Dinitrobenzoyl-alanine

FIGU RE 1.31 Separation factors for all-(5)/all-(R)-enantiomers of Af-3,5-dinitrobenzoylated alanine peptides (DNB-Alan-OH) and chromatogram for the DNB-protected decaalanine peptide, DNB-Alaio-OH, on a l,4-hw(9-0-quinidinyl)phthalazine-based CSP (5 xm) with LC-ESI-MS. Experimental conditions Column dimension, 150 mm x 4 mm ID mobile phase, methanol-0.5 M ammonium acetate buffer (80 20 v/v) (pHa 6.0) flow rate, 1 mLmin temperature, 25°C injection volume, 50 xL MS negative mode, SIM (C. Czerwenka et ah. Anal. Chem., 74 5658 (2002).)... 

Chiral drugs and chiral compounds (clomipramine, chlorodiazepoxide, diazepam, temazepam, doxepine, terbu-taline, clenbuterol, homoatropine, tropicamide, 3,5-dinitrobenzoyl alanine methyl ester)... 

FIGURE 1.19 X-ray crystal structures of selector-selectand complexes (ion-pairs) (a) O-9-(P-chloro-fert-butylcarbamoyl)quinine with iV-(3,5-dinitrobenzoyl)-(5)-leucine, (b) tbe pseudoenantiomeric complex of 0-9-( 3-cbloro-tert-butylcarbamoyl)quinidine with N-(3,5-dinitrobenzoyl)-(i )-leucine, (c) 0-9-( 3-cbloro-terf-butylcarbamoyl)quinine with N-(3,5-dinitrobenzoyl)-(5)-alanyl-(5)-alanine, and (d) comparison of tbe complexes of (a) and (c). Most hydrogens have been omitted for the purpose of clarity. (Reprinted from C. Czerwenka et al., Anal. Chem., 74 5658 (2002). With permission.)... 

As a further test of the etched open tubular approach for the analysis of optical isomers, another column was fabricated based on the selector naphthylethylamine that had been attached to porous silica by the silanization/hydrosilation method for use in HPLC [70]. As in the HPLC experiments, this column was best suited for the resolution of the optical isomers of dinitrobenzoyl methyl esters of amino acids. The best separation (a = 1.14) was obtained for the alanine derivative. In addition, the peak symmetry and efficiency for the naphthylethylamine column was significantly better than that obtained on the cyclodextrin column. However, as shown in HPLC experiments, changes in the amino acid moiety (replacing alanine with valine, etc.) often results in a loss of chiral resolution. In the case of optical isomers, the separation mechanism in HPLC and CEC modes is identical since only interaction between the solute and the bonded phase can result in resolution of the enantiomers. 

Type I CSPs have also been used with aqueous mobile phases. Pirkle et al. (32) have reported on the resolution of N-(3,5-dinitrobenzoyl) derivatives of M-amino adds and 2-aminophosphonic adds on an (l )-N-(2-naphthyl)-alanine-derived CSP using a mobile phase composed of methanol-aqueous phosphate buffer. The utility of achiral alkyltrimethylammoruum ion-pairing reagents was also investigated. Other examples include the following (1) The recently commercialized ot-Burke 1 CSP resolves the enantiomers of a number of underivatized p-blockers using an ethanol-dichlorornethane-ammonium acetate mobile phase (33) (2) an (R)-l-naphthylethylurea CSP was used to resolve N-(3,5-dinitrobenzoyI)-substituted amino adds and 3,5-dinitrobenzoyl amide derivatives of ibuprofen, naproxen, and fenoprofen with acetonitrile-sodium acetate mobile phases (34). 

A hollow-fiber liquid membrane was used in a separation of D,L-lactic acid and D,L-alanine resolution [196]. In this case, the enantioselective transport of solutes performed in one module was facihtated by N-3,5-dinitrobenzoyl-L-alanine octylester chiral selector, dissolved in toluene. The maximum D,L-lactic acid separation factor achieved was 2.00 and that for the D,L-alanine was 1.75. In both cases, the D-enantiomer flux was preferred. These values correspond to the enantiomeric excess 33.5% ee and 27.2% ee, respectively, and are not as good as in the first example. However, note that in this case, only one separation step took place and feed phase was circulated in the module. 

Oi et al. [725] studied the retention of six amino acids (alanine, valine, leucine, methionine, phenylglycine, and phenylalanine) as their A -acetyl methyl esters and A -(3,5-dinitrobenzoyl) derivatives on an (/ )- or (iS)-l-(a-naphthyl)ethylamine stationary phase (2 = 230 nm or 254 nm). Capacity factors and a values are tabulated for all pairs of amino acid derivatives. A 40/10/1, a 100/20/1, or a 200/20/1 hexane/1,2-dichloroethane/ethanol mobile phase was used to generate the separation. 

Hyun and coworkers reported fluorescent anion sensors 21 and 22 for recognition of AI-Boc or 3,5-dinitrobenzoyl (DNB) protected a-amino acids (Fig. 12). Amino acid such as alanine (Ala), valine (Val), threonine... 

Racemic dinitropyridyl, dinitrophenyl, and dinitrobenzoyl amino acids were resolved on C-18W/UV TLC and HPTLC plates (Macherey-Nagel) developed with 2% aqueous isopropanol containing 2-5% BSA. Development times were 1-2 h, and visualization was under 254 nm UV hght. Ri differences ranged from 0.06 to 0.49 [34]. The same plates with mobile phases composed of isopropanol -E BSA-E sodium tetraborate, acetic acid, or sodium carbonate served to separate enantiomeric D,L-methylthiohydantoin andphenylthiohydantoin derivatives of amino acids, kynureyne, 3-(l-naphthyl)alanine, lactic acid derivatives, alanine and leucine p-nitroanilides, and 2,2,2-trifluoro-l-(9-anthryl)ethanol [35], and with mobile phases composed of water with 5-7% BSA -E 2% isopropanol to separate dansyl amino acid derivatives [36]. 

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