Novel Bromo Metabolites From a Dictyoceratid Sponge of the Cacospongia Genus

Abstract

Two novel brominated metabolites, tribromocacoxanthene (3) and tetrabromocacoxanthene (4),have been isolated from a marine sponge of the Cacospongia genus (family Thorectidae ) along with 12-epideoxoscalarin (2). The structures of compounds (3), systematic name (2S,4aS,9aS)-2,7-dibromo-4a-bromomethyl-1,1-dimethyl-2,3,4,4a,9,9a-hexahydro-1H-xanthene, and (4), systematic name (2S,4aS,9aS)-2,5,7-tribromo-4a-bromomethyl-l,1-dimethyl-2,3,4,4a,9,9a-hexahydro-1H-xanthene , were deduced from analysis of ¹H and ¹³C n.m.r. data and that of (3) was confirmed by X-ray crystallographic structure analysis which provided the absolute configuration. The two new compounds are the first tricyclic examples of a carbon skeleton previously isolated only from algae. The chemotaxonomic implication of the isolation of these new compounds is discussed.