Rings D-seco and B,D-seco tetranortriterpenoids from root bark of Entandrophragma angolense.

Investigation of the root bark extract of Entandrophragma angolense led to identification of two gedunin-type limonoids 5-hydroxy-7-deacetoxy-7-oxogedunin and 5,6-dehydro-7-deacetoxy-7-oxogedunin, and three methyl angolensate derivatives, 6-deacetoxydomesticulide D, 6-deacetoxydomesticulide D 21-methylether, and entangosin, together with known compounds, methyl angolensate, 6-acetoxymethyl angolensate and secomahoganin. Their structures were established by extensive NMR experiments in conjunction with mass spectrometry. Entangosin is a rare example of a limonoid derivative having a fully O-substituted furan moiety.