4-deoxyannomontacin and (2,4-cis and trans)-annomontacinone, new bioactive mono-tetrahydrofuran annonaceous acetogenins from Goniothalamus giganteus.
4-Deoxyannomontacin (1) and a mixture of (2,4-cis and trans)-annomontacinone (2), new bioactive mono-tetrahydrofuran (THF) gamma-lactone and keto-lactone acetogenins, respectively, as well as five known mono-THF acetogenins [xylomaticin, longifolicin, longicoricin, (2,4-cis and trans)-gigantetrocinone, and (2,4-cis and trans)-gigantetroneninone], were isolated from the bark of Goniothalamus giganteus (Annonaceae) by activity-directed fractionation using the brine shrimp lethality test (BST). The structures were elucidated based on spectroscopic and chemical methods. The absolute stereochemistries of 1 and 2 were determined by the advanced Mosher ester method and by circular dichroism (CD). Determination of the absolute stereochemistry at C-10 as R for 1 is the first example of the direct determination of the absolute stereochemistry of a carbinol position isolated from other functional groups in the annonaceous acetogenins. 1 and 2 showed selective and potent cytotoxicities to certain human tumor cell lines and were comparable to the activity of rotenone against yellow fever mosquito larvae.