Merging lithium carbenoid homologation and enzymatic reduction: A combinative approach to the HIV-protease inhibitor Nelfinavir

An effective stereocontrolled synthesis of the HIV protease inhibitor Nelfinavir is reported. Two transformations were identified crucial for achieving success: the formation of a densely functionalized α-chloroketone via the homologation of a Weinreb amide with chloromethyllithium (LiCH₂Cl), followed by its erythro selective reduction into the corresponding chiral chlorohydrin. A commercially available enzyme P2-C02 was particularly well suited for this purpose, affording the key alcohol (in an excellent 99% de), which was then smoothly converted into the active biologically active agent.     

超KdV方程的相似解

本文利用Clarkson和Kruskal提出的直接法对超KdV方程进行对称性约化,给出其相似解。     

Determination of Zidovudine in Pharmaceuticals by Differential Pulse Voltammetry

The zidovudine (AZT) has been extensively used in the treatment of HIV patients due to its antiretroviral activity. The quality control of this substance in drugs is of outstanding importance to public health because of its undesirable effects and short therapeutic interval. For the determination of AZT in pharmaceuticals, an alternative analytical methodology using voltammetry was developed. The reduction of AZT at a hanging mercury drop electrode (HMDE) is at ?0.96 V at pH 8.0. The influence of electroanalytical parameters, such as scan rate (20 mV/s), amplitude (50 mV), nature of the support electrolyte (phosphate buffer), and pH (8.0) on the voltammetric signal, was optimized. Under these optimized conditions, the AZT peak current varied linearly with its concentration from 0.25 to 1.25 mg/L (1 to 5 μM). Detection and determination limits of 0.0025 and 0.025 mg/L, respectively, and recovery of 99.88% with a relative standard deviation of 0.95% were obtained. The results obtained using this methodology in analyzing drugs containing AZT were compared favorably with those obtained by technique liquid chromatography as recommended by The United States Pharmacopoeia.     

Voltammetric Determination of Methylparaban in Cosmetics Using a Multi-Wall Carbon Nanotubes/Nafion Composite Modified Glassy Carbon Electrode

A novel voltammetric sensor using multi-wall carbon nanotubes (MWNTs) coupled with Nafion modified glassy carbon electrode (GCE) was developed for the detection of methylparaben (MP). The sensor exhibited good electrocatalytic activity toward the oxidation of MP in the phosphate buffer solution (PBS, pH 6.5). It displayed good sensitivity, repeatability, reproducibility, and long-term stability. Under the optimized conditions, the anodic peak current was linear with the concentration of MP in the range of 3 × 10^?6 mol L^?1 to 1 × 10^?4 mol L^?1. The detection limit was 1 × 10^?6 mol L^?1. The proposed method was successfully applied to determine MP in cosmetics with satisfactory results.     

Modified Boussinesq System with Variable Coefficients： Classical Lie Approach and Exact Solutions

The Lie-group formalism is applied to investigate the symmetries of the modified Boussinesq system with variable coefficients. We derived the infinitesimals and the admissible forms of the coefficients that admit the classical symmetry group. The reduced systems of ordinary differential equations deduced from the optimal system of subalgebras are further studied and some exact solutions are obtained.     

Extrinsic lyoluminescence of aluminum induced by lanthanide chelates in alkaline aqueous solution

Reactive Al/OH⁻(aq) interface was studied and used as a source of chemical energy in the generation of chemiluminescence. The observed extrinsic lyoluminescence emission during dissolution of aluminum in an alkaline Tb(III) or Eu(III) chelate solution was clearly based either on ⁵D₄→⁷F_J radiative transitions of Tb(III) or ⁵D₀→⁷F_J transitions of Eu(III). In this process, these chelates were chemically excited via analogous one-electron redox pathways as known from extrinsic lyoluminescence of irradiated, electrolytically- or additively-colored alkali halides, and from hot electron-induced electrochemiluminescence. Calibration curves of Tb(III) chelates, peroxodisulfate and hydroxide ions were linear over several orders of magnitude of concentration. In addition, the method seems to be suitable for relatively rough chemical measurements of the thicknesses of aluminum oxide films free from trapped charges.     

高效液相色谱分离催化伏安检测微量稀土元素——钆、铽、镝、钬、铒

本文提出用Ag(Hg)-Pt-Ag三电极流动微电解池检测高效液相色谱柱流出液中痕量稀土的浓度。用Apple-Ⅱ微电脑采集伏安信号,再转换成色谱流出曲线。稀土元素的检测限可达0.5μg。     

The supramolecular structures and reactivities of some complexes of chiral crown ethers with borane ammonia

Whereas 1 1 crystalline complexes have been isolated between borane ammonia and methyl 4,6-O-benzylidene-2,3-dideoxy--d-galactopyranosido [2,3-b]-1,4,7,10,13,16-hexaoxacyclo-octadecane (1), methyl 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido [2,3-b] (methyl 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido [2,3-k]-1,4,7,10,13,16-hexaoxacyclo-octadecane (3), and (1R,2R,7R,24R)-3,5,8,11,14,17,20,23,26,28-decaoxatricyclo-[21.4.0.0^2,7]octacosane (4), the hosts, methyl, 4,6-O-benzylidene-2,3-dideoxy--d-mannopyranosido[2,3-b] 1,4,7,10,13,16-hexaoxacyclo-octadecane (2) and 1,4 1,4 3,6 3,6-tetra-anhydro-2,2 5,5-bis-O-oxydiethylenedi-d-mannitol (5) have yielded 2 1 (guest:host) crystalline complexes with borane ammonia as guest. X-ray analyses of the supramolecular structures of BH₃NH₃ ·1, (BH₃NH₃)₂ ·2, BH₃NH₃ ·3, BH₃NH₃ ·4, and (BH₃NH₃)₂ ·5 have been carried out and BH₃NH₃ ·1, BH₃NH₃ ·2, and (BH₃NH₃)₂ ·5 have been shown to reduce acetophenone with enantiomeric excesses of 5, 13, and 10% respectively. Supplementary Data relating to this article (atomic coordinates of the hydrogen atoms and thermal parameters) are deposited with the British Library as Supplementary Publication No. SUP 82017 (74 pages).Dedicated to Professor H. M. Powell.     

铕与醛糖及铕与D─核糖、L─氨基酸络合作用的伏安法研究

Ｅｕ（３＋）在ＨＡｃ－ＮａＡｃ（ｐＨ４．６）溶液中与五碳醛糖有弱的络合作用，用循环伏安法和微分脉冲极谱可以观察到Ｄ－核糖，Ｄ－阿拉伯糖，Ｄ－木糖对Ｅｕ（３＋）还原波形的络合影响，使还原和氧化过程变得较为可逆，其中Ｄ－核糖最为明显，而来苏糖无影响．Ｅｕ（３＋）与氨基酸在相同实验条件下有络合作用，且在汞电极上有吸附现象，因此分别加入Ｌ－苯丙氨酸、Ｌ－组氨酸和Ｌ－蛋氨酸等，进一步改善了Ｅｕ（３＋）的波形而接近于可逆氧化－还原过程，其中以Ｅｕ（３＋）－Ｄ－核糖－Ｌ－苯丙氨酸最明确。绘出了在电极表面形成三元络合物的示意图。