Total synthesis of (+)-breynolide

Abstract The total synthesis of (+)-breynolide ( 2 ) is described. The primary focus is the synthesis of the advanced aldehyde intermediate 12 , which comprises the cis -fused perhydrobenzothiophene ring system. Three stereoselective cyclohexene epoxidation/epoxide opening sequences and a glycolate ester Claisen rearrangement, by which all of the necessary oxygen functionality in 12 is introduced before installation of the thioether, are employed.