Total synthesis of cytotoxic metabolite ( ± )-desmethyldiaportinol from Ampelomyces sp.

A concise total synthesis of ( ± )-desmethyldiaportinol isolated from Ampelomyces sp. is described. Microwave-assisted cyclocondensation of 3,5-dimethoxyhomopthalic acid with 3,4-dibromobutanoyl chloride afforded the 3-(2,3-dibromopropyl)-6, 8-dimethoxyisocoumarin in 2-3 min as the pivotal step. The 3,4-dibromobutanoyl chloride was itself synthesised from 3-butenoic acid via bromination in carbon tetrachloride at room temperature to yield 3,4-dibromobutanoic acid followed by reaction with thionyl chloride. The replacement of bromo- by hydroxyl substituent was achieved under mild conditions involving the refluxing in a mixture of acetone and water to provide ( ± )-3-(2,3-dihydroxypropyl)-6,8-dimethoxyisocoumarin which on complete demethylation furnished the title natural product.