Vanadium-controlled crystallization of stereoisomers of NBu4[VO2(N-salicylidene-isoleucinato)] through epimerization

Lukáš Krivosudský; Peter Schwendt; Ján Šimunek; Róbert Gyepes

doi:10.1002/chem.201403125

Vanadium-controlled crystallization of stereoisomers of NBu4[VO2(N-salicylidene-isoleucinato)] through epimerization

Chemistry. 2014 Jul 14;20(29):8872-5. doi: 10.1002/chem.201403125. Epub 2014 Jun 17.

Authors

Lukáš Krivosudský¹, Peter Schwendt, Ján Šimunek, Róbert Gyepes

Affiliation

¹ Department of Inorganic Chemistry, Comenius University, Faculty of Natural Sciences, Mlynská dolina, 842 15 Bratislava (Slovakia), Fax: (+421) 2-60296-273.

PMID: 24938223
DOI: 10.1002/chem.201403125

Abstract

Reported herein is a simple synthetic and crystallization procedure for sequential isolation of two stereoisomers of isoleucine-derived vanadium(V) complexes from a racemic mixture with three stereogenic centers and therefore eight hypothetical species. The products of this crystallization were characterized by electronic and vibrational circular dichroism, NMR spectroscopy, and polarimetry to compare the chiroptic properties of the enantiomerically pure analogues prepared from L-isoleucine and D-allo-isoleucine. NMR studies pointed to the yet unobserved phenomenon of vanadium-catalyzed epimerization of isoleucine.

Keywords: Schiff bases; chiral resolution; circular dichroism; epimerization; vanadium.