在类固醇宿主化合物中,分子腔的受控扩张
1Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. sadakazu@ap.chem.eng.osaka-u.ac.jp
Journal of the American Chemical Society
|July 18, 2001
概括
研究人员通过延长胆酸侧链来扩大分子腔. 双酸是较大的有机分子的宿主,表现出强大的框架结构,可以适应客人的尺寸.
科学领域:
- 超分子化学 超分子化学
- 有机化学 有机化学
- 晶体学 晶体学是指结晶学.
背景情况:
- 胆酸是天然化合物,在超分子化学中具有作为宿主分子的潜力.
- 修改宿主分子的结构可以改变它们的结合特性和腔体大小.
- 了解宿主与客人的互动对于设计新材料和分离技术至关重要.
研究的目的:
- 调查侧链延长对胆酸衍生物分子腔体大小和宿主-客主性质的影响.
- 探索改良胆汁酸的增强包容能力的结构基础.
- 确定结构修改是否会影响主机框架的稳定性.
主要方法:
- 与胆酸 (1) 相比,具有延长的侧链的双酸 (2) 的合成.
- 宿主-客人复杂化研究,以确定各种有机物质的约束比率和容量.
- 进行X射线晶体分析以阐明宿主框架和包容复合体的三维结构.
主要成果:
- 双酸 (2) 有效地形成 1:1 宿主:客人复合体,包含各种有机物质.
- X射线结晶学揭示了双强的,同结构的主体框架 (bilayer和交叉类型) 在bishomocholic酸复合体.
- 双层框架中的宿主通道的宽度与包含的客分子的长度直接相关.
- 较大的芳香客,如1-甲甲和1-四旋,成功地被纳入了bishomocholic 酸,但没有被纳入胆酸.
结论:
- 延长胆酸宿主化合物的侧链有效地扩大了分子腔.
- 观察到的结构强度允许适应客人的尺寸增加.
- 与胆酸相比,双酸表现出包括较大的芳香客分子的增强能力.
相关概念视频
01:22Enlargement of the Plasma Membrane
Cell division and enlargement are processes that require precise control. The control ensures that cell division cannot proceed unless the cell has grown to a specific size. A spherical, dividing cell requires an approximately 1.6X increase in its surface area to double its volume. The secretory pathway also has a significant role in cell membrane enlargement. Secretory vesicles that bud off from the Golgi apparatus and later fuse with the plasma membrane during exocytosis are a major source of...
01:13Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis
Hydrolysis of esters under acidic conditions proceeds through a nucleophilic acyl substitution. In the presence of excess water, the reaction proceeds in a reversible manner, forming carboxylic acids and alcohols.
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
01:17Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene
The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.
01:23Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.
01:18Directing and Steric Effects in Disubstituted Benzene Derivatives
When disubstituted benzenes undergo electrophilic substitution, the product distribution depends on the directing effect of both substituents. When the directing effects of both substituents reinforce each other, a single product is obtained. For example, bromination of p-nitrotoluene occurs ortho to the methyl group and meta to the nitro group, which is the same position, resulting in a single product. However, if the directing effects of the two groups oppose each other, the more strongly...
01:08Esters to β-Ketoesters: Claisen Condensation Mechanism
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...