Process for preparing 16,17-(cyclohexyl methylene)bis(oxy)-11,21-dihydroxypregna-1,4-diene-3,20-dione or 21-isobutyrate thereof

摘要

In the present invention, there is disclosed a process for preparing 16,17-[(cyclohexyl methylene)bis(oxy)]-11,21-dihydroxypregna-1,4-diene-3,20-dione or 21-isobutyrate thereof of the general formula 1, in which R represents a hydrogen atom or isobutyryl of from more than 95 percent of epimerically pure form, comprising reacting a compound of the general formula 2 wherein R denotes a hydrogen atom, R1 represents methyl and R2 represents methyl with cyclohexane aldehyde using oxychlorine acid as a catalyst and a nitrated hydrocarbon as a solvent at a temperature ranging from 0 to 40 degC.