Stereochemistry of condensation and transaldimination of amino acids by pyridoxal

The stereochemistry of the products of condensation and transaldimination of L-α- and D-α- alanines with pyridoxal has been studied. Structure of intermediate amino alcohols, aminals, and of the final Schiff’s bases depends on their fragments location with respect to the pyridine ring plane. Basing on the collected data, we have proposed the reaction mechanism involving the in-plane attack of the carbonyl group, in contrast to commonly accepted out-of-plane attack.