UDP-N-trifluoroacetylglucosamine as an alternative substrate in N-acetylglucosaminyltransferase reactions

The synthesis of UDP-N-trifluoroacetylglucosamine [uridine 5′-(2-trifluoroacetamido-2-deoxy-α-d-glucopyranosyl diphosphate, UDP-GlcNAc-F3] is reported. The compound is found to serve as a substrate for the `core-2ʹ GlcNAc transferase (EC 2.4.1.102) that is involved in the biosynthesis of O-linked glycoproteins and for the GlcNAcT-V transferase (EC 2.4.1.155) that is a key biosynthetic enzyme controlling the branching pattern of cell surface complex Asn-linked oligosaccharides. The trisaccharide β-d-Galp-(1→3)-[β-d-GlcpNAc-F3(1→6)]-α-d-GalpNAc-OR [R=(CH2)8CO2Me] was prepared from β-d-Galp-(1→3)-α-d-GalpNAc-OR using the `core-2ʹ GlcNAc transferase. The tetrasaccharide β-d-GlcpNAc-(1→2)-[β-d-GlcpNAc-F3-(1→6)]-α-d-Manp-(1→6)-β-d-Glcp-OR [R=(CH2)7CH3] was prepared from β-d-GlcpNAc-(1→2)-α-d-Manp-(1→6)-β-d-Glcp-OR [R=(CH2)7CH3] using the GlcNAcT-V transferase. Removal of the trifluoroacetyl group was achieved under mild basic conditions to give the corresponding glucosamine containing tetrasaccharide. These examples demonstrate the feasibility of introducing masked forms of glucosamine residues into oligosaccharides using GlcNAc-specific transferases. The requirement for the trifluoroacetamido group as a specific recognition element was evident in the observation that neither UDP-glucosamine nor UDP-glucose served as a donor substrates for the `core-2ʹ GlcNAc transferase.