化合物2',3\',4\',6\'-四-O-乙酰基-β-d-吡喃葡萄糖基N\'-氰基-N-苯基-氨基甲酸酯基-硫基(C22H25N3O9S,5a),2\',3\',4\',6\'-四-O-乙酰基-β-d-半乳糖基-吡喃氨基-N\'-氰基-N-苯基-氨基甲酰亚胺-硫基-酯,(C22H25N3O9S,5b),2\',3\',4\',6\'-四-O-乙酰基-β-d-半乳糖基-吡喃氨基N\'-氰基-N-甲基-甲脒基-硫基-酯(C17H23N3O9S,5c),和2\',3\',4\',6\'-四-O-乙酰基-β-d-半乳糖基吡喃N\'-氰基-N-对甲苯基-氨基甲酸酯基-硫代-酯(C23H27N3O9S,5d)均在P212121中结晶,Z=4。对于所有四种结构,通过中心(形式)C=N(CN)双键的配置的氨基甲酸酯基硫基是Z。扭转角C5-O1-C1-S(标准糖编号)都接近180°,确认取代基的β位。化合物5b涉及分子内氢键N-H-O1;在5c中,这种接触是三中心相互作用的较弱分支,而在5a和5d中,H→O距离要长得多,并不代表明显的相互作用。氨基甲酸酯基-硫基的中心碳原子处的C-N键长几乎相等。乙酰基的所有C-O-C=O扭转角对应于同平面几何形状,但除此之外,所有四个摩尔单元都表现出高度的构象灵活性,等效组具有许多不同的扭转角。在水晶包装中,5a,5c和5d形成层结构,涉及经典的氢键N-H_N氰基和各种弱氢键C-H_O或C-H_S。5b的堆积几乎没有特征,涉及大量的“弱”氢键。在附录中,提出了用于结构确定的波长偏好的盆栽历史,并建议,即使对于非中心对称空间群中的小有机晶体,应考虑使用Mo辐射。
The compounds 2\',3\',4\',6\'-tetra-O-acetyl-β-d-gluco-pyranosyl N\'-cyano-N-phenyl-carbamimido-thio-ate (C22H25N3O9S, 5a), 2\',3\',4\',6\'-tetra-O-acetyl-β-d-galacto-pyranosyl N\'-cyano-N-phenyl-carbamimido-thio-ate, (C22H25N3O9S, 5b), 2\',3\',4\',6\'-tetra-O-acetyl-β-d-galacto-pyranosyl N\'-cyano-N-methyl-carbamimido-thio-ate (C17H23N3O9S, 5c), and 2\',3\',4\',6\'-tetra-O-acetyl-β-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 β position of the substituent. Compound 5b involves an intra-molecular hydrogen bond N-H⋯O1; in 5c this contact is the weaker branch of a three-centre inter-action, whereas in 5a and 5d the H⋯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-H⋯Ncyano and a variety of \'weak\' hydrogen bonds C-H⋯O or C-H⋯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.