摘要:
Both enantiomers of phosphinothricin (1), a naturally occuring amino acid that contains the unique methylphosphinate moiety, were prepared by asymmetric hydrogenation of alpha-acylamido acrylate precursors 7. L-1 and peptides containing L-1 are inhibitors of the enzyme glutamine synthetase (GS). Inhibition of GS is responsible for the antibiotical and herbicidal properties of these compounds. Synthesis of substrates 7 and parameters influencing the enantioselectivity are discussed. Substrate concentration and solvent polarity appear to have the most marked effects on enantiomeric excesses for a given catalyst system. Enantiomeric excesses reach 91 % for hydrogenations with (R,R)-NORPHOS- and (S,S)-CHIRAPHOS-derived catalysts.