A facile three-step synthesis of (dl)-6,8 dedihydroxyagrimonolide

摘要

3-[2-(4'-methoxyphenyl)ethyl]isocoumarin 2 has been prepared by the condensation of 4-methoxylphenyl-propanoyl chloride with homophthalic acid. Alkaline hydrolysis of 2 yields the keto-acid 3 which is reconverted back to 2 either by treatment with acetic anhydride or with slightly acidified methanol. The keto-acid 3 on reaction with methyl iodide or dry methanol in the presence of a catalytic amount of sulfuric acid affords the methyl keto-Ester-4. (dl)-6,8-Dedihydroxyagrimonolide 6 is obtained by reduction of 3 to the racemic hydroxyacid 5 followed by cyclodehydration using acetic anhydride.