A Synthetic Approach to 3-Hydroxy 4-Substituted Carboxylic Acids based on the Stereoselective Reduction of 1-Trimethylsilyl-1-alkyn-3-ones

The oxazaborolidine-mediated reduction of chiral, 4-substituted 1-trimethylsilyl-1-alkyn-3-ones followed by hydroboration affords syn or anti 3-hydroxy 4-substituted carboxylic acids, common substructures of a number of biologically active macrolides, peptides and depsipeptides, with high control on the new C(3) stereocenter. This strategy has been applied to the synthesis of (3S,4S)-3-hydroxy-4-methylheptanoic acid and of N-Boc-statine, constituents of permentin A and pepstatin, respectively.