Novel substrates for efficient enzymatic transglycosylation byBacillus circulans

Abstract

To develop transglycosylation for efficient preparation of N-acetyllactosamine (Galβ(1[Formula: see text]4)GlcNAc, LacNAc), β-galactosidase mediated transglycosylation using novel substrates Bacillus Circulans was explored. To make transglycosylation entropically favorable over hydrolysis, donor (lactose or galactose) and acceptor (N-acetyl glucosamine, GlcNAc) components were connected to a single molecule. For that purpose, 1,2- and 1,3-benzene dimethanol and 2-hydroxy-5-nitro- and 5-hydroxy-2-nitro-benzyl alcohol were screened as linkers and enzymatic transglycosylation was examined under several conditions. In the case of 2-hydroxy-5-nitro-benzyl connected substrate 40, an indication of the occurrence of intramolecular transglycosylation was observed, and the desired product (58) was obtained in 26% isolated yield. The same reaction in the presence of CMP sialic acid and α-(2[Formula: see text]6)-sialyltransferase gave sialyl LacNAc 87 in one pot in 39% isolated yield. Additionally, the effect of the C-2 substituent of the acceptor component was briefly examined using substrates containing NHAlloc (72), NHTroc (73), and N3(74) groups. Although the occurrence of intramolecular transglycosylation was not clear in these cases, disaccharides 81–83 were obtained in reasonable yields.Key words: galactosidase, intramolecular transglycosylation, N-acetyllactosamine, sialyltransferase.