CONFORMATIONAL STUDY BY DYNAMIC NMR SPECTROMETRY

拟议的研究分为四个部分，每个部分涉及 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”对于稳定 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，预计无法提供 完成芳香族六重奏的第三对电子，以及 将研究含有这些基团的化合物以确定是否 正如预期的那样，E 异构体的数量很大。 有能力 已知控制芳香酰胺的构象可用于 药物设计，拟议的研究有望提供一套 可用于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 生物化合物类别（酰胺、酯和硫酯）。 在第一部分中，将使用低温碳和质子核磁共振来研究 N-烷基甲酰胺稀溶液中的 E-Z 异构现象以及一系列 硫羟甲酸酯。 第二部分描述了采用相同方法的研究 构象平衡和可逆共价缔合 几种二硫代羧酸。 在第三部分中，构象 将研究烷基亚硝酸盐的平衡和势垒 与亚硝酸烷基酯相比。 亚硝酸盐的屏障 亚硝酸盐将提供有关相对重要性的证据 氧和硫形成π键。 第四部分是受阻核磁共振研究 围绕 (CH3)2N-C=CCOR 类型的炔烃中的三键旋转， 这将提供有关三键能力的信息 在供体和受体之间传递缀合。

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.