Separation and mutarotation of anomers of chitooligosaccharides

In the course of a study on the lysozyme-catalyzed reaction of chitooligosaccharides, it was found that each chitooligosaccharide gave two completely separated peaks on high-performance liquid chromatography with a partition column. Synthetic 2-acetamido-2-deoxy-beta-D-glucopyranose gave [alpha] D14 = -18.1 degrees (c = 0.51, H2O) and a large second peak with a minor first peak on high-performance liquid chromatography. When an aqueous solution of the beta-anomer was allowed to stand, the area of the first peak on high-performance liquid chromatography increased, together with a decrease in the area of the second peak and an increase in [alpha] D value. It was concluded that the two peaks of each chitooligosaccharide on high-performance liquid chromatography were due to the separation of alpha- and beta-anomers. The mutarotation of 2-acetamido-2-deoxy-beta-D-glucopyranose was followed by monitoring the [alpha] D value and in the peak area of the two peaks on high-performance liquid chromatography. It was found that the ratios of alpha- and beta-anomers of chitooligosaccharides produced by the lysozyme-catalyzed reaction of chitopentose were different from those of the corresponding authentic chitooligosaccharides which were allowed to stand in the absence of the enzyme under the conditions used for the enzymatic reaction.