Abstract
Digipronin, a digitanol glycoside, and its aglycone, γ-digiprogenin, were respectively converted to isodigipronin and its aglycone, α-digiprogenin, by treatment with dilute alkali or acid. On refluxing with acid, α-digiprogenin lost an element of water and formed β-digiprogenin. The structure of the ⊿4-3-oxo compound, obtained from β-digiprogenin by reduction with acetic acid and zinc dust followed by Oppenauer oxidation, was established as 14β, 17α-pregn-4-ene-3, 11, 15, 20-tetrone by comparison with the product of isomerization of pregn-4-ene-3, 11, 15, 20-tetrone with alkali or acid. Consequently, the structure of β-digiprogenin was presumed as 3β-hydroxy-14β-pregna-5, 16-diene-11, 15, 20-trione and the tertiary hydroxyl group in α-and γ-digiprogenin would be located at 17-position. In view of the stability of α-digiprogenin to dilute alkali or acid and its negative contribution to optical rotation compared to γ-digiprogenin, it would be appropriate to give the structure of 3β, 17α-dihydroxy-14β-pregn-5-ene-11, 15, 20-trione and 3β, 17α-dihydroxypregn-5-ene-11, 15, 20-trione to α-and γ-digiprogenin, respectively. Digipronin is a monodigitaloside of γ-digiprogenin.
