Planar boron heterocycles with nucleic acid-like hydrogen-bonding motifs
Planar boron heterocycles with nucleic acid-like hydrogen-bonding motifs
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DOI：
10.1021/ja963784i
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发表时间：
1997-08-20
影响因子：
15
通讯作者：
Robinson, PD
中科院分区：
文献类型：
--
作者：
Groziak, MP;Chen, LY;Robinson, PD
为了促进含硼嘌呤类似物在水溶液中以平面、非两性离子主导结构形式存在的发展，对1-羟基-1H-2，3，1-苯并恶唑硼烷（1）、1，2-二氢-1-羟基-2，3，1-苯并二氮杂硼烷（2）和相关的2，3，1-苯并二杂硼进行了严格的溶液和固态结构分析。借助于同位素富集的化合物，对1和2进行多溶剂H-1、C-13、B-11和N-15 NMR光谱分析，提供构成其杂环外围的所有非氧原子的结构诊断化学位移数据。此外，进行1和2的单晶X射线衍射分析。与它们的2，4，1异构体对应物形成鲜明对比，2，3，1-苯并氧杂氮杂-和苯并二氮杂硼杂环以平面结构形式存在于质子溶液和固态中，并显示质子解离和缔合趋势，反映了主要的布朗斯台德，但仍然具有刘易斯酸能力的特征，B-OH基团与C4-N3亚胺基团处的碱性基团一起。在固体状态下，1和2显示分子间氢键模式与某些天然核酸碱基的基序没有太大不同。通过VT-NMR显示，二氮杂硼杂环2与2 '，3'，5 '-三-O-保护的胞苷发生三氢键溶液缔合，证明了1-羟基-2，3，1-二杂硼杂环外围所具有的一种仿生潜力。一般来说，1，2，和相关的1-羟基-2，3，1-苯并二杂硼杂环被发现的特点是一个环境依赖的O 1-->N3布朗斯台德质子和B-OH基团布朗斯台德/刘易斯酸的两亲性如此敏感和微妙，某些过去遇到的困难，试图描绘他们的物理化学性质现在变得容易理解。
To promote the development of boron-containing purine analogues that exist in planar, non-zwitterionic dominant structural form in aqueous solution, rigorous solution and solid state structural analyses of 1-hydroxy-1H-2,3,1-benzoxazaborine (1), 1,2-dihydro-1-hydroxy-2,3,1-benzodiazaborine (2), and related 2,3,1-benzodiheteraborines were undertaken. With the aid of isotope-enriched compounds, a multisolvent H-1, C-13, B-11, and N-15 NMR spectroscopic analysis of 1 and 2 was conducted, providing structurally-diagnostic chemical shift data for all non-oxygen atoms that constitute their heterocyclic peripheries. In addition, single-crystal X-ray diffraction analyses of 1 and 2 were performed. In stark contrast to their 2,4,1 isomeric counterparts, the 2,3,1-benzoxaza- and benzodiazaborines exist in planar structural form in protic solution and in the solid state and display proton dissociative and associative tendencies reflective of the predominant Bronsted, yet still Lewis acidic-capable character of the B-OH group together with the basic one at the C4-N3 imine group. In the solid state, 1 and 2 display intermolecular hydrogen-bonding patterns not too dissimilar from the motifs of certain natural nucleic acid bases. Diazaborine 2 was shown by VT-NMR to undergo a triple hydrogen-bonding solution association with a 2',3',5'-tri-O-protected cytidine in a demonstration of one biomimetic potential held by a 1-hydroxy-2,3,1-diheteraborine periphery. In general, 1, 2, and related 1-hydroxy-2,3,1-benzodiheteraborine heterocycles were found to be characterized by an environment-dependent O1-->N3 Bronsted prototropy and B-OH group Bronsted/Lewis acid ambidency so sensitive and subtle that certain past difficulties encountered in attempts to delineate their physicochemical properties now become readily appreciated.