Crystal structures of four thio-glycosides involving carbamimido-thio-ate groups.
Acta Crystallogr E Crystallogr Commun
; 80(Pt 8): 829-839, 2024 Aug 01.
Article
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| MEDLINE
| ID: mdl-39108779
ABSTRACT
The compounds 2',3',4',6'-tetra-O-acetyl-ß-d-gluco-pyranosyl N'-cyano-N-phenyl-carbamimido-thio-ate (C22H25N3O9S, 5a), 2',3',4',6'-tetra-O-acetyl-ß-d-galacto-pyranosyl N'-cyano-N-phenyl-carbamimido-thio-ate, (C22H25N3O9S, 5b), 2',3',4',6'-tetra-O-acetyl-ß-d-galacto-pyranosyl N'-cyano-N-methyl-carbamimido-thio-ate (C17H23N3O9S, 5c), and 2',3',4',6'-tetra-O-acetyl-ß-d-galacto-pyranosyl N'-cyano-N-p-tolyl-carbamimido-thio-ate (C23H27N3O9S, 5d) all crystallize in P212121 with Z = 4. For all four structures, the configuration across the central (formal) C=N(CN) double bond of the carbamimido-thio-ate group is Z. The torsion angles C5-O1-C1-S (standard sugar numbering) are all close to 180°, confirming the ß position of the substituent. Compound 5b involves an intra-molecular hydrogen bond N-Hâ¯O1; in 5c this contact is the weaker branch of a three-centre inter-action, whereas in 5a and 5d the Hâ¯O distances are much longer and do not represent significant inter-actions. The C-N bond lengths at the central carbon atom of the carbamimido-thio-ate group are almost equal. All C-O-C=O torsion angles of the acetyl groups correspond to a synperiplanar geometry, but otherwise all four mol-ecules display a high degree of conformational flexibility, with many widely differing torsion angles for equivalent groups. In the crystal packing, 5a, 5c and 5d form layer structures involving the classical hydrogen bond N-Hâ¯Ncyano and a variety of 'weak' hydrogen bonds C-Hâ¯O or C-Hâ¯S. The packing of 5b is almost featureless and involves a large number of borderline 'weak' hydrogen bonds. In an appendix, a potted history of wavelength preferences for structure determination is presented and it is recommended that, even for small organic crystals in non-centrosymmetric space groups, the use of Mo radiation should be considered.
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01-internacional
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MEDLINE
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En
Revista:
Acta Crystallogr E Crystallogr Commun
Año:
2024
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Article
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Egipto