The stereochemistry of this hydroxyl group was determined
as α by NOESY experiment, which showed NOE correlations
between H-21β and H3-28 as well as H3-30, and by
comparison of its NMR data with those of related friedelane
triterpene [19]. The molecular structure of 1 was therefore
determined as a new 1,3-diketofriedelane triterpene 21α-
hydroxyfriedelane-1,3-dione.