Penaresidin A and B, two novel azetidine alkaloids with potent actomyosin ATPase-activating activity from the Okinawan marine sponge Penares sp.

Two novel sphingosine-derived azetidine alkaloids, penaresidin A, 1a, and B, 1b, were isolated as potent actomyosin ATPase activators from the Okinawan marine sponge Penares sp. and the structures elucidated on the basis of spectral data, especially two-dimensional NMR spectra of their acetates.