The structures of cirratiomycin A and B have been elucidated by a degradative study and 1H-and 13C-NMR spectral analysis It is revealed here that cirratiomycin A and B are heptapeptides containing three unusual new ammo acids, viz, hydroxymethylserine, 2, 3, 4, 5-tetrahydropyndazme-3-carboxyhc acid and 2, 3-didehydroisoleucine.
