NOVEL SPONGE-DERIVED AMINO-ACIDS .12. TRYPTOPHAN-DERIVED PIGMENTS AND ACCOMPANYING SESTERTERPENES FROM FASCAPLYSINOPIS-RETICULATA

This paper reports the bioactive constituents of Fascaplysinopsis reticulata collected from the Benga Lagoon of the Fiji islands. The previous literature of this genus includes two aplysinopsins (monomeric tryptophans) from F. reticulata, as well as fascaplysin (5a) (an apparent tryptophan dimer) and luffariellolide (3) (a sesterterpene) from Fascaplysinopsis sp. Our investigation of F. reticulata has revealed new sesterterpenes isodehydrouffariellolide (1) and dehydroluffariellolide diacid (2); unique alkaloid-sesterterpene salts fascaplysin A (5b) [fascaplysin cation/dehydroluffariellolide diacid anion] and homofascaplysin A cation/dehydroluffariellolide diacid anion (6); and novel neutral alkaloids homofascaplysin C (7), homofascaplysin B (8), and secofascaplysin A (9). These substances were accompanied by fascaplysin (5a) and the known alkaloid (+)-octopamine 4. The most important findings in this study are (a) fascaplysin derivative 5b is the first known salt comprised of a complex alkaloid cation and a terpene carboxylate anion, and (b) secofascaplysin A (9) is the first naturally occurring beta-carbolinone. An amino acid biogenesis pathway is outlined for each of the above alkaloids. The biological activity profile against the HIV reverse transcriptase is reported for selected metabolites.