Asymmetric Synthesis of (−)-Dihydroxanthatin by the Stereoselective Oshima−Utimoto Reaction

[reaction: see text]. The catalytic stereoselective Oshima-Utimoto reaction is useful for the construction of five-membered oxacycles from simple starting materials and was employed for the preparation of the lactone group in the asymmetric synthesis of (-)-11alpha,13-dihydroxanthatin. Completion of the synthesis is facilitated by ring-closing enyne metathesis and alkene cross metathesis reactions.