21-Acetoxy-9α-brom-11β-hydroxy-16α,17α-(methoxymethylendioxy)-1,4-pregnadien-3,20-dion 生成 [2-[(1S,2S,4R,8S,9S,11S,12S,13S)-11-hydroxy-6-methoxy-9,13-dimethyl-16-oxo-5,7-dioxapentacyclo[10.8.0.02,9.04,8.013,18]icosa-14,17-dien-8-yl]-2-oxoethyl] acetate