A novel synthetic route to the hexahydrobenzofuran subunit of the avermectins and milbemycins

Radical-induced intramolecular Michael cyclization of a bromovinyl-type appendage onto a functionalized cyclohexene carboxylic acid derivative produces the corresponding oxahydrindanes which can be transformed into oxahydrindenes (hexahydrobenzofurans) related to the title compounds. (−)-Quinic acid is a useful optically active precursor.