Azidonitration

For the synthesis of glycans containing 2-amino-2-deoxysugars, the regioselective azidophenylselenation of glycals is popular [524—528]. This methodology follows on from the classic azidonitration work of Lemieux and Ratdiffe, first reported in the... 

The propensity of the cesium salts of week acids to accelerate SN2 type displacement reactions was exploited for the stereodirected conversion of glycosyl nitrates into anomeric phosphotriesters by exposure of phosphoric acid diesters to cesium salts (Scheme 9).16 Thus, glycosyl nitrate 50, obtained by azidonitration of 3,4-di-O-acetyl-L-fucal, was treated with... 

Scheme 16 Azidonitration of Glycals and Conversion of the Nitro Intermediate into Various Glycosyl Donors1276-2861...

Of great use is the azidonitration of glycals by a similar procedure85,86. It is probable, but not certain, that the reaction is initiated by attack of an azide radical at the double bond rather than by a ceric azide species, although the steric bulk of the latter can explain the stereochemical course of the reaction. 

Caution The azidonitration is safely performed behind a barrier, even if under a wide range of conditions (i.c.. by varying the temperature, the solvent, and the relative amounts of reagents) no lack of control has been observed. Nevertheless, hazardous conditions may be encountered and all the azidonitrations must be conducted with due caution. Furthermore, the use and disposal of sodium azide must be carefully controlled. 

The azidonitration route to 2-amino-2-deoxy sugars from D-glycal should be compared with the alternative route exploiting the addition of nitrosyl chloride (Section 7.2.1.1). Both methods have been tested on the synthesis of intermediates of D-lactosamine, and the azidonitration method was considered more efficient95. 

The 5-thio analog of A -acetyl-D-glucosamine 50 was synthesized from suitably protected furanoid [98-100] or open-chain [101] D-glucosamine derivatives employing the general approach via the thiirane route [102], as well as from 5-thio-D-glucal 51 [103] via azidonitration [104]. 

Azidonitration Deoxygenation Dihydroxylation Epoxidation Hydrogenation Oxidation Photobromination Reduction... 

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