共查询到20条相似文献,搜索用时 78 毫秒
2.
反相高效液相法测定空气氧化青霉素衍生物反应的转化率 总被引:2,自引:0,他引:2
在空气氧化青霉素衍生物合成亚砜的反应中 ,用溶胶 凝胶法包容催化剂乙酰丙酮钴 (Ⅲ ) ,使反应在非均相条件下进行。采用反相高效液相法测定了该反应的转化率。采用的柱为C1 8反相柱 (4 6mmi d × 1 50mm ,1 0 μm) ,流动相为甲醇 水 (体积比为 85∶1 5)溶液。在 2 70nm检测波长下 ,青霉素G 对甲氧基苄基酯亚砜(PGPMBO)检测量在 0 0 5g·L- 1 ~ 0 40g·L- 1 时 ,与其峰面积具有良好的线性关系 ,线性相关系数为 0 9992。在不同反应条件下反应的最高转化率为 98 8%。该方法可直接对反应体系进行测定 ,可以快速准确地测定出反应的转化率 。 相似文献
3.
4.
5.
蛋白质蛋氨酸亚砜化是一种重要的氧化还原依赖的蛋白质翻译后修饰,不仅是氧化应激的重要标志物之一,也是一种蛋白质功能调控开关可影响活性氧信号转导,与一系列疾病尤其是神经退行性疾病的发生发展密切相关。 在许多生物体中,蛋氨酸亚砜还原酶是目前已经发现的唯一能将蛋白质蛋氨酸亚砜还原为蛋氨酸的物质,可以修复氧化损伤蛋白,恢复蛋白质功能,调控细胞氧还平衡,对相关疾病的治疗具有非常重要的意义。 本文重点介绍蛋氨酸亚砜和蛋氨酸亚砜还原酶的结构和催化机理,综述蛋氨酸亚砜和蛋氨酸亚砜还原酶荧光探针的部分研究进展,对该领域的研究前景进行展望。 相似文献
6.
7.
8.
烯亚砜作为一类重要的反应中间体在有机合成领域发挥着重要应用。常见的烯亚砜制备方法包括:硫羰基化合物氧化、亚磺酰衍生物β-消除反应、改进的Peterson反应、重氮甲基亚砜的杂原子-Wolff重排反应等。作为活性中间体的烯亚砜可以被亲核试剂进攻硫原子中心或者碳原子中心,分别得到亚砜化合物或者新的烯亚砜物种;而其自身亦可以作为亲核试剂,以氧原子作为亲核位点与其他亲电试剂反应。烯亚砜和酰基或者烯基烯亚砜可以分别作为亲双烯体或双烯体发生正常和逆电子需求的Diels-Alder反应。烯亚砜既可以作为亲偶极子,也可以作为偶极子发生偶极环加成反应。此外,烯亚砜自身还可以发生二聚、脱硫等反应。希望本文总结的内容能够对该研究领域感兴趣的化学工作者有所帮助,并促进烯亚砜化学的进一步发展。 相似文献
9.
用双对数法测出酒石酸石油亚砜萃合物的在观结构,并用红外光谱证明酸与亚砜以氢键相连。利用场解吸质谱可直接观察到有机酸亚砜萃合物的分子离子和准分子离子,比较多种有机酸纸层析的R_f值发现,亚砜萃取有机酸的机理中空腔效应起着重要作用。 相似文献
10.
11.
E. A. Savel’ev I. M. Volkova A. L. Kovalevskaya 《Russian Journal of Applied Chemistry》2010,83(7):1230-1237
Processes of synthesis, isolation, and purification of benzylpenicillin β-diethylaminoethyl ester hydroiodide were studied.
The optimal conditions of benzylpenicillin esterification with chloroethyldiethylamine in dimetylformamide and acetonitrile
were found. Processes for isolation of the target product were developed and its physicochemical properties were studied.
Product stabilization conditions providing a stable pH value in solutions of benzylpenicillin β-diethylaminoethyl ester hydroiodide
were found. 相似文献
12.
The reactivity of three ester organic solvents toward ammonolysis was examined in relation to the development of an ammonolysis‐based microencapsulation process. Ethyl acetate, ethyl chloroacetate, and ethyl fluoroacetate were chosen as ester organic solvents. Progesterone was considered as a model drug to be encapsulated into poly‐D , L ‐lactide‐co‐glycolide microspheres. A polymeric dispersed phase was emulsified in an aqueous phase, to which ammonia was added to initiate ammonolysis. The polarization status of a carbonyl group in the backbone of the ester was found to decide the magnitude of the ester reactivity. In fact, the simple ester ethyl acetate hardly reacted with ammonia, while ethyl chloroacetate and ethyl fluoroacetate showed greater reactivity toward ammonolysis. The rapid completion of ammonolysis led to the conversion of the water‐immiscible solvents into water‐soluble solvents, thereby providing an efficient tool for microsphere solidification. Among microencapsulation parameters, the type of dispersed solvent, the molar ratio of ammonia to a dispersed solvent, and the percentage of the progesterone payload decisively influenced the characteristics of the microspheres. Subsequently, variations in such parameters accompanied considerable influence on microsphere morphology, incorporation efficiency, thermal behavior, the degree of residual solvents, and the physical status of progesterone. Optimization of the process parameters would not only contribute to improving the ammonolysis‐based microencapsulation process, but would also permit the tailoring of microsphere properties to specific demands. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
13.
《Colloids and Surfaces》1988,29(3):305-321
The dispersion properties of concentrated (25.0 and 50.0 vol.%) dispersions of high purity barium titanate powder dispersed in a methyl ethyl ketone (MEK) -ethanol solvent of moderate dielectric constant were studied in an effort to improve the uniformity of tape cast and sintered bodies. An amphoteric phosphate ester surfactant was found to be an effective dispersant. The dispersion properties of the phosphate ester were subsequently investigated by rheological, adsorption, conductivity, and electrophoretic mobility methods in order to evaluate a dispersion mechanism.Optimum dispersion occurred at an azeotrope solution of MEK and ethanol. The barium titanate particles dispersed in dry solvents exhibited a greater degree of dispersion than particles dispersed in hydrated solvents. The adsorption isotherm for the adsorption of the phosphate ester onto barium titanate particle surfaces using dry solvents exhibited a well-defined plateau corresponding to monolayer surface coverage. The plateau was less well defined for particles dispersed in hydrated solvents. Polymer coverage remained essentially constant with varying solvent composition. Optimum dispersion and maximum zeta potential occurred at a concentration of phosphate ester which corresponded to initial monolayer coverage. A maximum in the zeta potential also occurred at the azeotrope solution of MEK-ethanol and again coincided with optimum dispersion.Conductivity data indicate a dynamic adsorption-desorption dissociation mechanism for the ionic phosphate ester at the solid/liquid interface. The adsorption and conductivity data indicate the mechanism of dispersion stability is a combination of electrostatic and steric phenomena. 相似文献
14.
15.
使用密度泛函理论B3LYP方法,对西红花酸二甲酯的结构、电子吸收光谱、热力学性质进行理论计算研究,并基于Tomasi的极化统一场模型(PCM)讨论溶剂效应.结果显示,溶剂对西红花酸二甲酯的前线分子轨道特征几乎无影响,溶剂作用使该分子的最大吸收波长红移约42 nm,红移程度与溶剂极性无关.西红花酸二甲酯分子的气态热力学性质与温度的关系式分别为:Cm p=189.782+0.925T,S m=457.503+1.366T,H m=1164.899+0.195T+4.671×10-4T2,Gm=1164.899-0.263T-8.989×10-4T2.298 K时,西红花酸二甲酯分子的气态标准摩尔生成焓和标准摩尔生成自由能分别为-1180.67和-733.23 kJ·mol-1. 相似文献
16.
Stefan H. Hüttenhain 《合成通讯》2013,43(7):1141-1146
Lactic acid methyl ester, lactic acid ethyl ester, and (2S)‐ethyl‐2‐methoxy propanate were used as solvents for acetophenone reduction by boron hydrides. Moderate enantiomeric excess up to 60% was obtained in the presence of stoichiometric amounts of ZnCl2. There is evidence for an intermediate between the solvents, the Lewis acid and the ketone, as the prerequisite for chirality transfer. The importance of the Lewis acid is to strengthen interaction between solvent and educt compared to the hydroxy group. 相似文献
17.
Methyl phenylpenicillenate (10) was formed by the interaction of 4-carbomethoxy-5,5-dimethyl- 2-thiazoline (6) and 2-phenyloxazol-5-one in pyridine, whereas in neutral solvents the preponderant product of the reaction was methyl phenylpenillonate (7). Similarly, under the latter conditions, 2-benzyloxazol-5-one (5) and the thiazoline (6) yield methyl benzylpenillonate (4, R= Ph·CH2, R=Me) identical with the product obtained from the methyl ester of benzylpenicillin.This contribution byA. B. A. Jansen andRobert Robinson is dedicated to ProfessorF. Wessely on the occasion of his 70th Birthday in admiration of his eminent services to chemistry as a teacher and original investigator. 相似文献
18.
The distribution ratios of TTA and its scandium chelate between aqueous perchlorate solutions (μ=0.1) and 15 ester solvents including ethyl acetate were determined at 25°. A good correlation was found between the distribution coefficients of TTA and the “solubility parameter” of the ester solvents. The relationship between the distribution coefficients of the scandium chelate (PM) and those of TTA (PHA) was shown to be, log PM=n log PHA+ const. The distribution of this chelate into another ester can thus be predicted. 相似文献
19.
PingZHAO YingWuYIN 《中国化学快报》2004,15(9):1043-1046
α-Aminonitriles were prepared efficiently from anodic cyanation of α-amino ester. The effect of different solvents and electrolytes was studied. The other byproducts were analyzed. 相似文献
20.
Santo M Giacomelli L Cattana R Silber J Blanco MM Schapira CB Perillo IA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(7):1399-1407
The solvatochromism in 8-hydroxy-1,6-naphthyridin-5(6H)-one-7-carboxylic acid methyl ester (1), 5-hydroxy-1,7-naphthyridin-8(7H)-one-6-carboxylic acid methyl ester (2), and 4-hydroxy-2-methyl-1(2H)-isoquinolone-3-carboxylic acid methyl ester (3), has been studied in solvents of different polarity and hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) ability. The relative stabilities of isomers for these naphthyridine derivatives and their interaction with the solvent are reported. Two intramolecular hydrogen-bonded structures contribute to the ground state of compound 1. Temperature effects on the absorption bands were recorded to analyse the possible equilibrium between covalent and zwitterionic forms. The formation of zwitterionic species was observed only in HBD solvents, from which is inferred the solvent assistance in the proton transference. AM1 and PM3 semi-empirical calculations were used in support of the proposed interpretations. 相似文献