The present paper describes the formation of N-triflyl-7,8-dihydro-8(R),5′-O-cyclonucleosides during our efforts to introduce the triflate leaving group at the 5′-position of purine ribonucleoside derivatives. The chemical structure of these original cyclonucleosides, including the absolute configuration at C-8, was unambiguously elucidated by elemental analysis, high-resolution mass spectrometry, NMR analysis and X-ray crystallography. Our results bring new insights into the reactivity of the 5′-O-triflate derivatives of purine ribonucleosides while providing an efficient access to original cyclonucleosides.