Elucidation of Crystallization Process and Crystal Engineering of Conglomerates

已知，一些由手性胺和非手性羧酸组成的盐结晶成团聚体。本项目旨在阐明这一因素，并建立一个将外消旋体转化为团聚体晶体的指导方针。通过对大量初级羧酸铵的晶体结构分析，试图提取砾岩晶体的特征结构特征。因此，对于大部分的盐晶体来说，酸和胺组分通过氢键构成了一个柱子，而晶体就是由这些柱子组成的。柱子可分为两类，一类为双螺纹轴，另一类为中心对称性。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无手性盐或外消旋化合物盐中以竞争的概率存在。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，可以通过聚集具有相同手性的柱来形成聚集体。然而，即使在这种情况下，通过以1：1的比例聚集对映体柱，外消旋化合物也是可能的。这两种类型的结构可以在外消旋化合物盐中以竞争的概率看到。影响这两种填料之间势能的因素是柱的形状和van der Waals势，可以用分子力学等计算方法来估计。手性胺衍生成含有非手性羧酸的盐而形成团聚体晶体的主要因素可以归因于旋光性螺旋柱的形成。用计算方法估计砾石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.