Synthesis of obscuraminol A using an organocatalyzed enantioselective Henry reaction

Abstract

The first synthesis of the polyunsaturated amino alcohol natural product obscuraminol A is reported. This stereoselective synthesis was based on an anti- and enantioselective organocatalyzed Henry reaction followed by a chemoselective SmI2-mediated reduction that affected only the nitro-group of the Henry product. These efforts yielded obscuraminol A where the configuration of the all-Z skipped double bonds was conserved from the starting material, i.e. the ethyl ester of (all-Z)-eicosa-5,8,11,14,17-pentaenoic acid. Our synthesis confirmed the reported structure of obscuraminol A.