Stereoselective Total Synthesis of the Marine Macrolide Sanctolide A

Abstract

The stereoselective total synthesis of sanctolide A, a 14-membered polyketide-nonribosomal peptide (PK-NRP) hybrid macrolide, was accomplished. Sanctolide A contains a rare N-methyl enamide and 2-hydroxyisovaleric acid functionality embedded into the macrocycle. The synthesis relied on Yamaguchi esterification and intramolecular dehydrative cyclization reactions to construct the core skeleton of the macrolide. The two key chiral centers were generated by Maruoka's allylation and Noyori's asymmetric ketone reduction reactions. Commercially available, inexpensive 2-hydroxyisovaleric acid and hexanaldehyde were utilized as the raw materials for the total synthesis.