The Aconite Alkaloids. XIX. The Structure of Kobusine. (1).

Abstract

Kobusine, C20H27O2N, m.p. 267∼267.5°, was hydrogenated over palladium-carbon in methanol, and α-dihydrokobusinone, C20H27O2N, m. p. 230∼232°, β-dihydrokobusinone, C20H27O2N, m.p. 240∼241°, and dihydrokobusine, C20H29O2N, m.p. 229∼231°, were obtained as the product. α-and β-Dihydrokobusinones were proved to be a ketone in six-membered ring. The β-isomer was also obtained from α-isomer or directly from kobusine on heating with 5% hydrochloric acid. Oxidation of kobusine with chromium trioxide in pyridine gave ketokobusinone, C20H23O2N, m.p. 189∼191°, and kobusinone, C20H25O2N, m.p. 273∼275°, both products showed the bands for α, β-unsaturated ketone in their infrared spectra. On catalytic hydrogenation, the former gave a saturated diketone, C20H25O2N, m.p. 173∼175, which was identified with the oxidation product of β-dihydrokobusinone. The latter gave α-dihydrokobusinone. Diacetylkobusine, C24H31O4N, m.p. 139∼141°, and also dibenzoylkobusine (hydrochloride, C34H35O4N·HCl·H2O, m.p. 290∼292°) were prepared. Allyl alcohol of the type of HO-C^^1-C^^1=CH2 and secondary hydroxyl group were thus confirmed as the functional groups in kobusine.