5′-脱氧-5′-氟-5-氟尿核苷的合成和性质

很多含氟核苷具有生理活性,因此,合成类似物引起人们的兴趣。5-氟尿核苷和5′-脱氧-5′-氟尿核苷的合成巳见报道。但是,5′-脱氧-5′-氟-5-氟尿核苷的合成及由于     

离子色谱-抑制电导法分别测定海水中阴离子和阳离子

以氢氧化钾为流动相,阴离子交换分离,抑制电导检测,可以同时分离F-、Cl-、Br-、NO3-、SO42-、PO43-I、-等海水中的常见阴离子,利用梯度淋洗可以使以上各种离子在其最佳保留时间和最佳峰形条件下出峰。以8 mmol/L H2SO4为淋洗液,阳离子交换分离,抑制电导检测,可以同时分离测定海水中的Na 、K 、Mg2 、Ca2 、Sr2 和Ba2 。在所采用的色谱条件下各阴阳离子均可以得到很好的线性和很低的检出限。     

鸢尾根致香成分分析及在造纸法再造烟叶中的应用

采用同时蒸馏萃取法,从鸢尾根中提取致香成分,对其主要化学成分进行GC/MS分析,用鸢尾根致香成分进行了造纸法再造烟叶加香试验,并将加香后的造纸法再造烟叶样品添加在卷烟配方中进行评吸。结果表明,鸢尾根致香成分中共鉴定出17个化合物,主要含有癸酸和棕榈酸;鸢尾根致香成分能改善造纸法再造烟叶的烟气品质,并具有降低刺激的作用,加香后的造纸法再造烟叶在卷烟中应用也具有相同的效果。     

5'-脱氧-5'-氟-5-氟尿核苷的合成和性质

叙述了5'-脱氧-5'-氟尿核苷和5'-脱氧-5'-氟-5-氟尿核苷的合成, 并比较了它们以及尿核苷和5-氟尿核苷的一些性质。     

Computational model investigating the effect of magnetic field on neural-astrocyte microcircuit

Extremely low-frequency magnetic field is widely used as a noninvasive stimulation method in clinical practice and basic research. Electrical field induced from magnetic pulse can decrease or increase neuronal electrical activity. However, the cellular mechanism underlying the effects of magnetic field is not clear from experimental data. Recent studies have demonstrated that "non-neuronal" cells, especially astrocytes, may be the potential effector for transcranial magnetic stimulation (TMS). In the present study, we implemented a neural-astrocyte microcircuit computational model based on hippocampal architecture to investigate the biological effects of different magnetic field frequencies on cells. The purpose of the present study is to elucidate the main influencing factors of MS to allow a better understanding of its mechanisms. Our model reproduced the basic characteristics of the neuron and astrocyte response to different magnetic stimulation. The results predict that interneurons with lower firing thresholds were more active in magnetic fields by contrast to pyramidal neurons. And the synaptic coupling strength between the connected neurons may be one of the critical factor to affect the effect of magnetic field on cells. In addition, the simulations show that astrocytes can decrease or increase slow inward currents (SICs) to finely tune neuronal excitation, which suggests their key role in excitatory-inhibitory balance. The interaction between neurons and astrocytes may represent a novel target for effective therapeutic strategies involving magnetic stimulation.     

脯氨酸催化的醛或酮反应中不同中间体的相互转换及异构平衡

烯胺、亚胺离子和恶唑烷酮是脯氨酸催化醛、酮反应中的关键中间体,在ωB97XD/6-311++G**理论水平上找到了连接其中任意两个中间体的过渡态. 计算结果表明无论在气相还是溶液中恶唑烷酮都是优势物种,这些物种是可以相互转化的,且异构平衡受控于所用溶剂和实验温度,这些物种存在与否以及发挥的作用取决于实验条件.提出了一条亚胺离子和恶唑烷酮通过亚胺水合物和恶唑烷酮水合物进行相互转换的新路径. 计算结果还表明在醛/酮与N-Boc亚胺的脯氨酸催化反应中,决速步骤是C-C键的形成而不是中间体的相互转换. 这些计算结果合理地解释了已有实验现象,并有利于优化醛、酮不对称有机催化反应的条件.     

天登烟挥发性香气成分的聚类分析

为更为系统的了解天登烟的品质特点,采用同时蒸馏萃取-气相色谱/质谱法分析了烟叶样品中挥发性香气成分,并结合DSP软件对18个烟叶样品中13个成分峰按欧式距离类平均法进行了聚类分析。结果表明,各天登烟样品可以有效地聚为一类,特别是2003年的样品差异非常小,进一步说明,天登烟自身的香气特征风格突出,在烟草主要特征香气成分含量与组成方面同国产香料烟与烤烟较为接近,而与白肋烟、晒黄烟之间的差异均较大。     

STUDIES ON ANTIHEPATITIC DRUGS——TOTAL SYNTHESIS OF (±)SCHIZANDRIN C AND ITS ANALOGS

This paper reports the total synthesis of (±) schizandrin, C, namely S, 6, 7, 8-tetrahydro-1,12-dimethoxy-2, 3, 10, 11-bismethylenedioxy-6, 7-cis-dimethyldibenzo (a, c) cyclooctene (12B), a new active SGPT lowering principle isolated from the Chinese medical plant Schizandra chinensis, and its 6, 7-trans-dimethyl isomer (16B). We also synthesized two more isomers, namely 5, 6, 7, 8-tetrahydro-3, 10-dimethoxy-1, 2, 11, 12-bismethylenedioxy-6, and 7-cis-(and trans-) dimethyldibenzo (a, c) eyelooctene (12A and 16A). The NMR, UV and mass spectra of these four isomers are discussed. IR (in chloroform), UV, NMR and MS of synthetic schizandrin C (12B) are identical with those of the natural compound.     

表面引发的原子转移自由基聚合法在聚偏二氟乙烯表面制备可控的聚甲基丙烯酸甲酯刷

采用表面引发的原子转移自由基聚合法(ATRP)在聚偏二氟乙烯(PVDF)表面制备结构可控的聚甲基丙烯酸甲酯刷。通过碱处理和紫外光照溴代的方法,将ATRP引入到PVDF表面; 然后采用ATRP法将甲基丙烯酸甲酯接枝到溴代的PVDF表面。采用傅里叶变换红外光谱和X-射线光电子能谱对改性前后PVDF表面的结构进行了表征。结果表明甲基丙烯酸甲酯成功地接枝到了PVDF表面。     

消旋棉酚拆分的研究——Ⅰ.(S)-1-甲基苯乙胺缩(±)棉酚六乙酰酯的分离

本文报道将(±)棉酚与(S)-1-甲基苯乙胺缩合并乙酰化,得(S)-1-甲基苯乙胺(±)棉酚六乙酰酯。硅胶色谱分得并鉴定了七个不同异构体的六乙酰酯。然后经水解分别得(+)、(-)棉酚。