ONE-STEP SYNTHESIS OF 3-(PHENYLETHENYL)ISOCOUMARIN AS A MODEL OF ACHLISOCOUMARIN-II AND ACHLISOCOUMARIN-III AND ITS CONVERSION TO 3,4-DIHYDRO-DERIVATIVE

3-(Phenylethenyl)isocoumarin (4) which is a model of achlisocoumarin I I (2) and achlisocoumarin III (3) was synthesised by the direct conden sation of homophtalic acid with cinnamoyl chloride. This isocoumarin ( 4) on hydrolysis with aqueous potassium hydroxide in ethanol yielded k eto-acid (5) which was characterized by the formation of keto-ester (6 ). Reduction of the keto-acid (5) with sodium borohydride followed by cyclodehydration gave (dl)-3-(phenylethenyl)-3,4-dihydroisocoumarin (8 ). Isocoumarin (4) and 3,4-dihydroisocoumarin (8) were screened out in vitro for antibacterial activity.