Diastereo- and enantioselective hydride reductions of ketone phosphinyl imines to phosphinyl amines - Synthesis of protected amines and amino acids

Three protocols involving asymmetric reductions of ketone phosphinyl imines (1) to enantiomeric or diastereomeric phosphinyl amines (2), (which represent protected versions of primary amines), are presented, including the use of substrates containing diastereotopic faces to stereoselectively generate diastereomers, employment of chiral reagents for enantioselective reductions, and the utility of chiral auxiliary attachments for diastereoselective reductions followed by release of enantiomeric amines. [GRAPHICS] rded rate of borane coordination and competition from the endo transition state. Relative enantioselectivities were correctly predicted by ab initio calculations, and the calculated structures, energetics, and the existence of key intermediates were demonstrated to be sensitive to the level of theory applied. Ab initio calculations and utility of diphenyloxazaborolidine are described in detail.