N -Glycosylation with sulfoxide donors for the synthesis of peptidonucleosides
The synthesis of glycopyranosyl nucleosides modified in the sugar moiety has been less frequently explored, notably because of the lack of a reliable method to glycosylate pyrimidine bases. Herein we report a solution in the context of the synthesis of peptidonucleosides. They were obtained after glycosylation of different pyrimidine nucleobases with glucopyranosyl donors carrying an azide group at the C4 position. A methodological study involving different anomeric leaving groups (acetate, phenylsulfoxide and ortho-hexynylbenzoate) showed that a sulfoxide donor in combination with trimethylsilyl triflate as the promoter led to the best yields.
Highly stereoselective synthesis of lamivudine (3TC) and emtricitabine (FTC) by a novel N -glycosidation procedure
The combined use of silanes (Et3SiH or PMHS) and I2 as novel N-glycosidation reagents for the synthesis of bioactive oxathiolane nucleosides 3TC and FTC is reported. Both systems (working as anhydrous HI sources) were devised to act as substrate activators and N-glycosidation promoters. Excellent results in terms of chemical efficiency and stereoselectivity of the reactions were obtained; surprisingly, the nature of the protective group at the N4 position of (fluoro)cytosine additionally influenced the stereochemical reaction outcome.
Caso, Maria Federica,Dalonzo, Daniele,Derrico, Stefano,Palumbo, Giovanni,Guaragna, Annalisa
supporting information
p. 2626 - 2629
(2015/06/16)
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