Isolation of the First Naturally Occurring Five-Membered Cyclitol as a Constituent of Aiolochrides, Unique Bioactive Glycolipids from the Caribbean Sponge Aiolochroia crassa

Cyclitols are polyhydroxycyclolalkanes structurally related to monosaccharides widely distributed in plants and animals, which serve as precursor of more complex molecules, such as phospholipids and phytates, which are components of cellular membrane structures. Until now, however. cyclitols having ring other than six membered were unknown as naturally occurring compounds. In the course of our investigation on bioactive compounds from marine invertebrates we have now isolated aiolochride-l and -2, two unique amphophilic glycerides. Aiolochrides are close analogues of glycolipids, in which the sugar moiety is replaced by a five-member cyclitol attached to glycerol through an ether linkage. Structures were determined by chemical aand spectroscopic analysis, including 2D NMR techniques (COSY. HETCOR and COLOC). The relative stereochemistries were established by extensive NOE difference experiments. Aiolochrides showed antifeedant activity against Carassius auratus.