Aldol reactions of the titanium enolate of (S)-N-propionyl-4-isopropyl-2-oxazolidinone (readily derived from L-valine) with representative aldehydes give high diastereofacial selectivities for the syn aldol adducts expected from chelation control. This represents a remarkable reversal in selectivity compared with the corresponding boron enolate, thus permitting either enantiomeric form of &hydroxy-a-methyl carboxylic acids to be made from ...
