Total Synthesis of Keramamides A and L from a Common Precursor by Late-Stage Indole Synthesis and Configurational Revision

Abstract

The marine natural products keramamide A and L, members of the class of anabaenopeptin-type peptides, were synthesized for the first time by a convergent and flexible route. The installation of the substituted tryptophan moieties was accomplished at the very end of the synthesis on the cyclic peptides, and thus enabled the synthesis of both natural products from one common precursor. The preparation of several epimers clearly indicates that the originally proposed relative configurations of both Keramamides A and L were not correct.

Keywords: anabaenopeptins; cyclopeptides; hydrostannation; natural products; tryptophan.