title: Unexpected isomeric equilibrium in pyridoxamine Schiff bases.
abstract: Pyridoxamine is a vitamin B(6) derivative involved in biological reactions such as transamination, and can also act as inhibitor in protein glycation. In both cases, it has been reported that Schiff base formation between pyridoxamine and carbonyl compounds is the main step. Nevertheless, few studies on the Schiff base formation have been reported to date. In this work, we conduct a comparative study of the reaction of pyridoxamine and 4-picolylamin (a pyridoxamine analog) with various carbonyl compounds including propanal, formaldehyde and pyruvic acid. Based on the results, 4-picolylamin forms a Schiff base as end-product of its reactions with propanal and pyruvic acid, but a carbinolamine with formaldehyde. On the other hand, pyridoxamine forms a Schiff base with the three reagents, but the end-product is in equilibrium with its hemiaminal form, which results from the attack of the phenolate ion of the pyridine ring on the imine carbon. This isomeric equilibrium should be considered in studying reactions involving amine derivatives of vitamin B(6).
authors.affiliation: Institut Universitari d'Investigació en Ciències de la Salut, Departament de Química, Universitat de les Illes Balears, Palma de Mallorca, Spain.
authors.forename: Miquel
authors.initials: M
authors.lastname: Adrover
authors.forename: Bartolomé
authors.initials: B
authors.lastname: Vilanova
authors.forename: Francisco
authors.initials: F
authors.lastname: Muñoz
authors.forename: Josefa
authors.initials: J
authors.lastname: Donoso
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D005557:Formaldehyde / Q000737:chemistry; D006031:Glycosylation; D007097:Imines / Q000737:chemistry; D007536:Isomerism; D007700:Kinetics; D008956:Models, Chemical; D010636:Phenols / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D011733:Pyridoxamine / Q000031:analogs & derivatives*; D019289:Pyruvic Acid / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry*; D013057:Spectrum Analysis; D013816:Thermodynamics; D014803:Vitamin B Complex / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D007097:Imines; D010636:Phenols; D011725:Pyridines; D012545:Schiff Bases; D014803:Vitamin B Complex; D005557:Formaldehyde; D011733:Pyridoxamine; D002244:Carbon; D019289:Pyruvic Acid; C005556:propionaldehyde; C023666:pyridine