Jover A, Meijide F, Soto Victor H, Vázquez Tato J, Núñez E Rodríguez, Ton-Nu H-T, Hofmann A F
Departamentos de Química Física y Física Aplicada, Facultade de Ciencias, Universidade de Santiago, Campus de Lugo, 27002 Lugo, Spain.
Steroids. 2004 Jun;69(6):379-88. doi: 10.1016/j.steroids.2004.03.007.
Crystal structures of p-xylene-crystallized deoxycholic acid (3alpha,12alpha-dihydroxy-5beta-cholan-24-oic acid) and its three epimers (3beta,12alpha-; 3alpha,12beta-; and 3beta,12beta-) have been solved. Deoxycholic acid forms a crystalline (P21) complex with the solvent with a 2:1 stoichiometry whereas crystals of the three epimers do not form inclusion compounds. Crystals of the 3beta,12beta-epimer are hexagonal, whereas the 3alpha,12beta-and 3beta,12alpha-epimers crystallize in the P2(1)2(1)2(1) orthorhombic space group. The three hydrogen bond sites (two hydroxy groups, i. e. O3-H, and O12-H, and the carboxylic acid group of the side chain, O24bO24a-H) simultaneously act as hydrogen bond donors and acceptors. The hydrogen bond network in the crystals was analyzed and the following sequences have been observed: two chains (abcabc... or acbacb... ) and two rings (abc or acb), which constitute a complete set of all the possible sequences which can be drawn for an intermolecular hydrogen bond network formed by three hydrogen bond donor/acceptor sites forming crossing hydrogen bonds. The orientation of O3-H (alpha or beta) determines the sequence of the acceptor and the donor groups involved in the pattern: O24a --> O12 --> O3 --> O24b when it is alpha and O24a --> O3 --> O12--> O24B when it is beta. These observations were used to predict the hydrogen bond network of p-xylene-crystallized 3-oxo,12alpha-hydroxy-5beta-cholan-24-oic acid. This compound has two hydrogen bond donor and three potential hydrogen bond acceptor sites. According to the previous sequence set, this compound should crystallize in the monoclinic P21 system, should form a complex with the solvent, O24b should not participate in the hydrogen bond network, and the chain sequence O24a --> O12 --> O3 would be followed. All predictions were confirmed experimentally.
对二甲苯结晶的脱氧胆酸（3α,12α - 二羟基 - 5β - 胆烷 - 24 - 酸）及其三种差向异构体（3β,12α -；3α,12β -；和3β,12β -）的晶体结构已得到解析。脱氧胆酸与溶剂形成化学计量比为2:1的晶体（P21）复合物，而三种差向异构体的晶体不形成包合物。3β,12β - 差向异构体的晶体为六方晶系，而3α,12β - 和3β,12α - 差向异构体在P2(1)2(1)2(1)正交晶系中结晶。三个氢键位点（两个羟基，即O3 - H和O12 - H，以及侧链的羧酸基团，O24bO24a - H）同时作为氢键供体和受体。分析了晶体中的氢键网络，观察到以下序列：两条链（abcabc... 或acbacb... ）和两个环（abc或acb），它们构成了由三个形成交叉氢键的氢键供体/受体位点形成的分子间氢键网络所有可能序列的完整集合。O3 - H（α或β）的取向决定了模式中涉及的受体和供体基团的序列：当为α时为O24a --> O12 --> O3 --> O24b，当为β时为O24a --> O3 --> O12 --> O24B。这些观察结果被用于预测对二甲苯结晶的3 - 氧代，12α - 羟基 - 5β - 胆烷 - 24 - 酸的氢键网络。该化合物有两个氢键供体和三个潜在的氢键受体位点。根据先前的序列集，该化合物应在单斜P21系统中结晶，应与溶剂形成复合物，O24b不应参与氢键网络，并且应遵循链序列O24a --> O12 --> O3。所有预测均通过实验得到证实。
