Chiral separation of enantiomers via selector/selectand hydrogen bondings

Chiral Separation for Enantiomeric Determination in the Pharmaceutical Industry

“…van der Waals, steric hindrance, dipole-dipole) become effectively involved. Secondary interactions can affect the conformation and the formation energy of diastereomeric associates [7].…”

“…These associates are in equilibrium with fast interconversion rates. Each form contributes to the total free energy according to its particular formation energy and its particular molar fraction [7,8]. These complexes between the selector and selectand should also be as mutually exclusive as possible, to prevent a given interaction from occurring at multiple sites in the diastereomeric complex [6].…”

“…These phases separated racemates of the more volatile members of the same compounds [12]. The diamide stationary phase contained two hydrogen bonding sites, a C5 and a C7 site, where hydrogen bonding selector/selectand-associations could take place [7]:…”

NMR and HPLC study of chiral selectors with naphthyl unit

“…Amide bond is planar and has a partial p-character, which leads to two separate cis and trans isomers. According to the NMR studies, secondary amides exist exclusively in trans conformation [2] due to the formation of polymeric associates through hydrogen bonds between carbonyl groups and the N-H groups of the neighbouring molecules [11]. Tertiary amides do not form these intermolecular hydrogen bonds and the presence of two isomers (rotamers) could be noted [12,13].…”

Separation of Enantiomers by Gas Chromatography on Chiral Stationary Phases

“…Further development of the direct enantioseparation by GC by dipeptide or α-amino acid diamide phases has been reviewed thoroughly [2,[25][26][27]. By way of ingenious experiments by Gil-Av and collaborators (reviewed in [25]), the evolution to optimum CSP performance was accomplished later.…”