Amines enantiomeric purity/absolute

Enzymatic treatment with Penicillin G acylase of the phenylacetamide of a RSMA leads to the specific hydrolysis of one enantiomer forming the amine in good yield and high enantiomeric purity (92%).236 Absolute configuration (R) and enantiomeric purity are determined by H1 NMR, after derivatization with (S)-a-trifluoromethylphenylacetic acid (Mosher s salt).302... 

A novel asymmetric synthesis of a-amino acids via electrophilic amination has been demonstrated by Zheng and Armstrong and co-workers.94 No +NHBoc was observed when lithium tert-butyl-A-tosyloxycarbamate (LiBTOC) was reacted with zinc and lithium enolates of 48. Transmetallation of the lithium enolate with copper cyanide was necessary to generate a reactive amide cuprate, which then added efficiently to the electrophile. The electrophilic amination of chiral cuprates with LiBTOC provided an expedient approach to a-amino acids with predictable absolute configuration in high enantiomeric purity and good yield (Scheme 24.23). 

The enantiomeric purities of primary and secondary amines have also been established by H NMR spectroscopy by their conversion into the corresponding sulfonamide. These derivatives often produce crystalline compounds that are suitable for X-ray crystallographic studies. For example, the enantiomeric purities of amines (5), (6), and (7) were determined by H NMR spectroscopy and the absolute stereochemistry of (7) was unequivocally established by X-ray crystallography. 

---