PREPARATION OF RACEMIC 2r-CARBOXY-TRANS,TRANS-3, 4-DIDEUTERO-PYRROLIDINE (DL-TRANS,TRANS-3, 4-DIDEUTERO-PROLINE) AND UNAMBIGUOUS ASSIGNMENT OF PROTONS IN THE 1H N.M.R. SPECTRUM OF PROLINE

Racemic trans, trans-3,4-dideutero proline has been prepared by catalytic deuteration of 3-pyrroline-2-carboxylic acid. The stereospecificity of the reduction (i.e. trans to the carboxylic group) was ascertained after transformation of the dideutero compound into the diketopiperazide c/Pro, Aib/, for which unambiguous proton assignments in the ¹H n.m.r. spectrum had been obtained previously. The identification of the configuration of the dideutero-proline allows for the affirmation of the correctness of proton assignments as previously proposed in literature.