乙酸酐 、
2-carboxy-5-hydroxy-11-oxy-3-oxaursa-1,12-dien-28-oic acid 以
吡啶 为溶剂,
以0.38 g的产率得到(4aS,6aR,6bS,8aS,11R,12S,12aS,14aS,14bR)-4a-Acetoxy-4,4,6a,6b,11,12,14b-heptamethyl-14-oxo-4,4a,5,6,6a,6b,7,8,9,10,11,12,12a,14,14a,14b-hexadecahydro-3-oxa-picene-2,8a-dicarboxylic acid