CONFORMATIONAL STUDY BY DYNAMIC NMR SPECTROMETRY

本研究共分为四个部分， 动态核磁共振波谱在构象问题中的应用 分析. 前三部分的项目预计将提供 实验证据表明，“芳香性”是重要的稳定 酯、仲酰胺（蛋白质）和相关的Z构象 化合物. 乙烯基、乙炔基、苯基和环丙基，以及 硫代酸的酸性质子，预期不能提供 第三对电子完成芳香六重态，和 含有这些基团的化合物将被研究，以确定是否 E-异构体的数量很大，正如所预期的。 的能力 已知控制芳族酰胺的构象可用于 药物设计，拟议的研究预计将提供一套 可以用来改变某些酯的构象的基团， 酰胺和相关化合物，除了有助于 了解三个重要的构象偏好 生物化合物的类别（酰胺、酯和硫酯）。 在第一部分中，将使用低温碳和质子NMR来研究 N-烷基甲酰胺稀溶液和一系列有机溶剂中的E-Z异构现象 硫代甲酸酯 第二部分描述了一个研究， 构象平衡和可逆共价缔合 几种二硫代羧酸。 在第三部分，构象 将研究烷基亚硫腈的平衡和势垒， 与亚硝酸烷基酯相比。 亚硝酸盐和 亚硫硝酸盐将提供证据，关于相对重要性， 氧和硫π键。 第四部分是受阻胺的核磁共振研究 在（CH 3）2N-C=CCOR型炔中围绕三键的旋转， 这将提供关于三键的能力的信息， 传递供体和受体之间的缀合。

The proposed research is divided into four parts, each of which involves the application of dynamic NMR spectroscopy to problems in conformational analysis. The projects of the first three parts are expected to provide experimental evidence that "aromaticity" is important for stabilizing the Z conformations of esters, secondary amides (proteins), and related compounds. Vinyl, ethynyl, phenyl, and cyclopropyl groups, and the acidic protons of thioacids, are expected to be incapable of providing the third pair of electrons to complete the aromatic sextet, and compounds containing these groups will be studied to determine whether the populations of E-isomers are large, as expected. The ability to control the conformation of aromatic amides is known to be useful in the design of drugs, and the proposed research is expected to provide a set of groups which can be used to change the conformation of certain esters, amides, and related compounds, in addition to contributing to an understanding of the conformational preferences of three important classes of biological compounds (amides, esters, and thioesters). In part I, low-temperature carbon and proton NMR will be used to study E-Z isomerism in dilute solutions of N-alkylforamides and in a series of thiolformate esters. Part II describes a study by the same method of conformational equilibration and reversible covalent association in several dithiocarboxylic acids. In part III, the conformational equilibria and barriers of alkyl thionitrites will be studied and compared with those of alkyl nitrites. The barriers for nitrites and thionitrites will provide evidence regarding the relative importance of oxygen and sulfur pi-bonding. Part IV is an NMR study of hindered rotation about the triple bond in alkynes of the type (CH3)2N-C=CCOR, which will provide information about the ability of the triple bond to transmit conjugation between a donor and an acceptor.