Reaction of (trifluoromethyl)trimethylsilane with oxazolidin-5-ones: Synthesis of peptidic and nonpeptidic trifluoromethyl ketones

(Trifluoromethyl)trimethylsilane (TMS-CF3, the Ruppert Reagent) reacts with a variety of amino acid derived N-substituted oxazolidin-5-ones in excellent yields. Mild acid hydrolysis of adducts with electron-releasing substituents at C-2 affords N-substituted cx-amino trifluoromethyl ketones (TFMKs). N-CBZ-protected alpha-amino TFMKs are converted into hitherto unreported hydrochloride salts of alpha-amino TFMKs by hydrogenolysis. Coupling with aminoacid fluorides gives access to peptidic TFMKs which are of utility as protease inhibitors.