Uncommon Three-, Four-, and Six-Membered Nucleosides

Over the past two decades, nucleoside analogues exhibiting uncommon sugar moieties rather than natural ribo‐ and 2′‐deoxyribofuranose rings have received growing attention because of the increased recognition of their various biological roles. In particular, countless reports have been published that describe the value of ring‐contracted analogues based on a three or four‐membered pseudo‐sugar unit in the treatment of viral infections. Within this latest context, the pursuit of carbocyclic nucleosides structurally related to natural furanose units has been driven by their distinguishing stability toward chemical and metabolic degradation, due to the absence of an anomeric center. In an effort to generate more effective therapeutics through modifications of the carbohydrate moiety of nucleosides, many powerful and innovative transformations have been accomplished, which led to the creation of an important structural variety, including three‐, four‐, and six‐membered ring analogues.