A new meroditerpenoid dimer from an undescribed Philippine marine sponge of the genus strongylophora

An undescribed Philippine marine sponge of the genus Strongylophora yielded a new meroditerpenoid-strongylophorine dimer (1) and the known meroditerpenoids, strongylophorine-2 (2), strongylophorine-3 (3), and strongylophorine-4 (4). The structures of the compounds were established on the basis of NMR spectroscopic and mass spectrometric data. The position of the inter-unit linkage in the new compound was elucidated after methylation and 1D 1H NOE difference experiments. This is the first report wherein the1H and 13C NMR data of the strongylophorine congeners are fully and unambiguously assigned on the basis of 2D NMR spectroscopy. Compounds 2 and 3 exhibited slight activity against Micrococcus luteus and Salmonella typhii, respectively. Compound 3 was active against the phytopathogenic fungusCladosporium cucumerinum and also against the neonate larvae of the polyphagous pest insectSpodoptera littoralis (EC50 of 69 [+/-0.48 (S.E.)] ppm) when incorporated into artificial diet. Compound 1 was found to be the most active in the brine shrimp lethality test with a LC50 of 10.5 [+/-0.43 (S.E.)] microg/mL.