SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF SOME NOVEL COUMARIN ANALOGUES

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF SOME NOVEL COUMARIN ANALOGUES

Sharanabasappa B. Patil ^{* 1} and N. M. Goudgaon ²

Department of Chemistry ¹, Ramaiah Institute of Technology, Bangalore - 560054, Karnataka, India.

Department of Studies and Research in Chemistry ², Gulbarga University, Kalburgi - 585106, Karnataka, India.

ABSTRACT: The desired target Compounds (4a-e), (5a-e) and (6a-e) were prepared in two steps. Reaction of 3-acetyl-6-bromo-2H-chromen-2-one (1) with 3-(Aryl)-1-phenyl-1H-pyrazole-4-carbaldehydes (2a-e) in presence of aqueous KOH solution and the reaction mixture stirred  for 2 hours and then filtered, furnished the desired 6-bromo-3-((E)-3-(3-(Aryl)-1-phenyl- 1H-pyrazole-4-yl) acryloyl)- 2H-chromen-2- ones (3a-e) crystalline solids in 60-70% yield (Scheme-1). Further, compounds (3a-e) reaction with thiourea, urea and hydrazine hydrate in the presence of a base in EtOH yielded the compounds (4a-e), (5a-e) and (6a-e) in 50-85% yield. All the synthesized compounds have been characterized by spectral data’s, and they are screened for anti-microbial activity. Among synthesized compounds 3b, 3c, 3d, 5a, and 5d exhibited good activity against bacterial strains S. aureus, P. aeruginosa, and E. coli, respectively. Whereas other compounds showed poor to moderate activity against all bacterial strains and compounds 3a, 3b, 3d, 4c, 5d, and 5c exhibited good antifungal activity against A. niger, and A. flavus and remaining compounds exhibited moderate antifungal activity. Results were tabulated in Table 2.

Coumarin derivatives and antimicrobial activity

INTRODUCTION:A variety of coumarin derivatives with diverse substituents at C-4 have been found to exhibit anticoagulant, ¹ cytochrome 450 inhibiting, ² antimicrobial and antitumour ³ activities. And also pyrimidines are well known nitrogen-containing six-membered heterocyclic compounds found to possess considerable biological activities, such as, antimycobacterial ⁴, antimicrobial ⁵, analgesic, antitumor ⁶ and antiviral activities.

In addition pyrazole derivatives have a broad spectrum of biological activities being used as antipyretic, antidepressant against rheumatoid arthritis, antibacterial ^{8, 9}, anticonvulsant, ¹⁰ antifilarial agents, ¹¹ herbicides, ^{12, 13} fungicides, pesticides, insecticides, anticancer agents ¹⁴ and dyestuffs in sunscreen materials. In view of above potent pharmacological activity, we became interested in synthesis and antimicrobial activity of  6- bromo- 3-((E)-3-(3-(Aryl)-1-phenyl-1H-pyrazol-4-yl)acryloyl)- 2H- chromen- 2- ones (3a-e), 6-bromo-3- (1,2,5,6-tetrahydro-6-(3-(Aryl)-1-phenyl-1H-pyrazol-4-yl)- 2- thioxopyrimidin- 4- yl)- 2H-chhromen-2-ones (4a-e), 4- (6-bromo-2-oxo-2H-chromen-3-yl)-5, 6- dihydro-6- (3-(Aryl)-1-phenyl-1H-pyrazol-4-yl) pyrimidin-2(1H)-ones (5a-e) and 6-bromo-3- (4, 5-dihydro-5-(3-(Aryl)-1-phenyl-1H-pyrazol-4-yl)- 1H- pyrazol-3-yl)- 2H- chromen- 2-ones (6a-e).

MATERIAL AND METHODS: Melting points were recorded by using Thomas-Hoover melting point apparatus and were uncorrected. IR spectra in KBr disc were recorded on Perkin-Elmer-Spectrum-one FTIR spectrophotometer (ν_max in cm^-1) and ¹H NMR in DMSO-d₆ and CDCl₃ on amx 400 MHz spectrophotometer using TMS as an internal standard. Mass spectra were recorded on a JEOL SX 102 Mass spectrometer using Argon/Xenon (6kv, 10 mA) as the FAB gas. The purity of the compounds was checked by TLC using silica gel ‘G’ plates obtained from Whatman Inc, and a fluorescent indicator. Elemental analysis was carried out on a Carlo Erba 1108 analyzer. 3-aryl-1-phenyl- 1H- pyrazole- 4- carbaldehydes were prepared by known literature method ²⁰.

Experimental:

Preparation of 6-bromo-3-((E)-3-(3-(Aryl)-1-phenyl-1H-pyrazol-4-yl) acryloyl)- 2H-chromen-2-ones (3a-e): 3-Acetyl-6-bromo-2H-chromen-2-one (1) (0.01 mol)  and  1,3-diphenyl-1H-pyrazole-4-carbaldehydes (2a-e) (0.01 mol) in absolute alcohol (30 ml) added 5 ml of 10% potassium hydroxide with constant shaking maintaining a temperature of 5-10 ºC. The mixture was stirred for 2 hours at room temperature and kept overnight. The solid separated was collected by filtration and crystallized from ethanol gave the desired 6-bromo-3-((E)-3-(3-(Aryl)- 1- phenyl- 1H- pyrazol-4 - yl) acryloyl)-2H-chromen-2-ones (3a-e).

6-Bromo-3-((E)-3-(1,3-diphenyl- 1H- pyrazol- 4-yl)acryloyl)-2H-chromen-2-one (3a): IR (KBr): 1681, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.0 (s, 1H, C₄H), 8.4 (s, 1H, C₅H of pyrazole), 7.8-7.2 (m, 13H ArH, 2H C=CH). Mass (m/z): 496 (M⁺, 100%). Elemental analysis: Calcd for C₂₇H₁₇BrN₂O₃: C, 65.20; H, 3.45; N, 5.63. Found: C, 65.18; H, 3.42; N, 5.61.

6-Bromo-3-((E)-3-(3-(4-nitrophenyl)- 1- phenyl-1H-pyrazol-4-yl) acryloyl)- 2H-chromen-2-one (3b): IR (KBr): 1691, ¹H NMR (DMSO-d6, δ in ppm): δ 10.1 (s, 1H, C₄H), 8.6 (s, 1H, C₅H of pyrazole), 8.4-7.2 (m, 12H ArH, 2H C=CH). Mass (m/z): 541 (M⁺, 10%). Elemental analysis: Calcd for C₂₇H₁₆BrN₃O₅: C, 59.79; H, 2.97; N, 7.75. Found: C, 59.77; H, 2.95; N, 7.72.

6- Bromo- 3- ((E)-3- (3- (4- methoxyphenyl)- 1-phenyl-1H-pyrazol-4-yl)acryloyl)- 2H- chromen-2-one (3c): IR (KBr): 1681, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.1 (s, 1H, C₄H), 8.6 (s, 1H, C₅H of pyrazole), 7.8-7.0 (m, 12H ArH, 2H C=CH), 3.8 (s, 3H, OCH₃). Mass (m/z): 526 (M⁺, 100%). Elemental analysis: Calcd for C₂₈H₁₉BrN₂O₄: C, 63.77; H, 3.63; N, 5.31. Found: C, 63.75; H, 3.61; N, 5.29.

6- Bromo- 3- ((E)- 3- (1- phenyl- 3-p-tolyl-1H-pyrazol-4-yl)acryloyl)-2H-chromen- 2- one (3d): IR (KBr): 1680, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.0 (s, 1H, C₄H), 8.6 (s, 1H, C₅H of pyrazole), 7.8-7.2 (m, 12H ArH, 2H C=CH), 2.4 (s, 3H, CH₃). Elemental analysis: Calcd for C₂₈H₁₉BrN₂O₃: C, 65.76; H, 3.75; N, 5.48. Found: C, 65.74; H, 3.72; N, 5.46.

3- ((E)-3- (3- (4-aminophenyl)- 1- phenyl- 1H-pyrazol-4-yl)acryloyl)-6-bromo-2H- chromen- 2-one (3e): IR (KBr): 1736, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.0 (s, 1H, C₄H), 8.5 (s, 1H, C₅H of pyrazole), 7.8-7.2 (m, 12H ArH, 2H C=CH, 2H NH). Mass (m/z): 512 (M⁺, 5%). Elemental analysis: Calcd for C₂₇H₁₈BrN₃O₃: C, 63.29; H, 3.54; N, 8.20. Found: C, 63.26; H, 3.50; N, 8.18.

Preparation of compounds (4a-e) and (5a-e): 6-Bromo-3-((E)-3-(3-(Aryl)-1-phenyl-1H-pyrazol-4-yl)acryloyl)-2H-chromen-2-ones (3a-e) (0.01 mol) was refluxed with thiourea or urea (0.01 mol) in presence of sodium hydroxide (0.04 mol) in ethanol was refluxed  for 15 h, then concentrated and cooled. The separated solid was filtered, washed with water and recrystallised from ethanol yielded the 6-bromo- 3- (1,2,5,6-tetrahydro-6-(3-(Aryl)-1-phenyl-1H-pyrazol-4-yl)- 2- thioxopyrimidin-4-yl)-2H-chhromen-2-ones (4a-e) or 4-(6-bromo-2-oxo-2H-chromen-3-yl)-5, 6- dihydro- 6- (3- (Aryl)-1-phenyl-1H-pyrazol-4-yl)pyrimidin-2(1H)-ones (5a-e) in 50-85% yield.

6- Bromo- 3-(1,2,5,6-tetrahydro-6-(1,3-diphenyl-1H- pyrazol-4-yl)- 2-thioxopyrimidin-4-yl)- 2H-chromen-2-one (4a): IR (KBr): 3225, 1772, ¹H NMR (DMSO-d6, δ in  ppm): δ 12.2 (s, 1H, NH), 8.8 (s, 1H, C₄H), 8.2 (s, 1H, C₅H of pyrazole), 7.8-7.0 (m, 13H, ArH). 6.4 (s, 1H, CH), 4.2 (s, 2H, CH₂). Mass (m/z): 554 (M⁺, 10%). Elemental analysis: Calcd for C₂₈H₁₉BrN₄O₂S: C, 60.55; H, 3.45; N, 10.09. Found: C, 60.55; H, 3.45; N, 10.09.

6- Bromo- 3- (1, 2, 5, 6- tetrahydro-6-(3-(4-nitro-phenyl)- 1- phenyl- 1H- pyrazol-4-yl)- 2-thioxo-pyrimidin-4-yl)- 2H- chromen-2-one (4b): IR (KBr): 3126, 1681, ¹H NMR (DMSO-d6, δ in ppm): δ 10 (s, 1H, NH), 9.2 (s, 1H, C₄H), 8.5 (s, 1H, C₅H of pyrazole), 8.0-7.4 (m, 12H, ArH), 7.2 (s, 1H, CH), 2.5 (s, 2H, CH₂). Elemental analysis: Calcd for C₂₈H₁₈BrN₅O₄S: C, 56.01; H, 3.02; N, 11.66. Found: C, 55.01; H, 3.01; N, 11.62.

6-Bromo-3- (1,2,5,6-tetrahydro-6-(3-(4-methoxy-phenyl)- 1- phenyl- 1H- pyrazol- 4-yl)- 2-thioxo-pyrimidin-4-yl)- 2H- chromen-2- one (4c): IR (KBr): 3124, 1674, ¹H NMR (DMSO-d6, δ in ppm): δ 10 (s, 1H, NH), 8.6 (s, 1H, C₄H), 7.8 (s, 1H, C₅H of pyrazole), 7.6-7.2 (m, 12H, ArH ), 7.0 (s, 1H, CH), 3.8 (s, 3H, OCH₃), 2.2 (s, 2H, CH₂). Elemental analysis: Calcd for C₂₉H₂₁BrN₄O₃S: C, 59.49; H, 3.62; N, 9.57. Found: C, 59.46; H, 3.60; N, 9.55.

6-Bromo-3- (1,2,5,6-tetrahydro-6- (1-phenyl-3-p-tolyl- 1H-pyrazol-4-yl)- 2-thioxopyrimidin-4-yl)-2H-chromen-2-one (4d): IR (KBr): 3321, 1699, ¹H NMR (DMSO-d6, δ in  ppm): δ 10 (s, 1H, NH), 9.4 (s, 1H, C₄H), 8.0 (s, 1H, C₅H of pyrazole), 7.6-7.4 (m, 12H, ArH, 1H, CH ), 3.4 (s, 3H, OCH₃), 2.5 (s, 3H, CH₃), 2.2 (s, 2H, CH₂). Mass (m/z): 568 (M⁺, 10%). Elemental analysis: Calcd for C₂₉H₂₁BrN₄O₂S: C, 61.16; H, 3.72; N, 9.84. Found: C, 61.14; H, 3.70; N, 9.81.

3-(6-(3-(4-Aminophenyl)- 1-phenyl- 1H-pyrazol-4-yl)-1,2,5,6-tetrahydro-2-thioxopyrimidin-4-yl)-6-bromo-2H-chromen-2-one (4e): IR (KBr): 3298, 1699, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.4 (s, 1H, NH), 9.8 (s, 1H, C₄H), 9.4 (s, 1H, C₅H of pyrazole), 7.8-7.4 (m, 12H, ArH ), 7.0 (s, 1H, CH), 4.0 (d, 2H, NH), 2.5 (s, 2H, CH₂). Elemental analysis: Calcd for C₂₈H₂₀BrN₅O₂S: C, 58.95; H, 3.53; N, 12.28. Found: C, 58.92; H, 3.50;  N, 12.25.

4- (6-Bromo- 2-oxo- 2H-chromen- 3- yl)- 5, 6-dihydro-6-(1,3-diphenyl-1H-pyrazol-4-yl) pyrimi din-2(1H)-one (5a): IR (KBr): 3107, 1624, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.0 (s, 1H, NH), 9.4 (s, 1H, C₄H), 8.0 (s, 1H, C₅H of pyrazole), 7.8-7.2 (m, 13H, ArH ), 7.0 (s, 1H, CH), 2.5 (s, 2H, CH₂). Mass (m/z): 538 (M⁺, 10%). Elemental analysis: Calcd for C₂₈H₁₉BrN₄O₃: C, 62.35; H, 3.55; N, 10.39. Found: C, 62.35; H, 3.55;  N, 10.39.

4- (6- Bromo-2-oxo-2H-chromen-3- yl)-5, 6- di-hydro- 6- (3- (4- nitrophenyl)-1-phenyl-1H-pyra-zol-4-yl) pyrimidin-2(1H)-one (5b): IR (KBr): 3045, 1624, ¹H NMR (DMSO-d6, δ in ppm): δ 10.4 (s, 1H, NH), 9.6 (s, 1H, C₄H), 9.2 (s, 1H, C₅H of pyrazole), 8.0-7.2 (m, 12H, ArH ), 7.0 (s, 1H, CH), 2.5 (s, 2H, CH₂). Elemental analysis: Calcd for C₂₈H₁₉BrN₄O₃: C, 57.55; H, 3.10; N, 11.98. Found: C, 57.52; H, 3.08; N, 11.95.

4- (6- Bromo- 2-oxo- 2H- chromen- 3- yl)- 5, 6-dihydro- 6-(3-(4-methoxyphenyl)- 1- phenyl- 1H-pyrazol-4-yl)pyrimidin-2(1H)-one (5c): IR (KBr): 2920, 1624, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.0 (s, 1H, NH), 9.4 (s, 1H, C₄H), 8.0 (s, 1H, C₅H of pyrazole), 7.8-7.5 (m, 12H, ArH, 1H, CH ), 3.4 (s, 3H, OCH₃), 2.5 (s, 2H, CH₂). Elemental analysis: Calcd for C₂₉H₂₁BrN₄O₄: C, 61.17; H, 3.72; N, 9.84. Found: C, 61.15; H, 3.70; N, 9.80.

4- (6- Bromo- 2- oxo- 2H- chromen- 3- yl)- 5, 6-dihydro- 6- (1-phenyl-3-p-tolyl-1H-pyrazol-4-yl) pyrimidin-2(1H)-one (5d): ¹H NMR (DMSO-d6, δ in  ppm): δ 11.8 (s, 1H, NH), 9.2 (s, 1H, C₄H), 8.8 (s, 1H, C₅H of pyrazole), 8.2-7.4 (m, 12H, ArH, 1H, CH ), 3.5 (s, 3H, CH₃), 2.5 (s, 2H, CH₂). Mass (m/z): 552 (M⁺, 10%). Elemental analysis: Calcd for C₂₉H₂₁BrN₄O₄: C, 62.94; H, 3.82; N, 10.12. Found: C, 62.91; H, 3.80; N, 10.10.

6- (3-(4-Aminophenyl)- 1- phenyl-1H-pyrazol-4-yl)- 4- (6-bromo-2-oxo-2H-chromen-3-yl)- 5, 6-dihydropyrimidin- 2(1H)-one (5e): ¹H NMR (DMSO-d6, δ in  ppm): δ 10.4 (s, 1H, NH), 9.8 (s, 1H, C₄H), 9.2 (s, 1H, C₅H of pyrazole), 8.5-6.5 (m, 12H, ArH, 1H, CH , 2H, NH), 2.5 (s, 2H, CH₂). Elemental analysis: Calcd for C₂₈H₂₀BrN₅O₃: C, 60.66; H, 3.64; N, 12.63. Found: C, 60.63; H, 3.62; N, 12.60.

Preparation of 6-bromo-3-(4, 5-dihydro-5-(3-(Aryl)-1-phenyl-1H-pyrazol-4-yl)-1H-pyrazol-3-yl)-2H-chromen-2-ones (6a-e): Reaction of compounds (3a-e) (0.01 mol) with hydrazine hydrate (0.01 mol) in ethanol (30 ml). The reaction mixture was refluxed for 5 h and then concentrated and cooled.

The solid separated was filtered, washed several times with water and recrytallised from ethanol yielded the desired compounds (6a-e).

SCHEME 1

6-Bromo-3-(4, 5-dihydro-5-(1, 3-diphenyl-1H-pyrazol-4-yl)- 1H-pyrazol-3-yl)- 2H-chromen- 2-one (6a): IR (KBr): 3121, 1661, ¹H NMR (DMSO-d6, δ in  ppm): δ 9.4 (s, 1H, NH), 9.2 (s, 1H, C₄H), 8.8 (s, 1H, C₅H of pyrazole), 8.0-7.2 (m, 12H, ArH, 1H, CH ), 2.5 (s, 2H, CH₂). Mass (m/z): 510 (M⁺, 10%). Elemental analysis: Calcd for C₂₇H₁₉BrN₄O₂: C, 63.42; H, 3.75; N, 10.96. Found: C, 63.40; H, 3.72; N, 10.91.

6-Bromo-3-(4, 5-dihydro-5- (3- (4-nitrophenyl)- 1-phenyl-1H-pyrazol-4-yl)-1H-pyrazol-3-yl)-2H-chromen-2-one (6b): IR (KBr): 3128, 1691, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.2 (s, 1H, NH), 8.4 (s, 1H, C₄H), 8.0 (s, 1H, C₅H of pyrazole), 7.5-7.0 (m, 12H, ArH, 1H, CH ), 2.5 (s, 2H, CH₂). Elemental analysis: Calcd for C₂₇H₁₈BrN₅O₄: C, 58.29; H, 3.26; N, 12.59. Found: C, 58.27; H, 3.22; N, 12.56.

6- Bromo- 3- (4, 5-dihydro-5- (3- (4- methoxy-phenyl)-1-phenyl-1H-pyrazol-4-yl)-1H-pyrazol-3-yl)-2H-chromen-2-one (6c): IR (KBr): 3203, 1637, ¹H NMR (DMSO-d6, δ in  ppm): δ 9.0 (s, 1H, NH), 8.4 (s, 1H, C₄H), 8.0 (s, 1H, C₅H of pyrazole), 7.5-7.0 (m, 12H, ArH, 1H, CH ), 3.5 (s, 3H, OCH₃), 2.5 (s, 2H, CH₂). Mass (m/z): 540 (M⁺, 10%). Elemental analysis: Calcd for C₂₈H₂₁BrN₄O₃: C, 62.12; H, 3.91;  N, 10.35. Found: C, 62.10; H, 3.88; N, 10.30.

6- Bromo-3- (4, 5-dihydro-5-(1-phenyl-3-p-tolyl-1H-pyrazol-4-yl)-1H-pyrazol-3-yl)-2H-chromen-2-one (6d): IR (KBr): 3367, 1861, ¹H NMR (DMSO-d6, δ in  ppm): δ 11.0 (s, 1H, NH), 9.0 (s, 1H, C₄H), 8.8 (s, 1H, C₅H of pyrazole), 8.4-7.0 (m, 12H, ArH, 1H, CH ), 3.4 (s, 3H, CH₃), 2.5 (s, 2H, CH₂). Mass (m/z): 524 (M⁺, 10%). Elemental analysis: Calcd for C₂₈H₂₁BrN₄O₂: C, 64.01; H, 4.03; N, 10.66. Found: C, 63.01; H, 4.01;  N, 10.63.

3- (5- (3-(4-Aminophenyl)-1-phenyl-1H-pyrazol-4-yl)-4,5-dihydro-1H-pyrazol-3-yl)-6-bromo-2H-chromen-2-one (6e): IR (KBr): 3207, ¹H NMR (DMSO-d6, δ in  ppm): δ 10.5 (s, 1H, NH), 9.2 (s, 1H, C₄H), 8.6 (s, 1H, C₅H of pyrazole), 8.4-7.0 (m, 12H, ArH, 1H, CH ), 3.2 (s, 3H, CH₃), 2.5 (s, 2H, CH₂). Mass (m/z): 525 (M⁺, 10%). Elemental analysis: Calcd for C₂₇H₂₀BrN₅O₂: C, 61.61; H, 3.83; N, 13.30. Found: C, 61.59; H, 3.80; N, 13.28.

RESULT AND DISCUSSION: The desired target compounds (4a-e), (5a-e) and (6a-e) were prepared in two steps. Reaction of 3-acetyl-6-bromo-2H-chromen-2-one (1) with 3-(Aryl)-1-phenyl-1H-pyrazole-4-carbaldehydes (2a-e) in presence of aqueous KOH solution and the reaction mixture was stirred  for 2 hours and then filtered, furnished the desired 6-bromo-3-((E)-3-(3-(Aryl)-1-phenyl-1H-pyrazole-4-yl) acryloyl)- 2H- chromen- 2- ones (3a-e) crystalline solids in 60-80% yield (Scheme-1). Its IR spectrum confirmed the formation of compound 3a shows absorption at 1681 cm^-1 due to C=O. Further compound 3a was confirmed by ¹H NMR spectrum shows signals at δ 10.0 (s, 1H, C₄H), 8.4 (s, 1H, C₅H of pyrazole), 7.8-7.2 (m, 13H, ArH, 2H, C=CH). The molecular ion peak of compound 3a was observed at (m/z): 496 (M⁺, 100%) in its mass spectrum. Further, compounds (3a-e) reaction with thiourea, urea and hydrazine hydrate in the presence of a base in EtOH yielded the compounds (4a-e), (5a-e) and (6a-e) in 50-85% yield. Its IR spectrum confirmed the formation of compound 4a shows absorption at 3225, 1772 cm^-1  due to NH and C=O. Further, compound 4a was confirmed by ¹H NMR spectrum shows signals at ¹H NMR (DMSO-d6, δ in ppm): δ 12.2 (s, 1H, NH), 8.8 (s, 1H, C₄H), 8.2 (s, 1H, C₅H of pyrazole), 7.8-7.0 (m, 13H, ArH). 6.4 (s, 1H, CH), 4.2 (s, 2H, CH₂). The molecular ion peak of compound 4a was observed at m/z = 554 (M⁺, 10%) in its mass spectrum. Formation of compound 5a was confirmed by its IR spectrum shows absorption at 3107 and 1624  cm^-1 due to the presence of NH, C=O stretching.

TABLE 1: PHYSICAL CONSTANT AND YIELD OF THE SYNTHESIZED COMPOUNDS

Further, compound 5a was confirmed by ¹H NMR spectrum shows signals at δ 10.0 (s, 1H, NH), 9.4 (s, 1H, C₄H), 8.0 (s, 1H, C₅H of pyrazole), 7.8-7.2 (m, 13H, ArH), 7.0 (s, 1H, CH), 2.5 (s, 2H, CH₂). The molecular ion peak of compound 5a was observed at m/z = 538 (M⁺, 10%) in its mass spectrum. Its IR spectrum confirmed the formation of compound 6a shows absorption at 3121 and 1661 cm^-1 due to the presence of NH and C=O stretching. Further, compound 6a was confirmed by ¹H NMR spectrum shows signals at δ 9.4 (s, 1H, NH), 9.2 (s, 1H, C₄H), 8.8 (s, 1H, C₅H of pyrazole), 8.0-7.2 (m, 12H, ArH, 1H, CH), 2.5 (s, 2H, CH₂). The molecular ion peak of compound 6a was observed at m/z = 510 (M⁺, 10%) in its mass spectrum. Physical constants and yield of all the synthesized compounds are tabulated in Table 1.

Antimicrobial Activity: The antimicrobial activities were performed by the cup plate method. The synthesized compounds, gentamycin and fluconazole was dissolved in DMF at the concentration of 1000 µg/ml. Antibacterial activity screened against, S. aureus, E-coli and, P. aeruginosa. Antifungal activity was carried out against A. niger and A. flavus under aseptic conditions. Gentamycin and fluconazole were used as a standard drug for antibacterial and antifungal activities. The zone of inhibition was compared with standard drug after 24 h of incubation at 25 ºC for antibacterial activity and 48 hours at 30 ºC for antifungal activity. Among synthesized compounds 3b, 3c, 3d, 5a, and 5d exhibited good activity against bacterial strains S. aureus, P. aeruginosa and E. coli, respectively. Whereas other compounds showed poor to moderate activity against all bacterial strains and 3a, 3b, 3d, 4c 5d, and 5c exhibited good antifungal activity against A. niger and A. flavus and remaining compounds exhibited moderate antifungal activity. Results were tabulated in Table 2.

TABLE 2: ANTIMICROBIAL ACTIVITY OF SYNTHESIZED COMPOUNDS

CONCLUSION: Among synthesized compounds 3b, 3c, 3d, 5a, and 5d exhibited good activity against bacterial strains S. aureus, P. aeruginosa and E. coli, respectively. Whereas other compounds showed poor to moderate activity against all bacterial strains and compounds 3a, 3b, 3d, 4c, 5d, and 5c  exhibited good antifungal activity against A. niger, and A. flavus and remaining compounds exhibited moderate antifungal activity.

ACKNOWLEDGEMENT: The authors are highly thankful to the Department of Chemistry, Gulbarga University Kalburgi, Karnataka for the needful support.

CONFLICT OF INTEREST: The authors declared no competing interests.

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    How to cite this article:

    Patil SB and Goudgaon NM: Synthesis and antimicrobial activity of some novel coumarin analogues. Int J Pharm Sci & Res 2019; 10(2): 960-65. doi: 10.13040/IJPSR.0975-8232.10(2).960-65.

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