Halichondrins-antitumor polyether macrolides from a marine sponge

Newantitunor polyether macrolides were successfully isolatedfron a marine sponge, Halichondria okadai Kadota. One of them, halichondrinB exhibited remarkable in vivo antitumor activity. Physiological propertiesand structures of these compounds are reported herein. The structures havebeen characterized by a long—straight carbon chain, a polyether macrolide,and a novel 2,6,9—trioxatricyclo[3.3.2.03'7]decane system which is the firstexample in natural products as far as we know.