Organolithium-mediated diversification of peptide thiazoles

[Reaction: see text] We report a one-step, racemization-free method for the diversification of peptide thiazoles via direct lithiation of the thiazole ring. The method is compatible with N-Boc, N-trityl, carboxylic ester, and carboxamide protecting groups and has been used to directly functionalize the thiazole ring of cyclopeptide natural products.     

Dual behavior of masked o-benzoquinones in intramolecular Diels-Alder reactions. Expedient synthesis of highly functionalized cis-decalins from 2-methoxyphenols

[Reaction: see text]. The potential dual behavior as dienes and dienophiles of the diene moieties of masked o-benzoquinones (MOBs) 10a-e-12a-e, generated upon oxidation of 2-methoxyphenols 1-3 with BTIB in the presence of appropriate dienols, in their intramolecular Diels-Alder (IMDA) reactions has been examined. The IMDA reactions of MOBs 10a-d, 11a,b,d, and 12a,b,d resulted in highly functionalized oxatricyclic compounds 18a-d, 19a,b,d, and 20a,b,d, respectively, with concomitant formation of cis-decalin derivatives 21a-d, 22a,b,d, and 23a,b,d in a highly regio- and stereoselective manner. However, the MOBs 10e-12e provided exclusively oxatricyclic compounds 18e-20e. The formation of cis-decalins in these IMDA reactions illustrates the dienophilic character of MOBs, in addition to their behavior as dienes. The ratio of the two cycloadducts obtained in each reaction as a result of the dual character of MOBs depends on the nature and/or position of the substituents on both the cyclohexadienone moiety and the added 2,4-dienol. The majority of the cycloadducts resulted from the diene property of MOBs in intramolecular Diels-Alder reactions smoothly underwent Cope rearrangement to furnish cis-decalins as sole products in excellent to quantitative yields that provides a short and efficient entry to polyfunctionized cis-decalins from 2-methoxyphenols. Furthermore, the variation of dienophilic and diene characters of MOBs in the IMDA reactions with the electron-donating or electron-withdrawing substituent of both cyclohexadienone moiety and the added conjugated acyclic diene or 2,4-dienol has been studied in detail.     

铈、镨二乙基磷酸盐的晶体结构

合成了Ce[PO_2(OC_2H_5)_2]_3和Pr[PO_2(OC_2H_5)_2]_3(简称Ce(DEP)_3和Pr(Pr(DEP)_3)。用四圆衍射仪测定了其晶体结构。它们均属三斜晶系,空间群P1。晶胞参数,对Ce(DEP)_3:α=10.324(4)A,b=12.861(4)A,c=13.998(5)A,x=106.49(3)°,β=112.83(4)° γ=115.61(3)°,V=1296(1)A~3,Z=2;对Pr(DEP)_3:α=10.27(1)A,b=11.81(1)A,c=12.51(1)A,x=109.93(9)°,β=111.9(9)°,γ=93.0(1)°,V=1293(3)A~3,Z=2。用Patterson法并经分块全矩阵最小二乘法修正,最后的R值,Ce的为0.1071,Pr的为0.1066。结构分析指出,两种配合物结构类似,Ce和Pr原子均由二乙基磷酸根的六个氧原子配位形成八面体构型。     

利用电荷迁移反应测定头孢羟氨苄

提出一种基于电荷迁移反应简便可靠地测定头孢羟氨苄的分光光度法。在甲醇－乙醇介质中，头孢羟氨苄与氯冉酸于５０℃反应１５ｍｉｎ能够形成稳定的１：１络合物，其λｍａｘ＝５２８ｎｍ，线性范围为２０￣４００ｍｇ／Ｌ。用拟定的方法测定原粉和胶囊，结果与药典法一致。对浓度１００ｍｇ／Ｌ的药物１０次测定相对标准偏差为１．４％，样品的标准加入回收率为９９．０％￣１００．８％。     

枸椽酸锗对小鼠免疫功能的影响

枸椽酸锗能明显提高小鼠血清溶血素抗体水平，增强二硝基氯苯（DNCB）致小鼠迟发型皮肤过敏反应。增加小鼠免疫器官胸腺和脾脏的重量，表明枸椽酸锗能增强小鼠体液免疫和细胞免疫水平。     

Asymmetric synthesis of syn-(2R,3S)-and anti-(2S,3S)-ethyl diamino-3-phenylpropanoates from N-(benzylidene)-p-toluenesulfinamide and glycine enolates

Addition of differentially N-protected glycine enolates to enantiopure sulfinimines affords syn- and anti-alpha,beta-diamino esters with high diastereoselectivities and good yields.     

相转移催化元素硫的歧化反应

本工作将相转移催化(PTC)应用于元素硫歧化反应,大大降低了反应温度,提高了反应速度。该反应被证实与熔态硫在水溶液中的歧化相同,即4S+6OH~-=2S~(2-)+S_2O_3~(2-)+3H_2O。比较了四乙基铵、四丁基铵、十六烷基三甲基铵和三辛基甲基铵四种相转移催化剂及四氯乙烯、二甲苯和四氯乙烷三种溶剂的影响。讨论了本体系相转移催化的证据。为改进以元素硫歧化反应为基础的提取冶金过程提供了依据。     

Ultrafine molybdenum carbide nanoparticles supported on nitrogen doped carbon nanosheets for hydrogen evolution reaction

Nitrogen doped carbon nanosheets supported molybdenum carbides nanoparticles (Mo_xC/NCS) have been synthesized by tuning the mass ratio of melamine and ammonia molybdate. The Mo₂C/NCS-10 exhibits superior electrocatalytic performance and stability for HER, which was attributed to N-doped carbon nanosheets, small particle size, mesoporous structure, and large electrochemical active surface area.     

High-speed gradient parallel liquid chromatography/tandem mass spectrometry with fully automated sample preparation for bioanalysis: 30 seconds per sample from plasma

In this work, a high-throughput and high-performance bioanalytical system is described that is capable of extracting and analyzing 1152 plasma samples within 10 hours. A Zymark track robot system interfaced with a Tecan Genesis liquid handler was used for simultaneous solid-phase extraction of four 96-well plates in a fully automated fashion. The extracted plasma samples were injected onto four parallel monolithic columns for separation via a four-injector autosampler. The use of monolithic columns allowed for fast and well-resolved separations at a considerably higher flow rate without generating significant column backpressure. This resulted in a total chromatographic run cycle time of 2 min on each 4.6 x 100 mm column using gradient elution. The effluent from the four columns was directed to a triple quadrupole mass spectrometer equipped with an indexed four-probe electrospray ionization source (Micromass MUX interface). Hence, sample extraction, separation, and detection were all performed in a four-channel parallel format that resulted in an overall throughput of about 30 s per sample from plasma. The performance of this system was evaluated by extracting and by analyzing twelve 96-well plates (1152) of human plasma samples spiked with oxazepam at different concentrations. The relative standard deviation (RSD) of analyte sensitivity (slope of calibration curve) across the four channels and across the 12 plates was 5.2 and 6.8%, respectively. An average extraction recovery of 77.6% with a RSD of 7.7% and an average matrix effect of 0.95 with a RSD of 5.2% were achieved using these generic extraction and separation conditions. The good separation efficiency provided by this system allowed for rapid method development of an assay quantifying the drug candidate and its close structural analog metabolite. The method was cross-validated with a conventional liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay.     

Catalytic Spectrophotometric Determination of Ultratrace Amounts of Silver with Solubilizing Effect of Nonionic Surfactant

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