New carbocyclic nucleosides: synthesis of carbocyclic pseudoisocytidine and its analogs

Cyclopentane-containing nucleoside analogs with a CC connection between the (heterocyclic) base and the carbocyclic scaffold are quite rare. Herein, we report the synthesis of previously unknown racemic carbocyclic pseudoisocytidine and its analogs, which were prepared in 13 steps from commercially available materials. Pseudoisocytidine and its sulfur analog were moderately active against the mantle cell lymphoma cell line, JVM-3. We also prepared a versatile cyclopentanone intermediate, which can be converted into novel carbocyclic nucleosides via highly stereoselective addition of organometallic nucleophiles; the adduct with phenyllithium, the stereochemistry of which was unambiguously confirmed by X-ray crystallography, inhibits glycosylase NEIL1 in a dose-dependent manner.