Enantioselective Synthesis of Diverse .alpha.-Amino Phosphonate Diesters
摘要:
An efficient, versatile protocol for the synthesis of highly enantioenriched alpha-amino phosphonate diesters has been devised. Addition of lithium diethyl phosphite to chiral chelating imines 31a-j, prepared from a variety of aldehydes and the chiral auxiliary (R)-(-)-1-amino-1-phenyl-2-methoxyethane (29), generated predominantly the (R,R) diastereomers 33. Hydrogenolysis then furnished alpha-amino phosphonates 15; in most examples, the enantiomeric purity exceeded 97% ee.
The Lewis acid promoted reaction of silyl enol ether to chiral imines and 1,3-oxazolidines derived from (R)-phenylglycinol afforded with good diastereoselectivity the (R,R)-β-amino ester derivatives from the imines, and the (R,S)-β-amino ester derivatives from the 1,3-oxazolidines.