异丁酸酐 、
(20R)-pregn-5-ene-3β,20-diol 3-(4-methylbenzenesulfonate) 在
吡啶 作用下,
以89%的产率得到Isobutyric acid (R)-1-[(3S,8S,9S,10R,13S,14S,17S)-10,13-dimethyl-3-(toluene-4-sulfonyloxy)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-17-yl]-ethyl ester