Protected Lactam-Bridged Dipeptides for Use as Conformational Constraints in Peptides

Article abstract of DOI:10.1021/jo00340a023

General methods have been devised for the synthesis of lactam-constrained dipeptide analogues having five-, six-, and seven-membered rings.Three different paths from protected chiral α-amino acids to lactams involving intramolecular alkylation, intramolecular acylation, and insertion of a one carbon unit by condensation with formaldehyde have been utilized.The first two methods produce chiral products stereospecifically, but considerable racemization occurs in the third route which leads to a 4-oxo-5-amino-1,3-thiazine (13).The products are prepared in good yield and have protecting groups making them suitable for incorporation into higher peptides by methods commonly used.