Muraceins--muramyl peptides produced by Nocardia orientalis as angiotensin-converting enzyme inhibitors. II. Isolation and structure determination

Three new muramyl peptides ( muraceins A, B and C) have been isolated from fermentations of Nocardia orientalis as inhibitors of angiotensin-converting enzyme (ACE). Structures 1 and 2, for muraceins A and B respectively, were deduced from their spectroscopic properties. Muracein C, 3, was shown to be a muramyl pentapeptide containing N-acetylmuramic acid, alanine, glutamic acid, serine and diaminopimelic acid in a 1:2:1:1:1 ratio based on the 1H NMR integration.