A rational approach for the design and preparation of two new "Crab-like" totally synthetic, brush-type chiral stationary phases is presented. Enantiopure diamines, namely 1,2-diaminocyclohexane and 1,2-diphenyl-1,2-ethylene-diamine were treated with 3-(triethoxysilyl)propyl isocyanate, to yield reactive ureido selectors that were eventually attached to unmodified silica particles through a stable, bidentate tether, through a facile two-step one-pot procedure. A full chemical characterization of the new materials has been obtained through solid-state NMR (both Si-29 and C-13 CPMAS) spectroscopy. Columns packed with the two Crab-like chiral stationary phases allow for different mechanisms of separation: normal phase liquid chromatography, reversed phase liquid chromatography and polar organic mode and show a high stability at basic pH values. In particular, the Crab-like column containing the 1,2-diphenyl-1,2-ethylene-diamine selector proved a promising candidate for the resolution of a wide range of racemates (including benzodiazepines, N-derivatized amino acids, and free carboxylic acids) both in normal phase and polar organic mode. An H-min of 9.57 at a mu(sf) of 0.80 mm/s (corresponding to 0.8 mL/min) was obtained through van Deemter analysis, based on toluene, for the Crab-like column with the 1,2-diphenyl-1,2-ethylene-diamine selector (250 mm x 4.6 mm I.D.), with a calculated reduced height equivalent to a theoretical plate (h) of only 1.91. Finally, comparative studies were performed with a polymeric commercially available P-CAP-DP column in order to evaluate enantioselectivity and resolution of the Crab-like columns
Bidentate urea-based chiral selectors for enantioselective high performance liquid chromatography: Synthesis and evaluation of "Crab-like" stationary phases
D Capitani;
2013
Abstract
A rational approach for the design and preparation of two new "Crab-like" totally synthetic, brush-type chiral stationary phases is presented. Enantiopure diamines, namely 1,2-diaminocyclohexane and 1,2-diphenyl-1,2-ethylene-diamine were treated with 3-(triethoxysilyl)propyl isocyanate, to yield reactive ureido selectors that were eventually attached to unmodified silica particles through a stable, bidentate tether, through a facile two-step one-pot procedure. A full chemical characterization of the new materials has been obtained through solid-state NMR (both Si-29 and C-13 CPMAS) spectroscopy. Columns packed with the two Crab-like chiral stationary phases allow for different mechanisms of separation: normal phase liquid chromatography, reversed phase liquid chromatography and polar organic mode and show a high stability at basic pH values. In particular, the Crab-like column containing the 1,2-diphenyl-1,2-ethylene-diamine selector proved a promising candidate for the resolution of a wide range of racemates (including benzodiazepines, N-derivatized amino acids, and free carboxylic acids) both in normal phase and polar organic mode. An H-min of 9.57 at a mu(sf) of 0.80 mm/s (corresponding to 0.8 mL/min) was obtained through van Deemter analysis, based on toluene, for the Crab-like column with the 1,2-diphenyl-1,2-ethylene-diamine selector (250 mm x 4.6 mm I.D.), with a calculated reduced height equivalent to a theoretical plate (h) of only 1.91. Finally, comparative studies were performed with a polymeric commercially available P-CAP-DP column in order to evaluate enantioselectivity and resolution of the Crab-like columnsI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
