PURPOSE: To obtain a steroid useful as an intermediate for preparing spironolactone as a diuretic simply in high yield, by reacting a specific acetylene adduct with androst-4-ene-3,17-dione to give a reaction product, followed by acetalizing it.

CONSTITUTION: Caustic potash is reacted with an alcohol in a nonproton solvent(e.g., tetrahydrofuran, etc.) at 10°CWabout the reflux temperature to give a reaction product, which is reacted with acetylene at -20W20°C. The prepared acetylene adduct is reacted with androst-4-ene-3,17-dione at -20W20°C to give a reaction product, which is acetalized with a glycol in the presence of a catalyst such as p-toluenesulfonic acid, etc., to give the desired 3,3-alkylenedioxy-17α- 17β-hydroxyandrostene.