A catalytic deuteration of protected 3,4-dehydro-L-proline using RuCl2
(PPh3)(3) followed by RuO4-oxidatian gave a 3,4-dideuterated L-pyroglu
tamic acid derivative which is considered to be a promising precursor
far various deuterated amino acids. The present study demonstrates a s
tereoselective reduction of the amide carbonyl moiety leading to L-pro
line derivatives in which all of the ring methylenes are stereoselecti
vely labeled with deuterium. (C) 1997 Elsevier Science Ltd.