Structural characterization and diffusional analysis of the inclusion complexes of fluoroadamantane with β-cyclodextrin and its derivatives studied via 1H, 13C and 19F NMR spectroscopy

This research conducts method development to study the diffusions of β-cyclodextrin and its derivatives (collectively called β-CDs) in biological systems. We proposed using fluoroadamantane (FA) β-CD inclusion complexes as a model system to study the diffusion of β-CDs by using ¹⁹F self-diffusion NMR technique. The use of ¹⁹F signal over ¹H signal arises from the advantage of being able to avoid the interference of ¹H signals from biological molecules and water. Another benefit of using FA is that the ¹⁹F relaxation times are not significantly influenced by viscous biological solutions due to the tumbling nature of FA in β-CD cavities. To synthesize the FA β-CD inclusion complexes, a FA THF (tetrahydrofuran) solution and a β-CD water solution were mixed together followed by lyophilization. The formation of the inclusion complexes in water were determined using HMQC and ROESY NMR experiments with the assistance of molecular modeling. To assess the method, both ¹H and ¹⁹F diffusion NMR were carried out to study the diffusions of four typical FA β-CD inclusion complexes. The results of this study illustrate that the diffusion coefficients obtained from the FA ¹⁹F signal truly measure those of the β-CDs’ diffusion coefficients in water. Thus, the proposed technique using our model system is valid to be used to study the diffusions of β-CDs in biological systems.     

A new monoterpenoid glycoside from Myrica esculenta and the inhibition of angiotensin I-converting enzyme

One new monoterpenoid glycoside, myresculoside (1), and eleven known compounds, were isolated from methanol extract of Myrica esculenta leaves by repeated column chromatography. The effects of these compounds on angiotensin I-converting enzyme (ACE) inhibition were investigated. Compounds 3 and 4 showed the most potent ACE inhibition with rates of 29.97% and 25.63% at concentration of 100 μM, respectively. Compounds 5, 6, and 11 showed weak activity with inhibitory rates of 0.07-1.41% at concentration of 100 μM.     

A chiral material with a new phase sequence: twist grain boundary smectic C phase-smectic blue phases

A new phase sequence: twist grain boundary smectic C (TGBC) to smectic blue phases (BP_Sm) is observed in a chiral compound (S)- or (R)-1-methyloctyl 3'-fluoro-4'-(3-fluoro-4-hexadecyloxybenzoyloxy)tolane-4-carboxylate. It is the first time that a TGBC phase has been found to occur under smectic blue phases in the absence of the twist grain boundary smectic A (TGBA) phase. These phases are characterized by polarizing optical microscopy, differential scanning calorimetry and X-ray scattering.     

基于分子识别的脯氨酸酰肼催化剂催化丙酮和α-酮酸的不对称aldol反应

基于分子识别作用机制,设计合成一类脯氨酸酰肼有机小分子催化剂,并发现它们能够高产率(最高达99%)和高选择性(ee值最高达90%)地催化丙酮和α-酮酸的直接aldol反应,生成具有季碳中心的α-羟基羧酸.     

氮杂环卡宾催化α,β-不饱和酰氯与亚硝基化合物的[4+2]环化反应

报道氮杂环卡宾催化的α,β-不饱和酰氯与亚硝基化合物的形式[4+2]环化反应合成氮杂-δ-内酯([1,2]嗪-6-酮)化合物.反应机理推测可能是卡宾进攻现场生成的烯基烯酮,得到烯基烯醇负离子,然后与取代的亚硝基苯发生[4+2]环合反应,从而得到的氮杂-δ-内酯产物.     

A new flavan from the Drynaria bonii H. Christ rhizomes

In Vietnam, the medicinal plant Drynaria bonii H. Christ is used for the treatment of osteoporosis, bone fractures, and stimulate the growth of hair, treat tinnitus (Ho 2002; Loi 2004). In this article, experiments were designed to investigate the proliferation activity of ethanol, n-hexane, chloroform, ethyl acetate and methanol extracts from D. bonii rhizomes on MG-63 human osteoblast-like cells. The results showed that methanol and hexane extracts had the ability to proliferate MG-63 cells at the concentration varying from 0.1 to 0.01 μg/mL. In particular, at the concentration of 0.01 μg/mL, hexane and methanol extracts illustrated the highest proliferation ratio with 9.31% and 6.16%, respectively. By column chromatography, a new compound named drynaether A (1) and five known compounds uracil (2), 4′-hydroxy-7-methoxyflavan (3), kaempferol (4), indole-3-carboxylic acid (5) and protocatechuic acid (6) were isolated and identified from the methanol extract.