Progress towards the Synthesis of (‐)‐Ushikulide A: Synthesis of C1‐C15 Aliphatic and C17‐C31 Spiroketal Fragments by an Aldol Approach

Abstract

A convergent approach towards the total synthesis of an immunosuppressant (‐)‐ushikulide A, has been described. Herein, we disclose the synthesis of the C1‐C15 linear fragment and the C17‐C31 spiroketal fragment of (‐)‐ushikulide A by the aldol approach. The C1‐C15 aliphatic fragment was synthesized by applying Evans syn aldol, acetate aldol reaction and the C17‐C31 spiroketal fragment of (‐)‐ushikulide A was achieved via non‐Evans syn aldol as well as spiroketalization reaction. The precursors for the spiroketalization reaction were synthesized from a common intermediate, derived from the non‐Evans syn aldol reaction.