Schiff bases. Part I. Thermal decarboxylation of α-amino-acids in the presence of ketones

Abstract

A number of Schiff bases derived from α-amino-acids and hydroxy-substituted aromatic ketones have been prepared. Their infrared spectra suggest that their relative stability to hydrolysis as compared with those from ketones with no hydroxy-groups is due to hydrogen bonding. The thermal decomposition of α-amino-acids in the presence of ketones, followed by hydrolysis, produces the amines corresponding to the amino-acids or the ketones (transamination) or both, depending on the nature of the amino-acid and the ketone used and also on the method of hydrolysis. In the case of amino-acids with a quaternary α-carbon atom, transamination is the principal reaction. The preparation of tyramine, tryptamine, and histamine in good yield from the corresponding amino-acids is described.