SYNTHESIS OF ANTIBACTERIAL ISOCOUMARINS - SYNTHESIS AND ANTIBACTERIALACTIVITY OF 3-ALKYLISOCOUMARINS AND (DL)-3-ALKYL-3,4-DIHYDROISOCOUMARINS

3-Pentyl- and 3-undecylisocoumarins 2a,b have been conveniently prepar ed in high yields by direct condensation of acyl chlorides with homoph thalic acid. Alkaline hydrolysis of 2a,b yields the corresponding keto acids 3a,b. The latter are reconverted to 2a,b either by treatment wit h acetic anhydride or with slightly acidified methanol. Treatment of 3 a,b with methyl iodide or dry methanol in the presence of a catalytic amount of sulfuric acid affords the methyl keto-esters 4a,b. (dl)-3,4- Dihydroisocoumarins 6a,b are obtained by reduction of 3a,b to the race mic hydroxyacids 5a,b followed by cyclodehydration using acetic anhydr ide. The isocoumarins 2a,b and dihydroisocoumarins 6a,b have been exam ined in vitro for their antibacterial activity. Compounds 2a and 6b sh ow significant activity comparable to the standard antibiotics.