Trijugins A and B, tetranortriterpenoids with a novel rearranged carbon skeleton from Heynea trijuga (Meliaceae)

Two new tetranortriterpenoids, trijugins A ( 1 ) and B ( 3 ), isolated from the leaves of Heynea trijuga (Meliaceae), have been shown to be derivatives of methyl angolensate but with a novel carbon skeleton having a contracted ring C. The structures were assigned on the basis of detailed 1 H and 13 C nuclear magnetic resonance spectroscopic examination including 2D long-range δ C / δ H correlation and homonuclear 1 H nuclear Overhauser effect difference experiments.