7-Deazapurine (Pyrrolo[2,3-d]pyrimidine) 2'-Deoxyribonucleosides: Syntheses and Transformations

This review reports on the synthesis of 7-deazapurine (pyrrolo[2,3-d]pyrimidine) 2'-deoxyribonucleosides, including β-D- and β-L-enantiomers, fluoro derivatives, and 2',3'-dideoxyribonucleosides. It covers the various aspects of convergent nucleoside synthesis. Stereochemically defined α-D and α-L 2'-deoxyribonucleosides as well as sugar derivatives were prepared by nucleobase anion glycosylation. This glycosylation reaction is regioselective for the pyrrole nitrogen and stereoselective for β-nucleoside formation. Common glycosylation protocols lead to 7-deazapurine 2'-deoxyribonucleosides with unusual glycosylation sites. 7-Deazapurine 2',3'- dideoxyribonucleosides were also obtained from 2'-deoxy- or 3'-deoxyribonucleosides by Barton-McCombie deoxygenation, by elimination of sugar hydroxyl groups or by anion glycosylation. Another aspect of the review is the functionalization of pyrrolo[2,3-d]pyrimidine nucleosides. A broad range of reporter groups were introduced by the Sonogashira cross coupling or the copper(I)-catalyzed Huisgen- Meldal-Sharpless “click” reaction. The application of 7-deazapurine nucleosides as antiviral or anticancer agents, and the use of 7- deazapurine nucleoside triphosphates in the Sanger dideoxy DNA-sequencing are also reported.