ジギタリス配糖体に関する研究 (第10報)

微生物による強心性物質の変換 その1 Rhizopus arrhizusによる7β-Hydroxydigitoxigeninの生成

抄録

Microbiological oxidation of digitoxigenin (I) by Rhizopus arrhizus gives a kind of monohydroxydigitoxigenin (IIa) which does not agree with either digoxigenin, gitoxigenin, or sarmentogenin. Since (IIa) forms a diacetate, it is not 11β-hydroxydigitoxigenin and since the bis-dehydro compound (IV) obtained by oxidation of (IIa) with chromium trioxide is not digoxigenone, (IIa) does not have a hydroxyl in 12-position. Infrared spectrum of (IV) suggests the presence of two six-membered ring carbonyls and this suggests that the new hydroxyl introduced into (IIa) is not in D-ring. Since the ultraviolet spectrum and ferric chloride reaction of (IV) do not indicate the presence of α- or β-diketone, the new hydroxyl cannot be in the A-ring. Treatment of (VI) with hydrochloric acid does not cause isomerization to the 5α compound, which denies 3, 6-diketone structure for (IV). These experimental results suggest that the newly introduced hydroxyl is in 7-position.
The presence of α, β-unsaturated ketone in the anhydro compound (V) of (IV) is indicated by its ultraviolet spectrum and this satisfies the above assumption. Application of carbonyl chloride to the 3-dehydro compound (IIIa) of (IIa) afforded 7β, 14β-carbonate (VI) and (IIa) was established as 7β-hydroxydigitoxigenin.