CHIRAL DISCRIMINATION IN CRYSTALLINE TRI-O-THYMOTIDE CLATHRATE INCLUSION COMPLEXES. CHEMICAL AND CRYSTALLOGRAPHIC STUDIES
CHIRAL DISCRIMINATION IN CRYSTALLINE TRI-O-THYMOTIDE CLATHRATE INCLUSION COMPLEXES. CHEMICAL AND CRYSTALLOGRAPHIC STUDIES
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结晶三邻胸腺肽包合物的手性辨别。
DOI：
10.1002/chin.198343098
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
G. Tsoucaris
中科院分区：
文献类型：
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作者：
R. Arad;B. Green;Marcel Knossow;G. Tsoucaris
三邻胸腺肽(TOT)从合适的外消旋客体的溶液中结晶得到包合物的手性单晶，其中客体对映体被不同程度地掺入其中。得到了通道型络合物(空间群P6‘)或笼型络合物(/G、L)。从前者的单晶中提取的客体具有均匀的低但显著的对映体过剩，而在后者中的这种过剩(Ee)变化很大。对映体纯度最高的是2，3-二甲基-锆杂环己烷(47%)、2，4-二甲基四氮杂环己烷(38%)和2-溴丁烷(37%)。手性客体的大尺度拆分可以通过外消旋客体和TOT的晶种溶液与包合物的粉末状单晶结晶来实现。光学纯度显著提高的客体可以通过使用部分富集型客体(在通道复合体中观察到出乎意料的高手性放大)重复TOT包结来获得。测定了每个包合物的TOT旋光度(+或-)和主客体手性R或S，发现客体手性与TOT绝对构型相关，如所有(S)-2-卤代烷都优先与/>；-(+)-TOT结晶。因此，TOT笼状化合物可用于客体构型分配。通过对A/-(-)-TOT-(/？)-2-溴丁烷、A/-(-)-TOT‘(7？，7？)-2，3-二甲基-/MnR-环氧乙烷、P-(+)-TOT-(S，5)-2，3-二甲基-TMZII-硫杂环己烷和/>；-(+)-TOT-2，3-二甲基环硫杂环己烷(R，R和S，S)的晶体结构分析提供了笼形尺寸和几何构型(椭球体，2重对称空腔)。有证据表明，手性区分是由晶体中的分子间相互作用来解释的，因此，晶体结构也决定了TOT主体分子与更有利和更不有利的客体对映体之间的区别作用。仅通过考虑客体对映体和最接近的主体原子之间的范德华接触是不可能预测首选客体对映体的，但晶体结构分析有助于阐明控制TOT包合物中手性区分的一些因素。
Crystallization of tri-o-thymotide (TOT) from solutions of appropriate racemicguest species affordschiral single crystals of clathrate inclusion complexes in which the guest enantiomers are incorporated to different degrees. Channel-type complexes (space group P6¡) or cage-type complexes (/G^ l) are obtained. The extracted guest from single crystals of the former has uniformly low, but significant, enantiomeric excess, while this excess (ee) in the latter varies widely. The highest enantiomeric purities were observed for 2, 3-dimethyl-Zriz/w-oxirane (47%), 2, 4-dimethyl-trazw-oxetane (38%), and 2-bromobutane (37%). Larger scale resolutions of chiral guests are possible by crystallization following seeding solutions of racemicguest and TOT with powdered single crystals of clathrate. Guests with appreciablyenhanced opticalpurity can be obtained by repeated TOT enclathration using a partially enriched guest (an unexpectedly high chiral amplification was observed in a channel complex). The TOT optical rotation,+ or-, and dominant guest chirality, R or S, were determined for each clathrate, and correlations between guest chirality and TOT absolute configuration were found, eg, all (S)-2-haloalkanes crystallize preferentially with/>-(+)-TOT. TOT clathrates may thus be used for guest configurational assignments. Crystal structure analyses of A/-(-)-TOT-(/?)-2-bromobutane, A/-(-)-TOT'(7?, 7?)-2, 3-dimethyl-/mnr-oxirane, the P-(+)-TOT-(S, 5)-2, 3-di-methyl-tmzii-thiirane clathrates, and the/>-(+)-TOT-2, 3-dimethyl-iraru-thiirane clathrate containing a 1: 2 ratio of the R, R and S, S enantiomers provided cage dimensions and geometry (an ellipsoidal, 2-fold symmetriccavity). Evidence that chiral discrimination is accounted for by the intermolecular interactions in the crystal has been obtained, and therefore the crystal structures also define the discriminating interactions between TOT host molecules and the more favored and less favored guest enantiomers. It is not possible to predict the preferredguest enantiomer solely by considering the van der Waals contacts between guest enantiomers and closest host atoms, but the crystal structure analyses help clarify some of the factors that govern chiral discrimination in TOT clathrates.