Abstract

A new direct method for β-selective glycosylation with an N-acetylglucosamine (GlcNAc) donor was developed. This substrate, which can be readily prepared from commercially available GlcNAc in two steps, contains a 4-O-tert-butyldimethylsilyl (TBDMS) protecting group as a key component. We found that this functionality could have a favorable effect on the reactivity of the GlcNAc donor. Glycosylation with the armed donor using primary alcohols in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate (TMSOTf) in 1,2-dichloroethane smoothly gave the desired coupling products in good yields with complete β-selectivity, while sterically hindered acceptors were less efficient.

Highlights

  • N-Acetylglucosamine (GlcNAc) is one of the most abundant naturally occurring monosaccharides, and it exists as a key component of oligosaccharides in glycoproteins and glycolipids that play important biological roles [1]

  • Www.mdpi.com/journal/molecules glycosyl donors, which led to the development of super-armed donors [13]

  • Demchenko and coworkers demonstrated that thioglycoside donors of Glc were dramatically Following Ling’s previous report [15], β-glycosylation with an N-acetylglucosamine (GlcNAc) tripivaloate 5 was prepared in 70% yield activated by the installation of electron-donating benzyl groups to both 4 and 6 positions, and disclosed by the reaction of free GlcNAc 4 with pivaloyl chloride in pyridine and dichloromethane (Scheme 1)

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Summary

Introduction

N-Acetylglucosamine (GlcNAc) is one of the most abundant naturally occurring monosaccharides, and it exists as a key component of oligosaccharides in glycoproteins and glycolipids that play important biological roles [1]. Hashimoto et al successfully developed glycosylations with a diethyl phosphite donor of GlcNAc 2 in the presence of stoichiometric bis(trifluoromethane)sulfonamide (Tf2 NH) at −78 ◦ C (Figure 1b), using sugar secondary alcohols, and proceeded smoothly to obtain the disaccharides in good yields with complete β-selectivity [12]. This glycosylation method requires a stoichiometric amount of Tf2 NH and cumbersome. Results ofmetal our implementation and the substrate scope of this synthetic sequence

Results and Discussion
Preparation
Optimization
General
General Experimental Procedure and Physical Data for All New Compounds
General Procedure for the Glycosylation with GlcNAc Donors
Conclusions
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