Amino Acid Enantioseparation via Coated Cellulose and Amylose Derivatives

Another useful type of chiral stationary phase for amino acids and their derivatives is based on the polymers of cellulose and amylose. Usually the polymers are derivatized to increase chiral selectivity or improve stability. The derivatized cellulose or amylose polymer is coated (not bonded) to a silica support. The fact that the chiral material is not bonded to the silica makes the material somewhat labile with respect to certain solvents.

Time (minutes)

Time (minutes)

Figure 1 The separation of a series of amino acid derivatives. The column was 10-cm long, 6 mm i.d. One mobile phase component (A) was 50 mM phosphate buffer (pH 6.0) and the second component (B) pure acetonitrile. The gradient used was isocratic for 12min 30% (B), then programmed from 12 to 29min from 30% (B) to 47% (B), then from 29 to 49 min 47-67% (B) and, finally, from 49 to 57 min, 67-93% (B). The flow rate was 1 mL min-1.1, L-serine; 2, D-serine; 3, L-threonine; 4, D-threonine; 5, L-alanine; 6, D-alanine; 7, L-valine; 8, D-valine; 9, L-methionine; 10, D-methionine; 11, L-leucine and isoleucine; 12, D-leucine and isoleucine; 13, L-tyrosine; 14, L-phenylalanine; 15, D-tyrosine; 16, D-phenylalanine; 17, L-tryptophan; 18, D-tryptophan; 19, L-lysine; 20, D-lysosine; 21, L-cystine; 22, D-cystine. (Courtesy of Iwaki K, Yoshida S, Nimura N and Kinoshita T (1987) Optical resolution of enantiomeric amino acid derivatives on a naphthylethylurea multiple-bonded chiral stationary phase prepared via an activated carbamate intermediate. Journal of Chromatography 404: 117-122.)

Both cellulose and amylose contain five chiral centres per unit and thus the polymeric material offers a large number of chirally interactive centres and high probability of interaction. There are basically two common types of cellulose and amylose derivatives that are used as stationary phases. The first type are simple esters usually formed from the acid chlorides such as acetyl chloride or benzoyl chloride. The more stable, and probably the more popular derivatives, are the carbamates which can be synthesized from the appropriate isocyanate. The most useful cellulose- and amylose-based chiral stationary phases are probably those derivatized with the different substituted tris(3,5-dimethylphenylcarbamates). An example of the separation of N-benzyloxycarbonyl alanine ethyl esters on cellulose tris(3,5-dimethyl-phenylcarbamate) is shown in Figure 2.

The column was 25-cm long, 4.6-mm i.d., and the mobile phase was hexane-2-propanol (90 : 10 v/v). The stationary phase was operated in the normal phase mode, consequently, retention and selectivity was again controlled by differential polar interactions.

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