Synthesis and antiviral studies of unsaturated analogues of isomeric dideoxynucleosides

Novel isomeric dideoxynucleosides with unsaturation in the carbohydrate moiety have been synthesized. For example, isod4A was synthesized through a rearrangement reaction involving a cyclonucleoside. Support for the structures of both purine and pyrimidine d4 compounds came from UV, NMR, HRMS and single crystal Xray data. Interestingly, the single crystal X-ray data for isod4C shows that the base is almost orthogonal to the carbon-carbon double bond of the sugar moiety. Consistent with this is the observation that the UV data of this compound does not show a bathochromic shift compared to the saturated compound implying that the pi-bond is not in conjugation with the pyrimidine base.