Takasawa Ryoichi, Yoshikawa Isao, Araki Koji
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Org Biomol Chem. 2004 Apr 21;2(8):1125-32. doi: 10.1039/b315769e. Epub 2004 Mar 18.
From all the 11 alkylsilylated guanosine and adenosine derivatives having different numbers and types of nonpolar and flexible alkylsilyl side chains, 13 crystals were obtained from appropriate solvents in spite of their low molecular symmetry, and their crystal structures were studied by X-ray crystallography and thermal analysis. In these crystals, a clear structural hierarchy was observed, and one-dimensional tape motifs were preferentially formed by multiple inter-base hydrogen bonds. The tape motifs were arranged in lamellar-like (L), herringbone (H) or widened lamella (WL) structures in the crystals. However, the alkylsilylated ribose unit adopted a variety of conformations with notable disorders at the alkylsilyl moiety. These results suggested that role of the adjustable and nonpolar alkylsilyl ribose unit was to provide cushioning or a filling effect as a molecular pad, which assisted the crystal packing of the robust tape motifs. The packing mode of the tape motifs could be understood from the size instead of the shape of the adjustable alkylsilyl ribose moiety, offering a novel approach to their crystal engineering.
从所有11种具有不同数量和类型的非极性且灵活的烷基硅烷基侧链的烷基硅烷基化鸟苷和腺苷衍生物中，尽管它们的分子对称性较低，但仍从合适的溶剂中获得了13种晶体，并通过X射线晶体学和热分析对其晶体结构进行了研究。在这些晶体中，观察到了清晰的结构层次，并且一维带状基序优先由多个碱基间氢键形成。带状基序在晶体中排列成层状（L）、人字形（H）或加宽层状（WL）结构。然而，烷基硅烷基化核糖单元呈现出多种构象，在烷基硅烷基部分存在明显的无序。这些结果表明，可调节的非极性烷基硅烷基核糖单元的作用是作为分子垫提供缓冲或填充效果，这有助于坚固的带状基序的晶体堆积。带状基序的堆积模式可以从可调节的烷基硅烷基核糖部分的大小而不是形状来理解，为它们的晶体工程提供了一种新方法。
