HYDROGENATION OF COMPLEXES OF DIASTEREOTOPIC N-BENZOYLDEHYDRODIPEPTIDES

The replacement of the N-acetyl group by an N-benzoyl group in N-acyld ehydrodipeptides results, first, in an increase in the asymmetric indu ction in their hydrogenation in the case of N-Bz-Delta Phe-(S)-Glu. N- Bz-(S)-Phe-(S)-Glu is obtained with a diastereomeric excess (de) of 52 %. Second, no poisoning of the Pd-catalyst by sulfur in N-Bz-Delta Ph e-(S)-Met occurs, and N-Bz-(R)-Phe-(S)-Met is obtained with a de of 26 %. The formation of complexes of N-Bz-Delta Phe-AA with Ca2+ and Mg2 ions does not, as a rule, affect the diastereoselectivity of the hydr ogenation. The structure of the dehydrodipeptides has been determined on the basis of H-1 NMR spectra, potentiometric titration, and molecul ar mechanics calculations.