Total Synthesis of Spiruchostatin A via Chemoselective Macrocyclization using an Accessible Enantiomerically Pure Latent Thioester

HDAC inhibitor Spiruchostatin A was synthesized via a route that differs significantly from previously reported routes. The key step involves a latent thioester that initiates a chemoselective transformation similar to native chemical ligation to form the macrocyclic alanine-cysteine amide bond. The easily prepared latent thioester-the first such moiety reported in enantiomerically pure form-is designed with a pendant carboxylic acid to serve as a solid-phase linker for the synthesis of cyclic, cysteine-containing, peptidic materials.