Type II Chiral Stationary Phases

Underivatized saccharides such as cellulose and starch have been used as chiral stationary phases. Cellulose, which contains c. 200 glucose units (micro-crystalline cellulose), has been extensively used for the chiral resolution of highly polar compounds such as amino acids, amino acid derivatives and dia-minodicarboxylic acids. The chiral recognition ability

Table 2 Chiral stationary phases for liquid chromatography

Type

Ligand

Trade name

A/-(3,5-Dinitrobenzoyl)-L-phenylglycine

N-(3,5-Dinitrobenzoyl)-L-leucine

Naphthyl-D-, naphthyl-L-alanine

Naphthyl-D-, naphthyl-L-leucine

A/-(3,5-Dinitrobenzoyl)-(R)-1-naphthylglycine

N-(3,5-Dinitrobenzoyl)-aminocarbonyl-L-valine

A/-[(S)-(1-Naphthyl) ethylaminocarbonyl]-L-valine

(R)-, (S)-I-Naphthylethylamine

Teicoplanin

Vancomycin

D-,L-Phenylglycine

D-,L-Leucine

D-, L-Naphthylalanine D-,L-Naphthylleucine Sumichiral OA-2500 Sumichiral OA-3100 Sumichiral OA-4000 LC-(R)-, LC-(S)-Naphthyl urea Chirobiotic T Chirobiotic V

Type II Microcrystalline cellulose triacetate

Cellulose fr/'s(4-methylbenzoate) Cellulose tribenzoate Cellulose triacetate Cellulose tricinnamate Cellulose f/"/s(3,5-dimethylphenylcarbamate) Cellulose fr/'s-phenylcarbamate Cellulose t7's(4-methylphenylcarbamate) Cellulose t7's(4-chlorophenylcarbamate) Amylose t7s(3,5-dimethylphenylcarbamate) Amylose t7s((S)-1-phenylethylcarbamate) Poly-W-acryloyl-(S)-phenylalanine ethylester (+)-Poly(triphenylmethyl methacrylate) (#)-Poly(diphenyl-2-pyridylmethyl methacrylate)

Chiralcel CA-1 Cellulose triacetate Chiralcel OJ, OJ-R Chiralcel OB, OB-H Chiralcel OA Chiralcel OK

Chiralcel OD, OD-H, OD-R Chiralcel OC Chiralcel OG Chiralcel OF Chiralpak AD Chiralpak AS ChiraSpher Chiralpak OT(#) Chiralpak Op(#)

Type III

2,2'-Diphenyl-1,1'-binaphthol derivatives of 18-crown-6

a-, ß-, y-Cyclodextrin ß-, y-Cyclodextrin ß-Cyclodextrin derivatives a-, y-Cyclodextrin derivatives

Crownpak CR(#)

Crownpak CR(-)

Cyclobond III, I, II

ChiraDex, ChiraDex Gamma

Ultron ES-PhCDb Nucleosil p-PMc

Cyclobond III Ac, II Ac

Type IV L-Hydroxyproline

2-Amino-1,2-diphenylethanol NS-Dioctyl-D-penicillamine

Nucleosil Chiral-1 Chiralpak WE Sumichiral OA-5000

Type V

Bovine serum albumin

Human serum albumin a1-Acid glycoprotein

Ovomucoid

Avidin

Cellulase

Pepsin

Resolvosil BSA-7, Ultron ES-BSA Chiral-BSA Chiral-HSA Chiral-HSA Chiral-AGP Ultron ES-OVM Bioptic AV-1 Chiral-CBH Ultron ES-Pepsin

BSA-7PX

aAc, Acetylate; SP, (S)-2-hydroxypropyl ether; RSP, racemic 2-hydroxylpropyl ether; SN, (S)-naphthylethylcarbamate; RN, (R)-naphthylethylcarbamate; DMP, 2,6-dimethylphenylcarbamate; PT, para-toluoyl ester. b PhCD, Phenylcarbamate. c^-PM, Permethylate.

of the cellulose is based on the microcrystallinity because, when treated with dilute alkali, cellulose loses its chiral recognition ability, resulting in a stable amorphous form.

It was found that microcrystalline cellulose triacetate preserved microcrystallinity and had excellent chiral recognition ability. In contrast, microcrystal-line cellulose triacetate precipitated from a solution

Figure 3 The more favoured diastereomeric complex between an A/-(3,5-dinitrobenzoyl)-a-amino amide and an A/-(2-naphthyl)-a-amino ester. A re-donor-acceptor interaction and two hydrogen-bonding interactions are indicated by arrows. (Reproduced with permission from Pirkle WH and Pochapsky TC (1987) Advances in Chromatography, vol. 27, p. 116. New York: Marcel Dekker.)

Figure 3 The more favoured diastereomeric complex between an A/-(3,5-dinitrobenzoyl)-a-amino amide and an A/-(2-naphthyl)-a-amino ester. A re-donor-acceptor interaction and two hydrogen-bonding interactions are indicated by arrows. (Reproduced with permission from Pirkle WH and Pochapsky TC (1987) Advances in Chromatography, vol. 27, p. 116. New York: Marcel Dekker.)

has another morphology, and different chiral recognition properties, compared with microcrystalline cellulose triacetate. The chiral stationary phases based on the cellulose triacetate precipitated from a solution are prepared by coating the polymer on a silica gel matrix. Many chiral stationary phases prepared by this technique are commercially available as triacetate, triben-zoate, trisphenylcarbamate, tribenzyl ether and tricin-namate derivatives of cellulose.

Chiral stationary phases based on cellulose and amylose derivatives could separate 78% of racemates examined. However, the disadvantage of stationary phases based on the cellulose and amylose derivatives coated on silica gels is the restriction of the eluents used; the coated polymer is soluble in some eluents and removed. Polysaccharide derivatives chemically bound to silica gel overcome this problem. The coated and the chemically bound polymers showed different chiral recognition properties.

With regard to the chiral recognition mechanism, the interaction of the solute and the chiral stationary phase based on cellulose phenylcarbamate derivatives has been investigated by computational chemistry and nuclear magnetic resonance measurements of the complex. It was found that n-n and hydrogen-bonding interactions play an important role in chiral recognition of the solute.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment