Asymmetric total synthesis and stereochemical revision of gymnangiamide.

The asymmetric total synthesis of the originally proposed structure of gymnangiamide, a cytotoxic pentapeptide isolated from the marine hydroid Gymnangium regae Jaderholm, has been achieved. Key to the synthesis was the use of asymmetric hydrogenation of alpha-substituted beta-ketoesters through dynamic kinetic resolution for the preparation of nonproteinogenic chiral amino acids. The disparity of the NMR spectra between the synthetic material containing the L-serine residue and the natural product required a revision of the proposed structure.