Glycosylidene glycosidation

Ohtake H, Ichiba N, Shiro M, Ikegami S (2000) Synthesis and structure of 6-0-, 6-O-glycosylidene glycosides. J Org Chem 65 8164—8170... 

Vasella et al. introduced an approach to glycoside synthesis using the glycosylidene carbene generated from the diazirine sugar as a novel type of glycosyl donor. The... 

Briner, K, Vasella, A, Glycosylidene Carhenes. 2. Synthesis of 0-aryl glycosides, Helv. Chim. Acta, 73, 1764-1778, 1990. 

K. Briner and A. Vasella, Glycosylidene carbenes. Part 6. Synthesis of alkyl and fluoroalkyl glycosides, Helv. Chim. Acta, 75 (1992) 621-625. 

C-glycosides Vasella has reviewed his work on glycosylidene carbenes which is of relevance to the subject, and the use of glycosyl carbanions in C-glycoside synthesis has also been surveyed. ... 

An entirely novel approach to glycosylation uses glycosylideneaziridines which can be oxidised to the relatively unstable diazirines from which glycosylidene carbenes are produced on warming to room temperature. In the presence of alcohols these give glycosides by insertion reactions (Scheme 1) attempts to... 

The glycosylideneaziridines (Vol. 23, p, 16), on photolysis, give glycosylidene carbenes which react with alcohols to give glycosides (Scheme 2). ... 

The course of the glycosidation of hydroxy compounds by glycosylidene diazirines is mainly dictated by four factors ... 

Glycosidation by Glycosylidene Diazirines 159 Table 1. Kinetic parameters for the thermolysis of 1-aziglycoses in MeOH. 

Scheme 2. Glycosidation of alcohols by glycosylidene carbenes derived from diazirines.

Exploratory experiments have shown that glycosylidene carbenes also insert into the N-H bond of sulfonamides, whereas carboxamides yield esters, as illustrated by the product obtained from an A-Boc-asparagine benzyl ester (Figure 7c) [32]. Presumably, such esters are formed by hydrolysis of the initially formed imino ether 0-glycosides, suggesting that glycosylidene diazirines may be used for (selective ) cleavage of peptidic bonds. 

Nucleophilic addition of glycosylidene carbenes to triligated boron compounds followed by migration of a boron substituent to the glycosidic center should lead to... 

Vasella s group has reported a series of new glycosylidene diazirines, for example 8, which undergo thermolysis in methanol to give methyl glycosides. Kinetic studies indicate the importance of... 

Full details of an earlier paper (Vol. 23, p.40, ref. 178) on the synthesis of a range of difluoromethyl C-glycosides by difluoromediylenation of sugar lactones followed by hydrogenation of the glycosylidene derivatives has appeared. ... 

---