乙酸酐 、
3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28->20β-olide 在
吡啶 作用下,
反应 24.0h,
以9%的产率得到(3aR,3bS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bS,14S,15R)-5a,5b,8,8,11a,14,15-heptamethyl-2,17-dioxo-2,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a,13b,14,15-icosahydro-3aH-15,3b-(epoxymethano)piceno[4,3-b]furan-3a,9-diyl diacetate