11β-Hydroxy-16β-methyl-16α,17α-methylene-pregna-1,4-dien-3,20-dione, an im-portant chemical intermediate and excellent medicinal candidate, was prepared from prednisolone through 7 steps of methylsulfonylation, methylation, dehydration and double 1,3-dipolar reaction followed by double thermal decomposition with the total yield of 23.5%. The results showed that 1,3-dipolar reaction and ther-mal decomposition were highly regio- and stereo-selectivities proved by the data of ¹H NMR.

Key words: medicinal intermediate, 1,3-dipolar reaction, stereoselectivity, synthesis, thermal decomposition, regioselectivity, 16α,17α-methylenepregnanes