A pair of humulane sesquiterpenoid enantiomers from Syringa pinnatifolia.

Two humulane-type sesquiterpenoids, namely (+)-alashanoid I (1a) and (-)-alashanoid I (1b), were isolated as a pair of enantiomers from the peeled stems of Syringa pinnatifolia. Their structures were elucidated by extensive spectroscopic data (1 D and 2 D NMR, UV, and IR), and the absolute configurations were resolved by X-ray diffraction and experimental and calculated ECD data analysis.