Specificity of Donor Structures for endo‐β‐N‐Acetylglucosaminidase‐Catalyzed Transglycosylation Reactions

Abstract

To demonstrate the structural specificity of the glycosyl donor for the transglycosylation reaction by using endo-β-N-acetylglucosaminidase from Mucor hiemalis (endo-M), a series of tetrasaccharide oxazoline derivatives was synthesized. These derivatives correspond to the core structure of an asparagine-linked glycoprotein glycan with a β-mannose unit of a non-natural-type monosaccharide, including β-glucose, β-galactose, and β-talose in place of the β-mannose moiety. The transglycosylation activity of wildtype (WT) endo-M and two mutants, N175Q and N175A, was examined by using these tetrasaccharide donors with p-nitrophenyl N-acetylglucosaminide (GlcNAc-pNp). The essential configuration of the hydroxy group for the transglycosylation reaction was determined. On the basis of these results, the transglycosylation reaction was investigated by using chemically modified donors, and transglycosylated products were successfully obtained.

A New Fluorogenic Probe for the Detection of endo‐β‐N‐Acetylglucosaminidase

“…To confirm our hypothesis, we synthesized the probe 1 and investigated its photochemical properties. Synthesis of the core pentasaccharide skeleton was performed by our original method, and then the Nma and Dnp groups were introduced at the non‐reducing and reducing ends, respectively (Scheme S1). The structure of 1 was confirmed by 2D NMR spectroscopy and high‐resolution mass spectrometry (see the Supporting Information).…”

Recent Chemical and Chemoenzymatic Strategies to Complex-Type N-Glycans

“…To sum up, there are three main chemical strategies so far for the construction of β-D-mannosidic bonds to synthesize complex-type N-glycans, including the βglycosylation-inversion strategy (Matsuo et al, 1999), intramolecular aglycon delivery (IAD) (Barresi and Hindsgaul, 1991), and 4,6-O-benzylidene protecting strategy (Crich's mannosylation) (Crich and Sun, 1996) (Figure 4). Because of the efficiency of the simple intermolecular reaction, and the predominant β-selectivity of Crich's mannosylation (for a recent example of β-glycosylationdouble inversion strategy, see Ishii et al, 2018) (for an example of an improved IAD, see Ishiwata et al, 2008), 4,6-O-benzylidene-protected glycosyl donors were trends to be selected, although the other methods also afford β-Dmannose in the acceptable stereoselectivity. Furthermore, some efforts have also been made to optimize this strategy (For example, the gold(I)-catalyzed glycosylation reaction with glycosyl ortho-alkynyl benzoates as donors, see: Zhu and Yu, 2015).…”

Chemoenzymatic Methods for the Synthesis of Glycoproteins

“…More recently, Matsuo and co-workers further demonstrated the structural requirement of the sugar oxazoline donors in the Endo-M catalyzed transglycosylation. 250 A series of tetrasac-charide oxazoline derivatives was synthesized in which the innermost β -mannose moiety was replaced with other monosaccharides including β -glucose, β -galactose, and β -talose, as well as a 4-alkynylated derivative. The transglycosylation activity ofEndo-M and its two mutants, N175Qand N175A, on these tetrasaccharide donors was tested with p-nitrophenyl N -acetylglucosaminide (GlcNAc-pNP) as the acceptor.…”

“…More recently, Matsuo and co-workers further demonstrated the structural requirement of the sugar oxazoline donors in the Endo-M catalyzed transglycosylation . A series of tetrasaccharide oxazoline derivatives was synthesized in which the innermost β-mannose moiety was replaced with other monosaccharides including β-glucose, β-galactose, and β-talose, as well as a 4-alkynylated derivative.…”