The Asymmetric Total Synthesis and Configuration Confirmation of Aplysiaenal and Nhatrangin A, Truncated Derivatives of Aplysiatoxin and Oscillatoxin.

Asymmetric total syntheses of aplysiaenal (1) and nhatrangin A (2), truncated derivatives of the aplysiatoxin/oscillatoxin family of marine natural products, from configurationally defined intermediates are described. NMR spectra of our synthesized nhatrangin A did not match with either those obtained from authentic samples of the natural product or material obtained via two other total syntheses, but were similar to that obtained from a sample obtained in a third total synthesis. By independently synthesizing the fragments used in its total syntheses, we were able to confirm the configuration of nhatrangin A and clarified that the discrepancy in the spectroscopic data is due to salt formation of the carboxylic acid moiety.