PROCESS AND INTERMEDIATES TO PREPARE 17.BETA.-HYDROXY-7.ALFA.-METHYL-19-NOR-17.ALFA.-PREGN-5(10)-EN-20-YN-3-ONE

The present invention is a process for the preparation of 17beta-hydroxy-7alpha-methyl-19-nor-17alpha-pregn-5(10)-en-20-yn-3-one (17alpha-ethynyl-17beta-hydroxy-7alpha-methyl-5(10)-estren-3-one, tibolone) of formula 1, which comprises hydrolysis of 17alpha-ethynyl-17beta-hydroxy-7alpha-methyl-5(10)-estrene 3,3 -cyclic ketals of formula 2, where groups R1, R2, R3 and R4 are hydrogen atoms or alkyl groups, or R1 and R3, taken together with the carbon atoms within the dioxolane ring to which they are attached, form an alicyclic ring fused to the dioxolane ring, with R2 and R4 being hydrogen atoms, or R1 and R3 together with the carbon atoms to which they are attached form an aromatic ring fused to the dioxolane ring, where R2 and R4, taken together, form a chemical bond within said aromatic ring. In addition, the present invention includes an intermediate, compound of formula 2 and two processes to prepare 17alpha-ethynyl-17beta-hydroxy-7alpha-methyl-5(10)-estrene 3,3 -cyclic ketals of formula 2: (a) by contacting 17alpha-ethynyl-17beta-hydroxy-7alpha-methyl-4-estren-3-one with vicinal diols in the presence of a protic acid, and (b) by contacting 7alpha-methyl-5(10)-estrene-17-one 3,3-cyclic ketals of formula 4, where R1-R4 are defined as above, with metal acetylides, in inert solvents.