同位素标记胞嘧啶的合成研究

设计了以正丁醇为溶剂,氰基乙醛缩二乙醇和同位素标记尿素混合回流反应,再在酸作用下进行环化反应制备得到标题化合物。设计的合成路线操作简单、工艺流程短、副产物少,收率可达80%,同位素丰度没有降低。产物经HPLC、IR、MS、1HNMR和13CNMR表征。结果表明,化学纯度99%,同位素丰度98 atom%。     

5-甲基胞嘧啶的合成

5-甲基胞嘧啶是一个非常重要的医药中间体,用来制备抗病毒和抗肿瘤等药物。以5-甲基脲嘧啶为原料,先与三氮唑反应制得中间体5-甲基-4-(1,2,4-三氮唑)-嘧啶-2-酮,接着该中间体在浓氨水的作用下水解生成最终产物5-甲基胞嘧啶,总收率为24.4%。     

分子印迹流动注射化学发光测定胞嘧啶核苷

以胞嘧啶核苷为目标分子,合成对其有专一性识别的分子印迹聚合物(MIP)。在酸性条件下,利用HCl-KMn O4-HCHO发光体系,结合流动注射化学发光(FI-CL)分析方法,创建对胞嘧啶核苷测定有特异性识别的MIP-FI-CL分析方法,其线性范围为8×10-5~1×10-3mol/L,检出限为4×10-5mol/L。利用此方法测定复杂样品中胞嘧啶核苷的含量,结果令人满意。     

精细催化合成的研究进展

一、配位催化的发展概况40年代由德国首次获得以(CO+H_2)催化合成烃类(Fischer—Tropsch 合成)和乙炔羰化合成丙烯酸(Reppe 合成)成功,奠定了基本有机化学工业基础。50～60年代Ziegler 发现α-烯烃定向聚合,Wacker 发现乙烯氧化制乙醛,并先后大规模投产,推进了配位催化的发展。70年代Monsanto 公司开发甲醇羰化合成醋酸,开辟了以煤为原料的C_1化学新领域。80年代广泛开展了各类型羰化合成的研究,已取得不少的研究成果。根据Waller 推测,在90年代可能实现工业化的项目如下:     

高效液相色谱法测定5-氟胞嘧啶片中氟尿嘧啶的含量

建立HPLC法测定5-氟胞嘧啶片中氟尿嘧啶含量的方法.该法简便、快速、灵敏度高,适用于5-氟胞嘧啶片中氟尿嘧啶的含量测定.     

无溶剂合成分子筛的研究进展

无溶剂法合成分子筛具有原料低廉、反应条件温和、合成路线简单和过程绿色环保等优势,近年来逐渐成为人们的研究热点。主要综述无溶剂法合成分子筛过程中的研究进展、分子筛合成机理和无溶剂法合成的优缺点,并且对该合成的应用前景和研究趋势进行展望。     

甲醇合成技术的研究进展

为了实现煤炭资源清洁高效的利用,甲醇合成技术的研究在能源结构的调整中起到至关重要的作用.目前影响甲醇合成技术的主要因素有合成反应器、催化剂及工艺流程的选择,本文通过对甲醇合成的反应机理和甲醇合成技术的简介,为未来甲醇合成技术的研究方向提供指导意义.     

细菌卟吩的合成研究进展

细菌卟吩在近红外区(700~900 nm)有较强的长波吸收,这一性质使其区别于其他四吡咯大环化合物,并且在光化学研究上具有不可比拟的优越性,成为光动力疗法治疗癌症优异的光敏剂。但由于细菌卟吩人工合成难度大,从而限制了其大规模的推广应用。概述了细菌卟吩的合成研究进展,主要包括以叶绿素和细菌叶绿素为母体合成细菌卟吩的半合成法,对卟啉或二氢卟吩的大环进行修饰的还原法,以及以简单化合物为起始物,通过多步反应制得细菌卟吩的全合成法等,通过这些方法可以合成出一些结构复杂的细菌卟吩。分析了目前几种细菌卟吩合成方法的优缺点及存在的问题,为未来的合成研究提供了参考。     

高岭土合成沸石的研究进展

介绍了高岭土合成沸石的研究进展,阐述高岭石性质和活化工艺对合成沸石品质的影响,并论述了目前以高岭土为原料合成沸石的合成工艺及其机理。     

3,3-二乙氧基丙腈合成工艺研究与表征

以乙腈、一氧化碳和乙醇钠为初始原料,乙醇为催化剂,合成出3,3-二乙氧基丙腈。通过对反应温度、反应物料配比、后处理过程对产物的分离方式进行研究,确定出合理的工艺条件。该合成工艺反应操作压力为0.3～1.5MPa,经济成本低,产率高。     

Acetyl-protected cytosine and guanine containing acrylics as supramolecular adhesives

Hydrogen bonding among nucleobase pairs serves as an efficient noncovalent interaction for designing supramolecular polymers with desired properties for pressure sensitive adhesives. Michael addition yielded acetyl-protected cytosine/guanine containing acrylic monomers with flexible spacers between the hydrogen bonding units and the acrylic backbone. Free radical polymerization of nucleobase-containing monomers afforded acetyl-protected cytosine/guanine homopolymers and random copolymers with n-butyl acrylate. Nucleobase incorporation significantly affected thermal, thermomechanical, rheological, morphological properties, and adhesive performance of polyacrylates. Guanine/cytosine-containing copolymers each exhibited a single glass transition (T_g) that increased with increasing nucleobase content. Self-association of acetyl cytosine and acetyl guanine units converted low T_g polyacrylates to physically crosslinked networks with mechanical integrity. Solution casting acetyl guanine-containing copolymers with 8 mol% or higher guanine content yielded free-standing films with microphase-separated morphologies. Acetyl cytosine-containing copolymers with 15 mol% or more cytosine formed free-standing films with less microphase-separation compared to the guanine copolymers. ¹H NMR titration experiments established a 1:1 binding stoichiometry between acetyl cytosine and acetyl guanine monomers in CDCl_3, similar to guanine-cytosine association. However, the acetyl protecting group hindered the formation of triple hydrogen bonding, resulting in double hydrogen bonding between acetyl cytosine and acetyl guanine with an intermediate binding strength comparable to their self-associations. Acetyl guanine-containing copolymers with 3 mol% acetyl guanine exhibited higher peel strength on stainless steel and higher extended service frequency range compared to cytosine-containing copolymers and various pressure sensitive adhesive controls.     

Kinetic modeling for chromatographic separation of cytosine monophosphate and uracil monophosphate

Kinetic modeling for preparative chromatography is a topic of present interest in the fine chemicals and pharmaceutical industries. In this study, chromatographic separation of the two nucleotides CMP and UMP was simulated by the equilibrium-dispersive (ED) model, and the adsorption isotherms in the ED model were determined by the inverse method. Prediction performance of the model was validated under three different kinds of conditions and the importance of selecting isotherms was discussed in detail. Excellent agreement was achieved with the experimental band profiles and the prediction of the ED model. The ED model with bi-Langmuir isotherm was especially suitable for simulating chromatographic separation of CMP and UMP. The error of prediction by the ED model with bi-Langmuir isotherm was about 9.4 times smaller than that with Langmuir isotherm.     

Three-zone simulated moving-bed (SMB) for separation of cytosine and guanine

Separation of guanine and cytosine base pairs in nucleotide is an interesting topic for investigation of DNA structure. Therefore, an understanding of nucleotide separation by chromatography is necessary to prepare DNA molecules. Guanine and cytosine separation in SMB was simulated by Aspen chromatography and it was experimented by assembled 3-zone simulated moving bed (SMB) with change of stream flow rates, sample concentration, and desorbent flow rate. The simulation of batch chromatography was also confirmed by HPLC experiments. Based on these, good operating conditions of SMB chromatography were determined. Three-zone SMB equipment was set up by connecting three C₁₈-HPLC columns, four HPLC pumps, and six multiposition valves. Batch chromatography of cytosine and guanine was conducted to determine the isotherms of the two nucleotides. The outlet streams of SMB, raffinate and extract were sampled and analyzed by analytical HPLC system. The adsorption isotherms of cytosine and guanine were H_C= 0.5 and H _G =1.05. The highest experimental purity of cytosine and guanine in SMB was obtained as 94.9% and 89.8% with operating parameters of Q _feed =0.2 mL/min, Q _desorbent =0.6 mL/min, Q _extract =0.2 mL/min, Q _raffinate =0.6 mL/min, and switching time=7 min.     

Random mutagenesis and selection of Escherichia coli cytosine deaminase for cancer gene therapy

Cytosine deaminase (CD) is currently being used as a suicide gene for cancer gene therapy. The premise of this therapy is the preferential deamination of 5-fluorocytosine (5FC) to 5-fluorouracil by cancer cells expressing cytosine deaminase. However, a lack of efficient gene transfer to tumors combined with inefficient 5FC turnover currently limits the clinical applications of this gene therapy approach. We have used random mutagenesis to create novel bacterial cytosine deaminases that demonstrate an increased preference for 5FC over cytosine. Among the 15 mutants isolated, one conferred sensitivity to Escherichia coli in a negative selection system at a concentration of 5FC that was 10-fold lower than a sublethal dose for wild-type CD. Evaluation of individual substitutions found in this double mutant (Q102R, D314G) demonstrated that the substitution at residue D314 was solely responsible for the observed increase in sensitivity to 5FC. Additional mutagenesis at D314 resulted in the identification of two more substitutions with the ability to confer enhanced 5FC sensitivity to E.coli. Structure determinations of the three CD variants in the presence and absence of a transition state 5FC analogue provide insights to the determinants of substrate binding specificity at the 5' position of the pyrimidine ring. CD mutant D314A is a promising candidate for further gene therapy studies.     

On the prebiotic synthesis of ribonucleotides: photoanomerisation of cytosine nucleosides and nucleotides revisited

Recent work has emphasised the importance of D-ribose aminooxazoline 1 in the synthesis of cytidine ribonucleosides under potentially prebiotic conditions. Upon treatment with cyanoacetylene, 1 is transformed into alpha-D-cytidine (alpha-2), and if an efficient means of anomerising this nucleoside or a derivative thereof were to be found, then the synthesis of one of the key beta-D-nucleosides required to make RNA would be realised. Photoanomerisation of alpha-2 has previously been described, but the yield was extremely low. Therefore, the present study was initiated to determine whether this low yield was the result of a low conversion or competing reaction pathways.     

The effect of cytosine on the two-step electroreduction of Zn ions in acetic buffers

Cytosine plays an important role in many biological processes since it constitutes the buildings blocks of DNA and RNA. A two-step reduction of Zn²⁺ ions at the dropping mercury electrode in acetic buffers at pH 4 and 5 in the presence of cytosine was examined. The measurements were performed using an impedance method in a wide potential and frequency ranges.The values of the standard rate constants k_s in the both studied system decrease from 3.8 × 10⁻³ to 2 × 10⁻³ cm s⁻¹ at pH 4 and from 5.1 × 10⁻³ to 2.5 × 10⁻³ cm s⁻¹ at pH 5. The values of the standard rate constants k_s1 characterizing the stage of the first electron transfer decrease similarly. However, the values of the standard rate constants k_s2 characterizing the stage of the second electron exchange decrease more markedly in the buffer at pH 4 than in the buffer at pH 5.     

Intracellular detection of cytosine incorporation in genomic DNA by using 5-ethynyl-2'-deoxycytidine

5-Ethynyl-2'-deoxycytidine triphosphate (EdCTP) was synthesized as a probe to be used in conjunction with fluorescent labeling to facilitate the analysis of the in vivo dynamics of DNA-centered processes (DNA replication, repair and cytosine demethylation). Kinetic analysis showed that EdCTP is accepted as a substrate by Klenow exo(-) and DNA polymerase β. Incorporation of 5-ethynyl-2'-deoxycytidine (EdC) into DNA by these enzymes is, at most, modestly less efficient than native dC. EdC-containing DNA was visualized by using a click reaction with a fluorescent azide, following polymerase incorporation and T4 DNA ligase mediated ligation. Subsequent experiments in mouse male germ cells and zygotes demonstrated that EdC is a specific and reliable reporter of DNA replication, in vivo.     

Characterization of BlsM, a nucleotide hydrolase involved in cytosine production for the biosynthesis of blasticidin S

Biosynthesis of the antifungal agent blasticidin S in Streptomyces griseochromogenes requires the formation of free cytosine. The blsM gene in the blasticidin S gene cluster is predicted to encode a protein that has sequence homology with several nucleoside transferases. In vitro analysis of recombinant BlsM revealed that the enzyme functions as a nucleotide hydrolase and catalyzes the formation of free cytosine by using cytidine 5'-monophosphate (CMP) as the preferred substrate. Cytosine production was significantly lower with CDP, CTP, and dCMP as alternate substrates. BlsM was also observed to have low-level cytidine deaminase activity, converting cytidine and deoxycytidine to uridine and deoxyuridine, respectively. Point mutations were introduced in blsM at putative catalytic residues to generate three mutant enzymes, BlsM Ser98Asp, Glu104Ala, and Glu104Asp. All three mutants lost CMP hydrolysis activity, but the Ser98Asp mutant showed a modest increase in cytidine deaminase activity.     

目标导向合成及差异导向合成在药物合成中的应用

介绍了目标导向合成和差异导向合成的基本概念,扼要阐述了目标导向合成在药物合成上的应用,着重综述了差异导向合成的固相有机合成法和液相有机合成法在合成有机小分子库以备药物筛选中的应用。认为差异导向合成在药物研究领域的作用必将变得更加重要。