Model Studies for the Synthesis of Erigerol Synthesis of 1-Deoxy-13-Epierigerol from Grindelic Acid

The stereoselective transformation of grindelic acid, through the known methyl 6α-hydroxygrindelate, into 1-deoxy-13-epierigerol is described.     

Analysis of food additives by ion-pairing electrokinetic chromatography.

A mixture of food additives is separated using ion-pairing electrokinetic chromatography with on-column ultraviolet detection at 190 nm. Tetrabutyl ammonium hydrogen sulfate (TBA) is used as modifier. The effect of the concentration of TBA on the migration behavior of the solutes is investigated. This method is used for the determination of the amount of additives in food samples. The percent relative standard deviation (%RSD) for the migration time is found to be less than 0.9% and that of the peak area is less than 2.5%.     

Derivative formation in the chromatographic analysis of food additives.

The use of derivatization in the analysis of food additivies by chromatographic means has been reviewed. The large majority of these derivatization techniques are employed to facilitate the gas-liquid chromatographic quantitation of various food additives. Silylation, alkylation, acylation, as well as transesterification, saponification, and chemical decomposition techniques are discussed. The review includes procedures for the analysis of emulsifiers and stabilizers, artificial sweeteners, antioxidants, preservatives, gums, and waxes, and draws in part, from work conducted in the authors' laboratory.     

Repeated migration of additives from a polymeric article in food simulants

The migration of three additives from polypropylene samples into a series of five liquid food simulants was investigated at 60 °C in a repeated migration regime. This regime was simulated by 20 migration periods each of 8 h and using initially additive free food simulants. Between these migration periods the bare samples were stored in an air conditioned room at around 23 °C for 16 h at working days and for 64 h during weekends. An asymptotic decrease of the additive level in the food simulants in the successive migration periods, from a maximum values towards zero, was observed when the additives easily solve in the food simulants. In contrast when the additives solve poorly in the food simulants this additive level decrease is almost linear and shows a slow decrease rate. In the first case the leaching/migration of the additives is controlled mainly by their diffusion in the matrix of the polymer. In the latter case this process is controlled mainly by the partitioning of the additives between the polymer and food simulants. Two approaches were used to model theoretically these results.In the first approach the mass transport equation was solved by using as input parameters overestimated diffusion and partitioning coefficients as estimated for polypropylene homopolymer, the used food simulants and the three additives according to the recommendations of a practical guidance document in support of migration modelling as stipulated in the Regulation (EU) 10/2011. As expected the results of these calculations overestimate the vast majority of the migration levels determined experimentally. However there are also situations in which this approach leads to underestimations of the real migration levels.In the second approach numerical fitting was applied with the same equation and using the diffusion and partition coefficients as adjustable parameters to obtain a best-fit between experimental and calculated results. It was found that the so obtained “realistic” diffusion coefficients are all lower than the overestimated ones mentioned above. Moreover these “realistic” coefficients depend not only on the nature of the additive but also on the nature of the food simulant in contact with the polymer. This suggests that interaction of food simulants with the polypropylene occurs, which changes the properties of the polymer and thus the mobility of the additive molecules in its matrix. For the “realistic” partition coefficients it was found that they all are higher than the conservative ones mentioned above. Using these “realistic” parameters a good fit between calculated and experimental migration results was found.     

异维A酸糖基衍生物的合成及其细胞毒活性研究

采用两种方法合成了2类新的异维A酸糖基衍生物(5a~5d, 6a, 10a~10c, 11a), 并进行了结构表征与确认. 采用MTT法测试了它们对肺癌细胞(A549)等的细胞毒活性. 结果显示, 含有糖苷结构的异维A酸衍生物明显比含有糖酯结构的异维A酸衍生物具有更好的细胞毒活性; 将糖环上的乙酰基脱去后, 相应的化合物活性有明显提高.     

Determination of additives in food by capillary electrophoresis

The application of capillary electrophoresis (CE) to the analysis of additives in food has been reviewed. Additives included in the review are preservatives, antioxidants, sweeteners, colourings, caffeine, niacin, choline, nitrate, and nitrite. The review highlights the versatility of CE in separating this often widely disparate group of compounds. The application of the methods to real food samples is also discussed.     

Modified coumarins. 13. Synthesis of cyclopentane-annelated pyranocoumarins

Modified pyranocoumarins containing a condensed cyclopentane fragment were synthesized by adjoining a 2,2-dimethyltetrahydropyran ring to a 2,3-dihydrocyclopenta[c]chromen-4-one system and annelation of a pyrone ring to a 2,2-dimethylchromane.Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 352–357, September–October, 2004.     

ITQ-13分子筛合成及酸性的DFT理论计算研究

以氢氧化已烷双铵(R(OH)2)和溴化六甲双铵(HMBr2)为模板剂分别合成了ITQ-13、B-ITQ-13、Al-ITQ-13分子筛,采用XRD、SEM-EDX、N2吸附-脱附、FT-IR、MAS NMR等手段对合成的分子筛进行表征,比较了两种模板剂合成的ITQ-13分子筛的性质,以溴化六甲双铵(HMBr2)为模板剂,在碱性加晶种的条件下,反应3~10 d合成出了ITQ-13以及含杂原子B、Al的ITQ-13分子筛,降低了合成的成本.以溴化六甲双铵为模板剂合成的ITQ-13晶貌有块状和球形针状堆积混合晶貌组成,孔道宽,晶粒因堆积形成的介孔居多.量子力学中的密度泛函理论(DFT)计算Ge、B、Al同晶取代Si在ITQ-13分子筛9个不同T位的分布,T5位对于ITQ-13分子筛的特殊骨架结构形成具有重要作用,对于骨架的电荷平衡以及几何约束力都有重要作用.Al原子容易替代的位置是位于九元环和十元环孔口相交处的T6、T7位.