Chemical Glycosylation by Single Electron Transfer

Abstract

O ligosaccharides play important roles in nature; however,c hemical synthesis of oligosaccharides is still difficult and not carried out in af ully automated manner. Among various methods, the activation of glycosyl donors by single electron transfer using electrochemical and photochemical methods has several benefits. In particular,electrochemical oxidation is ap owerful method to activate glycosyl donors, including thioglycosides, which are one of the most popular class of glycosyl donors in modern chemical glycosylations. This review article covers the pioneering works of electrochemical glycosylations, other chemical glycosylations achieved by single electron transfer,a nd our recent approach to the automated solution-phase synthesis of oligosaccharides based on the electrochemical method.Keywords: electrochemistry · electron transfer · glycosylation · oligosaccharides · synthetic methods Figure 1. Chemical glycosylation of ac halcogenoglycoside by SET.

Visible Light Enables Aerobic Iodine Catalyzed Glycosylation

“…Besides the activation of thioglycosides through an ionic pathway, their activation via SET‐reactions has also been studied in several cases . This has for example been utilized for the electrochemical O ‐glycosylation of thioglycosides through sulfur radical cations . In general, sulfides are also known to be easily oxidized through SET‐processes to give the corresponding radical cations .…”

Modern Electrochemical Aspects for the Synthesis of Value‐Added Organic Products

“…[109] Glycosylations are essential processes in the chemical synthesis of oligosaccharides.E lectrochemical oxidation is ap owerful method to activate glycosyl donors.F or example, Nokami et al developed ah ighly efficient electrochemical glycosylation reaction with Bu 4 NOTf as asupporting electrolyte.T hey also combined the electroglycosylation with asubsequent one-pot cleavage of af luorenylmethoxycarbonyl (Fmoc) protecting group.This one-pot reaction can be used as ahighly practical method for the synthesis of oligosaccharides (Scheme 27). [110] Ac omplete overview of electrochemical glycosylation was reported by Nokami et al [111] Theg eneration of furan derivatives from sugars is ac lassical conversion in chemistry.F urfural and 5-hydroxymethylfurfural can be generated by the acid-catalyzed dehydration of pentoses (C5) and hexoses (C6), respectively. Thepossibility of oxidation, dehydration, and hydrogenation of these furanic compounds makes them potential alternative commodity chemicals to fossil-fuel-based platform chemicals.…”

Recent Developments in Stereoselective Chemical Glycosylation

“…Chemists have long utilized ultraviolet (UV) light irradiation to perform glycosylation. The light energy either cleaves the aglycone directly to activate the donor, or is harvested by a photosensitizer for further activation …”