Glycals fluorination

Introduction of a fluorine atom at C-2 by addition to glycals is effected by electrophilic reagents, (Q is a strongly electron-withdrawing... 

Reaction of AcOF with glycals has been developed. Rozen and coworkers observed that elemental fluorine, which is practically insoluble in, and non-reactive with, acetic acid, gives rise to the active species, AcOF,... 

Korytnyk and coworkers have shown that reactions of xenon difluoride with acetylated glycals in the presence of boron trifluoride are a convenient route for the synthesis of 1,2-difluoro sugars, while the addition of fluorine to the double bond occurred predominantly from the less hindered side and cis adducts were mainly formed75, 76. Stereoselective transformation of tri-O-acetyl-D-galactal with xenon difluoride at -20 to +5 °C, without a catalyst in CFC13, after hydrolysis, afforded 2-deoxy-2-fluoro-D-galactose in 63% yield77. 

The fluorination and stereochemistry of the reaction of pyranoid and furanoid glycals with acetyl hypofluorite are described41. In related work42 the synthesis of 2-deoxy-2-fluoro-D-galactapyranose by treatment of 2-deoxy-D-galactapyranose with acetyl hypofluorite is described and the 18F-labelled product was similarly prepared through the use of Ac018F. 

As the project progressed, a major study was made of the electrophilic addition of various fluorinated species to the double bonds of peracylated carbohydrate glycals,... 

Time-consuming work-up procedures must be avoided in the synthesis of labeled diagnostics, but essentially the usual fluorination methods are used. [1 F]FDG can be prepared by electrophilic fluorination of a glycal with [ F acctyl hypofluorite [87] (Scheme 4.40). This reagent again is produced by reaction of F labeled fluorine gas with KOAc -2HOAc [88]. The synthesis of other [ F]fluor-odopa isomers is illustrated in Scheme 4.41. 

Electrophilic fluorination of glycals is a key step in the syntheses of Withers glycosidase inactivators and related potential pharmaceuticals. 

Glycosyl fluorides. Glycals t tion of Sip4 and an oxidant such as acetate (H2O). In such cases, a bra Fluorination. Fluorination < Sip4. The reagent combination als varenes. 

Fluorination of the anomeric carbon atom along with the adjacent carbon atom, occurs by the action of fluorine on acetylated glycals... 

Figure 6. Possible mechanism of addition of fluorine to glycals with Xep2. (a) Electrophilic addition of F from XeF2-BF3 complex, (b) addition of F on carboxonium ion,...

Selectfluor has been used for the fluorination of phosphonylated exo-glycals. Both diastereoisomers of UDP-fluoro-ejco-galactal (262) and (263) were synthesised. As expected, they displayed time-dependent inactivation of UDP-galactopyranose mutase (Scheme 105). ... 

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