title: Vanadium-controlled crystallization of stereoisomers of NBu4[VO2(N-salicylidene-isoleucinato)] through epimerization.
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.
authors.affiliation: Department of Inorganic Chemistry, Comenius University, Faculty of Natural Sciences, Mlynská dolina, 842 15 Bratislava (Slovakia), Fax: (+421) 2-60296-273.
authors.forename: Lukáš
authors.initials: L
authors.lastname: Krivosudský
authors.forename: Peter
authors.initials: P
authors.lastname: Schwendt
authors.forename: Ján
authors.initials: J
authors.lastname: Šimunek
authors.forename: Róbert
authors.initials: R
authors.lastname: Gyepes
keywords: Schiff bases; chiral resolution; circular dichroism; epimerization; vanadium