Elucidation of Crystallization Process and Crystal Engineering of Conglomerates

众所周知，一些由手性胺和非手性羧酸组成的盐结晶成聚集体。本项目旨在阐明外消旋体转化为砾岩晶体的影响因素，并建立一个指导方针。通过对大量伯胺羧酸盐的晶体结构分析，试图提取砾岩晶体的特征结构特征。因此，对于大多数盐晶体来说，酸和胺组成了一个由氢键构成的柱，晶体就是由这些柱组成的。该栏目可分为两类；一种是双螺旋轴，另一种是中心对称。在砾岩盐的情况下，只有前者是可能的，而这两种类型的柱在非手性盐或外消旋化合物盐中以竞争概率存在。当外消旋体形成中心对称柱时，盐可能是外消旋化合物。相反，当外消旋体形成螺旋柱时，可以将具有相同手性的柱聚集在一起形成聚类。然而，即使在这种情况下，通过以1:1的比例收集对映体列，也可以得到外消旋化合物。这两种结构可以在外消旋化合物盐中以竞争概率出现。影响这两种填料之间势能的因素是柱形和范德华势，可以用分子力学等计算方法来估计。手性胺衍生成含非手性羧酸盐的砾岩晶体形成的主要因素是形成旋光性螺旋柱。用计算方法估计砾岩晶体的形成是一个很有前途的课题。

It is known that a few salts consisting of a chiral amine and an achiral carboxylic acid crystallize into conglomerates. This project aimed to elucidate the factor and to establish a guideline for converting racemates into conglomerate crystals. By means of crystal structural analysis of a large number of primary ammonium carboxylates, we tried to extract the characteristic structural feature of conglomerate crystals. As a result, for the most part of the salt crystals, acid and amine components make a column constructed by hydrogen bonds, and the crystals were made up from these columns. The column could be classified into two categories ; one is characterized by a two-fold screw axis and others by centrosymmetry. In the case of conglomerate salts, only the former is possible, while the two types of columns exist in a competitive probability in achiral salts or racemic compound salts. When a racemate formed centrosymmetric columns, the salt could be a racemic compound. In contrast, when a racemate formed helical columns, a conglomerate can be formed by gathering the columns having the same chirality. However, a racemic compound is also possible even in this case by gathering the enantiomeric columns in 1 : 1 ratio. These two types of structures can be seen in racemic compound salts in a competitive probability. The factors influencing the potential energies between these two types of packing are the shape of column and van der Waals potential, and would be estimated by computational methodology such as molecular mechanics.The primary factor for the formation of a conglomerate crystal by derivatization of a chiral amine to a salt with an achiral carboxylic acid could be attributable to the formation of optically active, helical column. The estimation for the formation of a conglomerate crystal with computational methodology is a prospective subject.