Design and Synthesis of Novel 1,2,3-triazolyl

April 2018

Design and Synthesis of Novel 1,2,3-triazolyl-pyrimidinone Hybrids as Potential Anti-HIV-1 NNRT Inhibitors

Hanmant M. Kasralikar,a

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Suresh C. Jadhavar,a Sujit G. Bhansali,b Shivaji B. Patwari,c and Sudhakar R. Bhusarea* a

b

Department of Chemistry, Dnyanopasak College, Parbhani 431 401, India Poona College of Pharmacy, Bharati Vidyapeeth Deemed University, Pune 411 038, India c Department of Chemistry, L. B. S. Mahavidyalaya, Dist. Nanded, Dharmabad, India *E-mail: [email protected] Received October 31, 2017 DOI 10.1002/jhet.3103 Published online 5 February 2018 in Wiley Online Library (wileyonlinelibrary.com).

A novel series of 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-phenylpyrimidin-4 (3H)-one derivatives has been synthesized and studied their molecular docking as well as vitro assay as an anti-human immunodeficiency virus type-1 non-nucleoside reverse transcriptase inhibitors. The synthetic approach was started from the reaction of aldehydes, ethylchloroacetate, and thiourea to give the 6-aryl-5-chloro-2thiouracils derivatives. Then, reaction of the later compounds with propargyl bromide followed by azide cycloaddition reaction (click reaction) led to the formation of the title compounds in good yields. The obtained derivatives were studied as anti-human immunodeficiency virus type-1 non-nucleoside reverse transcriptase inhibitors. It was found that these compounds might have potent reverse transcriptase inhibition activity. J. Heterocyclic Chem., 55, 821 (2018).

INTRODUCTION As one of the leading causes of death globally, acquired immunodeficiency syndrome (AIDS) causes a great burden to both single human lives and the society as a whole. Although there have been progresses in the development and treatment of AIDS, the successful treatment of AIDS remains a challenge. Therefore, there is still an urgent need to search for some newer and safer anti-human immunodeficiency virus type-1 (HIV-1) agents. HIV infects an estimated 33 million people globally and poses an enormous healthcare dispute with high humanity and morbidity rates [1]. As effective HIV vaccines remain subtle despite incredible efforts [2,3], chemotherapy continues to provide the main influence in battling HIV/AIDS. Current standard therapy, the highly active antiretroviral therapy [4,5], involves the use of multiple antiviral with orthogonal mechanisms of action to create a large genetic barrier to resistance.

Because of its success in clinically managing HIV/AIDS notwithstanding, highly active antiretroviral therapy requires nearly perfect adherence [6,7] that can be difficult to achieve with the complex dosing of multitarget therapy. Human immunodeficiency virus-1 reverse transcriptase (RT) is a main enzyme in the HIV replication and has been a prime target for developing anti-HIV drugs. HIV RT inhibitors fall into two main classes, and two types of RT inhibitors have been developed [8,9] first termed as nucleoside RT inhibitors (NRTIs) and second as nonnucleoside RT inhibitors (NNRTIs). Four NNRTIs, nevirapine (Viramune) [10], delavirdine (Rescriptor) [11], efavirenz (Sustiva) [12], and tinofovir, have been approved by Food and Drug Administration for the treatment of HIV infection. Rilpivirine (TMC278, Edurant) and etravirine are the second-generation NNRTI with higher potency, longer half-life, and reduced side effect profile compared with

© 2018 Wiley Periodicals, Inc.

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H. M. Kasralikar, S. C. Jadhavar, S. G. Bhansali, S. B. Patwari, and S. R. Bhusare

older NNRTIs, such as efavirenz [13,14], rilpivirine entered phase III clinical trials [15,16] and was approved for use in the United States [17]. A fixed dose drug combining rilpivirine with emtricitabine and tenofovir was approved by the US Food and Drug Administration under the brand name Complera [18]. Rilpivirine is a diarylpyrimidine. Rilpivirine in combination with emtricitabine and tenofovir has been shown to have higher rates of virologic failure than Atripla in patients with baseline HIV viral loads greater than 100,000 copies/mm3. However, significant resistance has been developed against the current NNRTIs, and there is an urgent need to develop new anti-HIV agents that are effective against these resistant mutants (Fig. 1, 1 and 2). The multifunctionalized pyrimidinones scaffold represents a class of heterocyclic compounds with significant pharmacological and biological efficiency, including, anti-HIV [19,20], antiviral [21,22] antibacterial [23], and anticancer [24,25]. In addition, 1,2,3-triazoles are an important class of heterocyclic compounds due to their extensive range of pharmacological and medicinal applications [26]. 1,2,3Triazoles have fascinated continued significance to organic and medicinal researchers over the years because of their varied biological activities such as anti-allergic [27], antibacterial [28], antifungal [29], anti-HIV [30], anticonvulsant [31], anti-inflammatory, and b-lactamase inhibition properties [32]. It is quite marked that the favorable properties of 1,2,3-triazole ring like moderate dipole character, hydrogen bonding capability, rigidity, and stability under in vivo conditions are responsible for their improved biological activities [33]. The study of new hybrid systems in which 1,2,3triazole and pyrimidinone are combined comprises an unfamiliar field of research. These findings have encouraged us to investigate the potential synergistic effect of 1,2,3-triazole and pyrimidinone scaffolds. Herein, for the first time, we report the hybridization of these two pharmacophores and their anti-HIV-1 NNRTI ability. It has been hoped that combination of these active groups in the new molecular design would lead to better anti-HIV-1 agents. In this

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communication, we report the synthesis of newly designed 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6phenylpyrimidin-4(3H)-one derivatives starting from 6-aryl-5-chloro-2-thiouracils derivatives which has been synthesized from substituted aldehydes, ethylchloroacetate, and thiourea and their ability as anti-HIV agents.

RESULT AND DISCUSSION Chemistry. The general route for the synthesis of the target 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6phenylpyrimidin-4(3H)-one derivatives 6 was depicted in Scheme 1. The 6-aryl-5-chloro-2-thiouracils 4 were prepared via prolonged heating of aldehydes1, ethylchloroacetate2, and thiourea 3 in ethanol, in the presence of potassium carbonate [34]. A mixture of the appropriate 2-mercapto-dihydroyrimidine derivatives 4, the propargyl bromide, and anhydrous potassium carbonate was stir in dry dimethylformamide at 0°C then room temperature [35] to obtained 5-chloro-6-phenyl-2-(prop-2ynylthio)pyrimidin-4(3H)-one derivatives 5. These highly activated intermediates 5 were then reacted with CuCl and sodium azide in ethanol and dioxane (1:2) to obtain compound [36]. The compounds 6 were prepared via click reaction of compound 5 with appropriately sodium azide and cuprous chloride. Target compounds 6 were synthesized in moderate to high yield (Table 1). All the synthesized compounds of 2-((1H-1,2,3-triazol-4-yl)methylthio)-5chloro-6-phenylpyrimidin-4(3H)-one derivatives were fully characterized by infrared (IR), 1H, 13C NMR and gas chromatography-mass spectrometry. The structures of all the compounds of 4a–o, 5a–o, and 6a–o were confirmed by 1H and 13C NMR and high resolution mass spectrometry data analysis. Melting points, 1H, and 13C NMR can also confirm the conversion of the acetylene group of 5a–o into the triazole ring. Differences in melting point, solubility and 1 H and 13C NMR data, can easily be observed to distinguish the precursor 5a–o and the product 6a–o. A difference in the melting point, the high solubilities of 5a–o in CDCl3, and in dimethyl sulfoxide (DMSO),

Figure 1. Second-generation non-nucleoside reverse transcriptase inhibitors

Journal of Heterocyclic Chemistry

DOI 10.1002/jhet

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Novel 1,2,3-triazolyl-pyrimidinone Hybrids as Potential Anti-HIV-1 NNRT Inhibitors

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Scheme 1. Reagents and conditions: (i) K2CO3, EtOH, reflux; (ii) Propargyl bromide, K2CO3, DMF, Stir at 0°C then RT; (iii) CuCl, NaN3, EtOH: Dioxane (1:2) 80°C, 24 h.

Table 1 Exploration of the substrate scope for the synthesis of 2-((1H-1,2,3triazol-4-yl)methylthio)-5-chloro-6-phenylpyrimidin-4(3H)-one derivatives. R

Time (h)

Product

M.P. o ( C)

Yielda %

H 2-Cl 3-Cl 4-Cl 4-F 3-F 2-Cl,4-F 4-I 3-Br 4-Br 3-NO2 4-NO2 4-OCH3 4-CH3 4-isopropyl

16 17 17.5 16.5 19 18 16 18.5 20 19 18 16 15.5 16.5 17

6a 6b 6c 6d 6e 6f 6g 6h 6i 6j 6k 6l 6m 6n 6o

116 146 167 149 130 156 152 136 127 162 141 114 120 135 174

68 66 70 75 71 65 60 68 72 62 67 62 58 61 60

Entry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 a

Isolated yields.

while the product 6a–o is soluble only in DMSO, the 1H NMR spectra of 4a–o, the NH protons of pyrimidinone moiety resonated at δ 9.11–9.18 and 9.41–9.44 ppm as singlet. We have identified compound 5a–o from 1H NMR, 13C NMR, and mass spectroscopy (MS). The protons attached to S─CH2 and acetylene proton occurred at δ 4.00–4.02 and 2.26–2.29, respectively. The carbon attached to SCH2 and acetylene occurred at δ 20.36 and 71.17–71.63, respectively. Mass spectra of 5a–o were corresponding to their molecular weight. In addition, of sodium triazole to 5a–o, some direct C─H correlations were observed, confirming that the signals of the triazolyl chain carbons appeared at δ 130.96–131.00 ppm and carbon of C═C appeared at δ 143.00–143.44 ppm. The appearance of N─H peak of triazolyl ring in 6a–o at δ 10.22–10.55 ppm shows the formation of the final products. The presence of a molecular ion peak at

respective m/z value of all the products in the gas chromatography-mass spectrometry further confirmed the structure of 6a–o. For all the spectra of compounds, please refer to the Supporting information. Molecular docking. Docking score of compound 6e and 6h was found to be good around 10.246 and 9.516, respectively (as shown in Table 2). Synthesized derivatives of 1,2,3-triazolyl-pyrimidinone series were docked into the non-nucleoside inhibitor binding pocket of HIV-1 RT. As illustrated in Figure 2a and b and native ligand TMC 278 in Figures 2c and 3c, thiouracil (pyrimidinone) moiety of compound 6e and 6h of the 1,2,3-triazolyl-pyrimidinone ring interacts through hydrophobic interactions into the hydrophobic binding pocket, surrounded by the aromatic portion of Trp229, Tyr 183, Phe227, Tyr188, Val106, Pro236, Lue 234,Val 179, Lue 100, and Tyr314. Because of the presence of chlorine on thiouracil moiety, it increases the hydrophobicity, which enhances the anti-HIV activity. From the twodimensional (Figure 2a and b) and three-dimensional view (Figure 3a and b), it is observed that Tyr188 and Val106 is juxtaposed for better interaction with the thiouracil moiety of 1,2,3-triazolyl-pyrimidinone series. The H atom of the 1,2,3-triazolyl nucleus moiety at N-1 of compounds 6e and 6h forms the hydrogen bond interactions with the backbone N─H of Lys101 residue. The floro/iodo substituted aromatic rings of the thiouracil moiety of 1,2,3-triazolyl-pyrimidinone series (compound 6e and 6 h) make π–π interaction into the hydrophobic binding pocket, surrounded by the aromatic side chains of portion of Trp229 residue. The decrease in activity of compound 6k ( 6.372) of 1,2,3-triazolyl-pyrimidinone series was due to lack of hydrogen bond interaction with Lys101 by the nonexistence of N─H bond at 1,2,3-triazole ring (Figure 4), instead it is showing π–π stacking with Trp229 and Tyr 181. Docking score of compound 6e, 6h, and 6k was found to be 10.246, 9.516, and 6.372, respectively, while of


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Table 2 Molecular docking scores of the newly synthesized compounds due to binding interaction with active site of human immunodeficiency virus type-1 reverse transcriptase in complex with TMC278. Compounds Native ligand (ZDI 278) 6e 6h 6d 6j 6m 6e 6n 6o 6b 6f 6g 6c 6i 6a 6k

Docking Score

XP GScore

Glide gscore

Glide evdw

Glide ecoul

Glide energy

11.2081 8.90254 10.6366 11.0919 11.0176 11.0152 10.8934 10.7817 10.5413 8.55146 8.55274 8.48358 8.40528 10.5965 10.5405

40.2523 42.3041 40.9996 44.2747 45.8055 43.7447 45.9173 39.1996 42.2912 42.0661 39.4605 42.9792 41.0506 40.4784 42.8276

4.41227 1.70479 3.76871 4.35449 3.77142 3.49795 3.57518 4.06715 4.02191 1.7309 1.78389 1.62764 1.77682 4.69937 3.43316

44.6646 44.0089 44.7683 48.6291 49.577 47.2426 49.4925 43.2668 46.3131 43.797 41.2444 44.6068 42.8274 45.1778 46.2608

Glide einternal

Glide emodel

XP HBond

55.002 65.3353 53.1626 66.2766 67.5148 60.6851 71.5472 66.3466 60.5101 46.5047 48.7292 47.4113 53.7945 67.2955 64.7385

1.33 0.7 1.15769 1.28997 1.17821 1.16444 1.16688 1.04684 1.03029 0.7 0.7 0.7 0.62906 0.984 0.7

13.413 10.246 9.516 9.502 9.486 8.878 8.645 8.463 8.354 8.045 7.976 7.568 7.356 7.234 6.923 6.372

11.2081 8.90254 10.6366 11.0919 11.0176 11.0152 10.8934 10.7817 10.5413 8.55146 8.55274 8.48358 8.40528 10.5965 10.5405

3.450011 1.906349 6.621767 4.769957 9.609538 1.651443 3.589012 1.572492 3.819066 0.832788 4.589232 0.783946 0.655122 6.3318 10.90732

Figure 2. Two-dimensional view of the binding interaction of the most active compounds, 6e (a) and 6h (b), with active site of human immunodeficiency virus type-1 reverse transcriptase in complex with TMC278 and native ligand TMC 278 (2c) with human immunodeficiency virus type-1 reverse transcriptase. VAL, valine; LEU, leucine; GLY, glycine; ASP, aspartate; SER, serine; ALA, alanine; LYS, lysine; ILE, isoleucine; HIE, histidine epsilon H; MET, methionine; THR, threonine. [Color figure can be viewed at wileyonlinelibrary.com]

native ligand was found to be 13.413 which confirms that these compounds might have potent RT inhibition activity. Further, in silico binding studies suggested that inhibitors possessing hydrogen bonding with the main chain backbone of Lys101, π–π interaction with the aromatic side chains of Trp229, and introduction of chlorine on thiouracil moiety improve the inhibitor selectivity for RT and thus helps in further drug design attempts to obtain potent 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6phenylpyrimidin-4(3H)-one derivatives.

In vitro anti-human immunodeficiency virus assay.

According to the docking study of synthesized compounds, some of it showed the high inhibition activity and some with low activity. From the aforementioned conclusion, we studied in vitro anti-HIV assay for particular compounds to verify their activity. The HIV-RT inhibition assay was performed by using an RT assay kit (Roche), and the procedure for assaying RT inhibition was performed as described in the kit protocol (Roche Kit) [37]. The compounds presented in this study,


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Figure 3. Three-dimensional view of the binding interaction of the most active compounds, 6e (a) and 6h (b), with active site of human immunodeficiency virus type-1 reverse transcriptase in complex with TMC278 and native ligand TMC278 (c) with human immunodeficiency virus type-1 reverse transcriptase. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 4. Two (a) and three-dimensional (b) view for decrease in activity of compound 6k was due to lack of hydrogen bond interaction with Lys101. [Color figure can be viewed at wileyonlinelibrary.com]

namely, 24-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6phenylpyrimidin-4 (3H)-one derivatives (6e, 6h, and 6d) were evaluated for anti-HIV-1 activity by using enzymatic (RT) and cell-based assays. The HIV-1 RT inhibition activity range for these compounds showed from 65% to 92% inhibition at 100 μg/mL

concentrations. The compounds 6e and 6h showed the highest inhibitory activity both in docking and in cellbased study (91.97% and 90.50%, respectively), and compounds 6a and 6k show low activity (67.84% and 65.72%, respectively), whereas the control NNRTI marketed drug nevirapine showed 99.15% inhibition at

Table 3 Anti-HIV-1 activity, cytotoxicity, and selectivity index in HIV-1IIIB, ADAS5, and HIV-1 RT kit assay for compounds. Anti-HIV-1 activitya EC50b (μg/mL) Compound

R

6e 6h 6d 6a 6k Nevirapine

4-F 4-I 4-cl H 3-No2

HIV-1IIIB 0.69 0.9 0.8 1.38 1.02 0.05

SI d

CC50c (μg/mL)

ADA5

HIV-1 IIIB

ADA5

HIV-1 IIIB

1.05 0.29 0.32 1.20 0.82 0.05

40.5 39.3 38.6 50.8 3.4 76.12

42.4 44.8 46.5 48.3 5.5 76.15

58.69 43.66 48.25 36.81 3.33 1522.51

ADA5 40.36 154.48 145.31 40.25 6.70 1522.51

HIV-1, human immunodeficiency virus type-1; SI, selectivity index. Data represent the mean of two and three independent assays for EC50 and CC50, respectively. b EC50 is the 50% effective concentration required to reduce HIV-1 induced cytopathic effect of HIV-1 IIIB and HIV-1 ADA5. c The CC50 is the 50% cytotoxic concentration for HIV-1 IIIB and HIV-1 ADA5. d Selectivity index ratio CC50/EC50. a


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% Inhibition (HIV-RT kit assay) (100 μg/mL) 92.50 90.50 85.26 67.84 65.72 99.15

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100 μg/mL concentration. The enzyme assay results demonstrated that the compound 6e and 6h were more potent than remaining derivatives comparing against RT enzyme. Subsequently, the inhibitory activity of HIV-1 viral replication was also assessed by cell-based assay. The results are summarized in Table 3 along with standard nevirapine as reference drug. In the cell-based assay, the compounds 6e and 6h were the most potent inhibitors of HIV-1 replication against HIV-1 IIIB (EC50 = 0.69 and 0.9 μg/mL, respectively; the selectivity index = 58.69 and 43.66, respectively; CC50 with HIV-1 IIIB = 40.5 and 39.3 μg/mL, respectively) and HIV-1 ADA5 (EC50 = 1.05 and 0.29 μg/mL, respectively ;the selectivity index = 42.33 and 4.14, respectively; CC50 = 40.36 and 154.48 μg/mL, respectively). Some other compounds, 6a and 6k showed low anti-HIV-1 potency (EC50 = 1.38 and 1.20 and 1.02 and 0.82 μg/mL) against HIV-1 IIIB and HIV-1 ADA5 strains, respectively.

CONCLUSION A series of new class of 1,2,3-triazole pyrimidinone hybrids was synthesized and evaluated as potent inhibitors of HIV-1. Based upon the preliminary molecular docking studies of these new 1,2,3-triazole pyrimidinone hybrids, some structural requirements for high potency against HIV-1 were rationalized, which confirms that these compounds might have potent RT inhibition activity. In the series of 1,2,3-triazole pyrimidinone, compound 6e and 6h identified as potent inhibitor against the strains HIV-1 IIIB and HIV-1 ADA5. The decrease in activity of compound 6k of 1,2,3-triazolyl-pyrimidinone derivative was due to lack of hydrogen bond interaction with Lys101. This study suggested that inhibitors possessing hydrogen bonding with the main chain backbone of Lys101, π–π interaction with the aromatic side chains of Trp229, and introduction of chlorine on thiouracil moiety improve the inhibitor selectivity for RT.

EXPERIMENTAL General details. All solvents were used as commercial anhydrous grade without further purification. Aluminum sheets 20 × 20 cm, Silica gel 60 F254, Merck grade was used for thin-layer chromatography to determine progress of reaction. Melting points were determined in open capillary tube and are uncorrected. IR, 1H, and 13C NMR spectra were recorded on a Bruker AV-400 MHz and 100 MHZ spectrometer (Bruker, Billerica, MA) in CDCl3 and DMSO solvent. Mass spectra were taken on PolarisQ Thermoscintific MS (Thermo Fisher Scientific, Waltham, MA).

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General procedure for synthesis of 5-chloro-2, 3-dihydro-6phenyl-2-thioxopyrimidin-4(1H)-one (thiouracil) derivatives (4a–o). Aromatic aldehyde (1 mmol), ethylchloroacetate

(1 mmol), and thiourea (1 mmol) were mixed together in ethanol. Catalytic amount of K2CO3 (0.2 mmol) was added. Then reaction mixture was refluxed for appropriate time. After the completion of reaction indicated by thin-layer chromatography, reaction mixture was poured into crushed ice then yellow crystals obtained was filtered and dried. 5-chloro-2,3-dihydro-6-phenyl-2-thioxopyrimidin-4(1H)-one (4a). Yellow solid; M.P. (195°C): IR (cm 1): 3539, 3474,

3415, 3196, 3013, 2821, 2294, 1670, 1609, 1503, 1441, 1307, 1280; 1H NMR (300 MHz, DMSO): δ 7.40–7.58 (m, 5H), 9.11 (s, 1H, NH), 9.41 (s, 1H, NH). 5-chloro-2,3-dihydro-6-(4-nitrophenyl)-2-thioxopyrimidinYellow solid; M.P. (202°C): IR (cm 1): 4(1H)-one (4l).

3419, 3237, 3058, 2087, 1689, 1658, 1531, 1382, 1343, 1268, 1205, 1142, 1094; 1H NMR (300 MHz, DMSO): δ 6.94 (d, 2H), 7.76 (m, 2H), 9.18 (s, 1H, NH), 9.44 (s, 1H, NH). General procedure for the preparation of 5-chloro-6-phenyl-2-(prop-2-ynylthio)pyrimidin-4(3H)-one To a mixture of 6-aryl-5-chloro-2-thiouracil (5a–o).

(1 mmol) and K2CO3 (1.5 mmol) in dimethylformamide (10 mL), propargyl bromide (1.2 mmol) was added drop wise with stirring while maintaining the temperature of the reaction mixture at 0–50°C. Stirring was continued for 3 h at this temperature and continued for additional 2 h at room temperature. Water was added to the mixture and filtered. The aqueous filtrate was neutralized with acetic acid, and the precipitate was filtered and purified. 5-chloro-6-phenyl-2-(prop-2-ynylthio)pyrimidin-4(3H)-one Yellow solid; M.P. (210°C): 1H NMR (300 MHz, (5a).

CDCl3): δ 2.26 (t, 1H), 4.02 (d, 2H), 7.58–7.67 (m, 3H), 8.11–8.13 (t, 2H), 8.40 (s, 1H, NH); 13C–NMR (300 MHz, CDCl3): δ 168.73, 163.95, 151.42, 134.07, 132.72, 129.35, 129.02, 117.43, 78.17, 71.63, 20.36; MS: m/z 278.1 (M+). 5-chloro-6-(4-chlorophenyl)-2-(prop-2-ynylthio)pyrimidinYellow solid; M.P. (198°C): 1H NMR 4(3H)-one (5d).

(300 MHz, CDCl3): δ 2.29 (t, 1H), 4.00 (d, 2H), 7.55 (d, 2H), 8.07–8.11 (t, 2H),8.51 (s, 1H, NH); 13C–NMR (300 MHz, CDCl3): δ 167.41, 164.04, 151.19, 139.39, 132.39, 130.69, 129.40, 119.27, 78.10, 71.66, 20.40; MS: m/z 312.2 (M+). 6-(4-bromophenyl)-5-chloro-2-(prop-2-ynylthio)pyrimidinYellow solid; M.P. (215°C): 1H NMR 4(3H)-one (5j).

(300 MHz, CDCl3): δ 2.27–2.28 (t, 1H), 4.00 (d, 2H), 7.71 (d, 2H), 8.02 (d, 2H),8.27 (s, 1H, NH); 13C–NMR (300 MHz, CDCl3): δ 167.54, 164.06, 151.19, 132.85, 132.39, 130.78, 127.98, 117.24, 78.09, 71.65, 20.40; MS: m/z 355 (M+). 5-chloro-2-(prop-2-ynylthio)-6-p-tolylpyrimidin-4(3H)-one (5n). Yellow solid; M.P. (212°C): 1H NMR (300 MHz,

CDCl3): δ 2.26 (t,1H), 2.47 (s, 3H), 4.02 (d, 2H), 7.41 (d,2H), 8.05 (d, 2H), 8.26 (s,1H, NH); 13C–NMR


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(300 MHz, CDCl3): δ 168.53, 163.91, 143.76, 131.30, 129.76, 129.38, 120.96, 117.64, 78.24, 71.57, 21.69, 20.32; MS: m/z 290(M+). 5-chloro-6-(4-isopropylphenyl)-2-(prop-2-ynylthio)pyrimidinYellow solid; M.P. (190°C): 1H NMR 4(3H)-one (5o).

(300 MHz, CDCl3): δ 1.35 (d, 6H), 2.27–2.28 (t, 1H), 3.01–3.07 (m, 1H), 4.02 (s, 2H),7.45 (d, 2H), 8.08–8.10 (m, 2H), 8.70 (s, 1H, NH); 13C–NMR (300 MHz, CDCl3): δ 168.55, 163.92, 154.43, 143.97, 131.62, 129.53, 127.21, 117.66, 78.25, 71.57, 34.29, 23.66, 20.31; MS: m/z 318 (M+). General procedure for the preparation of 2-((1H-1,2,3triazol-4-yl)methylthio)-5-chloro-6-phenylpyrimidin-4(3H)-one derivatives (6a–o). The mixture of compound 5 (1 mmol),

cuprous chloride (1.5 mmol), and sodium azide (1.5 mmol) in a mixed solvent of methanol and dioxane (1, 2, and 50 mL). The temperature of the mixture is raised to 80°C and refluxed for 16–20 h. The color of the mixture was red brown in the beginning, gradually turned yellow and finally became white in 16–20 h. The mixture then was bubbled with hydrogen sulfide, and the precipitate was filtrated off. The solvent was removed from the filtrate, and a precipitate as crude product was obtained. The crude product was then dissolved in acetonitrile, and insoluble solid was filtered off. A yellowish white precipitate was obtained after evaporation of the solvent. The product can be further purified by column chromatography using silica gel as the stationary phase and a mixture of ethyl acetate and n-hexane as eluent. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-phenylpyrimidinWhite solid; M.P. (116°C): 1H NMR 4(3H)-one (6a).

(300 MHz, DMSO): δ 4.30 (s, 2H), 7.18–7.24 (d, 2H), 7.29–7.39 (t, 3H), 7.61–7.64 (d, 1H), 8.40 (s, 1H, NH), 10.5 (s, 1H, NH); 13C–NMR (300 MHz, DMSO): δ 168.88, 163.12, 152.24, 143.07, 136.65, 130.97, 129.65, 129.34, 128.21, 117.33, 26.37; MS: m/z 321 (M+). Anal. Calcd for C13H10ClN5OS (319.03): C, 48.83; H, 3.15; Cl, 11.09; N, 21.90; O, 5.00; S, 10.03. Found: C, 48.79; H, 3.17; Cl, 11.11; N, 21.87; O, 5.02; S, 10.01. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(2-chlorophenyl) pyrimidin-4(3H)-one (6b). White solid; M.P. (146°C): 1H

NMR (300 MHz, DMSO): δ 4.24 (s, 2H), 7.18–7.24 (d, 2H), 7.29–7.33 (d, 2H), 7.53 (s, 1H), 8.40 (s, 1H, NH), 10.33 (s, 1H, NH). Anal. Calcd for C13H9Cl2N5OS (352.99): C, 44.08; H, 2.56; Cl, 20.02; N, 19.77; O, 4.52; S, 9.05. Found: C, 44.04; H, 2.58; Cl, 20.01; N, 19.78; O, 4.50; S, 9.02. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(3-chlorophenyl) pyrimidin-4(3H)-one (6c). White solid; M.P. (167°C): 1H

NMR (300 MHz, DMSO): δ 4.40 (s, 2H), 7.18 (d, 2H), 7.29–7.33 (d, 2H), 7.47 (s, 1H), 8.42 (s, 1H, NH), 10.40 (s, 1H, NH). Anal. Calcd for C13H9Cl2N5OS (352.99): C, 44.08; H, 2.56; Cl, 20.02; N, 19.77; O, 4.52; S, 9.05. Found C, 44.06; H, 2.55; Cl, 20.00; N, 19.75; O, 4.51; S, 9.06.

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2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(4-chlorophenyl) pyrimidin-4(3H)-one (6d). White solid; M.P. (149°C): 1H

NMR (300 MHz, DMSO): δ 4.16 (s, 1H), 7.34–7.38 (d, 2H), 7.48–7.50 (d, 2H), 7.76–7.79 (d, 1H), 8.25 (s, 1H, NH), 10.48 (s, 1H, NH). 13C–NMR (300 MHz, DMSO): δ 167.77, 163.98, 152.21, 143.00, 134.63, 133.08, 131.59, 130.05, 128.12, 116.14, 25.68; MS: m/z 352 (M+). Anal. Calcd for C13H9Cl2N5OS (352.99): C, 44.08; H, 2.56; Cl, 20.02; N, 19.77; O, 4.52; S, 9.05. Found C, 44.06; H, 2.54; Cl, 20.04; N, 19.76; O, 4.54; S, 9.07. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(4-fluorophenyl) pyrimidin-4(3H)-one (6e). White solid; M.P. (130°C): 1H

NMR (300 MHz, DMSO): δ 4.26 (s, 1H), 7.54–7.38 (d, 2H), 7.79–7.76 (d, 2H), 7.81 (s, 1H), 8.16 (s, 1H, NH), 10.38 (s, 1H, NH). Anal. Calcd for C13H9ClFN5OS (337.02): C, 46.23; H, 2.69; Cl, 10.50; F, 5.62; N, 20.73; O, 4.74; S, 9.49. Found: C, 46.21; H, 2.70; Cl, 10.48; F, 5.60; N, 20.71; O, 4.74; S, 9.51. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(3-fluorophenyl) pyrimidin-4(3H)-one (6f). White solid; M.P. (156°C): 1H

NMR (300 MHz, DMSO): δ 4.26 (s, 1H), 7.10 (s, 1H), 7.24 (s, 1H), 7.26 (s, 1H), 7.48 (s, 1H), 8.23 (s, 1H, NH), 10.48 (s, 1H, NH). Anal. Calcd for C13H9ClFN5OS (337.02): C, 46.23; H, 2.69; Cl, 10.50; F, 5.62; N, 20.73; O, 4.74; S, 9.49. Found C, 46.23; H, 2.64; Cl, 10.48; F, 5.58; N, 20.69; O, 4.71; S, 9.50. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(2-chloro-4White solid; M.P. fluorophenyl)pyrimidin-4(3H)-one (6g).

(152°C): 1H NMR (300 MHz, DMSO): δ 4.25(s, 1H), 7.15(s, 1H), 7.24 (s, 1H), 7.30 (s, 1H), 7.47 (s, 1H), 8.30 (s, 1H, NH), 10.48 (s, 1H, NH). Anal. Calcd for C13H8Cl2FN5OS (370.98): C, 41.95; H, 2.17; Cl, 19.05; F, 5.10; N, 18.82; O, 4.30; S, 8.61. Found C, 41.96; H, 2.13; Cl, 19.01; F, 5.08; N, 18.80; O, 4.32; S, 8.60. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(4-iodophenyl) pyrimidin-4(3H)-one (6h). White solid; M.P. (136°C): 1H

NMR (300 MHz, DMSO): δ 4.26 (s, 1H), 6.96–6.51 (d, 2H), 7.25–7.21 (d, 2H), 7.51–7.47 (d, 1H), 8.25 (s, 1H, NH), 10.35 (s, 1H, NH). Anal. Calcd for C13H9ClIN5OS (444.93): C, 35.04; H, 2.04; Cl, 7.96; I, 28.48; N, 15.71; O, 3.59; S, 7.19. Found C, 35.04; H, 2.06; Cl, 7.93; I, 28.47; N, 15.68; O, 3.57; S, 7.21. 2-((1H-1,2,3-triazol-4-yl)methylthio)-6-(3-bromophenyl)-5White solid; M.P. chloropyrimidin-4(3H)-one (6i).

(127°C): 1H NMR (300 MHz, DMSO): δ 4.26 (s, 1H), 6.96–6.51 (d, 2H), 7.25–7.21 (d, 2H), 7.51–7.47 (d, 1H), 8.25 (s, 1H, NH), 10.35 (s, 1H, NH). Anal. Calcd for C13H9ClBrN5OS (396.94): C, 39.17; H, 2.28; Br, 20.04; Cl, 8.89; N, 17.57; O, 4.01; S, 8.04. Found C, 39.14; H, 2.26; Br, 20.01; Cl, 8.86; N, 17.59; O, 4.02; S, 8.03. 2-((1H-1,2,3-triazol-4-yl)methylthio)-6-(4-bromophenyl)-5White solid; M.P. chloropyrimidin-4(3H)-one (6j).

(162°C): 1H NMR (300 MHz, DMSO): δ 4.35(s, 2H), 6.42–6.96 (d, 2H), 7.21–7.25(d, 2H), 7.47–7.51 (d, 1H), 8.25 (s, 1H, NH), 10.32 (s, 1H, NH); 13C–NMR (300 MHz, DMSO): δ 167.77, 163.08, 152.21, 143.00,


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136.63, 131.59, 131.21, 128.12, 124.60, 116.14, 25.68; MS: m/z 398 (M+). Anal. Calcd for C13H9ClBrN5OS (396.94): C, 39.17; H, 2.28; Br, 20.04; Cl, 8.89; N, 17.57; O, 4.01; S, 8.04. Found: C, 39.15; H, 2.30; Br, 20.06; Cl, 8.91; N, 17.55; O, 4.04; S, 8.06. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(3-nitrophenyl) pyrimidin-4(3H)-one (6k). White solid; M.P. (141°C): 1H

NMR (300 MHz, DMSO): δ 4.31(s, 2H), 7.24–7.26(d, 2H), 7.32–7.34 (d, 1H), 7.52 (s, 1H), 8.25 (s, 1H, NH), 10.32 (s, 1H, NH). Anal. Calcd for C13H9ClN6O3S (364.01): C, 42.81; H, 2.49; Cl, 9.72; N, 23.04; O, 13.16; S, 8.79. Found C, 42.80; H, 2.46; Cl, 9.70; N, 23.06; O, 13.18; S, 8.76. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(4-nitrophenyl) White solid; M.P. (114°C): 1H pyrimidin-4(3H)-one (6l).

NMR (300 MHz, DMSO): δ 4.25 (s, 2H), 6.86–6.95 (d, 2H), 7.22–7.27 (d, 2H), 7.47–7.51 (d, 1H), 8.35 (s, 1H, NH), 10.26 (s, 1H, NH). Anal. Calcd for C13H9ClN6O3S (364.01): C, 42.81; H, 2.49; Cl, 9.72; N, 23.04; O, 13.16; S, 8.79. Found: C, 42.80; H, 2.50; Cl, 9.74; N, 23.07; O, 13.14; S, 8.75. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(4-methoxyphenyl) pyrimidin-4(3H)-one (6m). White solid; M.P. (120°C): 1H

NMR (300 MHz, DMSO): δ 3.33 (s, 3H), 4.26 (s, 2H), 7.03–7.05 (d, 2H), 7.20–7.31 (d, 2H), 7.45–7.60 (d, 1H), 8.12 (s, 1H, NH), 10.22 (s, 1H, NH). Anal. Calcd for C14H12ClN5O2S (349.8): C, 48.07; H, 3.46; Cl, 10.14; N, 20.02; O, 9.15; S, 9.17. Found C, 48.05; H, 3.48; Cl, 10.12; N, 20.04; O, 9.12; S, 9.18. 2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-p-tolylpyrimidinWhite solid; M.P. (135°C): 1H NMR 4(3H)-one (6n).

Vol 55

RT, using Glide (Glide 5.8, Schrodinger, 2012) [38]. Structure-based docking studies were carried out to investigate the intermolecular interaction between the ligand and the targeted enzyme. The coordinates of the non-nucleoside binding site were taken from the crystal structure of HIV-1 RT in complex with TMC278 (Rilpivirine) (PDB code: 2ZD1) [39]. Docking study of all the molecules from 1,2,3-triazolyl-pyrimidinone series was carried out with enzyme RT PDB ID: 2ZD1. The ligands were prepared by using LigPrep (LigPrep 2.5, Schrodinger, 2012) [40]. The protein was refined using the protein preparation wizard present in Maestro 9.3 (Maestro 9.3, Schrodinger, 2012) [41]. All the water molecules were deleted. H atoms were added to the protein, including the protons necessary to define the correct ionization and tautomeric states of the amino acid residues. Prime interface module incorporated in Maestro was used to add the missing residues of the side chain. Each structure minimization was carried out with the impact refinement module, using the OPLS2005 force field to alleviate steric clashes potentially existing in the structures. Minimization was terminated when the energy converged or the root mean square deviation reached a maximum cutoff of 0.30 Å. To find out active site grid was prepared using grid generation panel of glide with the default settings. Grid is prepared for defining the binding site of native ligand on the receptor. The ligand was selected to define the position and size of the active site [42,43]. Glide XP docking was used for docking purposes.

(300 MHz, DMSO): δ 2.30 (s, 3H), 4.25 (s, 2H), 7.10–7.12 (d, 2H), 7.24–7.26 (d, 2H), 7.48–7.51 (d, 1H), 8.23 (s,1H, NH), 10.47 (s,1H, NH); 13C–NMR (300 MHz, DMSO): δ 168.60, 163.15, 151.68, 143.44, 135.45, 133.37, 130.96, 129.94, 126.27, 116.47, 26.35,25.63; MS: m/z 333 (M+). Anal. Calcd for C14H12ClN5OS (333.05): C, 50.38; H, 3.62; Cl, 10.62; N, 20.98; O, 4.79; S, 9.61. Found C, 50.36; H, 3.65; Cl, 10.60; N, 21.00; O, 4.76; S, 9.60.

Acknowledgments. We acknowledge Dr S. S. Kadam, Dnyanopasak College, Parbhani for providing necessary facilities and Vishnu Chemical Laboratory, Hyderabad for providing spectral data which is highly appreciated, and also Poona College of Pharmacy, Bharati Vidyapeeth Deemed University, Pune for biological evolution.

2-((1H-1,2,3-triazol-4-yl)methylthio)-5-chloro-6-(4-isopropylphenyl) pyrimidin-4(3H)-one (6o). White solid; M.P. (174°C): 1H

REFERENCES AND NOTES

NMR (300 MHz, DMSO): δ 1.31–1.33 (s, 6H), 2.90– 2.97 (m, 1H), 4.26 (s, 2H), 7.02–7.04 (d, 2H), 7.20– 7.22 (d, 2H), 7.46–7.49 (s, 1H), 8.12 (s, 1H, NH), 10.22 (s, 1H, NH); 13C–NMR (300 MHz, DMSO): δ 168.50, 163.16, 153.98, 147.60, 143.12, 133.34, 132.12, 129.59, 117.60, 34.04, 26.30, 23.13; MS: m/z 361 (M+). Anal. Calcd for C16H16ClN5OS (361.08): C, 53.11; H, 4.46; Cl, 9.80; N, 19.35; O, 4.42; S, 8.86. Found: C, 53.14; H, 4.44; Cl, 9.84; N, 19.33; O, 4.40; S, 8.88. Material and methods for docking study. To guide the lead optimization strategy and rationalize the structure– activity relationships, modeling study was performed to examine the possible binding conformations of our newly synthesized compounds and their interaction mode with

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DOI 10.1002/jhet