Indian Journal of Chem istry Vo l. 40B. March 200 I. pp. 222-227

Synthesis and studies on biological activities of some substituted 2-benzopyran.­lH-one, lH-2-oxo-benzopyran-3-carboxylic acids and 2-benzofuran-1 (H)-one 1

NV Purohit

Department of Chemistry , Facu lty o f Science. M S Universi ty o f Baroda, Vadodara 390 002

Receil·ed 25 May / 999; accepted (revised) 23 February 2000

Prompted by the varied bi o logica l and herbicidal properti es, the title compounds have bee n convcni emly prepared by reflu xing o-acyl/aroy lbcnzoic ;~cids la-c I 4a-f with substituted I unsubstituted phen;~cyl bromides 2a-e or di ethy l brornomalonate 7_in e thy l methy l ketone in the prese nce o f potassium carbollJ te. A lithe compounds have been scree ned for different bi o log ical ac ti vities. The compounds 3b-e,i. Sb,d ,f, and 8a,b show sig nifi can t blood pressure e ffec t o n rat s_in ,.;,.u whereas spasmod ic contrac tio n is shown by 3c,c,i, and Sf in rat illium in t•itro. Blood ant icoagu lant ac tivity . bleeding time/c lott ing time has al so been reco rded for a few compounds 3a,c,c,i. A few isocoum:trins 3d,e,h,i,g have been ex;~ mined ag;~in s t different kinds o f microbes. PhthJ iidcs Sa-c show remarbbl e result s in growth and germination o f seeds pi geon pe;~

(Tuv;~r Var ICP) and triticum es tium (Wheat) in the recorded peri od.

A large number of heterocyc lic compounds have displayed va luable properties on chemotherapeutic agents. Several 2-benzopyran-1 H-one (isocoumarins) and 2-benzof uran-1 H-one (ph th alides) isolated from vari ous natural sourcesu showed a wide range of bio logical ac ti vity-'. Many of the i socoumarins~-6 have been sy nthes ised by earlier workers but aroyl substituted isocoumarins7 are relative ly less known and so are their bio logical activities. Some of the isocoumari ns are found to be antiallerg ic drugs8

, some of them have mild coronary dialating and an ti spasmodic ac ti vity9

• Dicoumaro l and its derivatives which are known for their anticoagulant properties are bi scoumarins. Isocoumarin-3-carboxylic acid was about one half as effecti ve as dicoumarol in re tard ing clotting of the blood and isocoumarins caused only a transient fall in bl ood pressure in anes theti zed cats10

•

lsocoumarins and 3,4-dihydroisocoumarins are the metabolites of a wide variety of fungi, bacteria, insects and higher plants·'- '' · Phthalides are found to be useful as herbicides, for the growth of germination of seeds 12

and show antimicrobial properties u. Keeping in view the above facts, we report herein

the structure activity and structure biological activity relationship of the title compounds

In the present paper attempts have been made to synthesize 3-aroyl-4-alkylisocoumarins 3a-i by refluxing o-acy lbenzoic ac id 1 wi th phenacyl bromide 2 in the presence of anhyd . potass ium carbonate in ethyl methyl ketone. No side product was detected

t Postcr presentatio n at ICOS- 12 at Ve nice (Italy). 28'h June-2"d July, 1998.

from the reaction mixture (Scheme I) . Different isocoumarins were sy nthes ized by using different substituted phenacy l bromides and by using propiophenone-o-carboxy li c acid lb. buty rophenone­o-carboxylic acid lc in place of acetophenone-a­carboxy lic acid.

We have extended thi s reaction to o-aroy lbenzoic ac ids 4a-f where we fai led to isolate the expected isocoumarins but a mi xture of two compounds, phthalides Sa-f and glyoxal 6 were obtained711

(Scheme II) which were characterized by elemental analyses and spectral (IR , 'H NMR and mass) data (Table I) .

As an ex tension of the work of Chattetjee et af;

some new 4-substituted isocoumarin-3-carboxy lic acids 8a-b were synthesized to record other bi ological activities apart fro m anticoagulant activity ' from o­acy l/aroy lbenzoic ac ids (lb, 4b) on re fluxing with diethy lbromo malonate 7 in the presence of potassium carbonate in ethyl methyl ketone (Scheme III).

Biological activity A chemical structure known to have a particul ar

biological activity is choosen and attempts are made to improve it by modification based on chemical institution and steric consideration until a h ighly active compound with minimal side effect is produced.

Blood Pressure effect 4-alkyl-3-aroylisocoumarins 3a-e,i 4-alkyl/aryliso­

coumarin-3-carboxy lic ac ids 8a,b and some 3-ary l phthalides Sb, d, f were tes ted on rats fo r observing

R

0

PUROHIT: SYNTHESIS OF SUBSTITUTED BENZOPYRANS

COAr COR

.,. Path-a ©:: + COOH

H R

B/' COM P•lh-b .. ©:1 0

R

COR

©::+ COOH

A anhydK2C03 ~COAr Br COAr --------:~ 0

~ 1 reflux, 8-10hr

2 0 3 0

1a, R=CH3

2a and 3a, Ar = ----© 1c, R = C3H7

2band3b, Ar= =---©--oH

HO

2f and 3f, Ar = ----© 2c and 3c, Ar= ~OH 2d and 3d, Ar = ----@-C~

2e and 3e, Ar = ----@-ocH3

2g and 3g, Ar= ----@-cH3

2h and 3h, Ar = :-© HO

2iand3i,Ar= ~OH Scheme I

©::COAr'+ A anhyd K2C03 ~:+ Br COAr

COOH ~ 1 reflux, 8-10hr

4 2a 0 5 0

Ar=© 4d and 5d, Ar' = --<Q>--cH3

4a and Sa, Ar' =--©

CH3

4b and 5b, Ar' = --6c~

4oood5o,M=-g

41 ood Sf, M = --s-OCH0

4oood5o,M=~Oio Scheme II

ArCOCHO

6

223

blood pressure effect which was recorded on student physiograph in vivo (Table II). B.P. effect was found to be more prominent where aryl group is resacetophenone hav ing two -OH groups (3c) and where OCH, is attached to napthyl or phenyl group

(Sf,3e) than ary l g roup without any substi tution or substitution with one -OH or one -CH, group

(3a,b, Sd, 8a,b) where it was found to be nominal. Thi s may be because biological activity apart from chemical and physical properties mainl y depends on

224 INDI AN J. C HEM., SEC. B, MA RCH 200 1

Table 1-The charac teri zatio n data o f compounds 3b,e,g,h,i,Sf, and Sa,b

Compd mp Mo l. Found o/o (Calcd) IH NMR Mass oc fo rmula (CDCI3 , 8, ppm) m/z

c H 3b 105-6 C l7 HI20 4 72.7 4. 27

(72.8 4.28) 3e semi - C1 sH1404 73.6 4 .86 2.55(s,3H,-CH3) 3.95

solid (73.4 4 .78) (s,3H -OCH3) 6.75-7.7

(m.,7H, ArH ) 7.95(d,J=8Hz, IH, C8 -H)

3g 142 C 19H1 60 J 77.53 6 . 11 2.2(q,2 H,CH2C H3) 2.45 (78.08 5.47) (s,6 H-CH2-CH.1) 7.2-7 .7

(m.Ar H), 7.9(d, J =8 Hz, I H at C8)

3h 11 8-1 9 C1 9H160 .1 78.02 5.49 (78.08 5.47)

31 60 CJ 9H Jr,O, 70.02 4. 19 1. 12( t,J=7 Hz 3H,-C H2-CHr Cfh ). (70.37 4 .9 ) 2 .8 -3 . 4(m,4H ,-CH2-CHrCH .~ )

7.4-7.8(m, 7H, ArH), 7.9(d,J=8Hz, I H, C8-H)

Sf 193-94 C1 9H140 3 78.4 4 .7 290(M.,41.37 %) (78.6 4 .8) 259(M· -o c H3.15 .91 %)

Sa 182-83 C 12H1004 66 4.5 1.36(t,J=7H z,3 H,C HrCfh). 2. 18(M+ ), 173 (M+ (66.1 4 .6) 3.3(q,J =7 Hz, 2H-CH2-CH3 -COOH )

7.6-8 .0(m,3H,Ar.H), 8.5 (d.J =8Hz. I H. C8-H)

8b 204-5 C 1sH1404 73.2 5.02 294(M +), (73.5 4.8) 279(M+ -Me).234

(M•-Me- COO H)

R

0 COR anhyd K2C03 ©(;tCOOH

+ BrC H (COOEt)?---------... O

1 COOH

7 /[(, reflux, 8-10hr

0 0 B

Scheme III

steric and polar effects and local electronic configuration. It is also fo und that biological acti vity mainl y depends on the electron density of the aromati c ring and prov ides a means of predicting acti vites of potential new compound. In our cases acetophenone havi ng two -OH groups is much more electron richer than acetophenone having one -OH or one -CH, group . It may be one of the reason for showing B.P. effect. In other compounds (Sf, 3e) where aryl group is naphtyl methyl ether, shows fall in B.P. si nce - OCH3 group is much more electron releasing than CH3 group so we can emphasize that electron negativity played an

important ro le fo r showing B.P. effect. Secondly, inter/intra molecular hydrogen bonding may be another factor fo r showing B.P. effec t.

Spasmodic contraction It was tested in rat ilium ( I mg/mL) in vitro in

isolated organ bath . Here much contraction was not found. For the same reason as in the case of B.P. effect in compounds, 3c,i having 2 -OH groups showed sli ght spas modic contraction (Table II) and a littl e effect was seen in 3e with aryl group as anisol (-OCH3) and in other cases it was found to be nil.

PUROHIT: SYNTHESIS OF SUBSTITUTED BENZOPYRANS 225

Table 11- Biood pressure e ffec t and spasmodic contraction in vivo

B.P.effect S2asmod ic contracti on Compd Dose Effect dose e ffect

3a IJ.J g/mL -ve -ve 1mg/mL -ve

3b 1J.J g/mL -ve -ve lmg/mL +ve

3c 1J.J g/mL +ve +ve

3d 1J.J g/mL -ve -ve lmg/mL +ve

3e IJ.l g/mL +ve lmg/mL +ve

31 1J.J g/mL +ve +ve

Sb IJ.J g/mL -ve -ve 1mg/mL +ve

Sd IJ.J g/mL -ve -ve lmg/mL +ve

Sf IJ.J g/m L +ve +ve

Sa IJ.l g/mL -ve -ve lmg/mL +ve

8b IJ.l glmL -ve -ve Jm o/mL +ve

Blood anticoagulant activity 15

Blood coagulation tests were performed in vitro. in cow blood and goat blood at a dose of 3 mg/ml (Table Ilia). Bleeding time and whole blood clotting time were recorded with samples 3c,e and 3i on different mice at a dose of 3 mg in vivo. Normal bleeding time on particular mice was found to be I 0 min (Table Illb). Here also, as in case of B.P. effect methoxy group attached to phenyl was found to be most active and all the rats remained alive after giving one dose.

Antiallergic properties, spasmodic contraction in gunipig is still in the process .

Antimicrobial activity Several isocoumarins and phthalides with a

variation in the substitution pattern at position -3 of the benzopyran and benzofuran ring have been screened in vitro for antibacteri al activity (Table IV). 0. 1 mL of I mg/mL solution of the compound in methanol was tested by cup pl ate method aga inst gram-positive bacteria as Staphylococus aureus and gram-negative bacteria as Escherichia coli and all compounds were found to be ac tive agains t the bacteria (Table IV) .

Table Ilia--Blood anticoagulant activity ill vitro at a dose of 3mg/mL

Animal Blood Compd. Coagulation time Cow 3a not favourab le

Goat 3i 3a 3e

not favourabl e 4-6 hr 5-6 hr

Table I lib--Bleeding time/clotting time ill vivo at a dose of 3mg

Animal Compd Bleeding time Tox ic ity (min)

3c 15 Nonotox ic (a ll rats

Mice 3e 15-1 8 were ali ve) 3i 15-1 8

Table IV-Antibacterial activity of compounds 3d,e,h,i,g, (Zone on inhibition in mm)

Compd 3d 3e 3h 3i 3g Methanol( control)

Herbicidal properties

E coli S.aureus

11.1 11.0 EO

11 11.2

11 11.3

To test the herbicidal properties of the phthalides (Scheme II) , compounds synthesised were tested on seeds pigeon pea (Tuver var ICP) and Triticum estium (wheat). The growth and germination was recorded in 48 hr, 96 hr and 144 hr, respectively and compari son with the control showed good results (Table V) .

As it is evident from the Table V (Scheme II) when ICP variety of pigeon pea was treated with given compounds (phthalides) good results were obtained in 48 hr and better results were obtained in 96 hr. In compound Sb,more number of secondary laterals were formed whereas in case of wheat the roots were more elongated. The results were good with Sa,c. But in case of Se with wheat the germination was nil in 48 hr and in 96 hr and only in 144 hr it was 60% and in case of pigeon pea the germination was 80%. 100% germination was recorded after 144 hr in case of Sd. In general the results show more pronounced growth in ICP variety of tuver than in wheat variety. When aryl group is napthyl , germination takes time but when ary l group is a-xyloyl (two methyl groups in the a­position) the result is excellent. Aryl group as phenyl, tolyl and p-xyloyl also gives the result but the effect of two -CH3 groups in ortho position helps much better

Experimental Section General. All mps were determined in open

capill aries and are uncorrected. The purity of the

226 INDIAN J. CHEM., SEC. B. M A RCH 200 1

compounds in add ition to e lemental analysis were checked by TLC. IR spectra were recorded on shimadzu 408 spectrophoto meter, 1H NMR spect ra on a Perk in-Elmer R-32 (90 MH z) spectrometer us ing TMS as internal standard and mass spec tra on a Jeol D-300 instru ment. Compounds 3a,c, d ,f and Sa-e were prepared by literature methods7· ~.~.

4-Methyl-3-( 4 1 -methoxyaroyl)-2-benzopyran-1 (H)­one 3e. A mixtu re of 4-bromoacetyl an isole 2e ( 1. 1 g, 0.005 mole), acetophenone-a-carboxylic ac id la (0.82g, 0.005 mole) and anhyd. potass ium carbonate (2.0g) in 15mL dry methyl ethyl ketone was reflu xed for 8-10 hr on a steam-bath . Solven t was then removed and water was added, it was ex trac ted with ether. Ethereal layer was washed with water and dried over anhyd. sodium sulphate. After removal of ether, the crude product was crystallised from petro leum ether (60-80"C) - methanol to g ive 3e (50-55%) . Compound 3b was prepared s imil arly. The characterization data of 3b,e are given in Table I. 2,4-Dinitro derivati ves were prepared fo r 3b-e whi ch gave sati sfactory nitrogen analys is.

4-Ethyl-3-( 4 1 -methylbenzoyl) -2-benzopyran-1(H)­one 3g. A mixture of 4-bromoacety lto luene 2b ( 1.065g, 0.005 mole), propiophenone-o-carboxy lic 1b (0.9g, 0.005 mole) and anhydrous potass ium carbonate (2.0 g) in 15mL dry methyl ethyl ketone was reflu xed fo r 8-10 hr on a steam-bath . Solvent was then removed and water was added. It was ex tracted with ether, ethereal layer was washed with water and dried over anhydrous sodium sulphate. After removal of ether the crude product was crystalli sed from petroleum ether (60-8QoC)-methanol to g ive 3g (50%) compound 3f was prepared simil arl y. The characteri zation data of 3g,f are given in Table I. 2,4-Dinitro deri vatives were prepared which gave sati sfactory nitrogen analysis.

4-Propyl-3-aroyl-2-benzopyran-1(H)-one 3h. A mi xture of 2-bromoacetophenone 2a (l g, 0.005 mole) buterophenone-a -carboxylic acid 1c (lg, 0.005 mole) and anhyd. potass ium carbonate (2.0 g) in 15mL dry methyl ethyl ketone was refluxed fo r 8-10 hr on a steam-bath. Solvent was then removed and water was added, it was extrac ted with water and dried over anhyd sodium sulphate. After removal of the ether, the crude product was crystalli sed fro m pe t. ether (60-800C)-methano l to give 3h (45 %).compound 3i was prepared simi larly . The characterization data of 3h,i arc given in Table I. 2,4- Din itropheny l hydrazone derivat ives were prepared whi ch gave satisfactory nitrogen analysis.

Table V-Percentage germi nation of pegeon pea tu ver seeds and wheat seeds (kudki) on 5 different phllhalides

Days % germi nati on of pegeon pea tuver seeds(% germ inati on of (k udk i) wheat seeds)

Sa Sb Sc Sd Se

2 4 6

90 (30) l OOt (30) lOOt (80)

90 (70) t 90t (80) ~

100* (90)

tshows more elongated roo ts ~more No. of roots

80 (-) l OOt(-) 100 (20)

80 (40) - (-) 80 (70) t - (-)

lOOt (I 00) 80 (60)t

(-)reading does not show any change data recorded at 24± 1°C

3-( 4 1 -Methoxynapthyl)-2-benzofuran-1 (H)-one Sf. A mixture of 2a bromoacetophenone (lg, 0 .005 mole), a-(4-methoxy napthoyl) benzoic ac id 4f ( 1.5g, 0.005 mole) in dry methyl ethyl ketone (15mL) was refl uxed for 10-12 hr. After removal of solvent sufficient water was added to di ssolve potass ium carbonate and ex trac ted with ether. Usual work-up resul ted in a crude mixture containing two compounds (T LC). The crude product was left overn ight in a mixture, of pet. ether (60-80°C) - methanol, when solid settled at the bottom. It was crystall ised from methanol (40-45%). From the mother liquor phenyl glyoxa l 6 was isolated . It gave osazone ( 149-50°C) and other sati sfactory chemical tests. Formati on of pheny l g lyoxal was finally comfirmed by its synthesis fo llowing the known procedure . ~.~ Compounds Sa-e were prepared simil arly. Melting points of all the phlthalides are known7

'14

•

4-Ethyi-1H-1-oxo-2-benzopyran-3-ca rboxylic acid Sa. To a mi xture of propiophenone a-carboxy lic acid 1b (l g 0 .005 mole) and anhyd potassium carbonate ( 1.6 g) diethyl bromomalonate 7 (l .OmL, 1.4g) was added and the mi xture was retluxed wi th methyl ethy l ketone (20 rnL) fo r 7-8 hr. After completion of react ion, reaction mi xture was taken out and solvent was removed . The product was treated with water to di ssolve excess of potass ium carbonate and extracted with ether. The ethereal layer was washed with water, dri ed and fin all y removal of ether resul ted in a thick oil. The o il was puri fied through a column of silica gel using methanol as eluent. The oil was dissolved in acetic acid (9 mL) and was heated for 2 hr with cone. HCI (1 2 mL). The hydrolysed prod uct was poured into water, left overnight. The precip itated product was filtered under suction, washed wi th water and finally dried . Recrystallisation from methanol result ed co lou rl ess crystal s (40%). S imi larly 8b was prepared (Table 1).

PUROHIT: SYNTHESIS OF SUBSTITUTED BENZOPYRANS 227

Acknowledgement Author is grateful to the Heads, CDRI, Lucknow,

Sun Pharmaceutical Industries Ltd . Baroda for I R, NMR and mass spectral analysi s, to Dr Balramman and Dr Rathore, Department of Pharmacy, M.S. University Baroda, to Dr Thakker, Dispensary of Verternary Polyclinic Baroda, Dr Geeta Padate Department of Zoology, M.S. University Baroda for screening B.P. effect, spasmodic contraction, Blood anticoagulant act tvtty etc., to Mrs Aparna S, Biotechnology Department, M. S. University, Baroda for antibacterial activ ity, to Dr Arun Arya Department of Botany M.S. University, Baroda for his guidance to check the herbicidal properties on different seeds.

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