Non-natural nucleosides bearing 4-aryldiazenylpyrazole aglycone

Ribosylation of 4-aryldiazenyl-3-R-5-R'-pyrazoles with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose in the presence of tin(IV) chloride gives α- and β-anomeric N-(2,3,5-tri-O‑acetylribofuranosyl)-substituted derivatives. Their HPLC separation and deacetylation (MeOH, MeONa) affords 1-(β-D-ribofuranosyl)-3-R-5-R'-4-(aryldiazenyl)-1H-pyrazoles.