Chiral differentiation of some cyclic β-amino acids by kinetic and fixed ligand methods
2010
Hyyryläinen, Anna R.M. | Pakarinen, Jaana M.H. | Forró, Enik | Fülöp, Ferenc | Vainiotalo, Pirjo
Differentiation of β-amino acid enantiomers with two chiral centres was investigated by kinetic method with trimeric metal-bound complexes. Four enantiomeric pairs of β-amino acids were studied: cis-(1R,2S)-, cis-(1S,2R)-, trans-(1R,2R)- and trans-(1S,2S)-2-aminocyclopentanecarboxylic acids (cyclopentane β-amino acids), and cis-(1R,2S)-, cis-(1S,2R)-, trans-(1R,2R)-, and trans-(1S,2S)-2-aminocyclohexanecarboxylic acids (cyclohexane β-amino acids). The results showed that the choice of metal ion (Cu²⁺, Ni²⁺) and chiral reference compound (α- and β-amino acids) had an effect on the enantioselectivity. Especially, aromaticity of the reference compound was noted to enhance the enantioselectivity. The fixed-ligand kinetic method, a modification of the kinetic method, was then applied to the same β-amino acids, with dipeptides used as fixed ligands. With this method, dipeptide containing an aromatic side chain enhanced the enantioselectivity.
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