Original scientific paper

Metal Ion Dependence of the Asymmetric Transamination of Phenylpyruvic Acid by Pyridoxamine in the Presence of β-Cyclodextrin

L. Casella ; Dipartimento di Chimica Inorganica e Metallorganica, Centro CNR, Via Venezian 21, 20133 Milano, Italy
M. Gullotti ; Dipartimento di Chimica Inorganica e Metallorganica, Centro CNR, Via Venezian 21, 20133 Milano, Italy
F. Piemontesi ; Dipartimento di Chimica Inorganica e Metallorganica, Centro CNR, Via Venezian 21, 20133 Milano, Italy
A. Pintar ; Dipartimento di Chimica Inorganica e Metallorganica, Centro CNR, Via Venezian 21, 20133 Milano, Italy

Abstract

Transamination reactions of phenylpyruvic acid and pyridoxamine
in the presence of metal ions and B-cyclodextrin as a chiral
auxiliary have been investigated in neutral aqueous solution.
The rate and extent of the transamination, and the asymmetric
induction observed in the reaction depend upon the nature of the
metal ion. In particular, while Zn2+and C02+yield preferentially
the aldimine complex of L-phenylalanine, Cu2' yields preferentially
the complex of D-phenylalanine and Ni2+only the racemic
product. It is proposed that the ketimine complexes are bound to
B-cyclodextrin through the phenyl group of the keto acid residue
and that the stereoselectivity of the reaction is originated by some
direct interaction of the hydroxyl groups of the cyclodextrin
moiety and the metal ions. Although the extent of asymmetric
induction is modest in these simple systems (10-20°/0 optical
purities), the present results show that transition metal complexes
can play a prominent role in determining the steric course of the
asymmetric reaction.

Keywords

Hrčak ID:

175501

URI

https://hrcak.srce.hr/175501

Publication date:

10.8.1989.

Visits: 522 *