No 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.

A tetronic acid (5), 5-[13-(furan-3-yl)-2,6,10-trimethyltrideca-2,6,8-trienyl]-4-hydroxy 3-methylfuran-2(5H)-one,* with weak antimicrobial activity has been isolated from the sponge Psammocinia sp. and characterized by analysis of 1H and 13C n.m.r. data including 'H-1H correlation (COSY) experiments. The compound may be identical to a tetronic acid isolated by the Roche group, previously assigned structure (3).

ChemInform Abstract A tetronic acid with weak antimicrobial activity is isolated from the title species and characterized as (I). This constituent may be identical with a tetronic acid previously reported to have structure (II).