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

Abstract Investigation of the root bark extract of Entandrophragma angolense led to identification of two gedunin-type limonoids 5-hydroxy-7-deacetoxy-7-oxogedunin ( 1 ) and 5,6-dehydro-7-deacetoxy-7-oxogedunin ( 2 ), and three methyl angolensate derivatives, 6-deacetoxydomesticulide D ( 3 ), 6-deacetoxydomesticulide D 21-methylether ( 4 ), and entangosin ( 5 ), together with known compounds, methyl angolensate ( 6 ), 6-acetoxymethyl angolensate ( 7 ) and secomahoganin ( 8 ). 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.