Glycosidation by Glycosylidene Diazirines

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

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

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... 

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. 

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