Triterpenoids from the stem bark of Melia toosendan and determination of their absolute configurations at C(24).

Six new triterpenoids, meliasenins S-X (1-6, resp.), were isolated from the stem bark of Melia toosendan. Their structures were elucidated by mass spectrometry, NMR experiments, and comparison with the known compounds. Particularly, the absolute configuration at C(24) in new compounds was determined through their CD spectra of the [Pr(FOD)3 ] complex (fod=1,1,1,2,2,3,3,7,7,7-decafluoroheptane-4,6-dione) in CCl4 , as well as by using Mosher's method.