SYNTHESIS OF NEW ACETAMIDE-CONJUGATED MONOBACTAM ANTIBIOTICS
HTML Full TextSYNTHESIS OF NEW ACETAMIDE-CONJUGATED MONOBACTAM ANTIBIOTICS
Venkateshwarlu Jetti *, Praveen Chidurala and Jyotsna S. Meshram
Department of Chemistry, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur – 440033, Maharashtra, India
ABSTRACT: In the present work, we have synthesized a new analoges of monocyclic β-lactam (2-(3-(2, 4-dichlorophenoxy)-2-(substituted aryl) - 4-oxoazetidin – 1 - ylamino) – N - (pyridin-2-yl) acetamide) derivatives in the presence of triethyl amine (TEA) and phosphorus oxychloride (POCl3) under classical method by using Dichloromethane (DCM) as a solvent. The designed compounds 4(a-l) were prepared by Staudinger reaction ([2+2] ketene-imine cycloaddition reactions). In which an azetidin-2-one motif connects with pyridine-2-acetamide nucleus with two aromatic rings. The target compounds were screened for in vitro antibacterial activity against clinically relevant Gram-negative (Escherichia coli and Klebsiella pneumonia) and Gram-positive species (Bacillus subtilis, Proteus vulgaris and Staphylococcus aureus). The obtained results have demonstrated that all the synthesized imidazole-conjugated monocyclic β-lactam derivatives showed good antibacterial activity. Particularly the compounds 4e and 4l found to be effective in P.vulgaris as equal to reference ampicillin and other compounds showed moderate to good activity against five human bacterial pathogens. All these compounds have been characterized by IR, 1H-NMR, 13C-NMR, Mass spectrometry and Elemental data.
Keywords: |
Pyridin-2-amine, Schiff base, monobactam (β-lactam) and antibacterial activity
INTRODUCTION: The β-lactam nucleus has fascinated synthetic and medicinal chemists worldwide because of its biological significance and synthetic potential.1-2 β-lactam form a class of antibiotics characterized by the presence of an azetidine-2-one ring, which is the core structure responsible for biological activity.3 The β-lactam ring is a common structural feature of a number of broad spectrum β-lactam antibiotics, including penicillins, cephalosporins, carbapenems.
It also exhibit some other biological activities, for which they are considered as enzyme inhibitors,4 potential chemo and neurotherapeutic drugs,5 Penicillin Binding Protein,6 human cytomegalovirus protease inhibitors,7 anti-hyperglycemic,8 antimalarial,9 anti-tumor,10 cholesterol absorption inhibitors,11 anti-HIV,12 protozoal,13 anti-inflammatory, antimicrobial, 14-16 cytotoxic17 and anticancer.18
he β-lactams have also been employed in the preparation of bis-β-lactams, pyrrolizidines, indolizidines, pyrrolidines, piperidines, cyclic enaminones, pyridones, oxazinones, and complex natural products through N1–C2 bond cleavage coupled with rearrangement reactions. However, microorganisms have built up resistance against the most traditional β-lactam antibiotics due to excess use of antibiotics.
Therefore there arises need to modify the structure of known active compounds and the development of new ones. Our research group has been largely involved in the synthesis of monocyclic β-lactam derivatives19-21 through Staudinger reaction ([2+2] ketene-imine cycloaddition reaction).
MATERIALS AND METHODS:
Materials: All the chemicals and solvents were used AR grade without further purification. Melting points were taken in an open capillary tube. IR spectra were recorded on a Shimadzu Dr-8031 instrument. 1H NMR spectra of the titled compounds were recorded on a Bruker-Avance (300 MHz) spectrophotometer using DMSO solvent and TMS as the internal standard. Elemental analyses were carried out using a Perkin-Elmer, CHN elemental analyzer model 2400. EI-MS spectra were determined on a LCQ ion trap mass spectrometer (Thermo Fisher, San Jose, CA, USA), equipped with an EI source. The reactions were monitored and the purity of products was checked out on pre-coated TLC plates (Silica gel 60 F254, Merck), visualized the spots under ultraviolet light and iodine chamber.
Biology:
The synthesized compounds were screened by agar diffusion method. All human pathogenic bacteria viz. Bacillus subtilis, Proteus vulgaris, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, were obtained from the Osmania University, Hyderabad, India. Stock solutions of compounds were diluted in dimethyl sulfoxide (DMSO) to give a final concentration for determining the Minimum inhibitory concentration (MIC) value. About 9 ml of nutrient agar media were poured into petri plates (9cmin diameter) and inoculated with respective test organism. Wells were made with cork borer on the solid agar and loaded with 100 mg/ml of the test compound with Ampicillin as control. Petri dishes were incubated at 37 0C for 24 h and the average diameter of the inhibition zone surrounding the wells was measured after specified incubation period.
METHOD:
General procedure for the synthesis of Schiff base 3(a-l): A quantity of 0.02 mol of aryl-aldehyde, 0.02 mol of 2-hydrazinyl-N-arylacetamide (2) and 2-3 drops of glacial acetic acid in 20 ml of ethanol was refluxed for ~1h. The reaction was monitored by TLC. After completion of the reaction, the residue was stirred with ice cold water, filtered and dried. The crude product obtained was purified by n-hexane and EtOAc.
(3a): Yield 75%; m.p. 162 0C; Chemical formula: C14H14N4O; IR (KBr, cm-1): 3125 (NH), 1589 (CONH), 1545 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.55 (s, 1H, NH), 3.6 (s, 2H, CH2), 6.7-7.7 (m, 9H, Ar-H), 8.48 (s, 1H, CONH), 8.71 (s, 1H, -CH=N-); 13C NMR: δ 54.2 (-CH2), 143.2 (N=CH), 167.8 (C=O), Aromatic carbons: 115.6, 119.3, 128.1, 130.5, 138.1, 146.2, 150.4; Elemental analysis: Calcd (found): C, 66.13 (66.22); H, 5.55 (5.47); N, 22.03 (22.11); Mass spectra, m/z = 254 (100%).
(3b): Yield 80%; m.p. 175 0C; Chemical formula: C14H14N4O2; IR (KBr, cm-1): 3118 (NH), 1608 (CONH), 1552 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.51 (s, 1H, NH), 3.65 (s, 2H, CH2), 6.5-7.8 (m, 8H, Ar-H), 8.51 (s, 1H, CONH), 8.75 (s, 1H, -CH=N-), 11.7(s, 1H, OH); 13C NMR: δ 143.5 (N=CH), 161.5 (OH-C), 53.8 (-CH2), 168.9 (C=O), Aromatic carbons: 116.1, 119.7, 128.5, 129.9, 138.4, 146.5,150; Elemental analysis: Calcd (found): C, 62.21 (62.15); H, 5.22 (5.29); N, 20.73 (20.64); Mass spectra, m/z = 270 (100%).
(3c): Yield 82%; m.p. 192 0C; Chemical formula: C16H19N5O; IR (KBr, cm-1): 3084 (NH), 1650 (CONH), 1554 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.50 (s, 1H, NH), 4.21 (s, 2H, CH2), 2.92 (s, 6H, -N(CH3)2), 6.6-7.9 (m, 8H, Ar-H), 8.49 (s, 1H, CONH), 8.19 (s, 1H, -CH=N-); 13C NMR: δ 41.5 (-CH3), 55.0 (-CH2), 147.7 (N=CH), 164.8 (C=O), Aromatic carbons: 114.5, 121.5, 125.7, 127.8, 129.7, 130.0, 136.3, 138.5; Elemental analysis: Calcd (found): C, 64.63 (64.71); H, 6.44 (6.36); N, 23.55 (23.62); Mass spectra, m/z = 297 (100%).
(3d): Yield 65%; m.p. 187 0C; Chemical formula: C15H16N4O2; IR (KBr, cm-1): 3097 (NH), 1625 (CONH), 1531 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.55 (s, 1H, NH), 3.69 (s, 2H, CH2), 3.78 (s, 3H, OCH3), 6.5-7.7 (m, 8H, Ar-H), 8.37 (s, 1H, CONH), 8.64 (s, 1H, -CH=N-); 13C NMR: δ 54.5 (-CH2), 55.3 (-OCH3), 143.6 (N=CH), 168.5 (C=O), Aromatic carbons: 114.2, 115.3, 119.7, 126.5, 130, 138.2, 146.6, 150.3, 163.4; Elemental analysis: Calcd (found): C, 63.37 (63.29); H, 5.67 (5.62); N, 19.71 (19.80); Mass spectra, m/z = 284 (100%).
(3e): Yield 75%; m.p. 196 0C; Chemical formula: C12H12N4O2; IR (KBr, cm-1): 3138 (NH), 1605 (CONH), 1550 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.49 (s, 1H, NH), 3.65 (s, 2H, CH2), 6.5-7.9 (m, 7H, Ar-H), 8.52 (s, 1H, CONH), 8.51 (s, 1H, -CH=N-); 13C NMR: δ 53.3 (-CH2), 134.2 (N=CH), 168.7(C=O), Aromatic carbons: 109.3, 110.1, 115.4, 120.3, 138.7, 143.4, 146.8, 149.1, 150.4; Elemental analysis: Calcd (found): C, 59.01 (59.07); H, 4.95 (4.85); N, 22.94 (23.03); Mass spectra, m/z = 244 (100%).
(3f): Yield 80%; m.p. 182 0C; Chemical formula: C15H16N4O; IR (KBr, cm-1): 3172 (NH), 1636 (CONH), 1539 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.56 (s, 1H, NH), 3.53 (s, 2H, CH2), 2.54 (s, 3H, CH3), 6.6-7.8 (m, 8H, Ar-H), 8.61 (s, 1H, CONH), 8.57 (s, 1H, -CH=N-); 13C NMR: δ 24.5 (-CH3), 54.7 (-CH2), 140.9 (N=CH), 168.7 (C=O), Aromatic carbons: 115.3, 119.2, 128, 129.5, 131.4, 138.5, 140.7, 146.6, 150.8; Elemental analysis: Calcd (found): C, 67.15 (67.07); H, 6.01 (6.09); N, 20.88 (20.74); Mass spectra, m/z = 268 (100%).
(3g): Yield 74%; m.p. 177 0C; Chemical formula: C14H13N5O3; IR (KBr, cm-1): 3193 (NH), 1662 (CONH), 1559 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.55 (s, 1H, NH), 3.7 (s, 2H, CH2), 6.6-7.8 (m, 8H, Ar-H), 8.62 (s, 1H, CONH), 8.8 (s, 1H, -CH=N-); 13C NMR: δ 143.8 (N=CH), 54.5 (-CH2), 168.2 (C=O), Aromatic carbons: 115.4, 119.4, 121.2, 130.5, 138, 140.4, 146.6, 150.2; Elemental analysis: Calcd (found): C, 56.18 (56.28); H, 4.38 (4.24); N, 23.40 (23.48); Mass spectra, m/z = 299 (100%).
(3h): Yield 82%; m.p. 180 0C; Chemical formula: C14H14N4O2; IR (KBr, cm-1): 3145 (NH), 1653 (CONH), 1522 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.47 (s, 1H, NH), 3.75 (s, 2H, CH2), 6.5-7.8 (m, 8H, Ar-H), 8.55 (s, 1H, CONH), 8.71 (s, 1H, -CH=N-), 11.5(s, 1H, OH); 13C NMR: δ 143.1 (N=CH), 161.9 (OH-C), 53.4 (-CH2), 168.3 (C=O), Aromatic carbons: 116.4, 119.2, 128.9, 130, 138.1, 146.9,150.5; Elemental analysis: Calcd (found): C, 62.21 (62.3); H, 5.22 (5.15); N, 20.73 (20.77); Mass spectra, m/z = 270 (100%).
(3i): Yield 71%; m.p. 189 0C: Chemical formula: C14H13ClN4O; IR (KBr, cm-1): 3167 (NH), 1668 (CONH), 1565 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.5 (s, 1H, NH), 3.7 (s, 2H, CH2), 6.5-7.7 (m, 8H, Ar-H), 8.59 (s, 1H, CONH), 8.88 (s, 1H, -CH=N-); 13C NMR: δ 54.7 (-CH2), 143.5 (N=CH), 168.8 (C=O), Aromatic carbons: 115.9, 119.4, 120, 130.7, 151.5, 136.2, 138.9, 146.6, 151.3; Elemental analysis: Calcd (found): C, 58.24 (58.17); H, 4.54 (4.45); N, 19.40 (19.54); Mass spectra, m/z = 288 (100%).
(3j): Yield 74%; m.p. 181 0C; Chemical formula: C14H13N5O3; IR (KBr, cm-1): 3134 (NH), 1634 (CONH), 1572 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.59 (s, 1H, NH), 3.64 (s, 2H, CH2), 6.5-7.9 (m, 8H, Ar-H), 8.66 (s, 1H, CONH), 8.74 (s, 1H, -CH=N-); 13C NMR: δ 53.7 (-CH2), 142.8 (N=CH), 167.6 (C=O), Aromatic carbons: 114.7, 119.5, 123.6, 125.4, 129.4, 134.3, 135.6, 138.4, 146.7, 148.5, 150; Elemental analysis: Calcd (found): C, 56.18 (56.14); H, 4.38 (4.46); N, 23.40 (23.33); Mass spectra, m/z = 299 (100%).
(3k): Yield 72%; m.p. 185 0C;Chemical formula: C15H16N4O; IR (KBr, cm-1): 3142 (NH), 1668 (CONH), 1532 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.46 (s, 1H, NH), 3.57 (s, 2H, CH2), 2.5 (s, 3H, CH3), 6.5-7.7 (m, 8H, Ar-H), 8.67 (s, 1H, CONH), 8.52 (s, 1H, -CH=N-); 13C NMR: δ 24.1 (-CH3), 54.9 (-CH2), 141.5 (N=CH), 168.2 (C=O), Aromatic carbons: 114.9, 118.8, 128.5, 129.2, 131.9, 138.1, 140.9, 145.3, 151.2; Elemental analysis: Calcd (found): C, 67.15 (67.23); H, 6.01 (6.05); N, 20.88 (20.77); Mass spectra, m/z = 268 (100%).
(3l): Yield 78%; m.p. 177 0C; Chemical formula: C16H18N4O3;; IR (KBr, cm-1): 3158 (NH), 1691 (CONH), 1561 (-CH=N-); 1H NMR (300 MHz, CDCl3) δ (ppm) = 2.49 (s, 1H, NH), 3.7 (s, 2H, CH2), 3.82 (s, 6H, OCH3), 6.5-7.8 (m, 7H, Ar-H), 8.59 (s, 1H, CONH), 8.65 (s, 1H, -CH=N-); 13C NMR: δ 54.4 (-CH2), 56.3 (-OCH3), 142.5 (N=CH), 169.1 (C=O), Aromatic carbons: 100.4, 106.3, 109.8, 115.2, 119.6, 131.2, 138.8, 146.6, 150.4, 161.5, 164.7; Elemental analysis: Calcd (found): C, 61.13 (61.05); H, 5.77 (5.85); N, 17.82 (17.76); Mass spectra, m/z = 314 (100%).
General Procedure for the synthesis of β-lactam 4(a-l):
The appropriate Schiff base (0.02 mol), 2,4-dichlorophenoxy aceticacid (0.02 mol) and triethylamine (0.05 mol) was stirred in anhydrous dichloromethane (DCM), while a solution of POCl3 (0.02 mol) in dry dichloromethane was added drop wise. The reaction mixture was stirred for ~14h. The completion of the reaction was monitored by TLC. The reaction mixture was washed with water and dried over sodium sulphate. The products obtained 4(a-l) after removing the solvent was purified from ethyl acetate and n-hexane.
(4a): Yield 72%; m.p. 188 0C; Chemical formula: C22H18Cl2N4O3; IR (KBr, cm-1): 3092 (NH), 1602 (CONH), 1732 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.21 (s, 1H, NH), 3.62 (s, 2H, CH2), 5.35 (d, 1H, CH-Ar, β-lactam), 5.85 (d, 1H, CH-CO, β-lactam), 6.5-7.7 (m, 12H, Ar-H), 8.51 (s, 1H, CONH); 13C NMR: δ 52.7 (-CH2), 59.8, 89.5, 168.9 (C=O), 173.2 (C=O), Aromatic carbons: 115.4, 117.6, 119.8, 124.2, 127.3, 126.6, 131, 138.5, 143.1, 146.8, 150.2; Elemental analysis: Calcd (found): C, 57.78 (57.69); H, 3.97 (3.90); N, 12.25 (12.33); Mass spectra, m/z = 456 (100%).
(4b): Yield 77%; m.p. 195 0C; Chemical formula: C22H18Cl2N4O4; IR (KBr, cm-1): 3060 (NH), 1612 (CONH), 1725 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.32 (s, 1H, NH), 3.56 (s, 2H, CH2), 5.30 (d, 1H, CH-Ar, β-lactam), 5.75 (d, 1H, CH-CO, β-lactam), 6.5-7.6 (m, 11H, Ar-H), 8.57 (s, 1H, CONH), 11.45 (s, 1H, -OH); 13C NMR: δ 52.3 (-CH2), 60.1, 90.4, 168.2 (C=O), 173.8 (C=O), 154.2 (OH), Aromatic carbons: 115.6, 117.2, 119.9, 121.2, 124.4, 127.7, 130.5, 131.1, 138.7, 146.4, 149.2; Elemental analysis: Calcd (found): C, 55.83 (55.69); H, 3.83 (3.95); N, 11.84 (11.73); Mass spectra, m/z = 472 (100%).
(4c): Yield 76%; m.p. 202 0C; Chemical formula: C24H23Cl2N5O3; IR (KBr, cm-1): 3080 (NH), 1624 (CONH), 1747 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.05 (s, 6H, -N(CH3)2), 3.41 (s, 1H, NH), 4.12 (s, 2H, CH2), 5.19 (d, 1H, CH-Ar, β-lactam), 4.91 (d, 1H, CH-CO, β-lactam), 6.55-7.83 (m, 11H, Ar-H), 8.45 (s, 1H, CONH); 13C NMR: δ 41.1 (CH3), 49.3 (-CH2), 53.4, 64.8, 166.9 (C=O), 170.1 (C=O), Aromatic carbons: 113.0, 115.5, 122.3, 123.3, 124.8, 125.2, 126.2, 127.1, 128.8, 146.7, 147.2, 152.1; Elemental analysis: Calcd (found): C, 57.61 (57.68); H, 4.63 (4.52); N, 14.0 (14.11); Mass spectra, m/z = 499 (100%).
(4d): Yield 67%; m.p. 192 0C; Chemical formula: C23H20Cl2N4O4; IR (KBr, cm-1): 3072 (NH), 1656 (CONH), 1754 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.25 (s, 1H, NH), 3.59 (s, 2H, CH2), 5.4 (d, 1H, CH-Ar, β-lactam), 5.72 (d, 1H, CH-CO, β-lactam), 3.83 (s, 3H, -OCH3), 6.5-7.7 (m, 11H, Ar-H), 8.5 (s, 1H, CONH); 13C NMR: δ 52.6 (-CH2), 55.4 (-OCH3), 59.5, 89.4, 168.1 (C=O), 174.1 (C=O), Aromatic carbons: 114.4, 115.5, 117.2, 124.1, 128.4, 131, 135.3, 146.6, 149.6, 159.2; Elemental analysis: Calcd (found): C, 56.69 (56.54); H, 4.14 (4.22); N, 11.50 (11.57); Mass spectra, m/z = 486 (100%).
(4e): Yield 65%; m.p. 210 0C; Chemical formula: C20H16Cl2N4O4; IR (KBr, cm-1): 3089 (NH), 1636 (CONH), 1755 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.28 (s, 1H, NH), 3.45 (s, 2H, CH2), 5.51 (d, 1H, CH-Ar, β-lactam), 5.76 (d, 1H, CH-CO, β-lactam), 6.6-7.9 (m, 10H, Ar-H), 8.51 (s, 1H, CONH); 13C NMR: δ 51.7 (-CH2), 57.2, 87.4, 168.5 (C=O), 173.9 (C=O); Aromatic carbons: , 105.5, 110.2, 115.7, 119.4, 124.4, 127.3, 131.6, 138.9, 141.5, 146.3, 149.3, 151.1; Elemental analysis: Calcd (found): C, 53.71 (53.78); H, 3.61 (3.73); N, 12.53 (12.46); Mass spectra, m/z = 446 (100%).
(4f): Yield 75%; m.p. 197 0C; Chemical formula: C23H20Cl2N4O3; IR (KBr, cm-1): 3094 (NH), 1625 (CONH), 1761 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.32 (s, 1H, NH), 3.66 (s, 2H, CH2), 5.41 (d, 1H, CH-Ar, β-lactam), 5.79 (d, 1H, CH-CO, β-lactam), 6.6-7.94 (m, 11H, Ar-H), 8.51 (s, 1H, CONH), 2.50 (s, 3H, CH3); 13C NMR: δ 25.1 (-CH3), 52.7 (-CH2), 59.4, 90.2, 169.2 (C=O), 174.1 (C=O), Aromatic carbons: 115.6, 117.2, 119.8, 124.6, 126.1, 131.2, 136.7, 138.4, 140.4, 146.2, 149.7; Elemental analysis: Calcd (found): C, 58.61 (58.55); H, 4.28 (4.22); N, 11.89 (11.96); Mass spectra, m/z = 470 (100%).
(4g): Yield 64%; m.p. 202 0C; Chemical formula: C22H17Cl2N5O5; IR (KBr, cm-1): 3086 (NH), 1636 (CONH), 1755 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.28 (s, 1H, NH), 3.59 (s, 2H, CH2), 5.41 (d, 1H, CH-Ar, β-lactam), 5.76 (d, 1H, CH-CO, β-lactam), 6.6-7.9 (m, 11H, Ar-H), 8.51 (s, 1H, CONH); 13C NMR: δ 51.7 (-CH2), 59.9, 89.5, 168.4 (C=O), 173.9 (C=O), Aromatic carbons: 115.5, 117.6, 119.2, 121.2, 124.5, 127.4, 131, 138.2, 149.6; Elemental analysis: Calcd (found): C, 52.60 (52.66); H, 3.41 (3.35); N, 13.94 (13.86); Mass spectra, m/z = 501 (100%).
(4h) Yield 62%; m.p. 189 0C; Chemical formula: C22H18Cl2N4O4; IR (KBr, cm-1): 3034 (NH), 1615 (CONH), 1739 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.27 (s, 1H, NH), 3.63 (s, 2H, CH2), 5.46 (d, 1H, CH-Ar, β-lactam), 5.75 (d, 1H, CH-CO, β-lactam), 6.53-7.78 (m, 11H, Ar-H), 8.56 (s, 1H, CONH), 11.56 (s, 1H, -OH); 13C NMR: δ 51.8 (-CH2), 59.9, 89.4, 168.7 (C=O), 174.1 (C=O), 156.6 (OH), Aromatic carbons: 115.8, 117.4, 119.5, 124.2, 127.4, 127.3, 128.4, 130.1, 131.5, 136.3, 138.6, 146.1, 149.5; Elemental analysis: Calcd (found): C, 55.83 (55.90); H, 3.83 (3.76); N, 11.84 (11.93); Mass spectra, m/z = 472 (100%).
(4i): Yield 70%; m.p. 199 0C; Chemical formula: C22H17Cl3N4O3; IR (KBr, cm-1): 3027 (NH), 1663 (CONH), 1758 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.36 (s, 1H, NH), 3.69 (s, 2H, CH2), 5.39 (d, 1H, CH-Ar, β-lactam), 5.84 (d, 1H, CH-CO, β-lactam), 6.5-8.0 (m, 11H, Ar-H), 8.51 (s, 1H, CONH); 13C NMR: δ 52.4 (-CH2), 59.8, 89.3, 168.1 (C=O), 180 (C=O), Aromatic carbons: 115.4, 117.2, 119.6, 124.1, 127.8, 131, 132.4, 138.7, 141.5, 146.2, 150; Elemental analysis: Calcd (found): C, 53.73 (53.65); H, 3.48 (3.54); N, 11.39 (11.45); Mass spectra, m/z = 490 (100%).
(4j): Yield 67%; m.p. 208 0C; Chemical formula: C22H17Cl2N5O5; IR (KBr, cm-1): 3109 (NH), 1651 (CONH), 1766 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.25 (s, 1H, NH), 3.56 (s, 2H, CH2), 5.43 (d, 1H, CH-Ar, β-lactam), 5.81 (d, 1H, CH-CO, β-lactam), 6.6-7.8 (m, 11H, Ar-H), 8.51 (s, 1H, CONH); 13C NMR: δ 51.8 (-CH2), 58.5, 89.6, 167.5 (C=O), 172.3 (C=O), Aromatic carbons: 115.2, 117.8, 119.8, 122.2, 124.4, 127.3, 131.3, 133.1, 138.6, 144.2, 146.5, 149.3; Elemental analysis: Calcd (found): C, 52.60 (52.53); H, 3.41 (3.50); N, 13.94 (13.99); Mass spectra, m/z = 501 (100%).
(4k): Yield 65%; m.p. 210 0C; Chemical formula: C23H20Cl2N4O3; IR (KBr, cm-1): 3057 (NH), 1678 (CONH), 1772 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.21 (s, 1H, NH), 3.71 (s, 2H, CH2), 2.36 (s, 3H, CH3), 5.39 (d, 1H, CH-Ar, β-lactam), 5.8 (d, 1H, CH-CO, β-lactam), 6.65-8.27 (m, 11H, Ar-H), 8.51 (s, 1H, CONH); 13C NMR: δ 24.7 (CH3), 52.5 (-CH2), 60.1, 89.2, 168.6 (C=O), 173.9 (C=O), Aromatic carbons: 115.2, 117.2, 119.8, 124.2, 127.5, 128.5, 131.1, 143.5, 146.7, 149.6; Elemental analysis: Calcd (found): C, 58.61 (58.67); H, 4.28 (4.33); N, 11.89 (11.82); Mass spectra, m/z = 470 (100%).
(4l): Yield 63%; m.p. 197 0C; Chemical formula: C24H22Cl2N4O5; IR (KBr, cm-1): 3115 (NH), 1652 (CONH), 1748 (CO, β-lactam); 1H NMR (300 MHz, CDCl3) δ (ppm) = 3.28 (s, 1H, NH), 3.67 (s, 2H, CH2), 3.82 (s, 6H, OCH3), 5.32 (d, 1H, CH-Ar, β-lactam), 5.83 (d, 1H, CH-CO, β-lactam), 6.73-8.25 (m, 10H, Ar-H), 8.63 (s, 1H, CONH); 13C NMR: δ 50.2, 52.1 (-CH2), 55.9, 56.5 (OCH3), 90.2, 167.4 (C=O), 172.6 (C=O), Aromatic carbons: 102.2, 106.5, 115.8, 117.4, 119.8, 121.7, 124.3, 127.7, 129, 138.4, 146.6, 149.8, 157.6, 159.4; Elemental analysis: Calcd (found): C, 55.72 (55.78); H, 4.29 (4.23); N, 10.83 (10.92); Mass spectra, m/z = 516 (100%).
RESULTS AND DISCUSSION:
Chemistry:
Assembling N-heterocycles is important in synthetic organic chemistry. The development of highly efficient scaffolds for the preparation of pyridine-2-acetamide conjugated monobactam derivatives is of considerable interest. In the present work, we prepared a new series of monocyclic β-lactam derivatives in which an azetidin-2-one motif connects with pyridine-2-acetamide nucleus with two aromatic rings. The designed compounds 4(a-l) were prepared by the following Staudinger reaction ([2+2] cycloaddition reactions).22-23
The Preparation of new compounds 4(a-l) is depicted on Scheme 1. 2-chloro-N-(pyridin-2-yl) acetamide (1) was synthesized by pyridin-2-amine with chloroacetyl chloride. The model reaction was carried out simply treatment of 2-amino pyridine with chloroacetyl chloride in the presence of K2CO3 yielded 2-chloro-N-(pyridin-2-yl)acetamide (1). These compounds, on amination with hydrazine hydrate afforded 2-hydrazinyl-N-(pyridin-2-yl) acetamide (2).
The condensation reaction of compound 2 with aromatic aldehydes yielded 2-(2-(substituted arylidene)hydrazinyl)-N-(pyridine-2-yl)acetamide 3(a-l). The compounds 3(a-l), on reaction with 2,4-dichlorophenoxy acetic acid in the presence of POCl3 and triethylamine (TEA) afforded azetidinones 4(a-l). These reactions are summarized in Scheme 1. The progress of the reaction was monitored by TLC.
TABLE 1: ANTIMICROBIAL ACTIVITIES OF SYNTHESIZED COMPOUNDS 4(a-l)
Compd |
Concentration of compounds 100 µg/mlZone of inhibition (mm) | ||||
Gram +Ve | Gram -Ve | ||||
Bacillus subtilis | Proteus vulgaris | Staphylococcus aureus | Escherichia coli | Klebsiella pneumonia | |
4a | 15 | - | 17 | 20 | 21 |
4b | - | 18 | - | 14 | - |
4c | 19 | 24 | 15 | 28 | 25 |
4d | 29 | 32 | 33 | 32 | 33 |
4e | 35 | >40 | 36 | 29 | 31 |
4f | - | 25 | 26 | 30 | 28 |
4g | - | 4 | 9 | - | 3 |
4h | 25 | 24 | - | 25 | 23 |
4i | 32 | 25 | 33 | 31 | 34 |
4j | - | 12 | - | - | 15 |
4k | 6 | 14 | 22 | 25 | 14 |
4l | 35 | >40 | 36 | 35 | 28 |
Ampicillin | >40 | >40 | >40 | >40 | >40 |
Key to symbols: Inactive = (inhibition zone - mm); slightly active = (inhibition zone (1 to 20 mm); moderately active = (inhibition zone 21 to 30 mm); highly active = (inhibition zone >31 mm).
Biological activity:
Antibacterial activity of acetamide conjugated β-lactams (agar diffusion assay):
The antibacterial activity of the synthesized twelve β-lactam compounds against human bacterial (Gram +ve and Gram -ve) pathogens as determined by agar diffusion method with Ampicillin as reference control was investigated the maximum antimicrobial activity and inhibition zone were observed for compounds 4e, 4i and 4l against B. subtilis while compounds 4d and 4h showed moderate activity and all other compounds showed low activity against this pathogen. For P. vulgaris the compounds 4d, 4e and 4l showed good antibacterial activity as that of the reference
compound Ampicillin while 4c, 4f, 4h and 4i showed moderate activity the other compounds showed low activity against this pathogen. The compounds 4d, 4e, 4i and 4l showed very good activity against the bacteria S. aures while compounds 4f and 4k showed moderate activity.
For the pathogen E. coli the compounds 4d, 4i, and 4l showed good inhibitory activity, while 4c, 4e, 4f, 4h and 4k showed moderate activity and all other compounds showed low activity against this pathogen. For the pathogen K. pneumonia the compounds 4d, 4e and 4i showed good inhibitory activity, while 4e, 4f, 4h and 4l showed moderate activity and all other compounds showed low activity against this pathogen. The compounds containing methoxy, chloro and furon groups showed good activity against all the pathogens in given concentration, which is comparable to the reference control.
he derived compounds 4d, 4e, 4i and 4l were found to be effective in controlling all the test pathogens and particularly the compounds 4e and 4l found to be effective in P. vulgaris. The activity is very much comparable to the reference control. Further biological studies are required to validate the effective compounds of the present study as an antimicrobial agent. The results are summarized in Table 1 antibacterial activity against five human bacterial pathogens. The overall antibacterial activity of the synthesized compounds attributed in the presence of acetamide conjugated β-lactam substituted compounds.
SCHEME 1: SYNTHETIC ROUTE FOR 2-(3-(2, 4-DICHLOROPHENOXL)-2-(SUBSTITUTED ARYL)-4-OXOAZETIDIN-1-YLAMINO)-N-(PYRIDIN-2-YL) ACETAMIDE
SCHEME 2: MECHANISM FOR THE SYNTHESIS OF β -LACTAM DERIVATIVES 4(a-l).
CONCLUSION: In conclusion, we have successfully synthesized a series of novel acetamide-conjugated β-lactam derivatives 4(a-l) of Staudinger [2 + 2] cycloaddition reaction. The obtained results have established that all the synthesized imidazole-conjugated monocyclic β-lactams showed good antibacterial activity. Particularly the compounds 4e and 4l found to be effective in P.vulgaris as equal to reference ampicillin and other compounds showed moderate to good activity against five human bacterial pathogens. The overall antibacterial activity of the synthesized compounds attributed to the presence of β-lactam substituent in all the compounds. Their antimicrobial activity study revealed that all the compounds tested showed moderate to very good antibacterial activity and some compounds are inactive against pathogenic strains. Consequently N-pyridine acetamide substituted monobactam derivatives represent a class that needs further investigation with the hope of finding new antimicrobial agents.
ACKNOWLEDGEMENT: We greatly acknowledge to Head, Department of Chemistry, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur (India) for laboratory facilities and Director, SAIF Chandigarh (India) for providing necessary spectral data. Special thanks are due to the Head, Department of Botany, Osmania University, Hyderabad for antimicrobial screening.
REFERENCES:
- Nathwani D, Wood M. J: Penicillins. Acurrent review of their clinical pharmacology and therapeutic use. Drugs 1993; 45(6):866-894.
- Setti, E. L.; Micetich, R. G. New Trends in Antimicrobial Development: Current Medicinal Chemistry 1998; 5:101-113.
- Subbiah N, Pandian A, Nanjian R, Anup S, M. Elizabeth S, Thangamuthu MD, Stereoselective synthesis of sugar-based β-lactam derivatives: docking studies and its biological evaluation: Tetrahedron 2012; 68: 3037-3045.
- Mulchande J, Oliveira R, Carrasco M, Gouveia L, Guedes RC, Iley J, Moreira R. 4-Oxo-β-lactams (Azetidine-2,4-diones) Are Potent and Selective Inhibitors of Human Leukocyte Elastase: Journal of Medicinal Chemistry 2010; 53:241-253.
- Banik B K, Banik E, Becker F F, Banik B K, Ed. Topics in Heterocyclic Chemistry: Springer: Berlin-Heidelberg 2010; 22: 349-374.
- Georges Dive, Camille Bouillon, Aline Sliwa, Bénédicte Valet, Olivier Verlaine, Eric Sauvage, Jacqueline Marchand-Brynaert. Macrocycle-embedded β-lactams as novel inhibitors of the Penicillin Binding Protein PBP2a from MRSA: European Journal of Medicinal Chemistry 2013; 64: 365-376.
- Borthwick, A. D.; Weingarten, G.; Haley, T. M.; Tomaszewski, M.; Wang, W.; Hu, Z.; Bedard, J; Jin, H.; Yuen, L.; Mansour, T. S. Design and synthesis of monocyclic beta-lactams as mechanism-based inhibitors of human cytomegalovirus protease: Bioorganic Medicinal Chemistry Letters 1998; 8:365.
- Goel, R. K.; Mahajan, M. P.; Kulkarni, S. K. Evaluation of anti-hyperglycemic activity of some novel monocyclic beta lactams J. Pharm. Pharm. Sci. 2004; 7:80.
- Kewal K, Bruno P, Marilyn M, Rémy A, Vipan K. 1H-1,2,3-triazole tethered mono- and bis-ferrocenylchalcone-β-lactam conjugates: Synthesis and antimalarial evaluation: European Journal of Medicinal Chemistry 2014; 86: 113-121.
- Veinberg G, Shestakova I, Vorona M, Kanepe I, Lukevics E. Synthesis of antitumor 6-alkylidenepenicillanate sulfones and related 3-alkylidene-2-azetidinones: Med. Chem. Lett. 2004; 14:147.
- Tonko D, Krešimir M, Vinay S, Martina M, Silva H, Jay V P, Sascha O, Sanja L, Ivan H, Dagmar K. Novel amino-β-lactam derivatives as potent cholesterol absorption inhibitors: European Journal of Medicinal Chemistry 2014; 87: 722-734.
- Sperka T, Pitlik J, Bagossi P, Tozser. Beta-lactam compounds as apparently uncompetitive inhibitors of HIV-1 protease: Bioorg. Med. Chem. Lett. 2005; 15:3086.
- Saturnino C, Fusco, B.; Saturnino, P.; De Martino, G.; Rocco, F.; Lancelot, J. C: Evaluation of analgesic and anti-inflammatory activity of novel beta-lactam monocyclic compounds. Biol. Pharm. Bull. 2000; 23:654.
- Natarajan A, Govindasami P, Raghavachary R, Subban K, Johnpaul M: Synthesis and antimicrobial activity of highly functionalised novel β-lactam grafted spiropyrrolidines and pyrrolizidines. European Journal of Medicinal Chemistry 2011; 46:600-607.
- Amit B, Runa P: Synthesis of β-lactam nucleoside chimera via Kinugasa reaction and evaluation of their antibacterial activity. Bioorganic & Medicinal Chemistry Letters 2005; 15:2015-2018.
- Natarajan A, Raghavachary R, Vellaisamy S, Narayanasamy M: Synthesis of novel β-lactam fused spiroisoxazolidine chromanones and tetralones as potent antimicrobial agent for human and plant pathogens. Bioorganic & Medicinal Chemistry Letters 2010; 20:3698-3702.
- Pardeep S, Raghu R, Gaurav B, Denver T H, Sachin H, LeGrande M S, Vipan K: β-Lactam synthon-interceded diastereoselective synthesis of functionalized octahydroindole-based molecular scaffolds and theirin vitrocytotoxic evaluation. European Journal of Medicinal Chemistry 2012; 58:513-518.
- Pardeep S, Raghu R, Vipan K, Mohinder P M, PMS Bedi, Tandeep K, AK Saxena: 1,2,3-Triazole tethered β-lactam-Chalcone bifunctional hybrids: Synthesis and anticancer evaluation. European Journal of Medicinal Chemistry 2012; 47:594-600.
- Jetti, R. Pagadala, Meshram JS: Zeolite-Supported One-Pot Synthesis of Bis-azetidinones under Microwave Irradiation. Journal of Heterocyclic Chemistry 2013; 50:E160.
- Pagadala, J. S. Meshram, H. Chopde, V. Jetti; Prediction of Theoretical Physicochemical Properties and One-Pot Synthesis of Bis-Azetidinones by [2+2] Ketene -Imine Cycloaddition in the Presence of Montmorillonite. Medicinal Chemistry. 2011; 7:325-332.
- Pagadala, J. S. Meshram, H. Chopde, V. Jetti; An expeditious one-pot synthesis of substituted phenylazetidin-2-ones in the presence of zeolite. J. Heterocyclic Chemistry. 2011; 48:1067.
- Bimal K. Banik, Indrani Banik, Frederick F. Becker. Asymmetric synthesis of anticancer β-lactams viaStaudinger reaction: Utilization of chiral ketene from carbohydrate. European Journal of Medicinal Chemistry 2010; 45: 846-848.
- Aliasghar J, Edris E, Véronique S, Christine L, Jean M B: Diastereoselective synthesis of potent antimalarial cis-β-lactam agents through a [2 + 2] cycloaddition of chiral imines with a chiral ketene. European Journal of Medicinal Chemistry 2014; 87:364-371.
How to cite this article:
Jetti V, Chidurala P and Meshram JS: Synthesis of New Acetamide-Conjugated Monobactam Antibiotics. Int J Pharm Sci Res 2015; 6(4): 1553-61.doi: 10.13040/IJPSR.0975-8232.6(4).1553-61.
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Article Information
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English
Ijpsr
Venkateshwarlu Jetti *, Praveen Chidurala and Jyotsna S. Meshram
Department of Chemistry, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur – 440033, Maharashtra, India
venkatesh.jetti@gmail.com
06 August, 2014
29 October, 2014
15 December, 2014
10.13040/IJPSR.0975-8232.6(4).1553-61
01 April, 2015