Arnoamines A and B, New Cytotoxic Pentacyclic Pyridoacridine Alkaloids from the Ascidian Cystodytes sp.

Two new cytotoxic pyridoacridine alkaloids, arnoamines A ( 1 ) and B ( 2 ), have been isolated from the ascidian Cystodytes sp. collected in the vicinity of Arno Atoll, Republic of Marshall Islands. Compounds 1 and 2 are proposed to be the first members of a new class of pentacyclic pyridoacridine alkaloids possessing a pyrrole ring fused to the pyridoacridine ring system. The structures of 1 and 2 were proposed on the basis of the interpretation of spectroscopic data, particularly those obtained from HMBC and NOE NMR experiments. The arnoamines were unexpectedly found to incorporate deuterium at C-10 and C-11 of the pyrrole ring when dissolved in CDCl 3 /TFA- d .