STRUCTURES OF 3 NEW CYCLIC HEPTAPEPTIDE HEPATOTOXINS PRODUCED BY THE CYANOBACTERIUM (BLUE-GREEN-ALGA) NOSTOC SP STRAIN 152

Three new hepatotoxic cyclic heptapeptides in the microcystin class were isolated from the cyanobacterium (blue-green alga) Nostoc sp. strain 152 and assigned structures based on their high-resolution FABMS, FABMS/MS, 1H and 13C NMR spectra, amino acid analysis, and GC on a chiral capillary column. All three toxins (1–3) have 9-acetoxy-3-amino-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid as an unusual structural component (Scheme I) instead of the corresponding 9-methoxyl derivative (Adda) found in the microcystins. © 1990, American Chemical Society. All rights reserved.