Synthesis of Natural and Sugar-Modified Nucleosides Using the Iodine/Triethylsilane System as N -Glycosidation Promoter.

The reagent system based on the combined use of Et 3 SiH/I 2 acts as an efficient N -glycosidation promoter for the synthesis of natural and sugar-modified nucleosides. An analysis of reaction stereoselectivity in the absence of C2-positioned stereodirecting groups revealed high selectivity with six-membered substrates, depending on the nucleophilic character of the nucleobase or based on anomerization reactions. The synthetic utility of the Et 3 SiH/I 2 -mediated N -glycosidation reaction was highlighted by its use in the synthesis of the investigational drug apricitabine.