Plant enzyme reactions leading to the formation of heterocyclic compounds. 3. Plant amine oxidase and the formation of pyrrolidine and piperidine alkaloids

Abstract

The oxidation of l:4-diaminobutane, l:5-diaminopentane, l:6-diaminohexane and l:10-diaminodecane, catalysed by purified plant amine oxidase preparations in the presence of catalase, took place without formation of CO2. When these oxidations were carried out in the presence of ji-oxo acids CO2 was formed. The outputs of CO2 sometimes exceeded the uptakes of O2 and arose by decarboxylation of the fj-oxo acids. The rates of decarboxylation in such systems depended on the amine used as substrate. It was greatest with l:4-diaminobutane and least with l:10-diaminodecane. Benzoylacetic acid, oxaloacetic acid and acetonedicarboxylic acid were decarboxylated more readily than was acetoacetic acid. The a-oxo acids tested were not decarboxylated. In manometric experiments evidence was obtained that the decarboxyla-tions were due to stoicheiometric reactions between the -0x0 acids and the oxidation products of the amines. The results of paper-chromato-graphic investigations suggested that the decarboxylations were dependent on condensation reactions between the unsaturated ring compounds, formed by the spontaneous cyclization of the products of oxidation of the amines, and the 0-oxo acids, which resulted in the formation of saturated ring compounds. This was established by the isolation of norhygrine and isopelletierine from large-scale reaction mixtures in which l:4-diamino-butane and l:5-diaminopentane respectively were oxidized in the presence of acetoacetate. The possible significance of the results in relation to alkaloid biosynthesis is discussed.