Chemoenzymatic preparation of 2-chloro-4-nitrophenyl β-maltooligosaccharide glycosides using glycogen phosphorylase b

In the present work, we aimed to develop a new chemoenzymatic procedure for the synthesis of β-maltooligosaccharide glycosides. The primer in the enzymatic reaction was 2-chloro-4-nitrophenyl β-maltoheptaoside (G7-CNP), which was synthesised from β-cyclodextrin (β-CD) using a very convenient chemical method [E. Farkas, L. Jánossy, J. Harangi, L. Kandra, A. Lipták, Carbohydr. Res., 303 (1997) 407–415]. Shorter chain length CNP-maltooligosaccharides in the range of dp 3–6 were prepared using rabbit skeletal muscle glycogen phosphorylase b (EC 2.4.1.1). Detailed enzymological investigations revealed that the conversion of G7-CNP was highly dependent on the conditions of phosphorolysis. A 100% conversion of G7-CNP was achieved during 10 min in 1 M phosphate buffer (pH 6.8) at 30 °C with the tetramer glycoside (77%) as the main product. Phosphorolysis at 10 °C for 10 min resulted in 89% conversion and G4-, G5-, and G6-CNP oligomers were detected in the ratio of 29:26:34%, respectively. The reaction pattern was investigated using an HPLC system. The preparative scale isolation of G3→6-CNP glycosides was achieved by size-exclusion column chromatography (SEC) on Toyopearl HW-40 matrix. The productivity of the synthesis was improved by yields of up to 70–75%.