Anomeric glycosylation

Anomeric Glycosyl Dianions as Intermediates in the Synthesis of C-Glycopeptides... 

M. Casillas, A. M. Gomez, J. C. Lopez, and S. Valverde, A simple entry to pyranoid glycals reaction of anomeric glycosyl sulfoxides with organolithiums, Synlett, (1996) 628-630. 

Both of the anomeric glycosyl trichloroacetimidates can be obtained in pure form, depending on the base (NaH, K2C03, or DBU) used for deprotonation of the reducing sugar). 

STRUCTURE OF ANOMERIC GLYCOSYL RADICALS AND THEIR TRANSFORMATIONS UNDER REDUCTIVE CONDITIONS... 

Generally, the reactions are carried out in refluxing benzene solution, since the yield in benzene is better than that in other solvents. Probably, the radicals formed may be somewhat stabilized by the weak orbital-orbital interaction between the radicals and benzene. However, from the environmental point of view, toluene or dioxane is recently used. As substrates, alkyl bromides or alkyl iodides are used, and the reactivity increases in the order prim-alkyl < seoalkyl < te/t-alkyl. Sugar anomeric bromide (3) is generally not so stable, so the reaction is carried out under irradiation conditions with a mercury lamp at room temperature (eqs. 4.2 and 4.3). There are two types of anomeric glycosyl radicals as shown in Figure 4.1. One is the axial radical [I], and the other is the equatorial radical [I ]. The axial radical is more nucleophilic than the equatorial radical due to the stereoelectronic effect, where this effect comes... 

Praly, J P, Structure of anomeric glycosyl radicals and their transformations under reductive conditions, Adv. Carbohydr. Chem. Biochem., 56, 65-152, 2000. 

Bianchi, A., Bernard , A. Selective synthesis of anomeric -glycosyl acetamides via intramolecular Staudinger ligation of the -azides. Tetrahedron Lett. 2004, 45, 2231-2234. 

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