Preparation and stereoselective hydrogenation of chiral (4-hydroxy-tetrafuranylidene)carboxylates: a new formal entry to functional anti- and syn-3,5-dihydroxyesters

New tert-butyl (Z)- and (E)-((S)-4-hydroxy-tetrafuranylidene)carboxylates have been prepared from (S)-4-chloro-3-hydroxybutyrate and AcOtBu-LDA enolate, and hydrogenated with various achiral and chiral catalysts to give the (2S,4S)- and (2R,4S)-diastereomers of (4-hydroxy-tetrahydrofuranyl)acetates in up to 93% de and 83% yield, and 80% de and 31% yield, respectively.