Synthesis of the Spiroketal Fragment of (–)‐Ushikulide A

Abstract

Abstract The stereoselective synthesis of the spiroketal fragment of the immunosuppressant (–)‐ushikulide A is described. The salient feature of this synthesis is the construction of the spiroketal moiety by hydrolysis of a dialkylated tosylmethyl isocyanide derivative derived from alkylation of tosylmethyl isocyanide (TosMIC) with suitably substituted halohydrin derivatives. The key functionalized tetrahydropyran ring was constructed by using Prins cyclization of the α‐acetoxy ether.