Ircinols A and B, First Antipodes of Manzamine-Related Alkaloids from an Okinawan Marine Sponge.

Abstract Two new manzamine-related alkaloids, ircinols A ( 1 ) and B ( 2 ), have been isolated from the Okinawan marine sponge Amphimedon sp. and the structures elucidated to be enantiomers of alcoholic forms at C-1 of ircinals A and B, respectively, on the basis of extensive 2D NMR data and chemical correlations. Compounds 1 and 2 are the first examples possessing opposite absolute configurations to those of manzamine alkaloids.