Structural Revision of Garcinielliptin Oxide and Garcinielliptone E

Previously, Lin et al. reported the
isolation and structural determination
of two triterpenoids, garcinielliptin oxide (GO) and garcinielliptone
E (GE). Their unusual structural features, which remained unparalleled
in subsequent decades despite the intervening discovery of hundreds
of other polycyclic polyprenylated acylphloroglucinols (PPAPs), caused
us to question the originally assigned structures, so GO was reisolated
from Garcinia subelliptica, and its NMR spectra were
reacquired. In this Note, we revise the structures of GO and the related
GE via NMR analysis, biosynthetic considerations, and chemical conversion.
Garcinielliptone T, a new PPAP, was also isolated and characterized.
GO exhibited weak inhibitory activity against acetylcholinesterase
with an IC50 value of 20.7 μM.