(1R,2R)-4,4-Dimethylpyrazolidine-3,5-dione-α-D-pyranosyl-2-deoxyriboside

The first example of a crystalline pyrazolidinedione nucleoside has been synthesized from the reaction of 2-deoxy-D-ribose with 4,4-dimethylpyrazolidine-3,5-dione and characterized by X-ray crystallography as a single α-pyranoside diastereomer [IUPAC name: 1-(2-deoxy-α-D-erythro-pentopyranosyl) 1(R), 2(R)-4,4-dimethylpyrazolidine-3,5-dione, C₁₀H₁₆N₂O₅]. Although the pyrazolidinedione ring is essentially planar, the two hydrazidic N atoms are pyramidal and chiral, their respective pyranosyl and H-atom substituents being trans-R,R configured. The intermolecular hydrogen bonding involves pyranose–pyranose and pyranose–pyrazolidinedione interactions. Each molecule is linked via six hydrogen bonds to four surrounding molecules in which the pyrazolidinedione hydrazidic N(H) atom is a donor and its adjacent carbonyl O atom is an acceptor, and the pyranose hydroxylic O atoms are donors as well as acceptors. The second carbonyl O atom has no hydrogen-bonding inter­actions with OH or NH, but exhibits a weak C-H...O intermolecular interaction with the pyranose ring. The pyranose ring O atom does not participate in hydrogen bonding. Substituting the OH groups with OD and the NH with ND resulted in no measurable changes in the structure (within error), including the hydrogen-bonding parameters.

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