Asymmetric Total Synthesis of 16-Methyleicos-(4E)-en-1-yn-3-ol from the Marine Sponge Cribrochalina vasculum: Establishment of Absolute Configuration of Chiral Centers

The first total synthesis of 16-Methyleicos-(4E)-en-1-yn-3-ol, a bioactive component of the marine sponge Cribrochalina vasculum was achieved by Evans auxiliary methylation followed by resolution of the corresponding racemates using lipase formulation Novozyme 435 and Mosher's ester method. We report the asymmetric syntheses of four diastereomers (1 a-d) of the natural compound 1 and established the absolute configuration of chiral centers, leading to the revision of the natural product configuration from 3 S to 3 R.