaryl oxazoline derivatives and dihydroquinazolinones [62]. The synthesis of 2, 3dihydroquinazolinones 46 was carried out by the condensation of aldehydes 45 and benzamide in the presence of p-toluene sulfonic Fig. 11. Mechanism of action of antiobesity drugs. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 607 Scheme 10. Synthesis of 6, 6, 6- tricyclic dihydroquinazolinones. (i) (COCl)2/CH2Cl; (ii) NH3/MeOH-THF; (iii) H2/10% palladium on carbon/MeOH; (iv) N-boc-aminoacetaldehyde/ pTsOH/toluene; (v) Na2CO3 or K2CO3/allyl bromide/DMF or DMA/140 C; (vi) OsO4/NaIO4/THF-H2O; (vii) TFA/Et3SiH/CH2Cl2. acid monohydrate. The hydroxyl group of phenyl ring in the 2nd position of dihydroquinazolinones was reacted with dibromoalkanes for further condensation reaction to yield the product 47. The condensation reaction between 3, 5-diaryl isoxazoline/3,5diaryl oxazoline 48 and 2, 3-dihydroquinazolinones 49 using potassium carbonate afforded the hybrid compounds 50 (Scheme 8). The compound was effective against nine types of cancer and 60 different cell lines. Based on the potency of the compound, the other derivatives were also tested for their activity against the cell lines. Most of the derivatives displayed significant activity against MCF-7 (breast cancer) and PC3 (prostate cancer) cell lines. Through the series of evaluation, the plausible mechanism of action for the anticancer activity of the potent compound 51 was explored. The inhibition of tubulin polymerization caused downregulation of CDK1 and cyclin B1 protein which in turn arrested the cell cycle progression in G2/M phase. Roopan et al. [63] investigated the three-component reaction of isatoic anhydride 20, heterocyclic aldehyde 52 and ammonium acetate using different catalysts (Scheme 9). The montmorillonite K10 was superior in terms of time and yield. Further, the cytotoxicity of the compounds was tested against the Ehrlich Ascites Carcinoma tumor cells. They displayed comparative cytotoxicity to that of the standard drug 5-fluorouracil. The Schiff bases [64] of 2, 3- dihydroquinazolinone derivatives 55 were obtained by refluxing one equivalent of aminobenzyhydrazide 53 with two equivalent of substituted aromatic salicylaldehyde 54 in methanol for 2 h (Scheme 9). The compounds were screened for their in vitro anticancer activity against MCF-10 breast cell line, normal WRL-68 hepatic cell line, and human MCF-7 breast adenocarcinoma cell line by MTT assay. The compounds showed suppressive action against only MCF-7 breast adenocarcinoma cell line. Mahdavi et al. synthesized the trans-stilbene scaffold containing N-substituted 2-arylquinazolinones with anticancer property. Isatoic anhydride 20 was used as a starting material and it was converted into anthranilamide 56 using primary amines. The condensation of anthranilamide 56 with trans-stilbene 57 derivative using potassium carbonate resulted in the formation of 2, 3dihydroquinazolinone derivative 58. Dihydroquinazolinones 58 were converted into quinazolinones 59 using TBAB mediated reaction (Scheme 9). The synthesized series were tested for their anticancer activity against three cancer cell lines (MCF-7, MDA-MB231, T-47D). Among the tested compounds, N-alkyl substituted derivatives displayed higher anticancer activity than the corresponding N-aryl and N-benzyl derivatives. The bulkiest and lengthiest N-alkyl substituents such as cyclopropyl, isopropyl and sec-butyl showed favorable interaction in the binding pocket and thereby it leads to the highest cytotoxic potency of the compounds [65]. 2.9. 5-HT2c receptor agonist The drugs targeting central 5-HT system has been implicated in the treatment of various ailments. The 5-HT2C receptor agonism is the valid target for the treatment of obesity [66]. This was confirmed through the 5-HT2C receptor knockout mice, which displayed hyperphagia and developed obesity. There are three members of the 5-HT2 receptor subclass (5-HT2A, 5-HT2B, 5-HT2C) sharing close sequence homology. The wide distribution of 5-HT2B subtype in the vascular and cardiac tissues causes valvulopathy. The drugs acting through the 5-HT2A receptor subtype results in the unwanted CNS related disorders [67,68]. To overcome these adverse effects the molecules which are selective towards the 5HT2C receptor subtype have to be designed. The activation of hypothalamic 5-HT2C receptors results in the stimulation of POMC, a precursor of a-MSH. The binding of a-MSH to the MC4R stimulates the feeling of fullness (Fig. 11). Three compounds series were designed on the basis of recently approved 5-HT2C receptor agonist, Lorcaserin. The 2-nitrobenzoic acids 60 are converted into their corresponding acid chlorides by the treatment with oxalyl chloride. Further reaction with ammonia followed by reduction using hydrogen and palladium on carbon afforded 2-aminobenzamides 61. The condensation of 2-aminobenzamides with N-boc-aminoacetaldehyde in the presence of p-toluenesulfonic acid resulted in the cyclized product 62. The N1 of the cyclized product was subjected to allylation using allyl bromide to the yield N-allyl substituted dihydroquinazolinones 63. In another reaction, 2fluorobenzoyl chlorides 65 are converted into their corresponding 2-fluorobenzamides and allylated 66 in the presence of ammonia and allylamine. The cyclized product 67 was obtained using Nprotected-3-amino-1-propanal. All these resulting olefins 63 and 67 were converted into intermediate aldehydes in the presence of sodium periodate and a catalytic amount of osmium tetroxide. The cyclization of these intermediate aldehydes with TFA and triethylsilane resulted in the formation of 6, 6, 6-tricyclic dihydroquinazolinones 64 (Scheme 10) and 6, 6, 7-tricyclic dihydroquinazolinones 68 (Scheme 11). The compounds containing halogens 69 & 70 were subjected to Stille-type coupling reaction 71, Suzuki Miyaura coupling 72 and Negishi coupling 73 with tetramethyltin, trimethylboroxine, and dimethyl zinc respectively. The 608 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 11. Synthesis of 6, 6, 7-tricyclic dihydroquinazolinones. (i) NH3/MeOH-THF; (ii) allylamine/K2CO3/DMA; (iii) N-cbz-3-amino-1-propanal/N-boc-3-amino-1-propanal/ pTsOH/dioxane; (iv) OsO4/NaIO4/THF-H2O; (v) Et3SiH/TFA/CH2Cl2; (vi) Boc anhydride/Et3N/THF; (vii) Me4Sn/Pd(Ph3P)4/LiCl/DMF; (viii) TFA/CH2Cl2; (ix)H2/10% Pd/C/MeOH; (x) Pd(Ph3P)4/trimethylboroxine/K2CO3,H2O-Dioxane; (xi) PdCl2(dppf)2/Me2Zn/dioxane; (xii) BH3eMe2S/Et2O, H2O2/NaOH; (xiii) Dess-Martin periodinane/CH2Cl2. deprotection was carried out by using TFA. The reduction in the presence of hydrogen and palladium on carbon afforded unsubstituted dihydroquinazolinones 74 & 75 (Scheme 11). The another isomeric 6, 6, 7-tricyclic dihydroquinazolinone 77 was obtained from the alcohol containing dihydroquinazolinone 76 in which the alcohol group was introduced by means of borane reagent followed by hydrogen peroxide treatment. The alcohols are converted into aldehydes using Dess-Martin periodinane as an oxidizing agent. The TFA and triethylsilane mediated cyclization afforded the isomeric 6, 6, 7-tricyclic dihydroquinazolinone 77 (Scheme 11) [67]. All the synthesized series for tested for their agonism against 5HT2C receptors and also its functional selectivity towards 5-HT2A and 5-HT2B. The functional selectivity towards 5-HT2c receptors and the absence of off-target effects was achieved using 6, 6, 6-tricyclic dihydroquinazolinones. The 6, 6, 6-tricyclic dihydroquinazolinones displayed suboptimal functional selectivity and reduced brain to plasma concentration. 2.10. Melanoma inhibitor Melanogenesis is a complex pathway and several proteins are involved in this pathway [69,70]. The process is initiated by the paracrine stimulator, POMC. It is the precursor of a-MSH, an endogenous peptide hormone of melanocortin family. Due to the induction of UV rays, the expression of POMC occurs in keratinocytes. The a-MSH cleaved from POMC acts through the MC1R. The remaining processes of melanogenesis are carried out by the second messenger, cAMP. The transcriptional activity was regulated through the phosphorylation of CREB and activation of the regulatory protein, MITF. Through the activation of the melanogenesisrelated protein, the melanogenetic enzyme tyrosinase was expressed out. This enzyme is responsible for the formation of melanin pigment through the series of reactions. If there is any change in the melanogenetic pathway, it will affect the pigmentation process (Fig. 12). Thangamalai [71] et al. reported the synthesis of quinazolinones and quinazoline-2-thiones with its activity profile against a-MSH induced melanin production. The amino compounds 78 on treatment with CDI in the presence of triethylamine yielded dihydroquinazolinone derivatives 79. The quinazolinones were converted into quinazoline-2-thione 80 by refluxing overnight with LR (Scheme 12). Quinazolinones displayed high IC50 value (>10 mM) when compared to the quinazoline-2-thione in aMSH induced melanin production in B16 melanoma cells. The smaller substituent does not affect the activity whereas the substitution of chlorine in the quinazoline-2-thione ring system resulted in slight variation. The presence of bulky ring system and the addition of substituents in the side chain phenyl ring decreased the activity. The number of methylene unit displayed marginal variation in activity but one methylene unit was found to be optimum. While predicting the mechanism of action, quinazoline-2thione inhibited the a-MSH induced melanin production in B16 melanoma cells whereas the normal catalytic activity of the tyrosinase enzyme was not affected. 2.11. T-type calcium channel antagonist The role of calcium ions has been implicated in various physiopathological processes [72]. There are various types of calcium channels in which T-type calcium channel plays a major role in the regulation of sleep, nociception, epilepsy, hypertension and cell cycle pathway. Because of the distribution of T-type calcium channel in the thalamus and cortex region, they are identified as K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 609 Fig. 12. Mechanism of action of melanoma inhibitor. Scheme 12. Synthesis of quinazolinone and quinazoline-2-thione. effective targets in the disorders of thalamocortical signaling pathway [73]. As per the reports of FLIPR tetra high-throughput cellular screening system, two piperidines 81, 82 and one quinazolinone analogs 83 were identified as T-type calcium channel antagonists for the treatment of epilepsy with minimal cardiovascular side effects. Barrow et al. [74] designed the series of 4, 4disubstituted quinazolin-2-ones based on the earlier reports and screened them for its antagonistic activity against the T-type calcium channel. The amino benzophenone 84 was cyclized in the presence of CDI in DCM followed by subsequent treatment with various primary amines. The cyclized product 85 was then heated with toluene in Dean-Stark apparatus to obtain the dehydrated product 86. The treatment of either the intermediates with Grignard reagent in THF resulted in the formation of dihydroquinazolinones 87 (Scheme 13). The compounds were tested for their potency against two types of FLIPR assays to identify their state dependent inhibition. Type 1 is based on measuring the potency in the inactivated state of the channel (depolarized assay) and type 2 is based on the resting state of the channel (hyperpolarized assay). All the compounds are selective towards the T-type calcium channel and the reading in the EEG displayed a reduction in the seizure time. The compound with the trifluoroethyl group in the 3rd position and fluorine in the 4th position of the phenyl ring displayed weak time dependent inhibition in the metabolic assay. Also, the compound acts as a weak substrate for the PXR which is responsible for the induction of metabolic enzyme (CYP3A4). In short, the compounds 88 and 89 are effective against harmaline induced tremor, active wake suppression, and epileptic seizures through the T-type calcium channel blockade. Schlegel et al. [75] extended the work on 4, 4-disubstituted quinazolin-2-ones as T-type calcium channel antagonists and increased the number of derivatives by varying the substituents on the quinazolinone ring system 90. The presence of trifluoro ethyl group in the 3rd position of quinazolinone is maintained constant because of its potency and metabolic stability. The halogen replacement in the 4th position phenyl ring 91 was carried by using either Suzuki Miyaura coupling reaction or by using cuprous iodide mediated coupling with morpholine. The Suzuki coupling involves the reaction of bromo derivative with boronic acid in the catalyst medium containing PCy3 and Pd2dba3 using potassium phosphate as a base. The amino benzophenone 92 containing fluorine in the 5th and 6th position follows the alternative way to form the quinazolinone nucleus. The quinazolinone obtained from the grignard reaction 93 and allyl magnesium bromide 94 was subjected to ozonolysis yields the aldehyde 95. The dimethyl sulfide acts as a reducing agent in the ozonolysis reaction. The aldehydes are directly converted into geminal difluorides 96 with DAST. The alkyl fluorides 97 are obtained after the reduction of the aldehyde into alcohols and then treated with DAST. The selection of various amino ketones as the starting material leads to the different substituents in the aromatic ring of the quinazolinone (Scheme 14). The racemic mixtures obtained through the synthetic routes were resolved into enantiomers using chiral HPLC. All these trifluoroethyl containing derivatives were subjected to preliminary evaluation of calcium channel antagonistic activity in the depolarized FLIPR assay. The compounds ability to activate the PXR was also evaluated. The metabolic stability of the compounds was found out by incubating the compounds with human liver microsomes. The potent compounds were studied for their pharmacokinetic profiling in the rat, dog, and monkey. The compound which is potent in the FLIPR assay, metabolically stable and has reduced PXR activation was subjected to further studies. The compound resulted in 70% inhibition against seizure, decreased the active wake and REM sleep. Based on these findings, the compound with T-type calcium channel antagonist 610 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 13. Synthesis of 4, 4-disubstituted quinazolin-2-ones-I. activity could be a valuable agent for the treatment of CNS disorders. 2.12. IMPDH inhibitor IMPDH is an enzyme which catalyzes the conversion of IMP to XMP. It is an example of oxidation reaction using NADþ as a cofactor in the biosynthesis of guanine nucleotides (GMP, GDP, and GTP). There are two isoforms, IMPDH I and IMPDH II. The upregulation of IMPDH II is expressed in highly proliferating cells. This acts as a key mechanism for the IMPDH inhibitors (Fig. 13). Therefore, the inhibition of IMPDH has been exploited in the therapeutic intervention of anticancer, antiviral, antiparasitic and immunosuppressive therapy [76,77]. From the earlier reports [78], 7-methoxy-6-oxazol5-yl]-1H-quinazoline-2, 4-diones 100 were identified as IMPDH II inhibitors with poor physical properties. A slight modification of the structure resulted in a series of 7-methoxy-6-oxazol-5-yl-2, 3dihydro-1H-quinazolin-4-ones 99 with potent IMPDH II inhibition. The compounds were prepared by EDC coupling of amino-acid 98 with appropriate amines (Scheme 15). These derivatives were designed with the objective of improving its potency along with the favorable DMPK properties. The replacement of 2-oxo moiety by gem-dimethyl group 101 resulted in a moderate decrease in activity with improved solubility. The substitution of one of the methyl group of the gem-dimethyl series by styrene moiety 102 improved the potency along with solubility. A range of spiro analogues was synthesized which showed comparable activity to that of dione and improved the potency in the PBMC proliferation assay. Many of the spiro-centered compounds generated chiral centre and the activity was reported in one of the enantiomers. The SAR of spiropyrrolidine containing compounds were studied by replacing the t-butyloxy group 103 with different electrophiles. The oxy-urea substituted spiro-pyrrolidine 104 displayed reduction in the hepatic clearance (CLint) with promising enzyme and cellular activities. Another set of experimentation was performed to rectify the increase in hepatic clearance rate. From the in vivo pharmacokinetic study, the major site of metabolism was identified in the pyrrolidine core. The pyrrolidine moiety was replaced by proline core 105 to create a metabolically stable structure. A pair of diastereomers was produced and they were purified by HPLC. The compound 105 having S stereochemistry at the spiro-centre reported less CLint value (18 mL/min/mg) with significant results aganist IMPDH II inhibition and PBMC proliferation assay. 2.13. Sodium/calcium exchange inhibitor NCX is a membrane protein responsible for the maintenance of calcium ions (Ca2þ) in the cardiac myocytes [79]. The role of Ca2þ is to control the contraction in myocytes. Any impairment in the exchange of Naþ and Ca2þ can affect the function of cardiac myocytes. The increase in Ca2þ overload causes an increase in the force of contraction of the heart thereby it leads to myofibril hyper contracture. The NCX inhibitor regulates the improper functioning of NCX and provides a valuable treatment in the case of reperfusion K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 611 Scheme 14. Synthesis of 4, 4-disubstituted quinazolin-2-ones-II. (i) AreB(OH)2, R ¼ Ar/P(Cy)3/Pd2dba3/K3PO4/Dioxane; (ii) Morpholine, R ¼ Morpholine/CuI, proline/K2CO3/DMSO; (iii) Triphosgene/Et3N/CF3CH2NH2/ether/0 C; (iv) Et3N/THF; (v) SOCl2/THF; (vi) RMgBr/THF; (vii) DAST/0 C/CH2Cl2; (viii) NaBH4/MeOH/0 C. Fig. 13. Mechanism of action of IMPDH inhibitor. 612 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 15. Synthesis of 7-methoxy-6-oxazol-5-yl-2, 3-dihydro-1H-quinazolin-4-ones. (i) EDC/CH2Cl2/R1-NH2; (ii)PTSA/ClCH2CH2Cl/ketone. injury [80]. Hasegawa et al. found that the derivatives of 3, 4dihydro-2(1H)-quinazolinone exhibited significant activity against the NCX inhibition (Fig. 14). The SAR study was carried out to evaluate the effect of substituents on the various positions of 3, 4-dihydro-2(1H)-quinazolinone nucleus. The reaction of 2-amino benzophenones 106 with trichloroacetyl chloride resulted in the formation of trichloroacetamide 107 which on subsequent reaction with primary amines gave cyclized products 108. Further treatment with NaBH4 resulted in the loss of trichloromethyl group and formed 3, 4dihydro-2(1H)-quinazolinone 109. Debenzylation 111 of the compound 110 can be achieved by the reaction with ammonium formate in the presence of Pd/C in methanol. The free NH group of quinazolinone 112 can be methylated 113 with iodomethane in the presence of NaH. NaH is a strong base and it acts as a deprotonating agent for the NeH bond. The carbonyl group of quinazolinone 112 can be converted into thiocarbonyl group 114 by treating with phosphorous pentasulfide in xylene. The introduction of piperidine ring is essential for the further derivatization of the dihydroquinazolinones. The cyclized product 116 was obtained by refluxing the aniline derivative 115 with CDI. Removal of benzyl group 117 was effected through the treatment with ammonium formate in the presence of palladium on carbon. The reductive amination 118 was favored when the aldehyde and sodium cyanoborohydride reacted with an amine. Alternatively, the amine can be N-alkylated 118 using alkyl halide and potassium carbonate Fig. 14. Mechanism of action of sodium/calcium exchange inhibitor. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 613 Scheme 16. Synthesis of dihydroquinazolinone as sodium/calcium exchange inhibitor. (i) CDI, THF; (ii) HCO2NH4, Pd/C, MeOH; (iii) NaBH3CN, HCl, MeOH/R-X, K2CO3, DMF. (Scheme 16). The compounds were evaluated for their fura 2 fluorescence ratio, an index for measuring the calcium ion concentration in an isolated left atria from guinea pigs. The inhibition against Naþ and Kþ free contracture was calculated as IC30 value. The removal of chlorine atom from the 6th position does not change the activity. The introduction of a methyl group and the conversion of carbonyl to thiocarbonyl diminished the activity. The presence of phenyl ring 119 in the 4th position was found to be optimum for retaining the activity. The side chain attached to the 3rd position should have tertiary nitrogen atom. The optimum of three carbon atoms between the ring and side chain nitrogen should be preferred. The inclusion of piperidine ring with benzyl group in the 3rd position and 3-methoxy substituent 120 in the phenyl ring was found to be essential for the inhibition [81,82]. The same author extended the work by synthesizing the citrate form of compound 112 and 116 using citric acid in methanol medium [83]. 2.14. PDE7 inhibitor Phosphodiesterases are a class of enzymes that plays the catalytic role in the degradation of cAMP/cGMP to AMP/GMP. PDE7 is one among the family and it selectively catalyzes the conversion of cAMP 614 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Fig. 15. Mechanism of action of PDE7 inhibitor. Scheme 17. Synthesis of dihydroquinazolinones as PDE7 inhibitor-I. (i) NIS, TFA, H2SO4; (ii) Pd(PPh3)4/2-pyridylZnBr/THF/RB(OH)2/K2CO3/DMF; (iii) SOCl2/toluene; (iv) R3R4NH/ toluene. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 615 Scheme 18. Synthesis of dihydroquinazolinones as PDE7 inhibitor-II. to AMP [84]. Therefore, inhibition of PDE7 leads to increase in the level of cAMP which affects various signal transduction pathways. The expression of PDE7 is highly upregulated in T-cells and B-lymphocytes. The inhibitors of PDE7 have been considered as a valuable therapeutics in the treatment of T-cell related diseases, autoimmune diseases, CNS disorders and airway disease (Fig. 15) [85]. The synthesis of dihydroquinazolinones was initiated by the reaction between ureas and different ketones in the presence of PPA. The mono substituted (2/4- substitution) ureas 124 resulted in the formation of single type cyclized product 125. The mixture of isomers 122, 123 (5, 6 and 6, 7-dichloro substituted quinazolinones) was obtained from 3-chloro substituted or 3, 4-dichloro substituted phenyl ureas 121. The chlorination reaction using NCS converted 6substituted derivatives 125 into 6, 8-disubstituted derivatives 126. The 8-chloro intermediates 127 were subjected to iodination reaction to afford 6-chloro-8-iodo intermediates 128. The iodide atom present in the intermediate was replaced with phenyl ring using Negishi/Suzuki coupling 129 reactions. The iodide atom reacted with 2-pyridyl zinc bromide and phenyl boronic acid in the negishi and Suzuki coupling reaction respectively. The carboxylic group present in the intermediate was transformed into acid chloride using thionyl chloride. The amide derivatives 130 were obtained by the reaction between an acid chloride and respective amines (Scheme 17). The compounds were screened for their effectiveness against PDE7A subtype inhibitory activity. The unsubstituted 4th position spirocyclohexyl ring, 6th position phenyl ring, and dihalogen substitution were the features essential for the potent action. The presence of carboxyl group increased the activity but the lack of selectivity towards the enzyme subtypes. Whereas the introduction of amide group with the linker containing 2e3 carbon atom displayed effective inhibition score and good selectivity against PDE7A enzyme. The amide containing piperazine derivatives displayed similar potency but decreased solubility [86]. Bernardelli et al. [87] extended the work on spiroquinazolinones by screening the potency and selectivity of various 5, 8disubstituted derivatives towards the PDE enzyme. The substituted anilines 131 reacted with potassium cyanate and transformed the amine derivatives into urea derivatives 132. The urea derivatives were cyclized into spiroquinazolinones 133 by reacting with cyclohexanone using PPA. The phenol containing quinazolinone 135 was obtained from the methoxy derivative 134 by using boron tribromide as a demethylating agent. The O-alkylation 136 of phenol intermediate was carried out in the presence of various alkyl halides (Scheme 18). The functionalization of 5hydroxy-8-chloro-spirocyclohexane-quinazolinone 137 was summarized in Scheme 19. The carboxylic acid 138 was introduced through the treatment of phenol 137 with ethyl bromoacetate followed by the hydrolysis of the ester with KOH. The nitrile 141 was synthesized using bromoacetonitrile and it reacted with azidotrimethyltin (IV) to form tetrazole 139. The nitrile 141 was also used in the synthesis of hydroxy-oxadiazole 140 through oximes 142 as an intermediate. The introduction of alcohol in the side chain 143 was obtained through the reaction with 2-(2-bromoethoxy) tetrahydro-2H-pyran followed by hydrolysis with HCl. The mesylate group 144 can be replaced either with morpholine 145 or ethyl glycinate 146 to form their corresponding derivatives. 2.15. p38 MAPK inhibitor The p38 MAPK pathway involves the sequential activation of three protein kinases: MAPK, MAPKK, and MAPKKK. p38 MAPK is responsible for regulating the biosynthesis of pro-inflammatory cytokines, namely IL-1 and TNFa [88]. The interruption of this pathway through p38 inhibitors was responsible for the treatment of rheumatoid arthritis (Fig. 16) [89]. Stelmach et al. [90] reported p38a MAP kinase inhibitory activity and pharmacokinetic profile of dihydroquinazolinones and they were designed on the basis of the reported structures. VX-745, 147 was reported as the phase II clinical trial undergoing drug for rheumatoid arthritis and they are selective for p38a MAP kinase. The compound 148 is the reduced isomeric analog of VX-745 with polar amine substituents in the C-7 position for increasing the potency and physicochemical properties. The thioether group in C-6 position can be replaced with C-5 phenyl ring for occupying the p38a hydrophobic pocket. The derivatives of dihydroquinazolinones containing C-5 phenyl ring 149 were prepared as per Scheme 25. The Ullmann type coupling reaction of 150 afforded cyclized product 151. The deprotection of PMB group was effected with TFA. The C-5 bromine was subjected to Suzuki coupling 152 with aryl boronic acids in the presence of Pd(PPh3)4. As a demethylating agent, boron tribromide converted C-7 methoxy group 153 into phenolic hydroxyl group 154. The conversion of phenolic OH into its triflates 155 was carried out by phenyl triflimide. The triflates reacted with vinyl trimethyltin in the presence of Pd(PPh3)4 and lithium chloride resulted in Stille type coupling product 156. The presence of lithium salt is to increase the polarity of the solvent for the easy removal of triflates. The platinum dioxide also known as Adam's catalyst was used for the 616 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 19. Synthesis of dihydroquinazolinones as PDE7 inhibitor-III. (i) Ethyl bromoacetate/K2CO3/DMF; (ii) KOH/THF; (iii) Bromoacetonitrile/K2CO3/DMF; (iv) NH2OH$HCl/NaOH, EtOH; (v)ClCO2Et/CHCl3/Et3N; (vi)DBU/ACN; (vii) Me3SnN3/Toluene; (viii)2-(2-bromoethoxy)tetrahydro-2H-pyran/K2CO3/DMF; (ix) HCl/THF/H2O; (x) Methanesulfonyl chloride/ Et3N/CH2Cl2/0 C; (xi) Morpholine/EtOH; (xii) Ethyl glycinate/CH3CN; (xiii) 6 N HCl/1, 4-dioxane. hydrogenation of vinyl group and N-boc can be deprotected using TFA (Scheme 20). The triflates 157 were also subjected to Buchwald-Hartwig coupling reaction 158 in the presence of amines. The Mitsunobu reaction was carried out to convert the phenolic OH 159 into ether 160 using DEAD and triphenylphosphine. The dihydroquinazolinones containing methylene linker 162 and carbonyl linker 163 at C-7 were obtained either by reductive amination and CDI coupling of ester 161 respectively (Scheme 21). The compounds containing piperazine/piperidine at C-7 position exhibited significant inhibition against p38a enzyme assay. They also inhibited the TNFa production. The rat pharmacokinetic profile displayed that these compounds resulted in low oral bioavailability and rapid clearance. The compound containing t-butyl group in the C-7 piperidine ring increased the oral bioavailability and decreased the clearance rate. Hunt et al. [91] investigated the p38 inhibitory activity of dihydroquinazolinones in addition to naphthyridinones 164 and quinolinones 165. The reaction scheme was initiated with 1, 3- dibromo-2-methyl-5-nitrobenzene 166. The reaction up to the synthesis of the intermediate 152 was followed as per the report of the previous author except deprotection of PMB group 167. The amine group 168 was introduced by means of reduction with hydrogen in the presence of palladium on carbon. The reductive alkylation of the amine with ketone was carried out by using the mild reducing agent, sodium triacetoxyborohydride. Finally, the PMB group was deprotected by TFA to yield the dihydroquinazolinones 169 (Scheme 22). The three series of C7piperidine and 4-aminopiperidine substituted naphthyridinones 164, quinolinones 165 and dihydroquinazolinones 169 were screened for their inhibition against p38a enzyme assay and TNFa production. The naphthyridinone and quinolinone derivatives were more potent and exhibited improved pharmacokinetic profile in the rat. The comparatively less potency of the dihydroquinazolinone derivatives was due to the difference in the C-4 position. The C-4 position was stabilized because of the sp2 hybridized centre, the clearance rate was lowered and oral K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 617 Fig. 16. Mechanism of action of p38 inhibitor. bioavailability was increased. This is the reason for the enhanced pharmacokinetic profile of the naphthyridinone derivatives. Schlapbach et al. [92] synthesized the dihydroquinazolinone derivatives from diclofenac and tested its inhibition score against the p38a enzyme. The a-arylamino phenylacetic acid 170 was subjected to curtius rearrangement in the presence of DPPA. The intramolecular ring closure of the isocyanate intermediate led to the formation of 1-(2, 6-dichlorophenyl)-3, 4-dihydroquinazolin2(1H)-one 171. The dihydroquinazolinone are subjected to C-6 functionalization by various reactions. The bromination and further coupling at the C-6 position were preceded via Buchwald-Hartwig reaction 172. The 2, 4-difluoro-thiophenol reacted with the bromine intermediate in the presence of tetrakis palladium and sodium tert-butoxide. The C-6 position was nitrated using potassium nitrate and reduced in the presence of hydrogen and palladium on carbon for introducing the amine group 173. The 6-amino1-(2, 6-dichlorophenyl)-3,4-dihydroquinazolin-2(1H)-one was utilized in the synthesis of arylamines, benzylamines, carboxamides or sulfonamides. The Buchwald-Hartwig coupling of the amine with 2, 4-difluoro-bromobenzene was carried out using Pd2dba3 and DPEphos afforded arylamine 174. The formation of benzylamines 175 through the reductive amination of amine and benzaldehyde was carried out with the aid of sodium cyanoborohydride. The reaction of amine with benzoyl chloride and the benzenesulfonyl-chloride resulted in the formation of carboxamide 176 and sulfonamide 177 respectively (Scheme 23). The phenyl ring at the N-1 position of dihydroquinazolinones replaced with various substituents as a p38a inhibitor was synthesized. The urea derivatives 178 were cyclized using palladium complex Pd2dba3 to afford N-1 substituted dihydroquinazolinones 179. The O-alkylated 180 and N-alkylated 181 derivatives of 1-(4-hydroxy-2, 6dimethylphenyl)-6-nitro-3, 4-dihydroquinazolin-2(1H)-one were obtained from chloropropyl-morpholine and 3-chloro-4-fluoro benzenesulfonylchloride respectively (Scheme 24). Because of the selectivity towards the p38 MAP kinase, significant inhibition of TNFa release and non-interference with liver enzymes, the compound was identified as a valuable candidate for drug discovery. 2.16. CDK5 inhibitor CDK5 is a proline-directed serine/threonine kinase and its activation requires various cyclin (cyclin I, E, and G1) and non-cyclin activators (p35, p39, and p67). This protein plays a vital role in the normal development of CNS and they have been involved in controlling several neuronal processes. The role of CDK5 has also been implicated in several non-neuronal functions (Fig. 17) [93]. The deregulation of CDK5 has been corroborated in several neurodegenerative diseases such as Alzheimer's disease, Huntington's chorea, stroke, Parkinson's disease and Lou Gehrig's disease [94]. Rzasa et al. [95] designed a series of 3, 4-dihydroquinazolin-2(1H)ones as CDK5 inhibitors. The molecule 183 was designed on the basis of intramolecular hydrogen bond formation between the two nitrogen atoms in the pyridyl urea 182. It was assumed that the intramolecular hydrogen bond between N1 and hydrogen atom from N3 occupies the active site of CDK5 enzyme. This assumption was confirmed from the cocrystallographic data of pyridyl urea 182 and CDK2, an analog of CDK5. Various modifications have been made in the A, B, C and D ring systems of the structure 183. From the SAR study, it was found that the compounds containing dihydroquinazolinones ring system (B ring: U]CH2) were more potent than the quinazolinedione and benzimidazolone ring. It is because of the van der waals contact with the amino acid residues found within the active site of the enzyme. The derivatives with the range of substituents were tolerated in the ring A, thiazolo moiety in the place of C ring and 4- pyridyl moiety in the ring D showed significant activity against HTRF human CDK5/p25 assay. The importance of 4pyridyl ring was supported by the formation of hydrogen bonding to the Asp145-Lys33 salt bridge. The anilines 184, 186, 189, 191 and 194 obtained through the various methodologies were cyclized using p-nitrophenyl chloroformate or CDI mediated reaction to give dihydroquinazolinones 185, 187, 190, 192 and 195. The ester containing dihydroquinazolinones 187 was hydrolysed and decarboxylated in the presence of alkaline and acidic medium to give the final product 188 (Scheme 25). 618 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 20. Synthesis of dihydroquinazolinones as p38 inhibitor-I. 2.17. RyR agonist Ryanodine is a natural insecticide and the receptor through which it acts is called RyR. RyR is an example of non-voltage-gated calcium channel and it causes the regulation of calcium release from intracellular storage [96]. Ryanodine type agonist causes the continuous release of calcium from the sarcoplasmic reticulum. Thereby the concentration of calcium in the myoplasm of insect increases and the muscles remain in the state of continuous contraction. The massive muscular contraction causes paralysis of muscles leading to the death of the insects (Fig. 18) [97]. Zhou et al. [98] carried out the synthesis of 2, 3-dihydroquinazolinones and tested their insecticidal activity against oriental armyworm (Mythimna separata). The 2-aminobenzoic acid 196 was used as a starting material for the synthesis of various amides. The amides 197 & 198 were obtained by the reaction of the 2-aminobenzoic acid with thionyl chloride/triphosgene/CDI followed by the treatment with corresponding amines. The ethyl 3-bromo-1-(3- chloropyridin-2-yl)-1H-pyrazole-5-carboxylate 199 was reduced into alcohol 200 in the presence of one equivalent of LiAlH4. Dechlorination of pyridine ring 201 was obtained from the treatment of more than two equivalent of reducing agent. The primary alcohol 200 & 201 was oxidized using PCC into aldehyde 202. The amide and the aldehyde were refluxed in the presence of PTSA and toluene medium to afford the dihydroquinazolinones 203. When the same reaction was carried out in the presence of ethanol, quinazolinones 204 were obtained (Scheme 26). The compound 205 exhibited 100% mortality against the larvae of Spodoptera exigua. The results of calcium imaging techniques demonstrated that RyR may be the possible site of action for the compounds containing dihydroquinazolinones. 2.18. Non-nucleoside reverse transcriptase inhibitor HIV is a member of retroviridae family and it specifically attacks the T-helper cells. The T-helper cells are the important component K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 619 Scheme 21. Synthesis of dihydroquinazolinones as p38 inhibitor-II. (i) NBS/Benzoyl peroxide/p-methoxy benzyl amine; (ii) 2, 6-di-Cl-PhNCO; (iii) CuI/K2CO3/DMF; (iv)TFA/(v) ArB(OH)2/Pd(PPh3)4; (vi) N-boc-4-trimethylstannyl-5, 6-dihydropyridine/Pd(PPh3)4/LiCl, (vii) H2, PtO2; (viii) TFA. Scheme 22. Synthesis of dihydroquinazolinones as p38 inhibitor-III. 620 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 23. Synthesis of dihydroquinazolinones as p38 inhibitor-IV. (i)Diphenylphosphoryl azide/NEt3/dimethoxyethane; (ii) Br2/CH2Cl2; (iii) 2, 4-difluoro-thio-phenol/Pd(PPh3)4/ NaOtBu/toluene; (iv) KNO3/H2SO4/0 C; (v) H2, Pd/C, ethanol; (vi) 2, 4-di-F-bromobenzene/Pd2dba3/DPEphos/NaOtBu/toluene; (vii) benzaldehyde/NaBH3CN/3% AcOH in DMF; (viii) Benzoyl chloride/NEt3/THF; (ix) Benzenesulfonyl chloride/DMAP/pyridine. Scheme 24. Synthesis of dihydroquinazolinones as p38 inhibitor-V. (i) Boc2O/DMAP/CH2Cl2; (ii) Pd2dba3/2-(dicyclohexyl-phosphino)biphenyl/K3PO4; (iii) Chloropropylmorpholine/CsI/DMF; (iv) H2/Pd/C/MeOH; (v) 3-chloro-4-fluoro benzenesulfonylchloride/pyridine/DMAP/CH2Cl2. of WBC helps to coordinate the immune response. HIV enters the host cell through binding with host cell CD4 receptors found on the surface of the cell. After entering into the host cell, HIV utilizes the host cell machinery for the replication process and leaves them as a mature virion. Several proteins are involved in the replication process and they can act as a valuable target for the treatment of HIV (Fig. 19) [99]. RT is an attractive target for HIV and they are categorized into NRTIs and NNRTIs. The development of NNRTI based drug candidate is advantageous because of its potency and low cytotoxicity [100]. Corbett et al. [101] synthesized dihydroquinazolinones from amino ketones 206 as starting materials. The aminols 207 were obtained by the reaction of amino ketones 206 with TMSNCO and TBAF. The trifluoromethyl ketimines 208 are the dehydrated product of aminols treated in the presence of K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 621 Fig. 17. The role of CDK5 inhibitors in neurodegenerative diseases. toluene or xylene and the moisture is absorbed by 4 Å molecular sieves. Then the ketimines were alkylated with lithiated alkynes using the catalytic amount of lewis acid like boron trifluoride etherate to afford quinazolinones 209 (Scheme 27). The analogs were screened for their in vitro inhibition of HIV-1 RT assay. The 5, 6-dihalogen compounds and the presence of trifluoromethyl group improved the overall resistance of the molecule. The compounds DPC 961 210, DPC 963 211, DPC 082 212, and DPC 083 213 exhibited pharmacokinetic property similar to that of efavirenz. These compounds also provided superior antiviral potency and safety profile against the mutant HIV variants (see Scheme 28). and they are synthesized from the wide variety of starting materials. Guan et al. [105] developed an efficient protocol for the synthesis of dihydroquinazolinones from anthranilamide obtained via indazoles. Indazoles 221 are either prepared by Buchwald-Hartwig reaction (i) or by copper-catalyzed aryl coupling reaction (ii). The indazole is converted into indazolium salts 222 by methylating with dimethylsulphate. The indazolium salts are reacted with potassium tert-butoxide in the presence of toluene and water gives the corresponding anthranilamides 223. The anthranilamides on treatment with 50% sulphuric acid and formaldehyde yielded 2, 3dihydro-4(1H)-quinazolinones 224 (Scheme 29). 2.19. Aldosterone synthase inhibitor 3.2. Copper oxide nanoparticle mediated synthesis of dihydroquinazolinones Aldosterone synthase is an important enzyme involved in the biosynthesis of aldosterone. Aldosterone is a mineralocorticoid hormone essential for the homeostasis of blood volume and electrolyte balance. The excessive secretion of aldosterone is responsible for the pathological conditions such as hypertension, cardiac fibrosis and congestive heart failure (Fig. 20) [102,103]. Grombien et al. [104] carried out the synthesis of moieties designed on the basis of 3, 4-dihydroquinolinone nucleus in which the methylene unit of 3, 4-dihydropyridinone were bioisosterically exchanged with various heteroatoms 214.2-(aminomethyl)aniline 216 was cyclized into 3, 4-dihydroquinazolinone 217 in the presence of triphosgene. The bromine atom was introduced in to 3, 4dihydroquinazolinone using NBS 218 and it was subjected to Suzuki Miyaura coupling 219 using heteroarylboronic acid. The compound 220 showed minor selectivity towards the human CYP11B1 gene responsible for encoding of the aldosterone synthase enzyme. The replacement of lactame 214 by sultame 215 moiety displayed significant reduction in the biological activity. 3. Miscellaneous synthesis and applications of dihydroquinazolinones 3.1. Synthesis of 2, 3-dihydroquinazolin-4(1H)-ones from Nheterocyclic carbenes of indazole Indazoles are medicinally and pharmaceutically important motif Zhang et al. [106] carried out the one pot condensation of isatoic anhydride 20, anilines 225 and aldehydes in the presence of various catalysts to afford dihydroquinazolinones 226 & 227 (Scheme 30). CuO nanoparticles were found to be superior among the catalyst. The experimentation on the effect of ethanol:water ratio on the yield of the product was tested. The increase in the amount of water substantially increased the yield. The yield was optimised at 1:1 ratio of ethanol: water and a further increase in the water decreased the yield. The 10 mol% of CuO nanoparticles was necessary to increase the yield. When the reaction was stirred at reflux temperature, it required 3 h for completion. In the presence of ultrasound irradiation (40 KHz and 250 W), the reaction was completed in 10e30 min. The condensation reaction between isatoic anhydride, ammonium chloride 228 and various aldehydes in the presence of CuO nanoparticles, quinazolinones 229 were obtained as a product. When the ethanol: water system was maintained at 3:1 ratio, there is a maximum conversion of quinazolinone. The reason for the unexpected formation of quinazolinones may be due to the intramolecular electron transfer and rearrangement in the presence of inorganic salts. 3.3. Y(OTf)3 mediated synthesis of dihydroquinazolinones The synthesis of dihydroquinazolinones was carried out by the condensation reaction between anthranilamide 230 and various 622 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 25. Synthesis of dihydroquinazolinones as CDK5 inhibitor. (i) p-nitophenyl chloroformate/Et3N/toluene/THF; (ii) CDI/NaH/DMF; (iii) NaOH/MeOH/H2SO4; (iv) iron dust/ NH4Cl/aq. EtOH. aldehydes 231. In the absence of a catalyst, traces of product were obtained even after long time treatment. The comparison of acidic catalyst resulted in improved yields. The uniqueness of the rare earth metal chloride as catalyst displayed effectiveness in yield. However, Y(OTf)3 was found to be superior among the rare earth metals. Ethanol was optimized as the suitable solvent for the reaction. These optimized reaction conditions yielded traces of quinazolinones 233 along with dihydroquinazolinones 232 (Scheme 31). The role of oxidants identified dimethyl sulfoxide in providing a satisfactory yield of quinazolinones [107]. 3.4. Boric acid mediated synthesis of dihydroquinazolinones Anthranilamide 234 was converted into 3, 5- K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 623 Fig. 18. The role of the ryanodine receptor in insecticidal activity. Scheme 26. Synthesis of dihydroquinazolinones as an insecticidal agent. (i) a) SOCl2, b) R2NH2/THF; (ii) a) triphosgene, b) CH3NH2/H2O; (iii) CDI/THF; (iv) NH3/H2O; (v) LiAlH4/THF; (vi)PCC/CH2Cl2; (vii) PTSA/toluene/reflux; (viii) CH3CH2OH/reflux. dibromoanthranilamide 235 using N-bromosuccinimide in chloroform-carbon tetrachloride mixture. It was then cyclized with benzaldehyde derivatives using boric acid as a catalyst in the presence of solvent-free condition to obtain 2-aryl-6,8-dibromo2,3-dihydroquinazolin-4(1H)-ones 236. Further derivativatization of dihydroquinazolin-4(1H)-ones was carried out by subjecting the bromine to Suzuki Miyaura coupling reaction. The coupling reaction between 2-aryl-6,8-dibromo-2,3-dihydroquinazolin-4(1H)ones and phenylboronic acid in the presence of PdCl2(PPh3)2-Xphos catalyst complex yields biarylated 2, 3-dihydroquinazolin-4(1H)one derivatives 237. The 2, 3-dihydroquinazolin-4(1H)-one derivatives were oxidized into quinazolin-4(3H)-one 238 derivatives in the presence of molecular iodine as an oxidant. The formation of lactam form of quinazolin-4(3H)-one derivative 239 was confirmed through the NMR spectra (Scheme 32) [108]. 3.5. Visible light mediated synthesis of dihydroquinazolinones Hemalatha et al. reported the visible light mediated synthesis of 2, 3- dihydroquinazolinones from isatoic anhydride and ketones in the presence and absence of acetic acid. The reaction was efficient in the presence of acetic acid. The solvatochromic effect of the synthesized series was carried out using various solvents of increasing polarity. All the compounds exhibited significant quantum yield and they yielded maximum fluorescence in dimethyl sulfoxide. Further the antioxidant activity and in vitro antiinflammatory activity of dihydroquinazolinones concluded those isatin containing derivatives 240 are most effective among the synthesized series (Fig. 21) [109]. The biological activity of the compounds was correlated with the docking studies carried out using PARP [110] enzyme. 624 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Fig. 19. Mechanism of action of anti-HIV drugs. Scheme 27. Synthesis of trifluoromethyl-containing dihydroquinazolinones. Scheme 28. Synthesis of 3, 4-dihydroquinazolinones as aldosterone synthase inhibitor. (i) Triphosgene/THF; (ii) NBS/DMF/0 C; (iii) Heteroarylboronic acid/Pd(PPh3)4/aq. Na2CO3/ DME/reflux. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 625 Fig. 20. Mechanism of action of aldosterone synthase inhibitor. Scheme 29. Synthesis of dihydroquinazolinones from indazoles. 3.6. Importance of 7-fluoro-2, 2-dimethyl-2, 3-dihydroquinazolin4(1H)one Due to the importance of fluorinated compounds in the field of drug discovery and development, the fluorine containing 2, 2dimethyl-2, 3-dihydroquinazolin-4(1H)one was synthesized. The amide 243 for the synthesis of the fluorinated derivative was prepared from the condensation reaction between 2-amino-4fluorobenzoic acid 241 and methylamine 242 in the presence of EDC and hydroxybenzotriazole. The amide 243 undergoes cyclization with acetone in the presence of concentrated HCl to afford the fluorinated derivative of 2, 3-dihydroquinazolinone 244 (Scheme 33). The interaction between the fluorinated derivative and lysozyme was predicted using NMR study in addition to the various spectrophotometric studies. The difference in the chemical shift value of the ligand after interaction with the protein confirmed the interaction between them. In silico prediction of the metabolic pathway of the fluorinated derivative confirmed that the presence of fluorine atom prevents the oxidation of aromatic ring and makes the molecule metabolically stable. From the MTT assay, 626 K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 Scheme 30. CuO nanoparticle-mediated synthesis of dihydroquinazolinones. Scheme 31. Y(OTf)3 mediated synthesis of dihydroquinazolinones. Scheme 32. Boric acid mediated synthesis of dihydroquinazolinones. K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 627 3.8. Suzuki Miyaura coupling of 2, 3-dihydroquinazolinones Fig. 21. Isatin containing dihydroquinazolinone derivative. Hemalatha et al. extended the work by subjecting the brominated derivatives of 2, 3-dihydroquinazolinones 248 to Suzuki Miyaura coupling (Scheme 35). The Suzuki coupled products 249 were screened for antifungal activity against the Aspergillus species. The interaction of dihydroquinazolinones containing CeO bond with the amino acid residues of the protein N-myristoyl transferase Scheme 33. Synthesis of 7-fluoro-2, 2-dimethyl-2, 3-dihydroquinazolin-4(1H)one. (i) EDC. HCl/HOBt/Et3N/DCM; (ii) Acetone/HCl. Scheme 34. Bromination of 2, 3-dihydroquinazolinones. was identified to be the reason for the superior antifungal activity of the compounds. The active compound among the synthesized series was subjected to lysozyme interaction studies. The interaction between the compound and the lysozyme was justified through various spectroscopic studies [113]. In another work, optimization of the same reaction using palladium nanoparticles was carried out. The coupling reaction carried out in the presence of both microwave and ultraviolet irradiation was resulted in maximum yield. The toxicity of the palladium nanoparticles was tested using Artemia salina bioassay and it was found to be non toxic. Environmental impact of the reaction conditions was assessed from the E-factor and eco scale value. The analysis confirmed the ecofriendliness of the reaction condition [114]. Scheme 35. Synthesis of 6-substituted 2, 3-dihydroquinazolinones via Suzuki Miyaura coupling. the concentration greater than 80 mM was identified as the cytotoxic concentration [111]. 3.7. Bromination of 2, 3-dihydroquinazolinones Hemalatha and co-worker carried out the bromination of 2, 3dihydroquinazolinones 245 using NBS as the brominating agent. In the presence of 1 equivalent of NBS, bromine was substituted in the 6th position of 2, 3-dihydroquinazolinones 246. However in the presence of 1.1 equivalent of NBS, there may be a chance for the substitution of bromine atom in the 5th position of 2, 3dihydroquinazolinones 247 I n addition to 6th position bromine atom (Scheme 34). The introduction of hydrophobic bromine atom was justified for the significant anthelmintic activity of the compounds. The interaction study with bovine serum albumin was determined from the spectroscopic studies [112]. 4. Conclusion The summation of the synthetic methodology will drive the interest of the chemist towards the dihydroquinazolinone nucleus. The compounds with the same reactivity can also be experimented using the same reaction condition. The schematic representation of the biochemical pathway will be clear cut for even the nonbiologist to understand the mechanism easily. The designing of the compounds based on the effects of the substituents will result in the development of an effective molecule for the future scenario. References [1] K. Hemalatha, G. Madhumitha, S.M. Roopan, Indole as a core antiinflammatory agent- a mini review, Che. Sci. Rev. Lett. 2 (2013) 287e292. [2] Y. Chen, C. Tang, Y. Wu, S. Mo, S. Wang, G. Yang, Z. Mei, Glycosmisines A and B: isolation of two new carbazole-indole-type dimeric alkaloids from Glycosmis pentaphylla and an evaluation of their antiproliferative activities, Org. Biomol. Chem. 13 (2015) 6773e6781. [3] A.J. Singh, J.D. Dattelbaum, J.J. Field, Z. Smart, E.F. Woolly, J.M. Barber, R. Heathcott, J.H. Miller, P.T. Northcote, Structurally diverse hamigerans from 628 [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 the New Zealand marine spongeHamigera tarangaensis: NMR-directed isolation, structure elucidation and antifungal activity, Org. Biomol. Chem. 11 (2013) 8041e8051. J. Palaniraja, S.M. Roopan, UV-light induced domino type reactions: synthesis and photophysical properties of unreported nitrogen ring junction quinazolines, RSC Adv. 5 (2015) 37415e37423. K. Hemalatha, G. Madhumitha, A. Kajbafvala, N. Anupama, S. Rajesh, S.M. Roopan, Function of nanocatalyst in chemistry of organic compounds revolution: an overview, J. Nanom. 2013 (2013) 1e23. A. Bharathi, S.M. Roopan, A.A. Rahuman, G. Rajakumar, (E)-2-Benzylidene-7chloro-9-phenyl-3, 4- dihydroacridin-1(2H)-ones: synthesis and larvicidal activity, Res. Chem. Intermed. 41 (2015) 2453e2464. A. Kalaiselvi, S.M. Roopan, G. Madhumitha, C. Ramalingam, G. Elango, Synthesis and characterization of palladium nanoparticles using Catharanthus roseus leaf extract and its application in the photo-catalytic degradation, Spectrochim. Acta Mol. Biomol. Spectrosc. 135 (2015) 116e119. S.M. Roopan, A. Bharathi, A. Prabhakarn, A.A. Rahuman, K. Velayutham, G. Rajakumar, R.D. Padmaja, M. Lekshmi, G. Madhumitha, Efficient phytosynthesis and structural characterization of rutile TiO2 nanoparticles using Annona squamosa peel extract, Spectrochim. Acta Mol. Biomol. Spectrosc. 98 (2012) 86e90. C. Jayaseelan, A.A. Rahuman, S.M. Roopan, A.V. Kirthi, J. Venkatesan, S.K. Kim, M. Iyappan, C. Siva, Biological approach to synthesize TiO2 nanoparticles using Aeromonas hydrophila and its antibacterial activity, Spectrochim. Acta Mol. Biomol. Spectrosc. 107 (2013) 82e89. G. Madhumitha, G. Rajakumar, S.M. Roopan, A.A. Rahuman, K.M. Priya, A.M. Saral, F.R.N. Khan, V.G. Khanna, K. Velayutham, C. Jayaseelan, C. Kamaraj, G. Elango, Acaricidal, insecticidal, and larvicidal efficacy of fruit peel aqueous extract of Annona squamosa and its compounds against bloodfeeding parasites, Parasitol. Res. 111 (2012) 2189e2199. G. Madhumitha, A.M. Saral, Screening of larvicidal activity of Crossandra infundibuliformis extracts against Anopheles stephensi, Aedes aegypti and Culex Quinquefasciatus, Int. J. Pharm. Pharm. Sci. 4 (2012) 485e488. G. Madhumitha, A.M. Saral, Preliminary phytochemical analysis, antibacterial, antifungal and anticandidal activities of successive extracts of Crossandra infundibuliformis, Asian Pac. J. Trop. Med. 4 (2011) 192e195. G. Madhumitha, A.M. Saral, B. Senthilkumar, A. Sivaraj, Hepatoprotective potential of petroleum ether leaf extract of Crossandra infundibuliformis on CCl4 induced liver toxicity in albino mice, Asian Pac. J. Trop. Med. 3 (2010) 788e790. G. Madhumitha, A.M. Saral, Free radical scavenging assay of Thevetia nerufolia leaf extracts, Asian J. Chem. 21 (2009) 2468e2470. K. Velayutham, A.A. Rahuman, G. Rajakumar, S.M. Roopan, G. Elango, C. Kamaraj, S. Marimuthu, T. Santhoshkumar, M. Iyappan, C. Siva, Larvicidal activity of green synthesized silver nanoparticles using bark aqueous extract of Ficus racemosa against Culex quinquefasciatus and Culex gelidus, Asian Pac. J. Trop. Med. 6 (2013) 95e101. S.M. Roopan, T.V. Surendra, G. Elango, S.H.S. Kumar, Biosynthetic trends and future aspects of bimetallic nanoparticles and its medicinal applications, Appl. Microbiol. Biotechnol. 98 (2014) 5289e5300. C.T. Walsh, Nature loves nitrogen heterocycles, Tetrahedron Lett. 56 (2015) 3075e3081. S.M. Roopan, F.R.N. Khan, ZnO nanoparticles in the synthesis of AB ring core of camptothecin, Chem. Pap. 64 (2010) 812e817. S.M. Patil, S. Kulkarni, M. Mascarenhas, R. Sharma, S.M. Roopan, A. Roychowdhury, DMSO-POCl3: a reagent for methylthiolation of imidazo[1, 2-a]pyridines and other imidazo-fused heterocycles, Tetrahedron 69 (2013) 8255e8262. P. Manivel, S.M. Roopan, R.S. Kumar, F.N. Khan, Synthesis of 3-substituted isoquinolin-1-yl-2-(cycloalk-2-enylidene) hydrazines and their antimicrobial properties, J. Chil. Chem. Soc. 54 (2009) 183e185. F.N. Khan, S.M. Roopan, V.R. Hathwar, S.W. Ng, 2-Chloro-3-hydroxymethyl6-methoxyquinoline, Acta Crystallogr. Sect. E.-Struct. Rep. Online 66 (2010) o201. R. Subashini, S.M. Roopan, F.N. Khan, Synthesis and free radical scavenging property of some quinoline derivatives, J. Chil. Chem. Soc. 55 (2010) 317e319. A. Bharathi, S.M. Roopan, A. Kajbafvala, R.D. Padmaja, M.S. Darsana, G. Nandhini Kumari, Catalytic activity of TiO2 nanoparticles in the synthesis of some 2,3-disubstituted dihydroquinazolin-4(1H)-ones, Chin. Chem. Lett. 25 (2014) 324e326. S.M. Roopan, F.R.N. Khan, Free radical scavenging activity of nitrogen heterocyclics-quinazolinones and tetrahydrocarbazolones, Indian J. Heterocycl. Chem. 18 (2008) 183e184. J. Palaniraja, S.M. Roopan, Iodine-mediated synthesis of indazoloquinazolinones via a multi-component reaction, RSC Adv. 5 (2015) 8640e8646. D.J. Connolly, D. Cusack, T.P.O. Sullivan, P.J. Guiry, Synthesis of quinazolinones and quinazolines, Tetrahedron 61 (2005) 10153e10202. I. Khan, A. Ibrar, W. Ahmed, A. Saeed, Synthetic approaches, functionalization and therapeutic potential of quinazoline and quinazolinone skeletons: the advances continue, Eur. J. Med. Chem. 90 (2015) 124e169. I. Khan, A. Ibrar, N. Abbas, A. Saeed, Recent advances in the structural library of functionalized quinazoline and quinazolinone scaffolds: synthetic approaches and multifarious applications, Eur. J. Med. Chem. 76 (2014) 193e244. [29] S.B. Mhaske, N.P. Argade, The chemistry of recently isolated naturally occurring quinazolinone alkaloids, Tetrahedron 62 (2006) 9787e9826. [30] U.A. Kshirsagar, Recent developments in the chemistry of quinazolinone alkaloids, Org. Biomol. Chem. 13 (2015) 9336e9352. [31] V.B. Labade, P.V. Shinde, M.S. Shingare, A facile and rapid access towards the synthesis of 2, 3-dihydroquinazolin-4(1H)-ones, Tetrahedron Lett. 54 (2013) 5778e5780. [32] Z. Liu, L. Ou, M.A. Giulianotti, R.A. Houghten, Solid-phase synthesis of Nsubstituted 3, 4-dihydroquinazolinone derivatives, Tetrahedron Lett. 52 (2011) 2627e2628. [33] Y. Kobayashi, Y. Nakano, M. Kizaki, K. Hoshikuma, Y. Yokoo, T. Kamiya, Capsaicinlike antiobese activities of evodiamine from fruits of Evodia rutaecarpa, a vanilloid receptor agonist, Planta Med. 67 (2001) 628e633. [34] J. Rosenberg, F. Gustafsson, S. Galatius, P.R. Hildebrandt, Combination therapy with metolazone and loop diuretics in outpatients with refractory heart failure: an observational study and review of the literature, Cardiovasc. Drug. Ther. 19 (2005) 301e306. [35] G.C. Roush, R. Kaur, M.E. Ernst, Diuretics: a review and update, J. Cardiovasc. Pharmacol. Ther. 19 (2014) 5e13. [36] J. Olesen, H.-C. Diener, I.W. Husstedt, P.J. Goadsby, D. Hall, U. Meier, S. Pollentier, L.M. Lesko, Calcitonin gene-related peptide receptor antagonist BIBN 4096 BS for the acute treatment of migraine, N. Engl. J. Med. 350 (2004) 1104e1110. [37] R.W. King, R.M. Klabe, C.D. Reid, S.K. Erickson-Viitanen, Potency of nonnucleoside reverse transcriptase inhibitors (NNRTIS) used in combination with other human immunodeficiency virus NNRTIS, NRTIS, or protease inhibitors, Antimicrob. Agents Ch 46 (2002) 1640e1646. [38] S. Li, J.-A. Ma, Core-structure-inspired asymmetric addition reactions: enantioselective synthesis of dihydrobenzoxazinone and dihydroquinazolinone based anti-HIV agents, Chem. Soc. Rev. 44 (2015) 7439e7448. [39] D.J. Foster, D.L. Choi, P.J. Conn, J.M. Rook, Activation of M1 and M4 muscarinic receptors as potential treatments for Alzheimer's disease and schizophrenia, Neuropsychiatr. Dis. Treat. 10 (2014) 183e191. [40] Y. Uruno, Y. Konishi, A. Suwa, K. Takai, K. Tojo, T. Nakako, M. Sakai, T. Enomoto, H. Matsuda, A. Kitamura, T. Sumiyoshi, Discovery of dihydroquinazolinone derivatives as potent, selective, and CNS-penetrant M1 agonists and M4 muscarinic acetylcholine receptors, Bioorg. Med. Chem. Lett. 25 (2015) 5357e5361. [41] B.S. Rayner, D.T. Love, C.L. Hawkins, Comparative reactivity of myeloperoxidase-derived oxidants with mammalian cells, Free Radic. Bio. Med. 71 (2014) 240e255. [42] E. Malle, T. Buch, H.-J. Grone, Myeloperoxidase in kidney disease, Kidney. Int. 64 (2003) 1956e1967. [43] Y. Li, T. Ganesh, A. Sun, B.A. Diebold, Y. Zhu, J.W. McCoy, S.M.E. Smith, J.D. Lambeth, Thioxo-dihydroquinazolin-one compounds as novel inhibitors of myeloperoxidase, ACS Med. Chem. Lett. 6 (2015) 1047e1052. [44] Y. Ma, D. Ren, J. Zhang, J. Liu, J. Zhao, L. Wang, F. Zhang, Synthesis, antibacterial activities evaluation, and docking studies of some 2-substituted-3(phenylamino)-dihydroquinazolin-4(1H)-ones, Tetrahedron Lett. 56 (2015) 4076e4079. [45] K. Janiyani, T. Bordelon, G.L. Waldrop, J.E. Cronan, Function of Escherichia coli biotin carboxylase requires catalytic activity of both subunits of the homodimer, J. Biol. Chem. 276 (2001) 29864e29870. [46] M. Brylinski, G.L. Waldrop, Computational redesign of bacterial biotin carboxylase inhibitors using structure-based virtual screening of combinatorial libraries, Molecules 19 (2014) 4021e4045. [47] K. Engen, J. Savmarker, U. Rosenstrom, J. Wannberg, T. Lundback, A. Jenmalm-Jensen, M. Larhed, Microwave heated flow synthesis of spirooxindole dihydroquinazolinone based IRAP inhibitors, Org. Process. Res. Dev. 18 (2014) 1582e1588. [48] W.G. Thomas, F.A.O. Mendelsohn, Angiotensin receptors: form and function and distribution, Int. J. Biochem. Cell. Biol. 35 (2003) 774e779. [49] S.Y. Chai, R. Fernando, G. Peck, S.Y. Ye, F.A.O. Mendelsohn, T.A. Jenkins, A.L. Albiston, The angiotensin IV/AT4 receptor, Cell. Mol. Life Sci. 61 (2004) 2728e2737. [50] P. Winstanley, Modern chemotherapeutic options for malaria, Lancet Infect. Dis. 1 (2001) 242e250. [51] P. Winstanley, S. Ward, Malaria chemotherapy, Adv. Parasitol. 61 (2006) 47e76. [52] U. D'Alessandro, Existing antimalarial agents and malaria-treatment strategies, Exp. Opin. Pharmacother. 10 (2009) 1291e1306. [53] F.K. Hansen, S.D.M. Sumanadasa, K. Stenzel, S. Meister, L. Marek, R. Schmetter, K. Kuna, A. Hamacher, B. Mordmuller, M.U. Kassack, E.A. Winzeler, V.M. Avery, K.T. Andrews, S. Duffy, T. Kurz, Discovery of HDAC inhibitors with potent activity against multiple malaria parasite life cycle stages, Eur. J. Med. Chem. 82 (2014) 204e213. [54] E.R. Derbyshire, R.K. Guy, J. Min, J. Clardy, W.A. Guiguemde, J.A. Clark, M.C. Connelly, A.D. Magalhaes, R.K. Guy, J. Clardy, Dihydroquinazolinone inhibitors of proliferation of blood and liver stage malaria parasites, Antimicrob. Agents Ch 58 (2014) 1516e1522. [55] V. Tzin, G. Galili, New insights into the Shikimate and aromatic amino acids biosynthesis pathways in plants, Mol. Plant 3 (2010) 956e972. [56] M. Okvist, P. Kast, R. Dey, S. Sasso, E. Grahn, U. Krengel, 1.6 Å crystal structure K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] of the secreted chorismate mutase from mycobacterium tuberculosis: novel fold topology revealed, J. Mol. Biol. 357 (2006) 1483e1499. D. Rambabu, S.K. Kumar, B.Y. Sreenivas, S. Sandra, A. Kandale, M.V.B. Rao, M. Pal, P. Misra, Ultrasound-based approach to spiro-2, 3-dihydroquinazolin4(1H)-ones: their in vitro evaluation against chorismate mutase, Tetrahedron Lett. 54 (2013) 495e501. R.N. Dubois, S.B. Abramson, R.A. Gupta, L.S. Simon, L. Crofford, L.B.A.V. Putte, P.E. Lipsky, Cyclooxygenase in biology and disease, FASEB J. 12 (1998) 1063e1073. E. Manivannan, S.C. Chaturvedi, Analogue-based design, synthesis and docking of non-steroidal anti-inflammatory agents. Part 2: methyl sulfanyl/ methyl sulfonyl substituted 2, 3-diaryl-2, 3-dihydro-1H-quinazolin-4-ones, Eur. J. Med. Chem. 20 (2012) 7119e7127. R.S. Hoonur, B.R. Patil, D.S. Badiger, R.S. Vadavi, K.B. Gudasi, P.R. Dandawate, M.M. Ghaisas, S.B. Padhye, M. Nethaji, Transition metal complexes of 3-aryl2-substituted 1, 2-dihydroquinazolin-4(3H)-one derivatives: new class of analgesic and anti-inflammatory agents, Eur. J. Med. Chem. 45 (2010) 2277e2282. S. Arora, X.I. Wang, S.M. Keenan, C. Andaya, Q. Zhang, Y. Peng, W.J. Welsh, Novel microtubule polymerization inhibitor with potent anti-proliferative and anti-tumor activity, Cancer Res. 69 (2009) 1910e1915. A. Kamal, E.V. Bharathi, J.S. Reddy, M.J. Ramaiah, M.K. Reddy, A. Viswanath, T.L. Reddy, T.B. Shaik, D. Dastagiri, N.C.V.L. Pushpavalli, M.P. Bhadra, Synthesis and biological evaluation of 3, 5-diaryl isoxazoline/isoxazole linked 2, 3-dihydroquinazolinone hybrids as anticancer agents, Eur. J. Med. Chem. 46 (2011) 691e703. S.M. Roopan, J.S. Jin, F.N. Khan, R.S. Kumar, An efficient one pot-three component cyclocondensation in the synthesis of 2-(2-chloroquinolin-3yl)-2, 3-dihydroquinazolin-4(1H)-ones: potential antitumor agents, Res. Chem. Intermed. 37 (2011) 919e927. F.L. Faraj, M. Zahedifard, M.J. Paydar, C.Y. Looi, N.A. Majid, H.M. Ali, N. Ahmad, N.S. Gwaram, M.A. Abdulla, Synthesis, characterization, and anticancer activity of new quinazoline derivatives against MCF-7 cells, Sci. World J. 2014 (2014) 1e15. M. Mahdavi, K. Pedrood, M. Safavi, M. Saeedi, M. Pordeli, S.K. Ardestani, S. Emami, A. Foroumadi, A. Shafiee, M. Adib, Synthesis and anticancer activity of N-substituted 2-arylquinazolinones bearing trans-stilbene scaffold, Eur. J. Med. Chem. 95 (2015) 492e499. B.J. Sargent, A.J. Henderson, Targeting 5-HT receptors for the treatment of obesity, Curr. Opin. Pharmacol. 11 (2011) 52e58. A.C. Dutton, N.M. Barnes, Anti-obesity pharmacotherapy: future perspectives utilising 5-HT2C receptor agonists, Drug Discov. Today Ther. Strateg. 3 (2006) 577e583. S. Ahmad, K. Ngu, K.J. Miller, G. Wu, C. Hung, S. Malmstrom, G. Zhang, E. O'Tanyi, W.J. Keim, M.J. Cullen, K.W. Rohrbach, M. Thomas, T. Ung, Q. Qu, J. Gan, R. Narayanan, M.A. Pelleymounter, J.A. Robl, Tricyclic dihydroquinazolinones as novel 5- HT2C selective and orally efficacious antiobesity agents, Bioorg. Med. Chem. Lett. 20 (2010) 1128e1133. J.M. Gillbro, M.J. Olsson, The melanogenesis and mechanisms of skinlightening agents-Existing and new approaches, Int. J. Cosmet. Sci. 33 (2011) 210e221. H. Kim, S. Lee, Induction of ATP synthase b by H2O2 induces melanogenesis by activating PAH and cAMP/CREB/MITF signaling in melanoma cells, Int. J. Biochem. Cell B 45 (2013) 1217e1222. P. Thanigaimalai, K. Lee, S. Bang, J. Lee, C. Yun, E. Roh, B. Hwang, Y. Kim, S. Jung, Evaluation of 3, 4-dihydroquinazoline-2(1H)-thiones as inhibitors of a-MSH-induced melanin production in melanoma B16 cells, Bioorgan. Med. Chem. 18 (2010) 1555e1562. D.J. Triggle, Calcium channel antagonists: clinical uses-Past, present and future, Biochem. Pharmacol. 74 (2007) 1e9. R.L. Kraus, Y. Li, A. Jovanovska, J.J. Renger, Trazodone inhibits T-type calcium channels, Neuropharmacology 53 (2007) 308e317. J.C. Barrow, P. Bondiskey, C. Tang, S.M. Doran, K.E. Rittle, G.B. McGaughey, J. Ballard, M.J. Marino, S.V. Fox, T.S. Reger, Y. Kuo, M.G. Bock, Z. Yang, G.D. Hartman, T. Prueksaritanont, S.L. Garson, V.K. Graufelds, R.L. Kraus, V.N. Uebele, C.E. Nuss, Y. Li, J.J. Renger, Discovery of 4, 4-disubstituted quinazolin-2-ones as T-type calcium channel antagonists, ACS Med. Chem. Lett. 1 (2010) 75e79. K.S. Schlegel, Z. Yang, T.S. Reger, Y. Shu, K.E. Rittle, P. Bondiskey, M.G. Bock, G.D. Hartman, R. Cube, C. Tang, Y. Kuo, T. Prueksaritanont, C.E. Nuss, S.M. Doran, S.L. Garson, R.L. Kraus, Y. Li, V.N. Uebele, J. Ballard, S.V. Fox, J.J. Renger, J.C. Barrow, Discovery and expanded SAR of 4, 4-disubstituted quinazolin-2-ones as potent T-type calcium channel antagonists, Bioorg. Med. Chem. Lett. 20 (2010) 5147e5152. L. Hedstrom, IMP dehydrogenase: structure, mechanism and inhibition, Chem. Rev. 109 (2009) 2903e2928. R. Petrelli, P. Vita, I. Torquati, K. Felczak, D.J. Wilson, P. Franchetti, L. Cappellacci, Novel inhibitors of inosine monophosphate dehydrogenase in patent literature of the last decade, Recent Pat. Anticancer Drug Discov. 8 (2013) 103e125. H.L. Birch, G.M. Buckley, N. Davies, H.J. Dyke, E.J. Frost, P.J. Gilbert, D.R. Hannah, A.F. Haughan, M.J. Madigan, T. Morgan, W.R. Pitt, A.J. Ratcliff e, N.C. Ray, M.D. Richard, A. Sharpe, A.J. Taylor, J.M. Whitworth, S.C. Williams, Novel 7-methoxy-6-oxazol-5-yl-2, 3-dihydro-1H-quinazolin-4-ones as IMPDH inhibitors, Bioorg. Med. Chem. Lett. 15 (2005) 5335e5339. 629 [79] L. Boyman, G.S.B. Williams, D. Khananshvili, I. Sekler, W.J. Lederer, NCLX: the mitochondrial sodium calcium exchanger, J. Mol. Cell. Cardiol. 59 (2013) 205e213. [80] T. Kalogeris, C.P. Baines, M. Krenz, R.J. Korthuis, Cell biology of ischemia/ reperfusion injury, Int. Rev. Cell Mol. Biol. 298 (2012) 229e317. [81] H. Hasegawa, M. Muraoka, K. Matsui, A. Kojima, A novel class of sodium/ calcium exchanger inhibitors: design, synthesis, and structure-activity relationships of 4-phenyl-3-(piperidin-4-yl)-3, 4-dihydro-2(1H)-quinazolinone derivatives, Bioorg. Med. Chem. Lett. 16 (2006) 727e730. [82] H. Hasegawa, M. Muraoka, K. Matsui, A. Kojima, Discovery of a novel potent Naþ/Ca2þ exchanger inhibitor: design, synthesis and structure-activity relationships of 3, 4-dihydro-2(1H)-quinazolinone derivatives, Bioorg. Med. Chem. Lett. 13 (2003) 3471e3475. [83] H. Hasegawa, K. Matsui, M. Muraoka, M. Ohmori, A. Kojima, A novel class of sodium/calcium exchanger inhibitor: design, synthesis, and structureactivity relationships of 3, 4-dihydro-2(1H)-quinazolinone derivatives, Bioorgan. Med. Chem. 13 (2005) 3721e3735. [84] Y. Endo, K. Kawai, T. Asano, S. Amano, Y. Asanuma, K. Sawada, K. Ogura, N. Nagata, N. Ueo, N. Takahashi, Y. Sonoda, N. Kamei, Discovery and SAR study of 2-(4-pyridylamino)thieno[3, 2-d] pyrimidin-4(3H)-ones as soluble and highly potent PDE7 inhibitors, Bioorg. Med. Chem. Lett. 25 (2015) 649e653. [85] J. Guo, A. Watson, J. Kempson, M. Carlsen, J. Barbosa, K. Stebbins, D. Lee, J. Dodd, S.G. Nadler, M. McKinnon, J. Barrish, W.J. Pitts, Identification of potent pyrimidine inhibitors of phosphodiesterase 7 (PDE7) and their ability to inhibit T cell proliferation, Bioorg. Med. Chem. Lett. 19 (2009) 1935e1938. [86] E. Lorthiois, A.-K. Mafroud, M. Idrissi, P. Bernardelli, A. Tertre, E. Proust, A. Descours, B. Bertin, F. Vergne, P. Soulard, L. Heuze, M. Coupe, C. Oliveira, F. Moreau, R. Wrigglesworth, P. Berna, Spiroquinazolinones as novel, potent, and selective PDE7 inhibitors. Part 1, Bioorg. Med. Chem. Lett. 14 (2004) 4623e4626. [87] P. Bernardelli, A.-K. Mafroud, F. Moreau, E. Chevalier, E. Lorthiois, F. Vergne, E. Proust, M. Idrissi, A. Descours, A. Tertre, N. Pham, C. Oliveira, P. Ducrot, B. Bertin, F. Berlioz-Seux, M. Coupe, P. Berna, M. Li, Spiroquinazolinones as novel, potent, and selective PDE7 inhibitors. Part 2: optimization of 5, 8disubstituted derivatives, Bioorg. Med. Chem. Lett. 14 (2004) 4627e4631. [88] P.P. Roux, J. Blenis, ERK and p38 MAPK-activated protein kinases: a family of protein kinases with diverse biological functions, Microbiol. Mol. Biol. Rev. 68 (2004) 320e344. [89] A. Cuenda, S. Rousseau, p38 MAP-Kinases pathway regulation, function and role in human diseases, Biochim. Biophys. Acta 1773 (2007) 1358e1375. [90] J.E. Stelmach, G. Scapin, J.R. Strauss, E.A. O'Neill, L. Liu, S. Singh, P.M. Cameron, D.M. Schmatz, D.M. Zaller, S.B. Patel, J.V. Pivnichny, C.E.C.A. Hop, E.A. Nichols, C.D. Schwartz, J.B. Doherty, Z. Wang, S.J. O'Keefe, C.M. Thompson, Design and synthesis of potent, orally bioavailable dihydroquinazolinone inhibitors of p38 MAP kinase, Bioorg. Med. Chem. Lett. 13 (2003) 277e280. [91] J.A. Hunt, S.X. McCormick, Z. Wang, F. Kallashi, J.E. Thompson, R.D. Ruzek, J.V. Pivnichny, S.J. O'Keefe, A. Woods, P.J. Sinclair, C.E.C.A. Hop, E.A. O'Neill, D.M. Zaller, I. Ita, S. Kumar, G. Porter, J.B. Doherty, p38 Inhibitors: piperidineand 4-aminopiperidine-substituted naphthyridinones, quinolinones, and dihydroquinazolinones, Bioorg. Med. Chem. Lett. 13 (2003) 467e470. [92] A. Schlapbach, R. Heng, F. Di Padova, A novel Pd-catalyzed cyclization reaction of ureas for the synthesis of dihydroquinazolinone p38 kinase inhibitors, Bioorg. Med. Chem. Lett. 14 (2004) 357e360. [93] A. Arif, Extraneuronal activities and regulatory mechanisms of the atypical cyclin-dependent kinase Cdk5, Biochem. Pharmacol. 84 (2012) 985e993. [94] J. Zhu, W. Li, Z. Mao, Cdk5: mediator of neuronal development, death and the response to DNA damage, Mech. Ageing Dev. 132 (2011) 389e394. [95] R.M. Rzasa, T.D. Osslund, H. Wang, M.R. Kaller, D. Powers, X. Xiong, G. Liu, V.J. Santora, W. Zhong, E. Magal, T.T. Nguyen, V.N. Viswanadhan, M.H. Norman, Structure-activity relationships of 3, 4-dihydro-1H-quinazolin-2-one derivatives as potential CDK5 inhibitors, Bioorgan. Med. Chem. 15 (2007) 6574e6595. [96] D.B. Sattelle, D. Cordova, T.R. Cheek, Insect ryanodine receptors: molecular targets for novel pest control chemicals, Invert. Neurosci. 8 (2008) 107e119. [97] S. Fleischer, Personal recollections on the discovery of the ryanodine receptors of muscle, Biochem. Biophys. Res. Commun. 369 (2008) 195e207. [98] Y. Zhou, Q. Feng, F. Di, Q. Liu, D. Wang, Y. Chen, L. Xiong, H. Song, Y. Li, Z. Li, Synthesis and insecticidal activities of 2, 3-dihydroquinazolin-4(1H)-one derivatives targeting calcium channel, Bioorgan. Med. Chem. 21 (2013) 4968e4975. [99] A. Engelman, P. Cherepanov, The structural biology of HIV-1: mechanistic and therapeutic insights, Nat. Rev. Microbiol. 10 (2012) 279e290. [100] D.A. Babkov, V.T. Valuev-Elliston, M.P. Paramonova, A.A. Ozerov, A.V. Ivanov, A.O. Chizhov, A.L. Khandazhinskaya, S.N. Kochetkov, J. Balzarini, D. Daelemans, C. Pannecouque, K.L. Seley-Radtke, M.S. Novikov, Scaffold hopping: exploration of acetanilide-containing uracil analogues as potential NNRTIs, Bioorgan. Med. Chem. 23 (2015) 1069e1081. [101] J.W. Corbett, S.S. Ko, J.D. Rodgers, L.A. Gearhart, N.A. Magnus, L.T. Bacheler, S. Diamond, S. Jeffrey, R.M. Klabe, B.C. Cordova, S. Garber, K. Logue, G.L. Trainor, P.S. Anderson, S.K. Erickson-Viitanen, Inhibition of clinically relevant mutant variants of HIV-1 by quinazolinone non-nucleoside reverse transcriptase inhibitors, J. Med. Chem. 43 (2000) 2019e2030. [102] Q. Hu, J. Kunde, N. Hanke, R.W. Hartmann, Identification of 4-(4-nitro-2- 630 [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] K. Hemalatha, G. Madhumitha / European Journal of Medicinal Chemistry 123 (2016) 596e630 phenethoxyphenyl)pyridine as a promising new lead for discovering inhibitors of both human and rat 11b-hydroxylase, Eur. J. Med. Chem. 96 (2015) 139e150. C.M. Grombein, Q. Hu, R. Heim, S. Rau, C. Zimmer, R.W. Hartmann, 1Phenylsulfinyl-3-(pyridin-3-yl)naphthalen-2-ols: a new class of potent and selective aldosterone synthase inhibitors, Eur. J. Med. Chem. 89 (2015) 597e605. C.M. Grombein, Q. Hu, S. Rau, C. Zimmer, R.W. Hartmann, Heteroatom insertion into 3, 4-dihydro-1H-quinolin-2-ones leads to potent and selective inhibitors of human and rat aldosterone synthase, Eur. J. Med. Chem. 90 (2015) 788e796. Z. Guan, K. Hillrichs, C. Unlu, K. Rissanen, M. Nieger, A. Schmidt, Synthesis of 2-anilinobenzimidates, anthranilamides, and 2, 3dihydroquinazolin-4(1H)ones from N-heterocyclic carbenes of indazole, Tetrahedron 71 (2015) 276e282. J. Zhang, D. Ren, Y. Ma, W. Wang, H. Wu, CuO nanoparticles catalyzed simple and efficient synthesis of 2, 3-dihydroquinazolin-4(1H)-ones and quinazolin4(3H)-ones under ultrasound irradiation in aqueous ethanol under ultrasound irradiation in aqueous ethanol, Tetrahedron 70 (2014) 5274e5282. Y. Shang, L. Fan, X. Li, M. Liu, Y(OTf)3-catalyzed heterocyclic formation via aerobic oxygenation: an approach to dihydro quinazolinones and quinazolinones, Chin. Chem. Lett. 26 (2015) 1355e1358. M.J. Mphahlele, M.M. Maluleka, T.A. Khoza, 2-Aryl-6, 8-dibromo-2, 3dihydroquinazolin-4(1H)-ones as substrates for the synthesis of 2, 6, 8triarylquinazolin-4-ones, Bull. Chem. Soc. Ethiop. 28 (2014) 81e90. K. Hemalatha, G. Madhumitha, C.S. Vasavi, P. Munusami, 2, 3Dihydroquinazolin-4(1H)-ones: visible light mediated synthesis, solvatochromism and biological activity, J. Photoch. Photobio. B 143 (2015) 139e147. K. Hemalatha, G. Madhumitha, Inhibition of poly(adenosine diphosphateribose) polymerase using quinazolinone nucleus, Appl. Microbiol. Biotechnol. (2016), http://dx.doi.org/10.1007/s00253-016-7731-1. K. Hemalatha, G. Madhumitha, N.A. Al-Dhabi, M.V. Arasu, Importance of fluorine in 2, 3-dihydroquinazolinone and its interaction study with lysozyme, J. Photoch. Photobio. B 162 (2016) 176e188. K. Hemalatha, G. Madhumitha, Study of binding interaction between anthelmintic 2, 3-dihydroquinazolin-4-ones with bovine serum albumin by spectroscopic methods, J. Lumin 178 (2016) 163e171. K. Hemalatha, G. Madhumitha, L. Ravi, V.G. Khanna, N.A. Al-Dhabi, M.V. Arasu, Binding mode of dihydroquinazolinones with lysozyme and its antifungal activity against Aspergillus species, J. Photoch. Photobio. B 161 (2016) 71e79. K. Hemalatha, G. Madhumitha, Eco-friendly synthesis of palladium nanoparticles, environmental toxicity assessment and its catalytic application in suzuki miyaura coupling, Res. J. Pharm. Tech 8 (2015) 1691e1700. Abbreviations 5-HT: 5-hydroxytryptamine ADP: adenosine diphosphate AMP: 50 -adenosine monophosphate AT4: angiotensin IV ATP: adenosine triphosphate BCCP: biotin-carboxyl-carrier protein Boc2O: di-tert-butyl-dicarbonate cAMP: 30 ,50 -cyclic adenosine monophosphate CDI: 1, 1-carbonyl diimidazole CDK1: cyclin-dependent kinase 1 CDK5: cyclin-dependent kinase 5 CF: continuous flow cGMP: 30 ,50 -cyclic guanosine monophosphate CGRP: calcitonin gene-related peptide CM: chorismate mutase CNS: central nervous system COX: cyclooxygenase CREB: cAMP-responsive element-binding protein CuO: copper (II) oxide CYP: cytochromes P450 DAST: diethylaminosulfur trifluoride DBU: 1, 8-diazabicycloundec-7-ene DCM: dichloromethane DEAD: diethyl azodicarboxylate DMAP: dimethylaminopyridine DME: dimethoxyethane DMPK: drug metabolism and pharmacokinetics DPEPhos: (Oxydi-2, 1-phenylene)bis(diphenylphosphine) DPPA: diphenylphosphoryl azide EDC: 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide EEG: electroencephalogram FLIPR: fluorometric imaging plate reader GDP: guanosine diphosphate GMP: guanosine monophosphate GTP: guanosine triphosphate HCl: hydrochloric acid HIV-1: human immunodeficiency virus type 1 HOBt: hydroxybenzotriazole HPLC: high performance liquid chromatography HTRF: homogenous time resolved fluorescence IL-1: interleukin 1 IMP: inosine 50 -monophosphate IMPDH: inosine-50 -monophosphate dehydrogenase IRAP: insulin-regulated aminopeptidase KOH: potassium hydroxide LiAlH4: lithium aluminium hydride LR: lawesson's reagent mAchR: muscarinic acetylcholine receptors MAPK: mitogen-activated protein kinase MAPKK: MAPK kinase MAPKKK: MAPKK kinase MC1R: melanocortin receptor 1 MC4R: melanocortin receptor 4 METH: methamphetamine MITF: microphthalmia-associated transcription factor MPO: myeloperoxidase MTT: 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide MW: microwave NaBH4: sodium borohydride NAD: nicotinamide adenine dinucleotide NaH: sodium hydride N-boc: tert-butyloxycarbonyl NBS: N-bromosuccinimide NCS: N-chlorosuccinimide NCX: sodium calcium exchanger NMR: nuclear magnetic resonance NNRTIs: nonnucleoside reverse transcriptase inhibitors NO: nitric oxide NRTIs: nucleoside reverse transcriptase inhibitors NSAIDs: non-steroidal anti-inflammatory drugs PARP: poly(adenosine diphosphate-ribose)polymerase PBMC: peripheral blood mononuclear cell PCC: pyridinium chlorochromate PCy3: tricyclohexylphosphine Pd(PPh3)4: tetrakis(triphenylphosphine)palladium(0) Pd2dba3: tris(dibenzylideneacetone)dipalladium(0) PdCl2(dppf): bis(diphenylphosphino)ferrocene]palladium(II) dichloride PdCl2(PPh3)2: bis(triphenylphosphine)palladium(II) dichloride PDE7: phosphodiesterase 7 PMB: p-methoxy benzyl POMC: proopiomelanocortin PPA: polyphosphoric acid Psi: per square inch PTSA: p-toluenesulphonic acid PXR: pregnane X receptor REM: rapid eye movement RT: reverse transcriptase RyR: ryanodine receptor SAR: structural-activity relationship SiC: silicon carbide TBAF: tetra-n-butylammonium fluoride TFA: trifluoroacetic acid THF: tetrahydrofuran TMSNCO: trimethylsilylisocyanate TNFa: tumor necrosis factor alpha UV: ultraviolet WBC: white blood cells XMP: xanthosine 50 - monophosphate Xphos: 2-dicyclohexylphosphino-20 , 40 , 60 -triisopropylbiphenyl Y(OTf)3: ytterbium(III) triflate a-MSH: alpha-melanocyte stimulating hormone