Insect antifeedant activity of three new tetranortriterpenoids from Trichilia pallida.

Three new tetranortriterpenoids, methyl 6-hydroxy-11 beta-acetoxy-12 alpha-(2-methylpropanoyloxy)-3,7-dioxo-14 beta,15 beta-epoxy-1,5-meliacadien-29-oate (3), methyl 6,11 beta-dihydroxy-12 alpha-(2-methylpropanoyloxy)-3,7-dioxo-14 beta,15 beta-epoxy-1,5-meliacadien-29-oate (4), and methyl 6-hydroxy-11 beta-acetoxy-12 alpha-(2-methylbutanoyloxy)-3,7-dioxo-14 beta,15 beta-epoxy-1,5-meliacadien-29-oate (5), have been isolated from the roots of Trichilia pallida. The related compounds hirtin (1) and deacetylhirtin (2) were also obtained. Compound 4 had the greatest antifeedant activity of 1-5 when tested against larvae of four species of Lepidoptera.