Glycosylation Using 2-Azido-3,4,6-tri-O-benzyl-2-deoxy-d-glucose, -galactose, and -mannose with the Aid of p-Nitrobenzenesulfonyl Chloride–Silver Trifluoromethanesulfonate–Triethylamine System

Abstract

This report describes a simple synthesis of 2-azido-3,4,6-tri-O-benzyl-2-deoxy-d-glucopyranose. Glycosylation using this as well as 2-azido-3,4,6-tri-O-benzyl-2-deoxy-d-galactopyranose and -mannopyranose was achieved with the aid of a reagent system consisting of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine, and its modifications. O-(2-Acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-O-α-d-mannopyranosyl-(1→4)-α-d-mannopyranose, the repeating unit of the main chain of the O-specific cell wall polysaccharide of E. coli 058 was synthesized.

Glycosylation with 2-Acetamido-2-deoxyglycosyl Donors at a Low Temperature: Scope of the Non-Oxazoline Method

“…The preparation of thioglycosides 58 and 59 began with phosphorylation of 2-azido-2-deoxymannose 60 (Scheme ) . Reaction of diphenyl phosphate 61 with thiophenol in the presence of BF 3 ·OEt 2 followed by chromatographic separation gave thioglycosides 62 and 63 in 25% and 67% yields, respectively.…”

“…Diphenylphosphoryl chloride (0.23 mL, 1.13 mmol) was added to an ice-cooled (0 °C) solution of hemiacetal 60 (490 mg, 1.03 mmol) and DMAP (304 mg, 2.49 mmol) in CH 2 Cl 2 (10 mL). After 30 min of stirring, the reaction was quenched with crushed ice, followed by stirring at room temperature for 15 min.…”

“…64 The preparation of thioglycosides 58 and 59 began with phosphorylation of 2-azido-2-deoxymannose 60 (Scheme 3). 65 Reaction of diphenyl phosphate 61 with thiophenol in the presence of BF 3 that β-CIP 68β and β-triflimide 70β exist in the reaction mixture. Therefore, the formation of α-glycoside 64 would be attributed to nucleophilic attack from the less hindered face of SSIP 69 (path a) as reported by the Crich group for αmannoside formation.…”

Recent trends in the synthesis of O-glycosides of 2-amino-2-deoxysugars

“…[126][127][128][129][130][131][132][133][134] The triflate moiety is typically introduced by reaction of an alcohol with Tf 2 O and pyridine in dichloromethane, see for example, the synthesis of 2-O-triflate 64 from 2-hydroxyl derivative 63 (Scheme 12). [135][136][137][138][139][140][141][142][143][144][145] As to the triflate displacement reaction, many modifications have emerged [135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152] since the pioneering work by van Boom and co-workers. 153 For example, the treatment of 64 with NaN 3 in DMF afforded 14b in 86% yield.…”

“…136 Apparently, the 2-azido-2-deoxy derivative 14b can then be converted into a suitable glycosyl donor and used in subsequent glycosylations. Amongst a variety of reaction conditions employed for the azide displacement of the triflyl moiety are the following: LiN 3 in DMF, 141,153 NaN 3 in DMF, [135][136][137]142,146,148,149,151,152 Bu 4 NN 3 in benzene, 139,140,143,144 or TMSN 3 and TBAF in THF. 145 55 derivatives developed by Č erný and Stanek occupy an important niche.…”