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Synthesis and evaluation of a novel quinoline-triazole analogs for antitubercular properties via molecular hybridization approach
Bioorganic & Medicinal Chemistry Letters 29 (2019) 126671
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl
Synthesis and evaluation of a novel quinoline-triazole analogs for antitubercular properties via molecular hybridization approach
T
Jurupula Ramprasada, Vinay Kumar Sthalama,b, Rama Linga Murthy Thampunuric, ⁎ Supriya Bhukyac, Ramesh Ummannic, Sridhar Balasubramaniand, Srihari Pabbarajaa,b, a
Department of Organic Synthesis & Process Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India Academy of Scientific and Innovative Research (AcSIR), CSIR-Human Resource Development Centre (CSIR-HRDC) Campus, Ghaziabad, Uttar Pradesh 201002, India c Applied Biology, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India d Laboratory of X-ray Crystallography, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India b
ARTICLE INFO
ABSTRACT
Keywords: Mycobacterium tuberculosis Quinoline 1,2,3-Triazole Single crystal X-ray diffraction Antimycobacterial activity Cytotoxicity studies
Towards a quest for establishing new antitubercular agents, we have designed new quinoline–triazole hybrid analogs in a six-step reaction sequence involving versatile reactions like Vilsmeier–Haack and click reaction protocol. The design is based on the structural modification of bedaquiline moiety and involves molecular hybridization approach. The structure of the synthesized product was elucidated by single crystal X-ray diffraction study. The synthesized target compounds were screened for their antitubercular activity against Mycobacterium bovis. Interestingly, two compounds of the series (8d and 8m) showed significant inhibition with MIC of 31.5 and 34.8 μM. Compounds bearing 3-fluoro phenyl and n-octyl groups on the 1,2,3-triazole ring emerged as the most potent leads among the compounds tested. Further these hit compounds were also screened for their cytotoxic effect on human embryonic kindey 293 (HEK293) cells and other cancer cell lines such as HeLa (Cervical), PC3 (Prostate), Panc-1 (Pancreatic) and SKOV3 (Ovarian) indicating to be safer with the minimal cytotoxicity.
Tuberculosis (TB) is one of the 10 causes of deaths worldwideand the leading cause from single infectious agent Mycobacterium tuberculosis (Mtb) when compared to HIV/AIDS. Based on the World Health Organization (WHO) report 2018,1 1.3 billion deaths are reported among HIV negative patients and there were also 3 lakh additional deaths reported from HIV positive patients. In 2017, about 558,000 people became resistant for rifampicin, which is the most potent first line drug for the treatment of TB.2 Hence, there is a need for newer drugs to treat the MDR-TB and XDR-TB. In the recent past, the strategies that are followed for the design of drug molecules include, (i) computer based designing on the protein–ligand interaction,3 (ii) molecular hybridization approach where in two active pharmacophoric units are combined into a single molecular framework,4,5,6,7 (iii) structural modification of the existing approved drug molecule8 and iv) the random selection of various structural fragments9,10 and proceeding further. All of these strategies are being considered to be promising in the development of cost-effective drugs. Quinolines have become more prominent scaffold because of their wide variety of applications in synthetic, medicinal chemistry as well as in the development of newer drug molecules.11,12,13 It has also various types of biological activities such as anticancer,14 antitubercular,15 ⁎
anticonvulsant,16 anti-inflammatory17 and cardiovascular activities.18 After 40 years, bedaquiline (I) (Fig. 1), a quinoline based drug has been approved by US FDA for treating multidrug-resistant TB in 2013. The stereo structural complexity of this molecule makes its accessibility rather difficult through synthesis in particularly getting the single isomer and hence attempts have been made to simplify the structure for easy availability with better properties.19,20. The most common side effects of bedaquiline reported include joint and chest pain, headache, and nausea.21 The current study describes the structural modification of bedaquiline, while preserving the core structural unit. Tong et.al (2017) reported 6-cyano analog of bedaquiline derivative (II) that showed an average MIC of 0.25 μM and improved lipophilicity.22 Ciprofloxacin (III) is the quinoline containing antibiotic drug, which has been widely used to treat bacterial infections for the past three decades.23 The 1,2,3-triazole moiety containing molecules attracted significant importance in terms of biological activity as well as their synthetic applications.24 Drugs like cefatrizine and tazobactam containing the core triazole moiety are used for treating various bacterial infections. Upadhayaya et al. reported the synthesis of quinoline containing 1,2,3triazole at 6-position. The compound-IV exhibited promising activity
Corresponding author at: Department of Organic Synthesis & Process Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India. E-mail address: [email protected] (S. Pabbaraja).
https://doi.org/10.1016/j.bmcl.2019.126671 Received 29 June 2019; Received in revised form 19 August 2019; Accepted 4 September 2019 Available online 05 September 2019 0960-894X/ © 2019 Elsevier Ltd. All rights reserved.
Bioorganic & Medicinal Chemistry Letters 29 (2019) 126671
J. Ramprasad, et al.
was evaluated in terms of minimum inhibitory concentration (MIC) values. The MIC values in μM of all test compounds 8a-s and standard compounds are presented in Table 2. Interestingly, two compounds (8d and 8m) of the series showed significant inhibitory activity against antitubercular strain. Compounds 8d and 8m containing 3-fluoro phenyl and n-octyl groups respectively on the 1,2,3-triazole ring were found to be the most potent leads with a MIC of 31.5 and 34.8 μM respectively. The nature of the substituents on 1,2,3-triazole affected the activity of the molecules. The presence of fluorine on meta position of phenyl ring showed superior activity, where as o- and p- flouro phenyl did not display any activity. Interestingly, 8f showed better activity (41.0 μM) campared to p-bromo phenyl (8b, 49 μM), whereas p-flouro phenyl (8c) did not show any activity. The alkyl substituted compounds in which R1 = n-propyl to n-octyl (8h-8m) showed MIC of 45.18, 50.2, 80.9, 44.4, 71.94, 34.88 μM respectively. Among them 8m showed superior activity with MIC of 34.88 μM. The triazoles of n-pentyl (8j) and n-heptyl (8l) showed least activity with MIC of 80.9 and 71.94 μM respectively. In case of aliphatic substituted alcohol (R-OH) derivatives, pentanol (R1, 8q) showed better activity (59.58 μM) compared to –CH2OH (8n, 130.8 μM) and -C2H5OH (8o, 132.8 μM). The compounds with R1 as n-propanol, cyclopropyl and ethyl carbonate did not show any activity. The three-dimensional structure of 8s was revealed by single crystal X-ray diffraction studies. The single crystal of 8s was grown from methanol and chloroform (1:1) solvent mixture by the slow evaporation of the solvent at room temperature. The crystal data of compound 8s is given in supporting information. To determine the cytotoxic effect of test compounds, the series of compounds synthesized were screened for cytotoxicity against HEK293 human embryonic kidney cells and different cancer cells, including HeLa (Cervical, PC3 (Prostate), Panc-1 (Pancreatic) and SKOV3 (Ovarian) cell lines by cell viability assays using sulphorhodamine B.29 The cytotoxic potential of the test compounds are represented in the Table 3. All the hybrid derivatives showed minimal inhibition of cell growth for all the tested cell lines indicating the lack of general cellular toxicity of these compounds. Compounds 8d and 8m showing better activity against Mycobacterium bovis displayed minimum or no growth inhibition for all the cell lines tested when the data were compared with standard drug doxorubicin. In conclusion, we have designed a series of quinoline-triazole analogs via molecular hybridization and structural modification of bedaquiline antitubercular drug. The antitubercular screening assays revealed the substantial inhibition of Mycobacterium bovis growth by the test molecules prepared from the current study. Interestingly, two compounds (8d and 8m) of the series showed remarkable inhibitory activity with MIC ≤ 31.5 and 34.8 μM. The structure–activity relationship (SAR) revealed that bearing 3-fluoro phenyl and n-octyl groups respectively on the 1,2,3-triazole ring emerged as the most potent leads. These results of the molecules showing encouraging activity attains the importance for further studies and development of new anti-
Figure 1. Representative quinoline and 1,2,3-triazole based antitubercular agents.
with MIC of 3.125 μg/mL.25 Compound 6-hydroxy-3-(1-(((4-morpho linophenyl)amino)-2-oxoethyl)-1H-1,2,3-triazol-4-yl)-2-phenylbenzofuran-5-carboxylic acid (V, IA-09) having triazole moiety is under preclinical trials to fight against tuberculosis.26 Further, Patpi et al. reported synthesis of different set of 1,2,3-triazole derivatives and 4-(2chloro-4-fluorophenyl)1-(1-(dibenzo[b,d]thiophen-2-yl)ethyl)-1H1,2,3-triazole (VI) showed excellent antitubercular activity with MIC of 0.78 μg/mL.27 Our interest was to build a triazole core unit and make analogues by replacing the naphthalene and N-alkyl portion of the bedaquiline and check the drug potency. The target quinoline-triazole analogues (8a-s) were synthesized as shown in Scheme 1. N-(4-bromophenyl)-3-phenylpropanamide (2a) was synthesized by the reaction of 4-bromo aniline (1a) with 3-phenylpropanoyl chloride (1b) and triethyl amine in DCM at 0 °C-RT for 5 h following reported protocol.20 Compound-2a was subjected to Vilsmeier–Haack formylation reaction and followed by cyclisation to give 3-benzyl-6-bromo-2-chloroquinoline (3a). 3a was further treated with NaOMe to get the compound 4a which on bromination with NBS, CCl4 and catalytic amount of dibenzoyl peroxide was converted to 6-bromo3-(bromo(phenyl)methyl)-2-methoxyquinoline (5a). 5a was converted to substituted azide compound (6a) using sodium azide, DMF, 80 °C for 5 h. The target compounds, quinoline-triazole derivatives (8a-s, Table 1) were synthesized by the reaction between substituted alkynes (7a-s) and substituted azide (6a) in acetonitrile under reflux conditions. The structure of the target molecules (8a-s) were confirmed by spectral (1H NMR, 13C NMR, ESI-MS, HR-MS and FT-IR) analysis. The structure of 8s was ambiguously confirmed by single crystal XRD studies (See Fig. 2). Antimycobacterial activities of the synthesized compounds (8a-s) were performed against Mycobacterium bovis growth using turbidometric assay.28 The concentration of 6.25, 12.5, 25, 50, 100 and 250 µM solutions were used to investigate the antimycobacterial activity and
Scheme 1. Synthesis of quinoline-triazole analogues (8a-s). Reagents and conditions: (i) Et3N, DCM, 0–5 °C, 5 h; (ii) DMF, POCl3, 80 °C, 16 h; (iii) NaOMe, MeOH, 65 °C, 6 h; (iv) NBromosuccinamide, dibenzoyl peroxide, CCl4, 80 °C, 2 h; (v) NaN3, DMF, 80 °C, 2 h; (vi) Substituted Alkyne (7a-s), Copper(I) iodide, acetonitrile, 80 °C, 3 h.
2
Bioorganic & Medicinal Chemistry Letters 29 (2019) 126671
J. Ramprasad, et al.
Table 1 Click
reaction
of
6a
with
7a-s
to
yield
8a-
8s.
Entry
Alkyne
Product
% of yield
m.p (°C)
1
8a
95
115–116
2
8b
92
219–220
3
8c
85
204–205
Figure 2. ORTEP diagram showing the X-ray crystal structure of compound 8 s. (CCDC No. 1912888).
4
8d
85
166–167
Table 2 In vitro antitubercular activity of quinoline-triazole hybrid derivatives (8a-s).
5
8e
82
160–161
6
8f
75
206–207
7
8g
70
121–122
8
8h
70
160–161
9
8i
73
129–130
10
8j
75
100–101
11
8k
79
98–99
12
8l
85
94–95
Product
C log Pa
MIC μM (90 %GI)
8a 8b 8c 8d 8e 8f 8g 8h 8i 8j 8k 8l 8m 8n 8o 8p 8q 8r 8s Bedaquiline Rifampicin Isoniazid
6.276 7.176 6.456 6.456 6.456 7.371 7.224 5.505 6.034 6.563 7.0925 7.6215 8.150 3.140 3.139 3.518 4.576 4.891 5.014 7.250 3.710 −0.668
160.51 48.98 NA 31.35 NA 41.00 173.99 45.18 50.21 80.90 44.38 71.94 34.88 130.88 132.82 NA 59.58 NA NA 0.15 2.20 12.52
a
Calculated using Chemdraw Ultra 16.0
13
8m
88
104–105
14
8n
76
163–164
15
8o
80
159–160
16
8p
81
73–74
17
8q
89
78–79
Acknowledgements
18
8r
75
170–171
19
8s
80
199–200
Authors are thankful to Director, CSIR-IICT, Hyderabad for providing the research facilities and JRP acknowledges SERB, New Delhi file number (PDF/2017/001819) for financial assistance. SVK acknowledges Sai life Sciences Limited. This work was also partly funded from CSIR-IICT (GAP-584). IICT communication no. IICT/Pubs/2019/ 231.
tubercular agents. Further the title compounds were also screened on HEK293, normal human embryonic kidney cells and other cancer cells including HeLa, PC3, Panc-1 and SKOV3 and found to be non cytotoxic with an indication to expand the library of compounds determining SAR and eventually develop new potential anti mycobacterial agents.
3
Bioorganic & Medicinal Chemistry Letters 29 (2019) 126671
J. Ramprasad, et al.
Table 3 In vitro cytotoxicity quinoline-triazole (8a-s) hybrid derivatives. Product
8a 8b 8c 8d 8e 8f 8g 8h 8i 8j 8k 8l 8m 8n 8p 8p 8q 8r 8s Doxorubicina a
of their antitubercular activity. Bioorg Med Chem Lett. 2015;25(19):4169–4173. 8. Lima LM, Barreiro EJ. Bioisosterism: a useful strategy for molecular modification and drug design. Curr Med Chem. 2005;12(1):23–49. 9. Cappoen D, Claes P, Jacobs J, et al. 1,2,3,4,8,9,10,11-Octahydrobenzo[j]phenanthridine-7,12-diones as New Leads against Mycobacterium tuberculosis. J Med Chem. 2014;57(7):2895–2907. 10. Claes P, Cappoen D, Uythethofken C, et al. 2, 4-Dialkyl-8, 9, 10, 11-tetrahydrobenzo [g]pyrimido[4,5-c]isoquinoline-1,3,7,12(2H, 4H)-tetraones as new leads against Mycobacterium tuberculosis. Eur J Med Chem. 2014;77:409–421. 11. Manske RH. The Chemistry of Quinolines. Chem Rev. 1942;30(1):113–144. 12. Suresh K, Sandhya B, Himanshu G. Biological Activities of Quinoline Derivatives. Mini-Rev Med Chem. 2009;9(14):1648–1654. 13. Afzal O, Kumar S, Haider MR, et al. A review on anticancer potential of bioactive heterocycle quinoline. Eur J Med Chem. 2015;97:871–910. 14. Shobeiri N, Rashedi M, Mosaffa F, et al. Synthesis and biological evaluation of quinoline analogues of flavones as potential anticancer agents and tubulin polymerization inhibitors. Eur J Med Chem. 2016;114:14–23. 15. Nayak N, Ramprasad J, Dalimba U. Synthesis and antitubercular and antibacterial activity of some active fluorine containing quinoline–pyrazole hybrid derivatives. J Fluor Chem. 2016;183:59–68. 16. Muruganantham N, Sivakumar R, Anbalagan N, Gunasekaran V, Leonard JT. Synthesis, Anticonvulsant and Antihypertensive Activities of 8-Substituted Quinoline Derivatives. Biol Pharm Bull. 2004;27(10):1683–1687. 17. Upadhyay KD, Dodia NM, Khunt RC, Chaniara RS, Shah AK. Synthesis and Biological Screening of Pyrano[3,2-c]quinoline Analogues as Anti-inflammatory and Anticancer Agents. ACS Med Chem Lett. 2018;9(3):283–288. 18. Pym AS, Diacon AH, Tang S-J, et al. Bedaquiline in the treatment of multidrug- and extensively drug-resistant tuberculosis. Eur Respir J. 2016;47(2):564–574. 19. Rode HB, Lade DM, Grée R, Mainkar PS, Chandrasekhar S. Strategies towards the synthesis of anti-tuberculosis drugs. Org Biomol Chem. 2019;17:5428–5459. 20. He C, Preiss L, Wang B, et al. Structural Simplification of Bedaquiline: the Discovery of 3-(4-(N, N-Dimethylaminomethyl) phenyl)quinoline-Derived Antitubercular Lead Compounds. ChemMedChem. 2017;12(2):106–119. 21. Pym AS, Diacon AH, Tang S-J, et al. Bedaquiline in the treatment of multidrug-and extensively drug-resistant tuberculosis. Eur Respir J. 2016;47(2):564–574. 22. Tong AST, Choi PJ, Blaser A, et al. 6-Cyano Analogues of Bedaquiline as Less Lipophilic and Potentially Safer Diarylquinolines for Tuberculosis. ACS Med Chem Lett. 2017;8(10):1019–1024. 23. Kennedy N, Fox R, Kisyombe GM, et al. Early bactericidal and sterilizing activities of ciprofloxacin in pulmonary tuberculosis. Am J Respir Crit Care Med. 1993;148(6):1547–1551. 24. Thirumurugan P, Matosiuk D, Jozwiak K. Click chemistry for drug development and diverse chemical–biology applications. Chem Rev. 2013;113(7):4905–4979. 25. Upadhayaya RS, Kulkarni GM, Vasireddy NR, et al. Design, synthesis and biological evaluation of novel triazole, urea and thiourea derivatives of quinoline against Mycobacterium tuberculosis. Bioorg Med Chem. 2009;17(13):4681–4692. 26. Shi D-Q, Zhou Y, Rong S-F. Ionic Liquid, [bmim]Br, as an Efficient Promoting Medium for Synthesis of 3-Acetoacetylcoumarin Derivatives Without the Use of Any Catalyst. Synth Commun. 2009;39(19):3500–3508. 27. Patpi SR, Pulipati L, Yogeeswari P, et al. Design, synthesis, and structure–activity correlations of novel dibenzo[b, d]furan, dibenzo [b, d]thiophene, and N-methylcarbazole clubbed 1,2,3-triazoles as potent inhibitors of Mycobacterium tuberculosis. J Med Chem. 2012;55(8):3911–3922. 28. Ramesh R, Shingare RD, Kumar V, et al. Repurposing of a drug scaffold: Identification of novel sila analogues of rimonabant as potent antitubercular agents. Eur J Med Chem. 2016;122:723–730. 29. Vichai V, Kirtikara K. Sulforhodamine B colorimetric assay for cytotoxicity screening. Nat Protoc. 2006;1(3):1112.
Cytotoxicity % of inhibition at 10 µM HEK293
HeLa
PC3
Panc-1
SKOV3
8.25 6.28 4.04 6.84 3.97 5.80 14.30 0.85 −3.47 −2.00 −3.17 0.17 14.58 11.52 4.54 27.44 7.96 8.22 2.00 75.63
13.86 6.92 4.27 9.04 14.07 −2.24 −1.30 −2.25 −2.87 −9.81 −0.97 9.70 0.10 0.25 0.85 11.33 1.08 −5.84 −3.67 74.09
5.97 7.43 16.35 14.55 13.41 21.60 17.40 8.30 5.54 11.42 2.32 4.42 2.27 4.65 15.53 14.71 12.92 22.64 16.14 86.70
30.09 10.40 14.86 15.54 14.71 11.66 11.44 11.31 5.46 5.07 6.08 16.55 12.12 14.99 19.83 25.49 19.61 21.78 15.43 96.07
13.66 13.40 14.34 12.65 7.33 14.75 9.55 11.24 11.08 10.51 7.17 10.54 2.06 3.23 8.46 13.79 8.69 3.52 2.01 83.31
% of inhibition at 2 µM
Appendix A. Supplementary data Supplementary data (Selected spectra and experimental details are available as Supplementary material) to this article can be found online at https://doi.org/10.1016/j.bmcl.2019.126671. References 1. World Health Organization. Global Tuberculosis Report. 2018. 2. Salvato RS, Schiefelbein S, Barcellos RB, et al. Molecular characterisation of multidrug-resistant Mycobacterium tuberculosis isolates from a high-burden tuberculosis state in Brazil. Epidemiol Infect. 2019;147:e216. 3. Åqvist J, Medina C, Samuelsson J-E. A new method for predicting binding affinity in computer-aided drug design. Protein Eng. 1994;7(3):385–391. 4. Lazar C, Kluczyk A, Kiyota T, Konishi Y. Drug evolution concept in drug design: 1 Hybridization method. J Med Chem. 2004;47(27):6973–6982. 5. Viegas-Júnior C, Danuello A, da Silva Bolzani V, Barreiro EJ, Fraga CAM. Molecular hybridization: a useful tool in the design of new drug prototypes. Curr Med Chem. 2007;14(17):1829–1852. 6. Ramprasad J, Nayak N, Dalimba U. Design of new phenothiazine-thiadiazole hybrids via molecular hybridization approach for the development of potent antitubercular agents. Eur J Med Chem. 2015;106:75–84. 7. Ramprasad J, Nayak N, Dalimba U, Yogeeswari P, Sriram D. One-pot synthesis of new triazole-Imidazo[2,1-b][1,3,4]thiadiazole hybrids via click chemistry and evaluation
4
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl
Synthesis and evaluation of a novel quinoline-triazole analogs for antitubercular properties via molecular hybridization approach
T
Jurupula Ramprasada, Vinay Kumar Sthalama,b, Rama Linga Murthy Thampunuric, ⁎ Supriya Bhukyac, Ramesh Ummannic, Sridhar Balasubramaniand, Srihari Pabbarajaa,b, a
Department of Organic Synthesis & Process Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India Academy of Scientific and Innovative Research (AcSIR), CSIR-Human Resource Development Centre (CSIR-HRDC) Campus, Ghaziabad, Uttar Pradesh 201002, India c Applied Biology, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India d Laboratory of X-ray Crystallography, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India b
ARTICLE INFO
ABSTRACT
Keywords: Mycobacterium tuberculosis Quinoline 1,2,3-Triazole Single crystal X-ray diffraction Antimycobacterial activity Cytotoxicity studies
Towards a quest for establishing new antitubercular agents, we have designed new quinoline–triazole hybrid analogs in a six-step reaction sequence involving versatile reactions like Vilsmeier–Haack and click reaction protocol. The design is based on the structural modification of bedaquiline moiety and involves molecular hybridization approach. The structure of the synthesized product was elucidated by single crystal X-ray diffraction study. The synthesized target compounds were screened for their antitubercular activity against Mycobacterium bovis. Interestingly, two compounds of the series (8d and 8m) showed significant inhibition with MIC of 31.5 and 34.8 μM. Compounds bearing 3-fluoro phenyl and n-octyl groups on the 1,2,3-triazole ring emerged as the most potent leads among the compounds tested. Further these hit compounds were also screened for their cytotoxic effect on human embryonic kindey 293 (HEK293) cells and other cancer cell lines such as HeLa (Cervical), PC3 (Prostate), Panc-1 (Pancreatic) and SKOV3 (Ovarian) indicating to be safer with the minimal cytotoxicity.
Tuberculosis (TB) is one of the 10 causes of deaths worldwideand the leading cause from single infectious agent Mycobacterium tuberculosis (Mtb) when compared to HIV/AIDS. Based on the World Health Organization (WHO) report 2018,1 1.3 billion deaths are reported among HIV negative patients and there were also 3 lakh additional deaths reported from HIV positive patients. In 2017, about 558,000 people became resistant for rifampicin, which is the most potent first line drug for the treatment of TB.2 Hence, there is a need for newer drugs to treat the MDR-TB and XDR-TB. In the recent past, the strategies that are followed for the design of drug molecules include, (i) computer based designing on the protein–ligand interaction,3 (ii) molecular hybridization approach where in two active pharmacophoric units are combined into a single molecular framework,4,5,6,7 (iii) structural modification of the existing approved drug molecule8 and iv) the random selection of various structural fragments9,10 and proceeding further. All of these strategies are being considered to be promising in the development of cost-effective drugs. Quinolines have become more prominent scaffold because of their wide variety of applications in synthetic, medicinal chemistry as well as in the development of newer drug molecules.11,12,13 It has also various types of biological activities such as anticancer,14 antitubercular,15 ⁎
anticonvulsant,16 anti-inflammatory17 and cardiovascular activities.18 After 40 years, bedaquiline (I) (Fig. 1), a quinoline based drug has been approved by US FDA for treating multidrug-resistant TB in 2013. The stereo structural complexity of this molecule makes its accessibility rather difficult through synthesis in particularly getting the single isomer and hence attempts have been made to simplify the structure for easy availability with better properties.19,20. The most common side effects of bedaquiline reported include joint and chest pain, headache, and nausea.21 The current study describes the structural modification of bedaquiline, while preserving the core structural unit. Tong et.al (2017) reported 6-cyano analog of bedaquiline derivative (II) that showed an average MIC of 0.25 μM and improved lipophilicity.22 Ciprofloxacin (III) is the quinoline containing antibiotic drug, which has been widely used to treat bacterial infections for the past three decades.23 The 1,2,3-triazole moiety containing molecules attracted significant importance in terms of biological activity as well as their synthetic applications.24 Drugs like cefatrizine and tazobactam containing the core triazole moiety are used for treating various bacterial infections. Upadhayaya et al. reported the synthesis of quinoline containing 1,2,3triazole at 6-position. The compound-IV exhibited promising activity
Corresponding author at: Department of Organic Synthesis & Process Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India. E-mail address: [email protected] (S. Pabbaraja).
https://doi.org/10.1016/j.bmcl.2019.126671 Received 29 June 2019; Received in revised form 19 August 2019; Accepted 4 September 2019 Available online 05 September 2019 0960-894X/ © 2019 Elsevier Ltd. All rights reserved.
Bioorganic & Medicinal Chemistry Letters 29 (2019) 126671
J. Ramprasad, et al.
was evaluated in terms of minimum inhibitory concentration (MIC) values. The MIC values in μM of all test compounds 8a-s and standard compounds are presented in Table 2. Interestingly, two compounds (8d and 8m) of the series showed significant inhibitory activity against antitubercular strain. Compounds 8d and 8m containing 3-fluoro phenyl and n-octyl groups respectively on the 1,2,3-triazole ring were found to be the most potent leads with a MIC of 31.5 and 34.8 μM respectively. The nature of the substituents on 1,2,3-triazole affected the activity of the molecules. The presence of fluorine on meta position of phenyl ring showed superior activity, where as o- and p- flouro phenyl did not display any activity. Interestingly, 8f showed better activity (41.0 μM) campared to p-bromo phenyl (8b, 49 μM), whereas p-flouro phenyl (8c) did not show any activity. The alkyl substituted compounds in which R1 = n-propyl to n-octyl (8h-8m) showed MIC of 45.18, 50.2, 80.9, 44.4, 71.94, 34.88 μM respectively. Among them 8m showed superior activity with MIC of 34.88 μM. The triazoles of n-pentyl (8j) and n-heptyl (8l) showed least activity with MIC of 80.9 and 71.94 μM respectively. In case of aliphatic substituted alcohol (R-OH) derivatives, pentanol (R1, 8q) showed better activity (59.58 μM) compared to –CH2OH (8n, 130.8 μM) and -C2H5OH (8o, 132.8 μM). The compounds with R1 as n-propanol, cyclopropyl and ethyl carbonate did not show any activity. The three-dimensional structure of 8s was revealed by single crystal X-ray diffraction studies. The single crystal of 8s was grown from methanol and chloroform (1:1) solvent mixture by the slow evaporation of the solvent at room temperature. The crystal data of compound 8s is given in supporting information. To determine the cytotoxic effect of test compounds, the series of compounds synthesized were screened for cytotoxicity against HEK293 human embryonic kidney cells and different cancer cells, including HeLa (Cervical, PC3 (Prostate), Panc-1 (Pancreatic) and SKOV3 (Ovarian) cell lines by cell viability assays using sulphorhodamine B.29 The cytotoxic potential of the test compounds are represented in the Table 3. All the hybrid derivatives showed minimal inhibition of cell growth for all the tested cell lines indicating the lack of general cellular toxicity of these compounds. Compounds 8d and 8m showing better activity against Mycobacterium bovis displayed minimum or no growth inhibition for all the cell lines tested when the data were compared with standard drug doxorubicin. In conclusion, we have designed a series of quinoline-triazole analogs via molecular hybridization and structural modification of bedaquiline antitubercular drug. The antitubercular screening assays revealed the substantial inhibition of Mycobacterium bovis growth by the test molecules prepared from the current study. Interestingly, two compounds (8d and 8m) of the series showed remarkable inhibitory activity with MIC ≤ 31.5 and 34.8 μM. The structure–activity relationship (SAR) revealed that bearing 3-fluoro phenyl and n-octyl groups respectively on the 1,2,3-triazole ring emerged as the most potent leads. These results of the molecules showing encouraging activity attains the importance for further studies and development of new anti-
Figure 1. Representative quinoline and 1,2,3-triazole based antitubercular agents.
with MIC of 3.125 μg/mL.25 Compound 6-hydroxy-3-(1-(((4-morpho linophenyl)amino)-2-oxoethyl)-1H-1,2,3-triazol-4-yl)-2-phenylbenzofuran-5-carboxylic acid (V, IA-09) having triazole moiety is under preclinical trials to fight against tuberculosis.26 Further, Patpi et al. reported synthesis of different set of 1,2,3-triazole derivatives and 4-(2chloro-4-fluorophenyl)1-(1-(dibenzo[b,d]thiophen-2-yl)ethyl)-1H1,2,3-triazole (VI) showed excellent antitubercular activity with MIC of 0.78 μg/mL.27 Our interest was to build a triazole core unit and make analogues by replacing the naphthalene and N-alkyl portion of the bedaquiline and check the drug potency. The target quinoline-triazole analogues (8a-s) were synthesized as shown in Scheme 1. N-(4-bromophenyl)-3-phenylpropanamide (2a) was synthesized by the reaction of 4-bromo aniline (1a) with 3-phenylpropanoyl chloride (1b) and triethyl amine in DCM at 0 °C-RT for 5 h following reported protocol.20 Compound-2a was subjected to Vilsmeier–Haack formylation reaction and followed by cyclisation to give 3-benzyl-6-bromo-2-chloroquinoline (3a). 3a was further treated with NaOMe to get the compound 4a which on bromination with NBS, CCl4 and catalytic amount of dibenzoyl peroxide was converted to 6-bromo3-(bromo(phenyl)methyl)-2-methoxyquinoline (5a). 5a was converted to substituted azide compound (6a) using sodium azide, DMF, 80 °C for 5 h. The target compounds, quinoline-triazole derivatives (8a-s, Table 1) were synthesized by the reaction between substituted alkynes (7a-s) and substituted azide (6a) in acetonitrile under reflux conditions. The structure of the target molecules (8a-s) were confirmed by spectral (1H NMR, 13C NMR, ESI-MS, HR-MS and FT-IR) analysis. The structure of 8s was ambiguously confirmed by single crystal XRD studies (See Fig. 2). Antimycobacterial activities of the synthesized compounds (8a-s) were performed against Mycobacterium bovis growth using turbidometric assay.28 The concentration of 6.25, 12.5, 25, 50, 100 and 250 µM solutions were used to investigate the antimycobacterial activity and
Scheme 1. Synthesis of quinoline-triazole analogues (8a-s). Reagents and conditions: (i) Et3N, DCM, 0–5 °C, 5 h; (ii) DMF, POCl3, 80 °C, 16 h; (iii) NaOMe, MeOH, 65 °C, 6 h; (iv) NBromosuccinamide, dibenzoyl peroxide, CCl4, 80 °C, 2 h; (v) NaN3, DMF, 80 °C, 2 h; (vi) Substituted Alkyne (7a-s), Copper(I) iodide, acetonitrile, 80 °C, 3 h.
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Bioorganic & Medicinal Chemistry Letters 29 (2019) 126671
J. Ramprasad, et al.
Table 1 Click
reaction
of
6a
with
7a-s
to
yield
8a-
8s.
Entry
Alkyne
Product
% of yield
m.p (°C)
1
8a
95
115–116
2
8b
92
219–220
3
8c
85
204–205
Figure 2. ORTEP diagram showing the X-ray crystal structure of compound 8 s. (CCDC No. 1912888).
4
8d
85
166–167
Table 2 In vitro antitubercular activity of quinoline-triazole hybrid derivatives (8a-s).
5
8e
82
160–161
6
8f
75
206–207
7
8g
70
121–122
8
8h
70
160–161
9
8i
73
129–130
10
8j
75
100–101
11
8k
79
98–99
12
8l
85
94–95
Product
C log Pa
MIC μM (90 %GI)
8a 8b 8c 8d 8e 8f 8g 8h 8i 8j 8k 8l 8m 8n 8o 8p 8q 8r 8s Bedaquiline Rifampicin Isoniazid
6.276 7.176 6.456 6.456 6.456 7.371 7.224 5.505 6.034 6.563 7.0925 7.6215 8.150 3.140 3.139 3.518 4.576 4.891 5.014 7.250 3.710 −0.668
160.51 48.98 NA 31.35 NA 41.00 173.99 45.18 50.21 80.90 44.38 71.94 34.88 130.88 132.82 NA 59.58 NA NA 0.15 2.20 12.52
a
Calculated using Chemdraw Ultra 16.0
13
8m
88
104–105
14
8n
76
163–164
15
8o
80
159–160
16
8p
81
73–74
17
8q
89
78–79
Acknowledgements
18
8r
75
170–171
19
8s
80
199–200
Authors are thankful to Director, CSIR-IICT, Hyderabad for providing the research facilities and JRP acknowledges SERB, New Delhi file number (PDF/2017/001819) for financial assistance. SVK acknowledges Sai life Sciences Limited. This work was also partly funded from CSIR-IICT (GAP-584). IICT communication no. IICT/Pubs/2019/ 231.
tubercular agents. Further the title compounds were also screened on HEK293, normal human embryonic kidney cells and other cancer cells including HeLa, PC3, Panc-1 and SKOV3 and found to be non cytotoxic with an indication to expand the library of compounds determining SAR and eventually develop new potential anti mycobacterial agents.
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Bioorganic & Medicinal Chemistry Letters 29 (2019) 126671
J. Ramprasad, et al.
Table 3 In vitro cytotoxicity quinoline-triazole (8a-s) hybrid derivatives. Product
8a 8b 8c 8d 8e 8f 8g 8h 8i 8j 8k 8l 8m 8n 8p 8p 8q 8r 8s Doxorubicina a
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Cytotoxicity % of inhibition at 10 µM HEK293
HeLa
PC3
Panc-1
SKOV3
8.25 6.28 4.04 6.84 3.97 5.80 14.30 0.85 −3.47 −2.00 −3.17 0.17 14.58 11.52 4.54 27.44 7.96 8.22 2.00 75.63
13.86 6.92 4.27 9.04 14.07 −2.24 −1.30 −2.25 −2.87 −9.81 −0.97 9.70 0.10 0.25 0.85 11.33 1.08 −5.84 −3.67 74.09
5.97 7.43 16.35 14.55 13.41 21.60 17.40 8.30 5.54 11.42 2.32 4.42 2.27 4.65 15.53 14.71 12.92 22.64 16.14 86.70
30.09 10.40 14.86 15.54 14.71 11.66 11.44 11.31 5.46 5.07 6.08 16.55 12.12 14.99 19.83 25.49 19.61 21.78 15.43 96.07
13.66 13.40 14.34 12.65 7.33 14.75 9.55 11.24 11.08 10.51 7.17 10.54 2.06 3.23 8.46 13.79 8.69 3.52 2.01 83.31
% of inhibition at 2 µM
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