Syntheis and structure of cis-peptidyl prolinamide mimetics based upon 1,2,5-triazepine-3,6-diones

The synthesis of novel constrained cis-peptidyl prolinamide mimetics for the dipeptide amides glycyl (2S)-prolinamide, (2S)-alanyl (2S)-prolinamide and (2R)-alanyl (2S) prolinamide and some analogues, based upon fused 1,2,5-triazepine-3,6-diones, is described; these are suitable for elaboration into larger peptides at both the carboxy and amino termini, X-ray crystal structures for some of the compounds and intermediates are also presented.