Chemical derivatization in combination with supercritical fluid chromatography to improve resolution of stereoisomers

Aim: Quantification of stereoisomers in biological matrices is of pivotal importance for drug development. Supercritical fluid chromatography paired with chiral stationary phases is the gold standard for resolution of enantiomers. However, this technique often proves inadequate for resolution of polar stereoisomers. Materials & methods: A combination of achiral chemical derivatization with supercritical fluid chromatography using chiral stationary columns to improve enantiomeric resolution is described. Results: Separation of four possible stereoisomers of linerixibat was achieved after derivatization with 3N HCl in n-butanol within 12 min (case1). Derivatization with acetic, propionic, butyric, isobutyric, valeric and isovaleric anhydrides significantly improved the separation of stereoisomers (case 2 and 3) within 10 min. The best stereoisomeric resolution was achieved using valeric and isovaleric anhydrides.

Different Strategies for Obtaining Enantiopure Hemicryptophanes

Hemicryptophanes have recently emerged as an attractive class of cages due to their interesting applications as supramolecular receptors and catalysts. Over the last decade, substantial advances have been made regarding the preparation of enantiopure versions of these synthetic receptors. Enantiopure hemicryptophanes are commonly obtained through the separation of diastereomers by chromatography, or by resolution of racemic mixtures using chiral HPLC. This short review summarizes the existing methods to access to these chiral organic architectures and discusses the benefits and drawbacks of each approach.1 Introduction2 Enantiopure Hemicryptophanes Obtained by Introducing Additional Chiral Units and Separation of Diastereomers2.1 Synthesis by Means of Intramolecular Macrocyclization Reactions2.2 [1+1] Coupling of the CTV and the Southern Part3 Enantiopure Hemicryptophanes Obtained by Means of Chiral HPLC Resolution of Enantiomers3.1 Resolution of Hemicryptophane Racemates3.2 Resolution of CTV-Based Precursor Racemates4 Conclusion

Spontaneous enantiomorphism in poly-phased alkaline salts of tris(oxalato)ferrate(III): crystal structure of cubic NaRb5[Fe(C2O4)3]2

We show here that the phenomenon of spontaneous resolution of enantiomers occurs during the crystallization of the sodium and rubidium double salts of the transition metal complex tris(oxalato)ferrate(III), namely sodium pentarubidium bis[tris(oxalato)ferrate(III)], NaRb5[Fe(C2O4)3]2. One enantiomer of the salt crystallizes in the cubic space groupP4332 withZ= 4 and a Flack absolute structure parameterx= −0.01 (1) and its chiral counterpart in the space groupP4132 withx= −0.00 (1). All metal ions are at crystallographic special positions: the iron(III) ion is on a threefold axis, coordinated by three oxalate dianions in a propeller-like conformation. One of the two independent rubidium ions is on a twofold axis in an eightfold coordination with neighbouring oxalate oxygen atoms, and the other one on a threefold axis in a sixfold RbO6coordination. The sodium ion is at a site ofD3point group symmetry in a trigonal–antiprismatic NaO6coordination.