Synthesis of the all-syn C35–C39 stereopentad of etnangien by the γ-hydroxybutenolide approach

Abstract

The synthesis of the all-syn C35–C39 stereopentad of etnangien has been achieved using the asymmetric aldol reaction of a γ-hydroxybutenolide (5-hydroxy-4-methylfuran-2(5H)-one) as the key step in the five-step synthesis. The reaction of the titanium enolate of (S)-4-isopropyl-3-propionyl-2-oxazolidinone with 5-hydroxy-4-methylfuran-2(5H)-one gave good yields and diastereoselectivity of corresponding lactone, which was converted into a lactone with an all-syn stereotriad.