The isomers of α-amino-acids with copper(II). Part 4. Catalysis of the racemization of optically active alanine by copper(II) and pyruvate in alkaline solution

Aqueous solutions containing copper(II) ions, pyruvate, and L(+)-alanine in the molar ratio 1 : 2 : 4 give rapid racemization of alanine. The reaction is first order in the concentration of base, kobs.=(5.43 × 10–2)[OH–] s–1 at 60 °C. For the molar ratios 1 : 1 : 4 ⩽[CuII] : [pyruvate] : [alanine]⩽ 1 : 4 : 4 the reaction is to a very good approximation first order in the concentration of added pyruvate, kobs.=(2.89 × 10–4)[pyruvate] s–1. We attribute the racemization to the involvement of Schiff-base formation. In similar systems containing CoII, NiII, or ZnII racemization is also promoted; with CuII the racemization of threonine and glutamic acid is also promoted.