The design, synthesis and rationale for the first example of a carbocyclic 7-deazapurine- pyrimidine hybrid nucleoside is described. The marriage of key structural features from the purine and pyrimidine nucleobase scaffolds has given rise to novel hybrid nucleobases designed to be recognized by biologically relevant purine- and pyrimidine-metabolizing enzymes. Pairing these hybrid bases with chemotherapeutically beneficial carbocyclic "sugars", in addition to utilizing the highly effective 7-deaza ring system, should result in chemotherapeutically useful nucleosides. The approach to realize the first 7-deazapurine-pyrimidine hybrid nucleoside