A series of Mannich products bearing quinoline nucleus was synthesized, characterized, and evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H 37Rv. The results showed that compounds 4b, and 4d found most active with percentage inhibition of 95, and 96, respectively, at minimum inhibitory concentration (MIC) of >6.25 μg/mL, among the synthesized compounds. Whereas, compounds 4a, 4c, 4e, and 4f exhibited considerable antitubercular activity with percentage inhibition of 71, 79, 55, and 68, respectively, at MIC of >6.25 μg/mL. The structures of synthesized compounds were elucidated by various spectroscopic tools like IR, 1H NMR, 13C NMR, mass and elemental analysis.
Tuberculosis (TB) is a global epidemic and an infectious disease caused by the pathogenic bacterium Mycobacterium tuberculosis (Mtb) [
Over the past few decades, Mannich bases of heterocyclic molecules have found to show versatile pharmacological activities [
Recognizing these facts and continuation of our earlier work based on u. v. absorbing materials as well as heterocyclic moiety [
Melting points were determined in open capillary tubes and are uncorrected. Formation of the compounds was routinely checked by TLC on silica gel-G plates of 0.5 mm thickness and spots were located by iodine. IR spectra were recorded Shimadzu FT-IR-8400 instrument using KBr pellet method. Mass spectra were recorded on Shimadzu GC-MS-QP-2010 model using Direct Injection Probe technique. 1H NMR and 13C NMR spectra were determined in DMSO-d6 solution on a Bruker Ac 400 MHz spectrometer. Elemental analysis of the all the synthesized compounds was carried out on Elemental Vario EL III Carlo Erba 1108 model and the results were in agreements with the structures assigned. All chemicals were purchased from commercial sources and used without further purification.
A mixture of 2,4-dihydroxybenzophenone 1.07 gm (0.005 M), 2-chloro-6-methoxyquinoline-3-carboxaldehyde 1.105 gm (0.005 M), various amides 0.30 gm (0.005 M) and EAN 30 ml (1 M) was refluxed with stirring at 80˚C temperature. The completion of reaction was monitored by TLC with using solvent system chloroform/methanol (v/v = 70:30). On completion of reaction, the reaction mixture was extracted thrice with 20 ml ethyl acetate. The extract was dried over anhydrous sodium sulfate, evaporated under vacuum and the residue was purified via recrystallisation from methanol or ethyl acetate to obtain pure new Mannich products 4(a-f) (Scheme 1).
1-((5-benzoyl-2,4-dihydroxyphenyl) (2-chloro-6-methoxyquinolin-3-yl) methyl) urea (4a)
Scheme 1. Synthesis of new Mannich products 4(a-f) bearing quinolinenucleous.
It was obtained as yellow solid color, yield: 84%; decomposition temperature 188˚C - 192˚C; IR (KBr, υmax/cm−1): 3463, 3440 (Ar-OH), 3198 (-NH), 3072 (CH, aromatic), 2974, 741 (CH aliphatic), 1705, 1628 (C=O, diaryl), 1605 (C=N), 1519 (C-N), 1481 (C-C, aromatic), 1212-1024 (C-O-C), 1101 (C-O), 732, 584 (for substituted benzene); 1H-NMR (CDCl3, 400 MHz): δ = 8.25-7.01 (4H, m, H-4, H-5, H-7, H-8, -CH for substituted quinoline), 7.97 (1H, s, Ar-OH, -intra), 7.84 (1H, d, J = 7.8 Hz, -NHCO-), 7.01-7.78 (7H, m, H-3’, H-6’, H-2”, H-3”, H-4”, H-5”, H-6”, Ar-H), 7.01 (1H, s, Ar?OH), 7.05 (1H, dd, J = 10.5, 3.5 Hz, -CHNH), 6.86 (2H, s, -CONH2), 4.06 (3H, s, -OMe); 13C NMR (CDCl3, 400 MHz,): δ = 203.1 (C, -C=O, benzoyl), 163.2 (C-4’, Ar-OH), 160.1 (C, NHCONH2),159.4, (C-2’, Ar-OH), 155.9 (C-6, C-OCH3), 150.2 (C-2,C-Cl), 148.6 (C, C-10), 132.7 (C, C-1”), 132.2 (C, C-9), 132.0 (C, C-8), 131.8 (C, C-4), 131.7 (C, C-1’), 131.6 (C, C-6), 130.5 (2C, C-2” & C-6”), 128.1 (C, C-4’), 122.8 (2C, C-3”& C-5”), 119.7 (C, C-5’), 109.4 (C, C-7), 107.5 (C, C-5), 104.1 (C, C-3’), 101.8 (C, C-3), 55.2 (C, -OCH3), 51.2 (C, aliphatic-CH); EI-MS m/z: 477 (M+1)+; Anal. Calc. for C25H20ClN3O5 (%): C, 62.83; H, 4.22; N, 8.79% found: C, 62.80; H, 4.19; N, 8.71%.
1-((5-benzoyl-2,4-dihydroxyphenyl) (2-chloro-6-methoxyquinolin-3-yl) methyl) thiourea (4b)
It was obtained as pale yellow solid color, yield: 88%; decomposition temperature 180-1840C; IR (KBr, υmax/cm−1): 3463, 3440 (Ar-OH), 3198 (-NH), 3072 (CH, aromatic), 2974, 741 (CH aliphatic), 1705, 1630 (C=O, diaryl), 1605 (C=N), 1519 (C-N), 1481 (C-C, aromatic), 1329 (C=S), 1212-1024 (C-O-C), 1101 (C-O), 732, 584 (for substituted benzene), 691 (C-S); 1H-NMR (CDCl3, 400 MHz,): δ = 8.25 - 7.25 (4H, m, H-4, H-5, H-7, H-8, -CH for substituted quinoline), 7.97 (1H, s, Ar-OH, -intra), 7.85 (1H, d, J = 7.8 Hz, -NH), 7.2-7.78 (7H, m, H-3’, H-6’, H-2”, H-3”, H-4”, H-5”, H-6”, Ar-H), 7.01 (2H, s, -CSNH2), 6.76 (1H, s, Ar-OH), 5.96 (1H, dd, J = 10.5, 3.5 Hz, -CHNH), 4.08 (3H, s, -OMe); 13C NMR (CDCl3, 400 MHz,): δ = 203.1 (C, -C=O, benzoyl), 176.5 (C, NHCSNH2), 166.0 (C-4’, Ar-OH), 158.7(C-2’, Ar-OH), 155.8 (C-6, C-OCH3), 152.1 (C-2, C-Cl), 150.0 (C, C-10), 135.4 (C, C-1”), 135.2 (C, C-9), 133.3 (C, C-8), 132.9 (C, C-4), 132.4 (C, C-1’), 131.9 (C, C-6), 131.7 (2C, C-2” & C-6”), 1128.6 (C, C-4’), 124.0 (2C, C-3” & C-5”), 122.1 (C, C-5’), 112.9 (C, C-5), 112.4 (C, C-3), 103.9 (C, C-7), 103.5 (C, C-3”), 57.4 (C, -OCH3), 55.2 (C, aliphatic-CH); EI-MS m/z: 493 (M+1)+; Anal. Calc. for C25H20ClN3O4S (%): C, 60.79; H, 4.08; N, 8.51%; found: C, 60.72; H, 4.03; N, 8.47%.
2-((5-benzoyl-2,4-dihydroxyphenyl) (2-chloro-6-methoxyquinolin-3-yl) methyl) hydrazine carboxamide (4c)
It was obtained as yellowish green solid color, yield: 82%; decomposition temperature 260˚C - 264˚C; IR (KBr, υmax/cm−1): 3463, 3440 (Ar-OH), 3198 (-NH), 3072 (CH, aromatic), 2974, 741 (CH aliphatic), 1705, 1629 (C=O, diaryl), 1605 (C=N), 1519 (C-N), 1481 (C-C, aromatic), 1212-1024 (C-O-C), 1101 (C-O), 732, 584 (for substituted benzene); 1H-NMR (CDCl3, 400 MHz,): δ = 8.25 (1H, s, Ar-OH, -intra), 7.97-7.55 (4H, m, H-4, H-5, H-7, H-8, -CH for substituted quinoline), 7.84 (1H, d, J = 7.8Hz, -NHNHCO-), 7.68-7.15 (7H, m, H-3’, H-6’, H-2”, H-3”, H-4”, H-5”, H-6”, Ar-H), 7.45 (1H, d, J = 8.1 Hz, -NHNHCO), 7.44 (2H, s, -CONH2), 7.03 (1H, s, Ar-OH), 6.69 (1H, dd, J = 10.5, 3.5 Hz, -CHNH), 3.96 (3H, s, -OMe); 13C NMR (CDCl3, 400 MHz,): δ = 203.1 (C, -C=O, benzoyl), 163.9 (C-4’, Ar-OH), 160.1 (C-2’, Ar-OH), 159.4 (C, -NHNHCONH2), 155.2 (C-6, C-OCH3), 150.7 (C-2,C-Cl), 148.1 (C, C-10), 132.4 (C, C-1”), 132.2 (C, C-9), 132.0 (C, C-8), 131.8 (C, C-4”), 131.4 (C, C-1’), 131.2 (C, C-6), 130.3 (2C, C-2” & C-6”), 128.8 (C, C-4), 122.4 (2C, C-3” & C-5”), 119.9 (C, C-5’), 109.2 (C, C-5), 107.9 (C, C-3’), 104.1 (C, C-7), 101.1 (C, C-3), 55.2 (C, -OCH3), 51.2 (C, aliphatic-CH); EI-MS m/z: 492 (M+1)+; Anal. Calc. for C25H21ClN4O5 (%): C, 60.92; H, 4.29; N, 11.37; %; found: C, 60.89; H, 4.22; N, 11.32%.
2-((5-benzoyl-2,4-dihydroxyphenyl) (2-chloro-6-methoxyquinolin-3-yl) methyl) hydrazinecarbothioamide (4d)
It was obtained as pale yellow color, yield: 86%; decomposition temperature 176˚C - 180˚C; IR (KBr, υmax/cm−1): 3463, 3440 (Ar-OH), 3198 (-NH), 3072 (CH, aromatic), 2974, 741 (CH aliphatic), 1705, 1633 (C=O, diaryl), 1605 (C=N), 1519 (C-N), 1481 (C-C, aromatic), 1329 (C=S), 1212-1024 (C-O-C), 1101 (C-O), 732, 584 (for substituted benzene), 690 (C-S); 1H-NMR (CDCl3, 400 MHz): δ = 8.20-7.14 (4H, m, H-4, H-5, H-7, H-8, -CH for substituted quinoline), 7.98 (2H, s, -CSNH2), 7.85 (1H, s, Ar-OH, -intra), 7.78-6.48 (7H, m, H-3’, H-6’, H-2”, H-3”, H-4”, H-5”, H-6”, Ar-H), 7.44 (1H, dd, J = 7.8Hz, -NHNHCS-), 6.99 (1H, dd, J = 8.1 Hz, -NHNHCS-), 6.79 (1H, s, Ar-OH), 6.00 (1H, dd, J = 10.5, 3.5 Hz, -CHNH), 3.96 (3H, s, -OMe); 13C NMR (CDCl3, 400 MHz): δ = 203.13 (C, -C=O, benzoyl), 176.1 (C, -NHNHCSNH2), 166.7 (C-4’, Ar-OH), 158.8 (C-2’, Ar-OH), 155.8 (C-6, C-OCH3), 152.9 (C-2, C-Cl), 150.2 (C, C-10), 135.3 (C, C-1”), 135.2 (C, C-9), 133.1 (C, C-8), 132.6 (C, C-4”), 132.3 (C, C-1’), 131.4 (C, C-6’), 131.0 (2C, C-2” & C-6”), 128.4 (C, C-4), 124.8 (2C, C-3” & C-5”), 122.9 (C, C-5’), 112.6 (C, C-5), 112.1 (C, C-3), 103.4 (C, C-7), 103.2 (C, C-3’), 57.4 (C, -OCH3), 55.2 (C, aliphatic-CH-); EI-MS m/z: 508 (M+1)+; Anal. Calc. for C25H21ClN4O4S (%): C, 58.99; H, 4.16; N, 11.01; %. found: C, 58.93; H, 4.12; N, 10.06%.
N-((5-benzoyl-2,4-dihydroxyphenyl) (2-chloro-6-methoxyquinolin-3-yl) methyl) acetamide (4e)
It was obtained as yellowish green color, yield: 89%; decomposition temperature 216˚C - 220˚C; IR (KBr, υmax/cm−1): 3463, 3440 (Ar-OH), 3198 (-NH), 3072 (CH, aromatic), 2974, 741, 650 (CH aliphatic), 1705, 1628 (C=O, diaryl), 1605 (C=N), 1519 (C-N), 1481 (C-C, aromatic), 1212-1024 (C-O-C), 1101 (C-O), 732, 584 (for substituted benzene); 1H-NMR (CDCl3, 400 MHz): δ = 8.85-6.83 (4H, m, H-4, H-5, H-7, H-8, -CH for substituted quinoline), 7.87 (1H, s, Ar-OH), 7.84 (1H, d, J = 7.8 Hz, -NHCO-), 7.68-6.78 (7H, m, H-3’, H-6’, H-2”, H-3”, H-4”, H-5”, H-6”, Ar-H), 6.47 (1H, s, Ar-OH), 6.60 (1H, dd, J = 10.5, 3.5 Hz, -CHNH), 4.00 (3H, s, -OMe), 1.84 (3H, s, -CH3); 13C NMR (CDCl3, 400 MHz): δ = 203.1 (C, -C=O, benzoyl), 169.4 (C, C=O, acetamide), 166.5 (C-4’, Ar-OH), 157.9 (C-2’, Ar-OH), 154.2 (C-6, C-OCH3), 152.0 (C-2, C-Cl), 150.2 (C, C-10), 135.4 (C, C-1”), 135.3 (C, C-9), 132.3 (C, C-8), 132.0 (C, C-4”), 131.6 (C, C-1’), 130.1 (C, C-6’), 129.8 (2C, C-2” & C-6”), 128.1 (C, C-4), 124.7 (2C, C-3” & C-5”), 122.8 (C, C-5’), 112.1 (C, C-5), 109.8 (C, C-3), 102.6 (C, C-7), 102.2 (C, C-3), 55.2 (C, -OCH3), 39.3 (C, aliphatic-CH), 23.9 (C,-CH3); EI-MS m/z: 476 (M+1)+; Anal. Calc. for C26H21ClN2O5 (%): C, 65.48; H, 4.44; N, 5.87%; found: C, 65.46; H, 4.41; N, 5.82%.
N-((5-benzoyl-2,4-dihydroxyphenyl) (2-chloro-6-methoxyquinolin-3-yl) methyl) benzamide (4f)
It was obtained as yellowish green color, yield: 85%; decomposition temperature 188˚C - 192˚C; IR (KBr, υmax/cm−1): 3463, 3440 (Ar-OH), 3198 (-NH), 3072 (CH, aromatic), 2974, 741 (CH aliphatic), 1705, 1627 (C=O, diaryl), 1605 (C=N), 1519 (C-N), 1481 (C-C, aromatic), 1212-1024 (C-O-C), 1101 (C?O), 732, 584 (for substituted benzene); 1H?NMR (CDCl3, 400 MHz): δ = 9.23 (1H, d, NH), 7.14-8.20 (4H, m, H-4, H-5, H-7, H-8,-CH for substituted quinoline), 6.48-8.03 (12H, m, H-3’, H-6’, H-2”, H-3”, H-4”, H-5”, H-6”, H-2”’, H-3”’, H-4”’, H-5”’, H-6”’, Ar-H), 6.16 (1H, dd, J = 10.5, 3.5Hz, -CHNH), 5.35 (2H, s, Ar-OH), 3.83 (3H, s, -OMe); 13C NMR (CDCl3, 400 MHz): δ = 203.1 (C, -C=O, benzoyl), 168.1 (C, -C=O, NHCOC6H5), 166.6 (C-4’, Ar-OH), 157.9 (C-2’, Ar-OH), 154.2 (C-6, C-OCH3), 152.0 (C-2, C-Cl), 150.2 (C, C-10), 137.1 (C, C-1”), 135.4 (C, C-9), 135.0 (C, C-8), 132.2 (C, C-4”), 131.6 (C, C-4”’), 130.7 (C, C-1’), 130.1 (C, C-6), 129.9 (2C , C-2” & C-6”), 129.8 (C, C-4), 129.5 (2C, C-3”’ & C-5”’), 128.1 (2C, C-2’” & C-6”’), 126.4 (C, C-5’), 124.2, (C,C-3” & C-5”) 122.8 (C, C-1”’), 111.6 (C, C-5), 109.8 (C, C-3), 102.6 (C, C-7), 102.2 (C, C-3’ & C-6’), 55.2 (C, -OCH3), 41.5 (C, aliphatic-CH); EI-MS m/z: 538 (M+1)+; Anal. Calc. for C31H23ClN2O5 (%): C, 69.08; H, 4.30; N, 5.20%; found: C, 69.01; H, 4.27; N, 5.17%.
All the newly synthesized compounds were evaluated for their in vitro antitubercular activity at the Tuberculosis Acquisition Antimicrobial Coordinating Facility (TAACF) screening program, Alabama, USA. Minimum inhibitory concentration (MIC) was determined against Mycobacterium tuberculosis H37Rv by using the radiometric BACTEC [
The promising results obtained on 2-chloro-6-methoxyquinoline-3-carboxaldehyde, 2,4-dihydroxybenzophe-
Compounds | R | Molecular Formula | MIC µg/mL | % Inhibition |
---|---|---|---|---|
4a | CONH2 | C25H20ClN3O5 | >6.25 | 71 |
4b | CSNH2 | C25H20ClN3O4S | >6.25 | 95 |
4c | NHCONH2 | C25H21ClN4O5 | >6.25 | 79 |
4d | NHCSNH2 | C25H21ClN4O4S | >6.25 | 94 |
4e | COCH3 | C26H21ClN2O5 | >6.25 | 55 |
4f | COC6H5 | C31H23ClN2O5 | >6.25 | 68 |
none and various amides using 1 M EAN as catalyst at the 80˚C temperature encouraged us to investigate the feasibility of solvent-free MCRs protocol to a wide range of chloro substituted aldehydes, amides/carbamates/ urea and 2,4-dihydroxybenzophenone for the synthesis of new Mannich products 4(a-f).
A bromo derivative of hetrocyclic aldehydes, amides/carbamates/urea possessing various electron donating and electron withdrawing functional groups reacted smoothly with 2,4-dihydroxybenzophenone under neat reaction conditions to give desired products in excellent yields over EAN at 80˚C temperature. The results illustrate that the one-pot three component condensation reactions show excellent performance irrespective of the presence of electron withdrawing or electron donating groups on aromatic/hetrocyclic aldehydes and hence solvent- free MCRs protocol is highly effective, promising and general for the synthesis of new Mannich products 4a-f. The substituted aromatic aldehydes with electron withdrawing group reacted with 2,4-dihydroxybenzophe-none and different amides provided desired products in excellent yields. The recovery and recyclability of EAN was still investigated for the synthesis of new Mannich products 4(a-f) by one-pot three component condensations of above said aldehyde, phenol and different amide as model substrates in the presence of EAN is under progress. The high yield of new Mannich products 4(a-f) using EAN at milder reaction condition compared to other ionic liquid can be rationalized due to high acidity associated with it (pH = 5) along with its capacity to absorb water formed during course of the reaction.
All the synthesized compounds 4(a-f) were purified by re-crystallization with suitable solvents and characterized by spectral FT-IR, 1H-NMR, 13C-NMR and elemental analysis. The results of elemental analyses of each new Mannich products 4(a-f) were consistent with the predicted structure, as shown in Scheme 1 and
The results from in vitro antitubercular screening against Mycobacterium tuberculosis H37Rv were very much encouraging. It may be predicted that Mannich base linkange would increase the lipophilicity of molecule hence help molecule to penetrate in the mycobacterium cell wall, and quinoline would generate reactive oxygen species. The compounds 4b and 4d found most active with percentage inhibition of 95 and 94, respectively, at minimum inhibitory concentration (MIC) of 6.25 µg/mL, among the synthesized compounds. Whereas, compounds 4a, 4c, 4d, and 4e, exhibited considerable antitubercular activity with percentage inhibition of 71, 79, 55, and 68, respectively, at MIC of >6.25 µg/mL. On evaluation of antitubercular screening data, it can be seen that extent of percentage inhibition is largely affected by the type of substitutions at phenyl ring irrespective of positions of substitution. Electron withdrawing group at phenyl ring considerably enhanced the antitubercular activity whereas electron releasing groups on phenyl ring strongly diminished the antitubercular activity, which can be evident by antitubercular screening results.
In the present paper, we report the synthesis, characterization and antitubercular activity of new Mannich products bearing quinoline moiety. The results indicate that quinoline moiety with increased lipophilicity and ability of Benzophenone to general reactive oxygen species make the molecule suitable candidate against Mycobacterium tuberculosis. The promising results from antitubercular screening make quinoline moiety as important class in the area of tuberculosis research. Moreover, incorporation of quinoline moiety will offer new possibilities of this class apart from conventional biological activities.
This work was funded by University Grant Commission, New Delhi, and File No. 41-300/2012 (SR). The authors wish to thank UGC for its financial support to the scheme. The authors are indebted to Micro Care Lab for biological tests. Authors are also thankful to C.V.M. for providing research facility.
Hitendra M. Patel, (2015) Synthesis of New Mannich Products Bearing Quinoline Nucleous Using Reusable Ionic Liquid and Antitubercular Evaluation. Green and Sustainable Chemistry,05,137-144. doi: 10.4236/gsc.2015.54017