Diastereochemical Differentiation of Some Cyclic and Bicyclic β-Amino Acids, Via the Kinetic Method

Stereochemical differentiation of five diastereomeric pairs of β-amino acids, di-endo- and di-exo-2,3-disubstituted norbornane and norbornene amino acids, cis- and trans-2-aminocyclohexane-, 2-amino-4-cyclohexene-, and 2-aminocyclopentanecarboxylic acids, was investigated via the kinetic method with metal-bound trimeric complexes. This is the first time that diastereomers (di-endo/di-exo and cis/trans) have been differentiated with metal-bound trimeric complexes and the kinetic method. Moreover, determination of diastereochemical excess by the kinetic method was applied to norbornane β-amino acids and cyclopentane β-amino acids. Experiments showed that a remarkable differentiation of the studied diastereomers was achieved. It was observed that better selectivity values correlated to more rigid structures. The reference compounds for the studied β-amino acids varied from α-amino acids to some β-amino acids. In addition, variation of the metal ion (Cu2+ and Ni2+) had some role in the selectivity values obtained. Ab initio and hybrid density functional theory calculations were performed to clarify the results obtained by mass spectrometry.

Graphical AbstractStereochemical differentiation of some β-amino acids was performed using the kinetic method with trimeric metal-bound complexes, and theoretical calculations to clarify the results obtained.Figure optionsDownload full-size imageDownload high-quality image (45 K)Download as PowerPoint slide