Convergent synthesis of the spiroacetal fragment of milbemycin β1
Abstract
Milbemycin spiroacetal 4 was prepared from (4S,5R)-4,5-dimethylpentan-5-olide 5 and (R)-1-(benzyloxymethyl)oxirane by alkylation and stereoselective reductive decyanation of the intermediate spiroacetal cyanohydrin 7.