Dinitrobenzoyl leucine

However, it was not until the beginning of 1994 that a rapid (<1.5 h) total resolution of two pairs of racemic amino acid derivatives with a CPC device was published [124]. The chiral selector was A-dodecanoyl-L-proline-3,5-dimethylanilide (1) and the system of solvents used was constituted by a mixture of heptane/ethyl acetate/methanol/water (3 1 3 1). Although the amounts of sample resolved were small (2 ml of a 10 inM solution of the amino acid derivatives), this separation demonstrated the feasibility and the potential of the technique for chiral separations. Thus, a number of publications appeared subsequently. Firstly, the same chiral selector was utilized for the resolution of 1 g of ( )-A-(3,5-dinitrobenzoyl)leucine with a modified system of solvents, where the substitution of water by an acidified solution... 

In order to perform such a correlation, our library was screened using a reciprocal CSP with an arbitrary bound chiral target (L)-(3,5-dinitrobenzoyl) leucine (Fig. 3-11). 

Fig. 3-18. Selectivity factors a determined for (3,5-dinitroben-zoyl)leucine diallylamide on CSP 15-24. Conditions analyte (3,5-dinitrobenzoyl)leucine diallylamide column 150 x 4.6 mm i.d. mobile phase 20 % hexane in dichloromethane flowrate 1 mL min f UV detection at 254 nm.

To illustrate this beneficial effect of the carbamate-binding increment. Figure 1.10 compares the separation of A/-(3,5-dinitrobenzoyl)leucine (DNB-Leu) enantiomers... 

The use of antibiotic-based CSPs has been reported in capillary electrochromatography (CEC) for chiral resolution [60]. Teicoplanin CSP covalently bonded to silica gel was used to resolve the enantiomers of tryptophan and dinitrobenzoyl leucine by CEC [61]. Good levels of enantioselectivity were obtained with optimized separations. Vancomycin covalently bonded to silica gel was also evaluated in CEC for the chiral resolution of thalidomide and jS-adrenergic blocking agents under all the three mobile phase modes. The... 

Note DNBGP=3,5-dinitrobenzoyl phenylglycine DNBLeu=3,5-dinitrobenzoyl leucine. 

FIGURE 10 Chiral recognition model showing three simultaneous bondings between (5)-methyl-X-(2-naphthyl)alaninato and (5)-iV-(3,5-dinitrobenzoyl)leucine n-propylamine. (From Ref. 9.)... 

Fig. 6.28. Effect of the hydrophilicity of chiral monolithic columns on the electrochromatographic separation of N-(3,5-dinitrobenzoyl)leucine diallylamide enantiomers (Reprinted with permission from [13]. Copyright 2000 Wiley-VCH). Conditions monolithic column, 100 pm i.d. x 30 cm active length mobile phase, 80 20 vol./vol. mixture of acetonitrile and 5 mmol/L phosphate buffer pH 7 UV detection at 215 nm voltage, 25 kV pressure in vials, 0.2 MPa injection, 5 kV for 3 s. Stationary phase with butyl methacrylate (a), glycidyl methacrylate (b), and hydrolyzed glycidyl methacrylate (c).

Peters et al. reported on rod-CEC on a chiral monolith [50] which was prepared by copolymerization of the chiral monomer 2-hydroxyethyl methacrylate (A -L-valine-3,5-dimethylanilide) carbamate with ethylene dimethylacrylate, 2-acrylamido-2-methyl-l-propanesulfonic acid and butyl or glycidyl methacrylate in the presence of a porogenic solvent. The electrochromatographic enantiomer separation of 7V-(3,5-dinitrobenzoyl)leucine diallylamide was feasible at 25 kV the inlet and outlet buffer vials were both pressurized. 

Peters et al. [143] used a valine-based chiral selector as the template molecule to prepare monolithic capillaries. These capillaries were used to successfully separate enantiomers of N-(3,5-dinitrobenzoyl)leucine. However, they found that the hydrophobicity of the monomers had a direct effect on the resolution and efficiency of the capillaries. The peaks tailed drastically due to reverse-phase interactions between the enantiomers and the monolith. They found that increasing the hydrophilicity of the monolith by the hydrolysis of the epoxide functionalities of the glycidyl methacrylate moieties resulted in a much more efficient separation. 

Bartik, P. et al. Advanced statistical evaluation of the complex formation constants from electrophoretic data II diastereomeric ion-pairs of (R,S)-N-(3,5- dinitrobenzoyl)leucine and tert-butylcarbamoylquinine. Anal. Chine Acta 2004, 506, 105-113. 

FIGURE 9.4 Schematic depiction of (A) ideal and (B) nonideal stereochemical arrangements for diastereomeric complex formation between a chiral selector and a pair of enantiomers. Shown in (C) is an aimotated X-ray crystal stmctnre, which shows the optimal alignment of noncovalent forces to initiate diastereomer complex formation between chloro-ferf-bntylcarbamoyl quinine (top) and 5 -(3,5-dinitrobenzoyl)-leucine (bottom) (Reprinted from Reference [87] with permission from the American Chemical Society 2005). 

FIGURE 9.5 Measurement and treatment of data for a host-guest screening experiment. The chiral selector, ferf-butylcarbamoyl quinidine (tBuCQD) is shown to provide a high degree of enantioselectivity toward the discrimination of enantiomers of N-(3,5)-dinitrobenzoyl-leucine (DNB-Leu) using ESI-MS [87]. 

QN, quinine QD, quinidine DIPPCQN, diisopropylphenylcarbamoyl quinine DIPPCQD, diisopropylphenylcarbamoyl quinidine tBuCQN, tert-butylcarbamoyl quinine tBuCQD, tert-butylcarbamoyl quinidine DNB-Leu, (3,5)-dinitrobenzoyl-leucine nd, not determined np, no preference. 

Zu, C., Brewer, B.N., Wang, B., Koscho, M.E. (2005) Tertiary amine appended derivatives of N-(3,5-dinitrobenzoyl)leucine as chiral selectors for enantiomer assays by electrospray ionization mass spectrometry. Anal. Chem., 77, 5019-5027. 

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