Phosphorus Pentachloride Promoted gem-Dichlorination of 2'- and 3'-Deoxynucleosides.

Halogen substitution at various positions of canonical nucleosides has generated a number of bioactive structural variants. Herein, the synthesis of two unique series of sugar modified nucleosides bearing a gem-dichloro group is presented. The synthetic plan entails the controlled addition of phosphorus pentachloride to suitably protected 2'- or 3'-ketodeoxynucleoside intermediates as the key step, facilitating the rapid construction of such functionalized molecules. Under the same reaction conditions, the highest chemoselectivity was observed for the formation of 2',2'-dichloro-2',3'-dideoxynucleosides, while a competing 2',3'-elimination process occurred in the case of the 3',3'-dichloro counterparts.

NMR-based conformational analysis of 2',6-disubstituted uridines and antiviral evaluation of new phosphoramidate prodrugs.

Six novel phosphoramidate prodrugs of uridine analogues, with structural modifications introduced at the 6- and 2',6-positions, have been prepared and evaluated for selective antiviral activity against hepatitis C virus, as well as other positive-stranded RNA viruses. An analysis of the conformational properties of the parent nucleosides was carried out using two-dimensional NMR spectroscopy based experiments, highlighting a 3'-endo (North) sugar puckering preference and syn orientation.

Deoxygenation at the C3 position of D- and L-arabinofuranose: stereospecific access to enantiomeric cordycepose derivatives.

Efficient synthesis of 3-deoxy-1,2-O-isopropylidene-ß-D- and ß-L-threo-pentofuranose (1,2-O-isopropylidene-ß-D- and ß-L-cordycepose) was accomplished starting from D- and L-arabinofuranose derivatives, respectively, by the action of LiBH(Et)3 on corresponding intermediate 3-O-lyxofuranosyl trifluoromethanesulfonates.

Dimethyl hydrazine-1,2-dicarboxyl-ate-triphenyl-phosphine oxide (1/1).

In the crystal structure of the title compound, C(4)H(8)N(2)O(4)·C(18)H(15)OP, two triphenyl-phosphine oxide mol-ecules and two dimethyl hydrazine-1,2-dicarboxyl-ate mol-ecules are connected via N-H⋯O hydrogen bonds of moderate strength and are related via a twofold rotational axis. Weak C(ar)-H⋯ O contacts strengthen the crystal structure.