methyl (20S)-20-(2'-chlorothiazolyl-5'-methenyl)-3-oxo-5α-pregnan-21-oate                                                                                                                                                              在
                                                                                                                                                                                 
pyridinium hydrobromide perbromide                                                                                                                                  作用下,
                                                                                                                以
                                                                                         
四氢呋喃                                                                                  为溶剂,
                                                                                                                                                    反应 0.5h,
                                                                                                                以95%的产率得到methyl (2R)-2-[(2R,5S,8R,9S,10S,13S,14S,17R)-2-bromo-10,13-dimethyl-3-oxo-1,2,4,5,6,7,8,9,11,12,14,15,16,17-tetradecahydrocyclopenta[a]phenanthren-17-yl]-3-(2-chloro-1,3-thiazol-5-yl)propanoate