Synthesis of quinone pyrano-.gamma.-lactone antibiotics. 1. Synthesis of 9-deoxykalafungin

An efficient synthesis of 9-deoxykalafungin (lb) in six steps from readily available starting materials is described. The key step, in which all of the carbon atoms present in the target molecule are assembled, is the addition of 2-tert-butoxyfuran to 2-acetyl-l,4-naphthoquinone. Hydride reduction, followed by removal of the tert-butyl protecting group and addition of the C-1 alcohol to the unmasked hutenolide, affords intermediate 13, which can be oxidized with argentic oxide to lb in 17% overall yield.