Total Synthesis of the Cyclic Depsipeptide YM-280193, a Platelet Aggregation Inhibitor

The first total synthesis of YM-280193, a cyclic depsipeptide that inhibits the ADP-induced aggregation of human platelets, is described. The monomer and dipeptide fragments were prepared using conventional chemistry and subsequently assembled by Fmoc-solid-phase peptide synthesis (Fmoc-SPPS). A late-stage novel bis-alkylation-elimination of cysteine on-resin was employed to introduce the unnatural N-methyldehydroalanine moiety. The final step involved execution of a key macrolactamization reaction between the hindered unnatural N,O-dimethylthreonine and beta-hydroxyleucine residues.