Total Synthesis of 13β-Allylgonanes. I. Synthesis of dl-17α-Ethynyl-17β-hydroxy-13β-allylgon-4-en-3-one

dl-17α-Ethynyl-17β-hydroxy-13β-allylgon-4-en-3-one (XXIV) was synthesized via 17β, 2'-epoxy pentaene (X). The double bonds at C-14 and -8 of X was hydrogenated sequentially by conventional methods. 17β, 2'-Epoxy triene (XIII) was treated with p-toluenesulfonic acid in acetic anhydride to give 13β-allylgonane (XIV) as a major product. Birch reduction of the tetrahydropyranyl ether (XIX) followed by acid treatment yielded the 4-en-3-one compound (XXI), which was oxidized with chromium trioxidepyridine complex to the 17-ketone (XXII). The enol ether (XXIII) was treated with lithium acetylide in ethylenediamine, and then with acid to yield XXIV. The progestational activity of XXIV is as potent as norgestrel.