Studies of Molecular Recognition by Solid NMR

确定无长程有序的粉末样品中的分子结构一直是化学中长期悬而未决的问题之一，并且最近的大部分独创性都致力于发展固体NMR作为开发固体结构信息的工具。本工作的目的是将我们迄今为止发展起来的固体核磁共振结构测定技术应用于分子识别的微观机理这一长期而重要的问题。我们涉及结构和分子识别机制。对于分子识别体系，我们采用一维客体配位法研究了手性胆酸主体中光学分辨的7-戊内酯（瓦尔）、（S）-（-）-对映体（SVAL）和R-（+）对映体（R瓦尔）的配位。已知CA识别S和R对映体，优选包体SVAL。为了研究这种识别过程，我们制备了甲基质子被氘代，碳原子被13 C取代的SVAL，并将其包合到CA上。 ...更多信息 然后，我们进行了一维自旋扩散实验之间的甲基碳的SAVL和RVAL的CA的一维通道。在一维CA通道中，假设包合过程为一级Malkov过程，计算得到瓦尔的分子排列，可以成功地模拟自旋扩散过程。结果表明，相同对映体之间存在吸引力，这是光学拆分的关键机理。此外，为了提高自旋扩散的效率，我们开发了一种新的^1H-^<13>C偶极辅助旋转共振方法。这是通过一次实验粗略确定自旋之间距离的方法。这种高发射距离的测定方法一直是人们所期望的，并发表在Chem. Phys. Lett.，344，631-637（2001）。由于这种方法不需要对要观察的自旋进行射频辐射，因此自旋扩散时间受到通常较长的自旋-晶格相对时间的限制。换句话说，我们可以进行远距离测量。这种方法不仅可以充分享受高分辨率的观察，而且还具有适用于多标记分子的特点。少

Determination of a molecular structure in a powder sample without no long range order has been one of the long-pending problems in chemistry, and most of recent ingenuity has been devoted to develop solid-state NMR as a tool to exploit structural informations in solids. The aim of this work is to apply solid NMR techniques for structural determination developed so far by ourselves to the long-standing and important problem of microscopic mechanisms of molecular recognition. We relate structure and molecular recognition mechanisms. For a molecular recognition system, we take up one-dimensionalguest alignment of optical resolved 7-valerolactone (VAL), (S)-(-)-enantiomer (SVAL) and R-(+) enantiomer (RVAL), enclathrated in chiral cholic acid host (CA). It has been known that CA recognizes the S and R enantiomer and preferably enclathraes SVAL. To study this recognition process, we prepared SVAL whose methyl protons are deuterated and its carbon is replaced by 13C, and enclathrate it to CA. … More We then undertook one-dimensional spin-diffusion experiments among the methyl carbons of SAVL and RVAL in the one-dimensional channel of CA. The spin diffusion can be successfully simulated by the molecular alignment of VAL in the one-dimensional CA chanel calculated by assuming the inclusion process to be the 1st order Malkov process. We can show that there exists attractive force between same enantiomers, which is the key mechanism of optical resolution. Further, in an effort to achieve better efficiency for spin diffusion, we developed a new ^1H-^<13>C dipolar-assisted rotational resonance method. This is a method for determining distances among spins roughly by one experiment. This kind of high throuput distance determination method has been long desired and was published in Chem. Phys. Lett., 344, 631-637 (2001). Since this method does not require rfiradiation to spins to be observed, the spin-diffusion time is limited by a generally long spin-lattice relxation time. In other words, we can conduct a long-range distance measurement. This method allows us to fully enjoy high-esolution observation, and has another desirable features suitable for application to multiply labeled molecule. Less