Stereoselective formation of optically active 2-oxy-1,3-oxazolidin-4-ones and an efficient synthesis of optically active secondary 2-pyrrolidones

Treatment of (−)-O-acyllactamides or mandelamides with TBSOTf in the presence of base gives optically active 2-oxy-1,3-oxazolidin-4-ones stereoselectively, which serve as useful precursors for the preparation of optically active secondary 2-pyrrolidones via radical cyclization and subsequent one-step removal of mandelic acid.