Oxocyclostylidol, an Intramolecular Cyclized Oroidin Derivative from the Marine Sponge Stylissa caribica

Pyrrole-imidazole alkaloids are widely distributed in marine sponges of the orders Halichondrida and Agelasida. Chemical investigation of the Caribbean sponge Stylissa caribica has led to the isolation of the first brominated pyrrole-imidazole alkaloid containing an oxidized pyrrole moiety. The isolation and structure elucidation of oxocyclostylidol (1) are discussed in detail.