Eight new crystal structures of 5‐(hydroxymethyl)uracil, 5‐carboxyuracil and 5‐carboxy‐2‐thiouracil: insights into the hydrogen‐bonded networks and the predominant conformations of the C5‐bound residues. Issue 5 (5th April 2016)

• Record Type: Journal Article
• Authors: Seiler, Vanessa Kristina; Hützler, Wilhelm Maximilian; Bolte, Michael
• Is Part Of: Acta crystallographica. Volume 72:Issue 5(2016)
• Page Start: 379
• Page End: 388
• Publication Date: 2016-04-05
• Subjects: hydrogen bonds -- (8) patterns -- crystal structure -- uracil derivatives -- crystal engineering -- cocrystals; Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229616004861
• Languages: English
• ISSNs: 2053-2296

Abstract

Abstract : Eight crystal structures of 5‐(hydroxymethyl)uracil, 5‐carboxyuracil and 5‐carboxy‐2‐thiouracil are presented as the results of a study of their preferred hydrogen‐bonding patterns and a conformational study. In six of the structures, intramolecular S (6) interactions are formed by the carboxy group, while in one structure, intermolecular (8) motifs are observed instead. A coplanar conformation of all non‐H atoms is preferred in all structures. Abstract : In order to examine the preferred hydrogen‐bonding pattern of various uracil derivatives, namely 5‐(hydroxymethyl)uracil, 5‐carboxyuracil and 5‐carboxy‐2‐thiouracil, and for a conformational study, crystallization experiments yielded eight different structures: 5‐(hydroxymethyl)uracil, C5 H6 N2 O3, (I), 5‐carboxyuracil– N, N ‐dimethylformamide (1/1), C5 H4 N2 O4 ·C3 H7 NO, (II), 5‐carboxyuracil–dimethyl sulfoxide (1/1), C5 H4 N2 O4 ·C2 H6 OS, (III), 5‐carboxyuracil– N, N ‐dimethylacetamide (1/1), C5 H4 N2 O4 ·C4 H9 NO, (IV), 5‐carboxy‐2‐thiouracil– N, N ‐dimethylformamide (1/1), C5 H4 N2 O3 S·C3 H7 NO, (V), 5‐carboxy‐2‐thiouracil–dimethyl sulfoxide (1/1), C5 H4 N2 O3 S·C2 H6 OS, (VI), 5‐carboxy‐2‐thiouracil–1, 4‐dioxane (2/3), 2C5 H4 N2 O3 S·3C6 H12 O3, (VII), and 5‐carboxy‐2‐thiouracil, C10 H8 N4 O6 S2, (VIII). While the six solvated structures, i.e. (II)–(VII), contain intramolecular S (6) O—H…O hydrogen‐bond motifs between the carboxy and carbonyl groups, the usually favoured R 2 2 (8) pattern between two carboxy groups is formed in the solvent‐free structure, i.e. (VIII). Further R 2 2 (8) hydrogen‐bond motifs involving either two N—H…O or two N—H…S hydrogen bonds were observed in three crystal structures, namely (I), (IV) and (VIII). In all eight structures, the residue at the ring 5‐position shows a coplanar arrangement with respect to the pyrimidine ring which is in agreement with a search of the Cambridge Structural Database for six‐membered cyclic compounds containing a carboxy group. The search confirmed that coplanarity between the carboxy group and the cyclic residue is strongly favoured.