beta-galactosidase-catalyzed intramolecular transglycosylation

A novel transglycosylation strategy for efficient preparation of N-acetylla ctosamine (Gal beta1 --> 4GlcNAc, LacNAc) and sialyl LacNAc was developed u sing beta -galactosidase from Bacillus circulans. In order to minimize the competing hydrolysis by forcing the enzymatic transglycosylation to proceed in an intramolecular manner, a novel substrate 9 carrying the donor (galac tose) and the acceptor (N-acetylglucosamine) components linked via a 2-hydr oxy-5-nitro-benzylalcohol derived tether was prepared. Treatment with beta -galactosidase from B. circulans afforded the transglycosylation product 11 in 26% yield. Furthermore, addition of sialyltransferase and CMP-sialic ac id to this system gave sialyl LacNAc 18 in 39% yield. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.