(2,2-dimethyltrimethylenedioxy)-cis-bicyclo[3.3.0]octan-3-one-2-carboxylic acid methyl ester 生成 [(8R,9S,13S,14S,17S)-3-methoxy-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthren-17-yl] 5',5'-dimethyl-2-oxospiro[1,3,3a,4,6,6a-hexahydropentalene-5,2'-1,3-dioxane]-1-carboxylate