Total Synthesis and Structural Establishment/Revision of Antibiotics A54145.

A54145 is a family of antibacterial cyclic lipodepsipeptides structurally resembling daptomycin. Since its discovery in 1990, only the ambiguous structures of the methoxy-aspartic acid (MeO-Asp) and the hydroxy-asparagine (HO-Asn) have been reported. We have developed efficient routes to obtain the fully protected l-MeO-Asp and l-HO-Asn building blocks compatible with Fmoc-SPPS, and a total synthesis of A54145 that enabled us to establish its structure, consisting of l-3 S -HO-Asn and l-3 R -MeO-Asp, revising the wrongly proposed structure of l-3 S -MeO-Asp.