The first stereoselective synthesis of (3R, 4E)-19-methylicos-4-en-1-yn-3-ol, an immunosuppressive and antitumoral metabolite isolated from the Caribbean sponge Cribrochalina vasculum, has been achieved and its stereostructure has been confirmed. The key step of the synthesis involves a borane-mediated reduction of the parent (E)-19-methyl-1- trimethylsilylicos-4-en-1-yn-3-one in the presence of a chiral oxazaborolidine.
