Homoscalarane sesterterpenes from Lendenfeldia frondosa.

The marine sponge Lendenfeldia frondosa, collected from the Solomon Islands, has yielded homoscalarane sesterterpenes. Two new metabolites, epihomoscalaralactone IIA [5] and homoscalarate II [10], were accompanied by two known metabolites, homoscalaralactone IIA [1] and homoscalaralactone IIB [7]. These structures were established by analysis of 2D nmr data, trends in 13C-nmr shifts, and comparison of experimental with molecular-mechanics-calculated nmr J's. Each of the alcohols 1, 2, and 3 was converted to its corresponding acetate, 2, 6, and 8, respectively. Compound 6 exhibited moderate anti-inflammatory activity.