Enantiomer recognition optical purity

By X-ray structural study of the complexes of 14b with (-)-34b and of 14c with (+)-34b, mechanism of the chiral recognition has been clarified.16 Optical purities of all enantiomers obtained by the resolution were determined by H NMR measurements in the presence of the new chiral shift reagent 3.17... 

Conversion of amino acids to produce a diaster-eoisomeric peptide by reaction with an N-carboxy-anhydride, e.g., L-Phe-N-carboxy-anhydride, has been used for determination of optical purity using RPC. Alternatively, for analysis of amino acid enantiomers without derivatization, two options are available (1) chiral mobile phases such as the N,N-di- -propyl-L-alanine-copper(n) complex can be used with reversed-phase columns, and (2) stationary phases with a covalently bound ligand capable of stereo recognition can be used. Such ligands include cyclodextrins, albumins, glycoproteins, and copper(II) complexes. 

General Synthesis.—One of the more significant publications of 1976 is a full report 1 from Meyer s group on the preparation of chiral a-alkylalkanoic acids (2) in up to 80% optical yield, by alkylation of chiral 2-oxazolines (1) (Scheme 1). The thorough study has revealed that alkyl iodides or activated halides afford maximum yields, and that no racemization occurs on hydrolysis thus the propanediol derivative (3) can be recycled. In addition, it is possible to predict which enantiomer of acid (2) will be obtained on double alkylation of oxazoline (4) by due consideration of the order of alkylation. The carbanion from (4) has also been found to be capable of chiral recognition of racemic secondary alkyl iodides to afford 3-alkylalkanoic acids in ca. 40% optical purity. In similar studies, oxazoline... 

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