New sesquiterpenes from Crossopetalum tonduzii.

Five new sesquiterpenes (1-5) with a dihydro-beta-agarofuran skeleton were isolated from Crossopetalum tonduzii. Their structures were elucidated by means of 1H and 13C NMR spectroscopic studies, including homonuclear and heteronuclear correlation experiments (COSY, ROESY, HMQC, and HMBC). The absolute configurations of 1 and 2 were determined by CD studies and chemical correlation. Compounds 1-3 were assayed against Spodoptera littoralis in an election test and showed low insect-antifeedant activity.