11β,17α,21-trihydroxypregn-4-ene-3,20-dione-21-acetate 在
4-二甲氨基吡啶 、
N-溴代丁二酰亚胺(NBS) 、
sulfur(IV) oxide * pyridine 作用下,
以
吡啶 为溶剂,
以98.2 %的产率得到2-((10S,13S,17R)-17-hydroxy-10,13-dimethyl-3-oxo-2,3,6,7,8,10,12,13,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-17-yl)-2-oxoethyl acetate