Structural and Stereochemical Studies on Brominated Meroterpenoids From the Dictyoceratid Sponge Cacospongia sp.

Abstract

The structures of seven minor metabolites, (5)-(11), from the encrusting sponge Cacospongia sp. Were deduced by ¹H, ¹³C and mass spectrometric data. Compounds (5)-(7) are hydroxy derivatives of the previously isolated tribromocacoxanthene (1); their relative stereochemistry was determined from ¹H-¹H coupling information. Compounds (8)-(11) represent an alternative cyclization mode of a cyclocymopol-related precursor (15) and possess a spiro-fused bicyclic ring system; the relative stereochemistry of (8)-(10) was deduced by ¹H n.O.e. difference spectroscopy. The biological role of brominated meroterpenoids in Cacospongia sp. is discussed.