Brefeldin A全合成研究新进展

Brefeldin A(布雷菲德菌素甲)是一种天然抗生素, 最早发现于1958年, 许多种微生物中都能产生该化合物. 由于其有趣的结构和显著的抗真菌、抗病毒、抗肿瘤等生物活性, 该化合物很早就引起合成化学家们的注意. 到目前为止, 文献中有报道的全合成和表观合成已有30多种. 对近十年来的全合成及部分表观合成进行了综述, 对各路线的主要优缺点也进行了简要的分析. 一些类似物的合成也一并予以简介.     

Chemistry of renieramycins. Part 7: Renieramycins T and U, novel renieramycin-ecteinascidin hybrid marine natural products from Thai sponge Xestospongia sp.

Two new bistetrahydroisoquinoline marine natural products, renieramycins T (1) and U (2), were isolated from the Thai blue sponge Xestospongia sp. and their structures were elucidated by comparing spectral data with those of renieramycin M (3a) and ecteinascidin 770 (4a). These compounds are the first reported examples of novel ecteinascidin-renieramycin hybrid natural products. Renieramycin T (1) showed strong cytotoxicity to several human cancer cell lines, its IC₅₀ values ranging from 4.7 to 98 nM.     

C(3)-酯基取代的1,5-苯并硫氮杂卓的合成、晶体结构及抑菌和构效关系的研究

设计、合成了三类C(3)酯基取代的1,5-苯并硫氮杂卓衍生物: 2,3/2,5-二氢和2,3,4,5-四氢-1,5-苯并硫氮杂卓-3-甲酸乙酯, 采用元素分析、IR、MS、1H NMR及X射线衍射法确定了标题化合物的分子结构．结构分析表明, 2,5-二氢-1,5-苯并硫氮杂卓-3-甲酸乙酯属单斜晶系, C2/c空间群, 晶胞参数为: a＝2.0319(4) nm, b＝1.4985(3) nm, c＝1.3659(3) nm, α＝90°, β＝120.49(3)°, γ＝90°, V＝3.5840(12) nm3, Z＝8, Dc＝1.397 g/cm3, μ＝0.351 mm－1, F(000)＝1560, R＝0.0478, Rw＝0.1304; 研究了2,3/2,5-二氢-1,5-苯并硫氮杂卓的合成反应条件, 发现该两种互变异构体分别是速度控制产物和平衡控制产物; 抑菌活性及抑真菌构效关系研究表明, 亚胺型的2,3-二氢-1,5-苯并硫氮杂卓具有明显的抑菌活性, 亚胺官能团是其抑真菌的药效团．     

反相高效液相色法测定水产品中三聚氰胺

采用反相高效液相色谱法(RP-HPLC) 测定了水产品中的三聚氰胺. 色谱柱为Symmetry C18 (5 μm, 4.6 mm×250 mm), 流动相为含有0.01 mol/L庚烷磺酸钠和0.01 mol/L柠檬酸的乙腈(1+4)水溶液, 检测器为紫外检测器, 检测波长240 nm. 线性范围为1～50 μg/mL, 相关系数为0.9998, 最低检出限为0.24 μg/mL, 样品平均加标回收率为78.8%～96.1%, 相对标准偏差为3.7%～6.4%. 方法可用于水产品中三聚氰胺的测定.     

Enantioseparation of paroxetine intermediate on an amylose-derived chiral stationary phase by supercritical fluid chromatography

The enantioseparation of trans-3-ethoxycarbonyl-4-(4′-fluorophenyl)-1-methyl piperidine-2,6-dione (3), which is one of the important racemic precursors of trans-(−)-paroxetine, has been investigated using supercritical fluid chromatography on a Daicel Chiralpak AD column. Supercritical CO₂ modified with methanol, ethanol and 2-propanol were used as mobile phase. The influence of type and concentration of alcohol modifier on retention factor, enantioselectivity and resolution were studied. Among methanol, ethanol and 2-propanol, 2-propanol was proved to be the most favorable modifier, and 9.5% (v/v) of 2-propanol was the preferred concentration at which racemate 3 could be separated with resolution of 15.86 and retention factor of 6.323. The effects of pressure and temperature were investigated at 9.5% (v/v) of 2-propanol in the pressure range of 12–24 MPa and temperature range of 303.15–318.15 K. It was found that the lower pressure and temperature were favorable to the enantioseparation. Using van’t Hoff plot, the isoenantioselective temperature was calculated to be 410 K. The enantioseparation process was “enthalpically driven” under experimental conditions. Finally, the retention factors were satisfactorily correlated by a simplified lattice–fluid model with average absolute relative deviation (AARD%) of both enantiomers smaller than 1.76%.     

微波消解-催化褪色光度法测定农产品中痕量铜

建立了微波消解-过氧化氢氧化酸性铬兰K催化动力学褪色光度法测定农产品中痕量铜的分析方法,对实验条件进行了选择、优化.方法的线性范围为0.128～14.08 μg/25mL,检出限为0.016 μg/25mL,回收率为98.1%～101.6%.该方法方便、较灵敏,符合农产品中痕量元素的分析要求.     

Mass defect filter technique and its applications to drug metabolite identification by high‐resolution mass spectrometry

Identification of drug metabolites by liquid chromatography/mass spectrometry (LC/MS) involves metabolite detection in biological matrixes and structural characterization based on product ion spectra. Traditionally, metabolite detection is accomplished primarily on the basis of predicted molecular masses or fragmentation patterns of metabolites using triple‐quadrupole and ion trap mass spectrometers. Recently, a novel mass defect filter (MDF) technique has been developed, which enables high‐resolution mass spectrometers to be utilized for detecting both predicted and unexpected drug metabolites based on narrow, well‐defined mass defect ranges for these metabolites. This is a new approach that is completely different from, but complementary to, traditional molecular mass‐ or MS/MS fragmentation‐based LC/MS approaches. This article reviews the mass defect patterns of various classes of drug metabolites and the basic principles of the MDF approach. Examples are given on the applications of the MDF technique to the detection of stable and chemically reactive metabolites in vitro and in vivo. Advantages, limitations, and future applications are also discussed on MDF and its combinations with other data mining techniques for the detection and identification of drug metabolites. Copyright © 2009 John Wiley & Sons, Ltd.     

Utility of reaction intermediate monitoring with photodissociation multi-stage (MS) time-of-flight mass spectrometry for mechanistic and structural studies: Phosphopeptides

In tandem mass spectra of phosphopeptides, intact sequence ions are often missing or appear weakly. Instead, dephosphorylated sequence ions appear prominently. In this work, we used photodissociation (PD) multi-stage (MSⁿ) time-of-flight mass spectrometry that can monitor reaction intermediates with lifetime as short as 100 ns to study the formation of dephosphorylated sequence ions such as y_n-H₃PO₄. y_n-H₃PO₄ was found to be formed mainly by H₃PO₄ loss from y_n. For doubly phosphorylated peptides, y_n seemed to lose H₃PO₄ stepwise and form y_n-H₃PO₄ and y_n-2H₃PO₄. Even when y_n was absent in PD-MS² spectrum, its m/z could be predicted from those of y_n-H₃PO₄ and/or y_n-2H₃PO₄. Complete sequence coverage was possible when the data from PD-MS² and PD-MS³ were combined, demonstrating the utility of transient ion detection by PD-MS³ for structure analysis.     

Sparse p-version BEM for first kind boundary integral equations with random loading

We consider the weakly singular boundary integral equation on a deterministic smooth closed curve with random loading g(ω). Given the kth order statistical moment of g, the aim is the efficient deterministic computation of the kth order statistical moment of u. We derive a deterministic formulation for the kth statistical moment. It is posed in the tensor product Sobolev space and involves the k-fold tensor product operator . The standard full tensor product Galerkin BEM requires unknowns for the kth moment problem, where N is the number of unknowns needed to discretize Γ. Extending ideas of [V.N. Temlyakov, Approximation of functions with bounded mixed derivative, Proc. Steklov Inst. Math. (1989) vi+121. A translation of Trudy Mat. Inst. Steklov 178 (1986)], we develop the p-Sparse Grid Galerkin BEM to reduce the number of unknowns from to .     

循环图C(10,2)与路P_n的笛卡尔积的交叉数

证明了循环图C(10,2)与路P_n的笛卡尔积的交叉数是10n及循环图C(2m,2)的一点悬挂和两点悬挂的交叉数分别是m,2m.