A New Saponin Transformed from Ginsenoside Rh1 by Bacillus subtilis

A novel saponin was isolated from the transformed products of ginsenoside Rh1 by Bacillus subtilis. It‘s structure was determined to be 3-O-β-D-glucopyranosyl-6-O-β-D-glucopyranosyl-20 (S)-protopanaxatriol on the basis of the spectral data.     

Large scale Biginelli reaction via water-based biphasic media: a green chemistry strategy

An important stage in process development is kilo scale preparation of the target compound. For this reason, a procedure involving water-based biphasic reaction media has been developed for conducting some exothermic reactions on a large scale. This protocol is illustrated by the energy-efficient and rapid preparation of dihydropyrimidinones by a solvent-free, green chemistry procedure applied to the Biginelli reaction using p-toluenesulfonic acid as catalyst.     

Aza-Diels-Alder reaction in fluorinated alcohols. A one-pot synthesis of tetrahydroquinolines

Hexafluoroisopropanol and trifluoroethanol are found to promote imino-Diels-Alder reactions of the N-aryl aldimine 1 with alkyl vinyl ethers to afford the corresponding tetrahydroquinolines in good yields without Lewis acid under mild and neutral conditions. The reaction is also efficient in a three component process from aldehyde, amine and vinyl ethers.     

Synergistic mechanisms of β-diketone derivatives and zinc-calcium soaps in PVC stabilisation

It has been possible to explain the mechanisms of stabilisation and of the synergistic effects of the β-diketone derivatives claimed in a patent as new stabilisers for improving the efficiency of those recipes based upon zinc and calcium soaps in the prevention of the initial discoloration of poly(vinyl chloride).Using chlorohexene as a model compound for allylic chloride structures and benzoylacetone as a model compound for enolised β-diketone derivatives, it has been shown that the benzoylacetone can substitute allylic chlorine atoms through a C-alkylation reaction which takes place only in the presence of ZnCl₂ as catalyst. This reaction drastically changes the percentage of the enol and causes the appearance of two bands at 1720 cm^?1 and 1680 cm^?1 in the infra-red spectrum due to the ketonic structures During the processing of the PVC on a rolling mill at 180°C in the presence of zinc and calcium stearates and benzoylacetone there is grafting of the ketone derivative through a C-alkylation reaction. There is a closed parallelism between the influence of the benzoylacetone on the dehydrochlorination of the chlorohexene and on the accumulation of chloride ions in the polymer matrix in the presence of zinc and calcium stearate. The synergistic effect of the benzoylacetone in the prevention of the initial discoloration is related to the substitution reaction through a C-alkylation which takes place only in the presence of zinc stearate which generates ZnCl₂ which, in turn, acts as a catalyst for both the C-alkylation and dehydrochlorination.     

石墨炉原子吸收分光光度法测定血清中铜

铜系人体内含有的微量元素。测定血清中Cu/Zn比值,有助于病因分析和提供诊断依据。目前,测定血清铜所用的仪器分析方法甚多。本法无需对血清样进行预处理,取样量仅20—50μl。碱金属和碱土金属卤化物无干扰。特征质量m。为5.6pg/0.0044A.S,回收率98～102%,变异系数1.7-2.7%。     

Aqueous Titanate Sols from Ti Alkoxide-α-Hydroxycarboxylic Acid System and Preparation of Titania Films from the Sols

Aqueous titanate sols were prepared by reactions of titanium tetraisopropoxide (TIP) with -hydroxycarboxylic acids in water. IR and Raman spectra, and elemental analyses of the precipitates obtained from the sols revealed that the carboxylates were chelated to titanium but the Ti species were polymerized to form a cluster that had a colloidal nature. Spin-coating of titania (TiO₂) thin films from these sols was also examined. Interestingly, it was found that (004) preferentially oriented anatase films with refractive index of 2.54 were obtained from TIP-lactic acid-NH₃ (1:1:1, molar ratio) aqueous sol. This crystallographic orientation was characteristic of the TIP-lactic acid-NH₃ (1:1:1) system, and was not affected by the kinds of substrates used and the heating rate of the film. TEM observation indicated that small anatase grains had already formed at 200°C. Therefore, the crystallographic orientation might depend strongly on the structure of the chemical species of the precursor solutions.     

Modeling the reaction mechanisms of the amide hydrolysis in an N-(o-carboxybenzoyl)-L-amino acid

Reaction mechanisms of the amide hydrolysis from the protonated, neutral, and deprotonated forms of N-(o-carboxybenzoyl)-l-amino acid have been investigated by use of the B3LYP density functional method. Our calculations reveal that in the amide hydrolysis the reaction barrier is significantly lower in solution than that in the gas phase, in contrast with the mechanism for imide formation in which the solvent has little influence on the reaction barrier. In the model reactions, the water molecules function both as a catalyst and as a reactant. The reaction mechanism starting from the neutral form of N-(o-carboxybenzoyl)-l-amino acid, which corresponds to pH 0-3, is concluded to be the most favored, and a concerted mechanism is more favorable than a stepwise mechanism. This conclusion is in agreement with experimental observations that the optimal pH range for amide hydrolysis of N-(o-carboxybenzoyl)-l-leucine is pH 0-3 where N-(o-carboxybenzoyl)-l-leucine is predominantly in its neutral form. We suggest that besides the acid-catalyzed mechanism the addition-elimination mechanism is likely to be an alternative choice for cleaving an amide bond. For the reaction mechanism initiated by protonation at the amidic oxygen (hydrogen ion concentration H(0) < -1), the reaction of the model compound with two water molecules lowers the transition barrier significantly compared with that involving a single water molecule.     

葡聚糖为载体的双亲型LDL吸附剂吸附动力学研究

合成了以葡聚为载体，同时具有亲水性磺酸基和疏水性胆固醇两类配基的新型低密度脂蛋白（LDL）吸附剂。通过对LDL纯溶液中吸附等温线的测试，比较了以Dextran G-75为载体的双亲型LDL吸附剂与单一亲水型磺酸基配基，单一疏水型胆固醇基吸附剂吸附量和亲和吸附系数的关系。对双亲型LDL吸附剂的吸附动力学进行了初步研究，在LDL溶液中，亲水型磺酸基，疏水型胆固醇配基，双亲型LDL吸附剂对LDL的吸附曲线基本上符合Langmuir吸附方程，另外通过高离子强度NaCl洗脱实验，测定了双亲型LDL吸附剂上具有的磺酸基与胆固醇两类基在对低密脂蛋白吸附过程中所起的配合效果，为下一步作用力机制研究提供了参考依据。     

Construction and Analysis of N-phosphoryl Peptide Libraries

N-Phosphoryl peptide libraries were constructed by transformation from homo-oligopeptide libraries, which was synthesized by self-assembly of amino acids with the assistance of phosphorus oxychloride. Electrospray ionization mass spectrometry (ESI-MS) was used to monitor the reaction.     

n-Hexane dehydrocyclization over Pt?Ni supported on alumina catalysts

Pt–Ni/-Al₂O₃ catalysts have been prepared and studied in n-hexane dehydrocyclization. The selectivity for benzene and toluene, a chain lengthening product formation was improved by Ni and correlated with its content.

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Pt–Ni/-Al₂O₃ -. Ni . Ni , .