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Accueil du site > Production scientifique > Origin of enantioselective reduction of the tertiary copper D,L amino-acid complexes under collisional activation conditions

Origin of enantioselective reduction of the tertiary copper D,L amino-acid complexes under collisional activation conditions

Date de publication: 16 août 2011

C. Afonso, D. Lesage, F. Fournier, V. Mancel, J.-C. Tabet
Int. J. Mass Spectrom. 312 185 (2012). DOI

Travail réalisé sur le site de l’Université Pierre et Marie Curie.

Abstract

Phenylglycine (Phg), a non natural amino acid was used as chiral selector for the distinction of l/d amino acids through enantioselective CuII reduction. The investigation of the chiral effects was performed based on the dissociation of copper quaternary complexes involving phenylglycine : [CuII,(Phg,AA1,AA2-H)]+. The main cleavage was the competitive formal loss of Phg and [Phg-H] yielding the [CuII,(AA1,AA2-H)]+ and [CuI,(AA1,AA2)]+ ions respectively. The later involving a stepwise process with CO2 loss and a concomitant CuII reduction. The relative extent of this competitive process appeared to be strongly enantioselective. This led us to explore the origin of the observed enantiomeric reduction from dissociations of copper AAs complexes. With this aim, smaller [CuII,(Phg,AA-H)]+ ternary complexes have been investigated and MSn together with double resonance–IRMPD experiments have been conducted. The existence of zwitterions was considered in order explain the role of gas phase acidity and proton affinity on the enantioselective reduction.