Compound representatives of a new type of triterpenoid from Aglaia odorata.

[structure: see text] A novel triterpenoid, 21,25-cyclodammar-20(22)-ene-3beta,24alpha-diol, has been isolated from Aglaia odorata. Its structure was elucidated on the basis of 1D- and 2D-NMR and MS spectra and then confirmed by X-ray diffraction. It represents a new type of natural five-membered-ring triterpenoid, named cyclodammarane. Its possible biopathway was that squalene-2,3;22,23-diepioxide was directly cyclized to form 24,25-epoxydammar-20(21)-en-3-ol, followed by protonation of the remaining 24,25-epoxide and the cation attacking 21(20) methylene to generate the E ring.