Total synthesis of cyclotheonamides E 2 and E 3: application of cyano ylide methodology

Abstract

A total synthesis of cyclotheonamides E 2 and E 3 is reported. A key step in the synthesis involves the formation of the α-keto amide linkage by application of the cyano ylide activation of a carboxyl group as developed in our earlier syntheses of cyclic peptides in the family of protease inhibitors.