Computational Chemical Software to Aid in the Structural Determination of Organic Molecules by Means of Nuclear Magnetic Resonance

(1)程序CONFLEX用于柔性分子的构象激发该程序于1992年内完成，并已保存在日本化学程序交换所供公众使用。CONFLEX算法的独特之处在于，该程序不仅对可旋转键进行系统旋转，而且还模拟了热构象相互转换中发生的基元过程。该算法的一个显著特点是它能够将搜索限制在低能区域内，并且仍然能够通过跨越能量障碍在构象空间中找到新的结构域。人们可以根据计算机资源的性质和搜索的目的任意控制搜索的范围。仔细的测试表明，CONFLEX在其性能上级任何其他现有的程序。因此，该程序已被应用于许多悬而未决的问题，包括红霉素的区域特异性O-甲基化反应的起源，红霉素的区域特异性O-甲基化反应的原因等。 ...更多信息 紫杉烷合成中的失败以及大环构象和大环化反应中的其他问题。(2)通用分子力学计算程序在1992年内，我们已经能够完成分子力学力场程序的一部分，该程序负责仔细评估溶剂对分子内空间相互作用的影响。这一部分的最初想法依赖于哥伦比亚大学的克拉克斯蒂尔，但我们已经在相当大的程度上修改了原来的公式。从技术上讲，我们使用分子体积的一阶和二阶解析导数作为关键变量，而不是像其他研究者那样使用分子表面。本部分是通用的，可以在其他力场程序中实现。(3)用于计算邻位偶合常数的程序3 JHH 2已经批判性地分析了程序3 JHH 2的当前版本以及用于计算偶合常数的其它已知算法在各种有机分子上的性能。事实证明，所有目前已知的方法在再现和预测耦合常数方面具有出乎意料的低精度。出乎意料的是，最大的误差来源是实验精度。最后得出结论，在使用Karplus方程时，有必要采取一种新的方法。根据这个结论，我们将从1993年开始一个新的项目。少

(1) Program CONFLEX for Conformational Sparch of Flexible Molecules The program was completed within the year 1992 and has been deposited in the Japan Chemistry Program Exchange for public use. The algorithm of CONFLEX is unique in that the Program not only effects systematic rotations to the rotatable bonds, but also simulates elementary processes occurring in the thermal conformational interconversions. A remarkable aspect of this algorighm is its ability of confining the search to within the low-energy region and still capable of finding new domains in the conformational space by crossing over energy barriers. One can arbitrarily control the extent of search depending on the nature of computer resource and the purpose of search. Careful tests revealed that CONFLEX is superior in its performace than any other existing programs. Thereupon the program has been applied to a number of pending problems including the origin of regiospecific O-methylation reaction of Erythromycins, the caus … More e of failure in taxane synthesis and other problems involving macrocyclic conformation and macrocyclization reactions.(2) Program for Universal Molecular Mechanics Calculations Within the year 1992, we have been able to complete that part of molecular mechanics force field program which takes care of the careful evaluation of solvent effects on intramolecular steric interactions. The original idea of this part rests on Clark Still, Columbia University, but we have modified the original formulations to a considerable extent. Technically speaking, we use the first and second analytical derivatives of molecular volume, not the molecular surface as other investigators does, as the key variables. This part is general and can be implemented in other force field programs.(3) Program 3JHH2 for Calculation of Vicinal Coupling Constants The present version of program 3JHH2 has been critically analyzed, together with other known algorithmus for computing coupling constants, for its performance over a variety of organic molecules. As it turned out, all of the presently known methods have unexpectedly low precision in reproducing and predicting coupling constants. Unexpectedly, the greatest source of error is the experimental precision. It is concluded that a new approach is necessary in the use of Karplus equation. Based on the conclusion we will start a new project beginning from the year 1993. Less