methyl (2R)-2-[(8S,9S,10R,11S,13S,14S,17R)-11,17-dihydroxy-10,13-dimethyl-3-oxo-2,6,7,8,9,11,12,14,15,16-decahydro-1H-cyclopenta[a]phenanthren-17-yl]-2-methoxycarbonyloxyacetate 在
4-二甲氨基吡啶 作用下,
以
二氯甲烷 为溶剂,
生成 methyl (4R,5R,8'S,9'S,10'R,11'S,13'S,14'S)-11'-hydroxy-10',13'-dimethyl-2,3'-dioxospiro[1,3-dioxolane-5,17'-2,6,7,8,9,11,12,14,15,16-decahydro-1H-cyclopenta[a]phenanthrene]-4-carboxylate