Glycosyl Fluorides and Azides

Micheel, Fritz, and Klemer, Almuth, Glycosyl Fluorides and Azides, 16, 85-103... 

Glycosyl fluorides and azides, F. Micheel and A. Klemer, AJu Carbohydr. Chem., 16 (1961). Developments in the chemistry of thio sugars, D. Horton and D. H. Hutson, Adv. Carbohydr. Chem., 18 (1963). 

Although the major portion of this review is concerned with the glycosyl fluorides and their derivatives, short Sections on the closely related glycosyl azides and on carbohydrates containing fluorine at non-glycosidic carbon atoms have been included. 

Another method for the synthesis of glycosyl fluorides consists of 1,3-dipolar cycloaddition of glycosyl azides with di-f-butyl acetylenedicarboxylate and subsequent treatment of the triazole derivatives with HF-pyridine. ... 

W. Broder and H. Kunz, A new method of anomeric protection and activation based on the conversion of glycosyl azides into glycosyl fluorides, Carbohydr. Res., 249 (1993) 221-241. 

A mixture of 2,3,, 6-tetra- -benzyl-a- and B-D-glucopyranosyl azides in the ratio 10 1 has been obtained in 90 yield from the corresponding anomerlc mixture of glycosyl fluorides on treatment... 

Maltoheptaosyl bromide 152 [153] was converted (Scheme 40) into glyco-syl azide 153 under mild conditions using trimethylsUyl azide in the presence of tetrabutylammonium fluoride (TBAF). Final cycloaddition reaction between propargylic derivative 151 and glycosyl azide 153 in the presence of Cu(Ph3P)3Br as catalyst [133], at room temperature and prolonged reaction times, afforded 154 in a 27% yield. 

A range of densely functionalized five- and six-membered nitrones were formed in this way, and the method is proposed as suitable for the synthesis of the alkaloid laccarin. Under the influence of nucleophilic fluoride sources, including TBAT, a carbamoyl silane undergoes addition to ketones and aldehydes to give a-silyloxyamide products. TBAT can be used in combination with Mc3SiN3 to effect glycosyl azide formation, and finally it can be used to effect self-condensation of some unsaturated carbonyl compounds, a process in which fluoride presumably acts as a base. ... 

Copper-catalyzed azide-alkyne cycloaddition (CuAAC) has been widely used in the post-glycosylation of pre-formed polymers, for which the protected aUcyne monomers can be first polymerized by various LRP strategies followed by removal of trimethylsilyl (TMS) protection groups using tetrabutylammonium fluoride (TBAF)/ acetic acid for click reaction with azido functional sugars (Fig. 3) [59, 60]. This approach avoids the use of hazardous azide-functionalized monomers and utilizes the diversity of well-documented azido functional sugars [59]. 

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