Indian Journal of Chemistry Vol. 41 B, June 2002, pp. 1263-1267

Synthesis of some of the antibacterial compounds from 4-hydroxycoumarins: Part II

v V Mulwad*& J M Shirodkar

Department of Organic Chemistry, Institute of Science, IS, Madam Cama Road, Mumbai 400032,India

Received 24 April 2001; accepted (revised) 6 December 2001

4-Hydroxy-2H -2-oxo-3-methy lidene-urea[ I )benzopyrans 2a-d , 4-hydroxy-2H-2-oxo-3-methy lidene-thiourea[ I )benzo­pyrans 2e-h, 4-hydroxy-2H-2-oxo-3-methylidene-guanidine[I]benzopyrans 2i-1 are obtained from la-d on treatment with urea, thiourea, and guanidine respectively in ethanol- acetic acid. Compounds 2a-1 on heating with PZ0 5 give I, 2-dihydro­SH-2, S-dioxo[ I ]benzopyrano [4,3-d] pyrimidines 3a-d, I, 2-dihydro-SH-2-thio-S-oxo[ I ]benzopyrano [4 ,3-d] pyrimidines 3e-h, and I , 2-dihydro-SH-2-imino-S-oxo[I]benzopyrano [4,3-d] pyrimidines 3i-1. IH, 4H-4-0xo-benzopyrano [4 ,3-c] pyra­zoles 4a-d, 4H-4-oxo-I-phenyl-benzopyrano[4,3-c]pyrazoles 4e-h, 4H-4-oxo-benzopyrano[3, 4-c]isoxozoles Sa-d, 3-benzamido-2, S-dioxopyrano [3,2-c]benzopyrans 6a-d and 3-acetamido-2, S-dioxo-pyrano[3,2-c] benzopyrans 6e-h are ob­tained by retluxing la-d with hydrazine hydrate, phenyl hydrazine, hydroxylamine hydrochloride, hippuric acid and N­acetyl glycine, respectively in ethanol-acetic acid solution.

Coumarins reported to possess biological activityl, are used in the treatment of vitilago, psoriasis and other dermal diseases2. The physiological properties of natural and synthetic [1]benzopyran-2(H)-ones have been reviewed by various workers3-6. In recent times [1] benzopyran-2(H)-ones have been extensively used as laser materials7, photosensitizers8, brighters9 as in­ter-mediates for dyes, pesticides and pharmaceuti­cals lo as well as in perfume formulations ll .12 and in enzymology as biological probes 13. Coumarins show activities such as antifungal 14, anticoagulant l5 , anti­bacterial 16 and insecticidal 17.

Since pyrazole, isoxazole, pyrimidines and pyrans are useful heterocyclic moieties as they possess a broad spectrum of biological activities such as anti vi­ra1 18, CNS depressant l9, bactericidal2o, ulcer inhibi­tor21 etc. We report herein the synthesis of some new fused heterocycles incorporating the above moieties in benzopyran ring system.

With a view to introducing five and six membered rings on a benzopyran ring, various reactions have been carried out on 3-formyl-4-hydroxycoumarin22

.23.

A few methods are described in literature for the syn­thesis of 4H-4-oxo-l-phenyl-benzopyrano[4,3-c ]pyra­zole and 4H-4-oxo-benzopyrano[3,4-c]isoxazole from 4-chloro-3-formylcoumarin in two steps24. However, herein we report the one-step synthesis for the above compounds and their derivatives using 3-formyl-4-hydroxycoumarins.

When 3-formyl-4-hydroxy-2-oxo-2H-[1] benzo­pyrans la-d are treated with ethanolic solution of hydroxylamine hydrochloride in acetic acid gave 4H-4-oxo-benzopyrano[3,4-c ]isoxazoles Sa-d. Com­pounds Sa-d do not show any colouration with ferric chloride. IR spectrum did not show peak at 3422 cm- I. IH NMR spectrum showed singlet at 88.1 due to pro­ton of C3 and disappearance of aldehyde proton at 87.95.

3-Forrnyl-4-hydroxy-2-oxo-2H-[1]benzopyrans la-d when refluxed with ethanolic solution of hydrazine hydrate, phenyl hydrazine, hippuric acid and N-acetyl glycine separately in acetic acid gave corresponding IH, 4H-4-oxo-benzopyrano [4,3-c] pyrazoles 4a-d, 4H-4-oxo-l-phenyl-benzopyrano[ 4,3-c] pyrazoles 4e-h, 3-benzarnido-2, 5-dioxo-pyrano [3, 2-c] benzopyrans 6a-d, and 3-acetamido-2, 5-dioxo-pyrano[3, 2-c]benzopyrans 6e-h, respectively (Table I, Scheme I). IH NMR spectra of compounds 4a-d showed singlet at 87.2 due to proton on nitrogen which is D20 ex­changeable and a singlet at 88.15 due to proton on C3.

IH NMR spectra of compounds 6a-d showed singlet at 88 due to proton of C4 and singlet at 811.35 due to proton on nitrogen, which is D20 exchangeable. IH NMR spectra of compounds 4a-h and 6a-h showed absence of peak at 87.95 due to proton of aldehyde group.

Another method also has been developed for the preparation of compounds 6a-h by heating com­pounds la-d in an oil-bath with acetic anhydride and

1264 INDIAN J. CHEM., SEC B, JUNE 2002

R R RNHNH2

+---­CH3COOH

I HOH RN--N HO

R ~NORHCI

CHO

O--N

R"CONHC1~;:':;H;:;&2C~0.::...0..::..H=----...L...---------'! CH3COOH

CH3COOH HOH

HOH ~N-C-~ R3 II

R

o

o II

NH-C-R"

2a,3a:R1 =R2=R3=H, X=O

2b, 3b : Rl = CH3, R2 = R3 = H, X = 0 2c,3c:R2=CH3,R1 =R3=H, X=O 2d,3d:R3=CH3,R1 =R2=H, X=O 2e,3e:R1 =R2=R3::H, X=S

2f, 3f : Rl = CH3, R2 = R3 = H, X = S 29,39: R2 = CH3, Rl = R3 = H, X = S 2h, 3h : R3 = CH3, Rl = RF H, X = S

2i,3i:Rl=R2=R3=H, X=NH 2j, 3j : Rl = CH3, R2 = R3 = H, X = NH 2k, 3k : R2 = CH3, Rl = R3 = H, X = NH 21, 31 : R3 = CH3, Rl = R2 = H, X = NH

4a, 5a : Rl = R2 = R3 = H, R = H 4b, 5b : Rl = CH3, R2 = R3 = H, R = H

:

X

R

CH=N-C-NHz II x

4c, 5c: R2 = CH3, Rl = R3 = H, R = H

4d, 5d: R3 = CH3, Rl = R2 = H, R = H 4e : Rl = R2 = R3 = H, R = Ph 4f : Rl = CH3, R2 :: R3 :: H, R = Ph

49: R2 = CH3• Rl = R3 = H, R = Ph 4h : R3 = CH3, Rl = R2 = H, R = Ph

6a : Rl = R2 = R3 = H, Rn:: Ph

6b : Rl = CH3, R2 = R3 = H, Rn = Ph

6c : R2 = CH3, Rl = R3 = H, Rn = Ph

6d : R3 = CH3• Rl = R2 = H, Rn = Ph

6e : Rl = R2 = R3 = H, Rn = CH3 6f: Rl = CH3, R2 :-:: R3 = H, Rn = CH3

69 : R2 = CH3, Rl = R3 = H, Rn = CH3 6h : R3 :: CH3, Rl = R2 = H, Rn = CH3

Scheme I

pyridine. However, the yield obtained by this method is much less than compared to the above method. The structure identification has been confirmed by super­imposible IR and NMR spectra.

When la-d were refluxed with ethanolic solution of either urea, thiourea or guanidine in acetic acid gave 4-hydroxy-2H-2-oxo-3-methylidene-

urea[1] benzopyran, 4-hydroxy-2H-2-oxo-3-methyl­idene-thiourea[I]benzopyran and 4-hydroxy-2H-2-oxo-3-methylidene-guanidine[ 1 )benzopyran, respec­tively. These compounds gave smell of ammonia on boiling with dilute NaOH. IR spectra of these com­pounds in KBr showed a band at 1720 cm- t (>C=O) and 1670, which is due to >C=O of ·-CONH2 group.

MULWAD et ai. : ANTIBACTERIAL COMPOUNDS FROM 4-HYDROXYCOUMARINS 1265

Table I - Characterization data of compounds 2a-l, 3a-l, 4a-l, 6e C'4H9NOS >260 A-75 B-64 5a-d and 6a-h

6f C,sH"NOs >260 A-77 B-65 Compd Mol. Formula* m. poC Yield

(%) 6g C,sHIINOs 210 A-76 B-65

2a C II HgN20 4 255 71 6h C,sH"NOs 250 A-78 B-64

2b C'2HION20 4 225 70 2b : I3C NMR: 025 (CH3), 112 (-CH=N), 116.3 (C6-C),

2c C'2HION20 4 210 75 118(Cr C), 123-134 (aromatic carbons), 134 (C-8b),

2d C'2HION20 4 200 73 156 (C-8a), 169 (C4-C), 174 & 0192 (carbonyl car-bons); M+ 246.

2e C"HgN20 3S 222 70 'H NMR (DMSO-d6): 02.4 (s, 3H, CH3), 7-7.5 (m, 3H, 2c:

2f C'2HION20 3S 245 69 Ar-H), 7.66 (s, IH, -CH=N), 7.7 (s, 2H, -NH2), 07.8 (s, 2g C 12HION20 3S 260 76 IH, -OH).

2h C'2HION20 3S 245 70 3d: 'H NMR (DMSO-d6): 02.4 (s, 3H, CH3), 7.2-7.6 (m, 2i CII H9N30 3 160 71 3H, Ar-H), 7.85 (s, IH, C4-H), 08.1 (s, I H, -NH); I3C

2j C 12H"N30 3 250 75 NMR: 021(CH3), 117 (C-4a), 119 (CrC), 125-135 (aromatic carbons), 133 (C-lOa), 135 (C-4b), 156 (C4-

2k C 12HII N)O) 260 73 C), 157 (C-lOb), 161 (carbonyl carbon), 179 (CrC),

21 C'2HIIN3O) 245 72 193 (carbonyl carbon); M+ 228.

3a C II H6N2O) 254 82 3h: 'H NMR (CDCI): 02.4 (s, 3H, -CH) , 7.2-7.6 (m, 3H,

3b C'2HgN20 ) 270 80 Ar-H), 7.9 (s, IH, C4-H), 0 8.7 (s, IH, NH).

3c C'2HgN20 ) 190 81 3j : 'H NMR (CDC I) : 02.4 (s, 3H, -CH), 7.1-7.6 (m, 3H,

3d C'2HgN20 ) 200 82 Ar-H), 7.8 (s, IH, NH), 8 (s, IH, C4-H), 9.8(s, IH , NH); I3C NMR: 021 (CH3), 115 (C-4a), 116 (C9-C),

3e C"H6N20 2S 180 83 122-134 (aromatic carbons), 133 (C-lOa), 134 (CAb), 3f C '2HgN20 2S >265 81 155 (C-lOb), 157 (C4-C), 161 (carbonyl carbon), 0189

3g C'2HgN20 2S 168 85 (CrC); M+ 227.

3h C'2HgN20 2S >263 82 4b: 'H NMR (DMSO-d6): 02.4 (s, 3H, CH), 7:22 (s, IH,

3i C"H7N)02 >265 80 -NH), 7-7.7 (m, 3H, Ar-H), 8.15 (s, IH, C3-H); I3C NMR: 021 (CH), 116 (Cg-C), 122-138 (aromatic car-

3j C'2H9N)02 240 85 bons), 134 (C-9a), 143 (C-3b), 149 (C-9b), 113 (C-3a),

3k C'2H9N)0 2 230 83 153 (CrC), 163 (carbonyl carbon); M+ 200.

31 C'2H9N30 2 190 81 4f: 'H NMR (CDCI): 02.4 (s, 3H, CH), 7.1-7.8 (m, 8H,

4a C IOH6N20 2 260 72 -Ar-H), 7.95 (s, IH, C3-H); I3C NMR: 021 (CH), 115 (C-3a), 116.9 (Cg-C), 122-134 (aromatic carbons), 132

4b C"HgN20 2 245 70 (C-9a), 144 (q-c of phenyl ring), 147 (C-3b), 154 (C-

4c C"HgN20 2 >270 74 9b), 155 (CrC), 167 (carbonyl carbon) ; M+ 276.

4d C"HgN20 2 225 71 5b: 'H NMR (DMSO-d6): 02.4 (s, 3H, CH), 7.2-7.8 (m,

4e C'6HION20 2 150 74 3H, Ar-H), 08.1 (s, IH, C3-H).

4f C 17H'2N20 2 128 76 6b: 'H NMR (CHCI): 02.4 (s, 3H, -CH), 7.2-7.9 (m, 8H,

4g C 17H'2N20 2 220 70 Ar-H), 8 (s, I H, C4-H), 11.35 (s, I H, -NH) .

4h C 17H'2N20 2 240 73 6d: 'H NMR (CHCI3): 02.4 (s, 3H, -CH), 7.2-7.9 (m, 8H,

Sa CIOHsNO) >280 63 Ar-H), 8 (s, I H, C4-H), 11.2 (s, I H, -NH); I3C NMR: 025 (-CH), 113 (q-c of phenyl ring), 115 (C-4a), 116-

Sb C"H7NO) >285 65 135 (aromatic carbons), 117 (CrC), 135 (C-lOa), 0137

Sc C"H7Nt» 260 64 (CrC), 148 (CAb), 149 (C-lOb), 152 (C4-C), 165, 173 & 192 (carbonyl carbons); M+347.

5d C"H7NO) >282 65

6a C'9H"NOs 259 A-76 B-62 6h: 'H NMR (CHCI): 02.4 (s, 3H, -CH), 2.5 (s, 3H,

-CH), 7.3-7.9 (m, 3H, Ar-H), 8.2 (s, IH, C4-H), 9. I(s, 6b C2oH13NOs 260 A-75 B-60 IH, -NH).

6c C2oH13NOs 200 A-75 B-61

6d C2oH, )NOs 220 A-77 B-63 A-Method A, B-Method B *All the comQounds gave satisfactoQ: C, H, N, S analysis_

1266 INDIAN 1. CHEM., SEC B,1UNE 2002

IH NMR spectra of compounds 2a-R showed singlet at 87.66 due to proton of CH=N and also at 87.7 and 7.8 due to proton on nitrogen atom andl oxygen atom, re­spectively which is D20 exchangeable. Compounds 2a-1 on heating with P20 S at 180aC gave I, 2-dihydro-5H-2, 5-dioxo[l ]benzopyrano[4,3-d]pyrimidines 3a-d, I , 2-dihydro-5H-2-thio-5-oxo[1 ]benzopyrano[4,3-d]pyri­midines 3e-h, and I, 2-dihydro-5H-2-imino-5-oxo[ I ]benzopyrano[ 4,3-d]pyrimidines 3i-l, respec­tively. These compounds did not give smell of ammo­nia on boiling with dilute NaOH . IH NMR spectra of compounds 3a-d showed singlet at 87.85 due to pro­ton on C4 and singlet at 88.1 due to proton on nitro­gen, which is D20 exchangeable and absence of peak at 87.8, indicating the absence of proton.

Biological Screening The compounds 3d, 3h, 31, 4d, 4g, 6d were

screened for their antibacterial activity against both gram-positive and gram-negative bacteria (Table-II). Minimum inhibitory concentration (MIC) of these compounds was determined by tube dilution method2s

•

Table II - Antibacterial act ivity of compounds 3d, 3h, 31, 4d, 4g and 6d

Compd S. typhi S. aureus

3d ++ + 3h + 31 + + 4d ++ ++ 4g + + 6d +++ +

- = No activity, + = 200 1!gmlML, ++ = 100 1!gmIML, +++ = 50 1!gmlML

Experimental Section General. Melting points were taken in open capil­

laries and are uncorrected. The IR spectra were re­corded on a Perkin-Elmer 257 spectrophotometer us­ing KBr; and I3C NMR and IH NMR on a YXR-300 spectrometer using TMS as internal standard. The homogeneity of the compounds was described by TLC on silica gel plates; the spots were developed in iodine chamber.

4-Hydroxy-2H-2-oxo-3-methylidene-urea[1]benzo­pyrans 2a-d, 4-hydroxy-2H-2-oxo-3-methylidene­thiourea[l]benzopyrans 2e-h, and 4-hydroxy-2H-2-oxo-3-methylidene-guanidine [1] benzopyrans 2i­I. A mixture of 1a-d (0.01 mole) and urea! thiourea! guanidine was refluxed separately in (45 mL)

ethanol-acetic acid (2: I) mjxture for 10 hr. The solid obtained on cooling was filtered, washed with water and crystallized from ethanol.

1, 2-Dihydro-5H-2, S-dioxo[l]bcnzopyrano[ 4,3-d]pyrimidines 3a-d, 1, 2-dihydro-5H-2-thio-S-oxo­[l]bcnzopyrano[ 4,3-d]pyrimidines 3e-h, and 1, 2-dihydro-SH -2-imino-S-oxo[l ]benzopyrano[ 4,3-d]­pyrimidines 3i-l. A mixture of 2a-l (0.2g) and phos­phorous pentoxide (0.2g) was heated in an oil-bath at 180aC for 1.5 hr. It was then decomposed in water. The black solid obtained was filtered, washed with water and cold NaOH. It was then extracted with chloroform; after the evoparation of chloroform; brown coloured compound was obtained. It was then crystallized from ethanol-dimethyl formamide mjx­ture.

1H, 4H-4-0xo-benzopyrano[4,3-c]pyrazoles 4a-d and 4H-4-oxo-1-phenyl-benzopyrano[ 4,3-e ]pyra­zoles 4e-h. A mixture of 1a-d (0.01 mole) and hydra­zine hydrate (0.0 1 mole)/ phenyl hydrazine (O.Olmole) was refluxed separately in ethanol-acetic acid (2: 1) mixture (45 mL) for 10 hr. Solid obtained on cooling was filtered, washed with water and crystallized from ethanol.

4H-4-0xo-benzopyrano[3,4··e]isoxazoles Sa-d. A mixture of 1a-d (lg) and hydroxylamjne hydrochlo­ride (1.5 g) was refluxed in ethanol-acetic acid (2:1) mixture (45 mL) for 8 hr. The solid obtained on cool­ing was filtered, washed with water, and crystallized from ethanol.

3-Benzamido-2, S-dioxo-pyrano[3, 2-e ]benzo­pyrans 6a-d and 3-acetamido-2, S-dioxo-pyrano[3, 2-e]benzopyrans 6e-h. Method A: A mixture of 1a-d (O.Olmole) and hippuric acid (O.Olmole) or N-acetyl glycine (O.Olmole) was refluxed in ethanol-acetic acid (2:1) mixture (45 mL) for 8 hr. Solid obtained on cooling was filtered, washed with water and sodium bicarbonate. It was crystallized from ethanol, yield 75-78%.

Method B: A mixture of 1a-d (O.Olmole) and hip­puric acid (O.Olmole) or N-acetyl glycine (0.01 mole) was heated separately with acetic anhydride and pyri­dine in an oil bath at 150 aC for 12 hr. Mixture was poured on ice. The sticky mass obtained was extracted with dichloromet ane. On evaporation of dichloro­methane compounds 6a-h were obtained, yield 60-65%.

Acknowledgement We are thankful to Mr. S V Chiplunkar, U D C T

Mumbai for elemental analysis, Director, R SIC,

MULWAD et al. : ANTIBACTERIAL COMPOUNDS FROM 4-HYDROXYCOUMARINS 1267

I I T Mumbai and T I F R for I3C NMR and IH NMR spectral analysis, Haffkine Institute, Mumbai for studies in microbial activities and to Govt. of Maharashtra and Lady Tata Memorable Trust for the award of scholarship.

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