Unguisins A and B: new cyclic peptides from the marine-derived fungus emericella unguis

Unguisin A (1) and B (2), the first cyclic heptapeptides containing GABA in the ring, were isolated from a marine-derived strain of Emericella unguis. The chemical structures of 1 and 2 were elucidated by extensive 2D NMR techniques, and the stereochemistry of the individual amino acids was determined using Marfey's method.