Facile synthesis of 1′,2′-cis-β-pyranosyladenine nucleosides

1′,2′-cis-β-Glycosyladenine nucleosides, such as β-altroside, β-mannoside, and β-idoside, were efficiently synthesized from the corresponding 1′,2′-trans-β-6-chloropurine derivatives, β-glucoside, and β-galactoside. Nucleophilic substitution of the O-trifluoromethanesulfonyl groups at the C-2′ and/or 3′ was carried out using tetrabutylammonium acetate or cesium acetate under mild conditions. Subsequent deprotection and amidation afforded the desired compounds, 1′,2′-cis-β-pyranosyladenine nucleosides.