Alkaloids of the Australian Rutaceae: Pentaceras australis Hook. F. II. Identification of 5-Methoxycanthinone

Abstract

The alkaloid C₁₅H₁₀O₂N₂, present in the bark of Pentaceras australis Hook. f., has been shown to be 5-methoxycanthin-6-one. It is oxidized by potassium permanganate to β-carboline-1-carboxylic acid and its lactam ring may be opened by alkali to give a β-carbolylmethoxyacrylic acid which readily recyclizes to the alkaloid. The position of the methoxyl group is demonstrated by demethylation and condensation of the resulting hydroxy-compound with o-phenylenediamine to give a hydroxyquinoxaline. Attempted hydrogenation of the alkaloid or the derived methoxyacrylic acid led to elimination of methoxyl.