5,6-Diaminocytidine, a versatile synthon for pyrimidine-based bicyclic nucleosides

Unexpected Observation of the Dimroth Rearrangement in the Ribosylation of 4-Aminopyrimidines

A method for the preparation of 1-(N-ribofuranosyl)-6-imino-1,6-dihydropyrimidin-4-amines 3 or 4-(N-ribofuranosyl)-6-aminopyrimidines 4 via glycosylation of 4-aminopyrimidines 2 or 5 is described. Silylated 4-aminopyrimidines 2 or 5 upon ribosylation with 1 provide products 3. When intermediates 3 contain a strongly electron-withdrawing group, such as C(4)-Cl or C(5)-NO₂, they rearrange to products 4 in the presence of aqueous ammonia. A mechanism is proposed that involves a ring-opening/ring-closing (Dimroth) rearrangement.

Synthesis and biological activity of 5',9-anhydro-3-purine-isonucleosides as potential anti-hepatitis C virus agents

In order to study structure-activity relationships among the derivatives and congeners of 5',9-anhydro-3-(beta-D-ribofuranosyl)xanthine for anti-hepatitis C virus activity, a series of 5',9-anhydro-purine-isonucleosides with a substituent (s) at 6- or/and 8-position of the purine moiety were synthesized, and their anti-hepatitis C virus activity and cytotoxicity were evaluated and discussed.

Synthesis and antiviral activity of 5-substituted cytidine analogues: identification of a potent inhibitor of viral RNA-dependent RNA polymerases

As part of our studies of lethal viral mutagens, a series of 5-substituted cytidine analogues were synthesized and evaluated for antiviral activity. Among the compounds examined, 5-nitrocytidine was effective against poliovirus (PV) and coxsackievirus B3 (CVB3) and exhibited greater activity than the clinically employed drug ribavirin. Instead of promoting viral mutagenesis, 5-nitrocytidine triphosphate inhibited PV RNA-dependent RNA polymerase (K(d) = 1.1 +/- 0.1 microM), and this inhibition is sufficient to explain the observed antiviral activity.