First Example of a Crystalline Urazole Nucleoside: (1R,2R)-Urazole-α-D-pyranosyl-2-deoxyriboside

The first example of a crystalline urazole nucleoside has been synthesized from the reaction of D-deoxyribose with urazole and characterized by X-ray crystallography as a single α-pyranoside diastereomer [IUPAC name: 1-(2-deoxy-α-D-erythro-pentopyranosyl) 1R, 2R, 4-triazolidine-3,5-dione, C₇H₁₁N₃O₅]. The pyranosyl group and H atom on the two pyramidal hydrazidic N atoms have an R, R-trans configuration, and the H atom on the trigonal imidic N atom is coplanar with the ring. Intermolecular hydrogen bonding is extensive and involves pyranose–pyranose, pyranose–urazole and urazole–urazole interactions. Each molecule is linked via eight hydrogen bonds to six surrounding molecules in which the urazole hydrazidic N(H) atom and imidic N atom are donors and carbonyl O atoms are acceptors, and the pyranose hydroxylic O atoms are donors as well as acceptors. The pyranose-ring O atom does not participate in conventional hydrogen bonding but may be involved in a weak intermolecular C-H...O interaction.

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