Dalhus B, Görbitz C H
Department of Chemistry, University of Oslo, PO Box 1033, Blindern, N-0315 Oslo, Norway.
Acta Crystallogr B. 2000 Aug;56(Pt 4):715-9. doi: 10.1107/s0108768100002172.
DL-Allylglycine (DL-2-amino-4-pentenoic acid, C5H9NO2) yields crystals with Pca2(1) symmetry and two crystallographically independent yet pseudo-inversion-related enantiomers. The distribution among the common space groups of other crystalline racemates with more than one molecule in the asymmetric unit has been established. The conformational similarities between crystallographically independent enantiomers in 114 non-centrosymmetric racemates were quantified using the r.m.s. deviation for a molecular superposition. The analysis shows that in the majority of crystals the conformations of the crystallographically independent molecules are very similar with mean r.m.s. deviation = 0.190 A. In almost 80% of the structures the mean r.m.s. deviations is in the interval 0-0.2 A. It is estimated that racemates constitute 23% of the centrosymmetric organic structures in the Cambridge Structural Database.
DL-烯丙基甘氨酸（DL-2-氨基-4-戊烯酸，C5H9NO2）形成具有Pca2(1)对称性的晶体，且有两个晶体学独立但呈伪反演相关的对映体。已确定在不对称单元中有多个分子的其他晶体外消旋体在常见空间群中的分布情况。使用分子叠加的均方根偏差对114个非中心对称外消旋体中晶体学独立对映体之间的构象相似性进行了量化。分析表明，在大多数晶体中，晶体学独立分子的构象非常相似，平均均方根偏差 = 0.190 Å。在近80%的结构中，平均均方根偏差在0 - 0.2 Å范围内。据估计，外消旋体在剑桥结构数据库中占中心对称有机结构的23%。
