7-Functionalized 7-deazapurine β-d and β-l-ribonucleosides related to tubercidin and 7-deazainosine: glycosylation of pyrrolo[2,3-d]pyrimidines with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-d or β-l-ribofuranose

Several 7-functionalized 7-deazapurine ribonucleosides were prepared. Glycosylation of 7-halogenated 6-chloro-7-deazapurines with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-d-ribofuranose or 1-O-acetyl-2,3,5-tri-O-benzoyl-β-l-ribofuranose gave the protected β-d-nucleosides 8c–e (53–62%) and the β-l-nucleosides 9b–e (57–72%), which were transformed to 7-halogenated 7-deazapurine ribonucleosides related to tubercidin and 7-deazainosine. 7-Alkynyl derivatives (1f,g) and (2f,g) were obtained from the 7-iodo nucleosides 1e and 2e employing the palladium-catalyzed Sonogashira cross-coupling reaction. Within the series of 7-deazaadenosine (tubercidin) analogues and 7-deazainosine derivatives physical data such as pKa values, chromatographic mobilities, 13C NMR chemical shifts were determined and correlated to each other.