生物有机化学及合成化学界面之最新探索:生物系统中醣识别研究之化学—酶催化探讨(英文)

此报告叙述醣中介细胞粘附最近之研究工作,其中包括合成之新方法发展,细胞粘附过程中牵连之酶抑制及仿醣之设计及合成。     

酶催化脱保护方法及在生物有机化学中的应用

系统地介绍和评述了近年来氨基、羧基、巯基和羟基等到基团的酶催化脱保护方法的进展。由于酶催化脱保护方法具有反应条件温和(中性,水溶液)、选择性和专一性高、副反应少等到优点,故在多肽缀合物、糖等敏感多官能团化合物的研究中有很广阔的应用前景。     

异辛醇中酶催化高效合成阿莫西林的研究

通过比较6种有机溶剂作为反应介质时对阿莫西林合成的影响,发现反应介质在保持酶的催化活性和稳定性方面发挥着非常重要的作用,确定异辛醇为酶催化合成阿莫西林的反应介质.通过研究不同温度下异辛醇中酶催化合成阿莫西林的时间曲线,确定了最佳反应温度和反应时间,通过对底物浓度和酶浓度进行响应面优化,最终得到阿莫西林合成的最优反应条件,在最优条件下可得到91.37%的最大阿莫西林产率.     

4-乙基苯酚低聚物的酶催化合成及抗氧化性能研究

以辣根过氧化物酶为催化剂制备了4-乙基苯酚低聚物,利用红外光谱、凝胶渗透色谱、热重对其进行了表征.4-乙基苯酚低聚物具有良好的清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基和2,2-联氮双(3-乙基苯并噻唑啉-6-磺酸)二铵盐(ABTS)阳离子自由基的性能.4-乙基苯酚低聚物作为添加剂与聚丙烯复合后,可明显提高聚丙烯的抗热氧性能,与聚丙烯相比,4-乙基苯酚低聚物(0.5%)/聚丙烯复合物的氧化诱导温度提高了41℃,氧化诱导时间提高了11.5 min,抗氧化能力不仅大大高于4-乙基苯酚单体,而且优于市售抗氧剂2,6-二叔丁基-4-甲基苯酚(BHT)和丁基羟基茴香醚(BHA).加速老化试验表明,添加4-乙基苯酚低聚物的聚丙烯在120℃的空气氛围中老化72 h后,其化学组成没有明显变化.因此,酚类化合物的酶催化聚合在新型抗氧剂的合成方面有潜在的应用前景.     

不同溶剂中酶催化合成油酸酯研究初探

对几种非水溶剂中脂肪酶催化合成油酸酯 (油酸乙酯、油酸正辛酯和油酸油酯 )进行了初步考察。结果表明 ,在环己烷、正庚烷和甲苯等有机溶剂中 ,上述酯化反应都有很高的转化率 ;在所考察的实验条件下 ,超临界CO2 中反应的转化率略比上述有机溶剂中的低 ,但该结果已初步显示以超临界CO2 替代有机溶剂合成油酸酯具有很大的应用潜力。     

离子液体中β-葡萄糖苷酶生物催化合成红景天甙

比较了聚乙二醇修饰的β-葡萄糖苷酶在三种离子液体([bmim]PF6,[bmim]BF4,[bmim]Tf2N)及两种常用有机溶剂(1,4-二氧六环、正己烷)中的催化性能,确定了适宜的反应介质;考察了底物浓度、温度、体系含水量和反应时间等因素对β-葡萄糖苷酶催化合成红景天甙反应的影响.结果表明,在最佳反应介质[bmim...     

辣根过氧化物酶催化水溶性聚对苯二胺-对氨基苯磺酸的合成及表征

以辣根过氧化物酶(HRP)为催化剂,H2O2为氧化剂,催化对苯二胺与对氨基苯磺酸共聚,合成了聚对苯二胺-对氨基苯磺酸(PAn-I)。利用紫外光谱、红外光谱、XPS、GPC、循环伏安、热重分析等方法对合成的PAn-I进行了结构表征与分析,测定了其电导率、电活性和热稳定性等。结果显示,合成的PAn-I不仅具有一定的电活性和热稳定性,且在水溶液中具有良好的溶解性。合成过程中采用去离子水作为反应介质,避免了使用有机溶剂,反应条件温和,酶的用量也较少。     

酶-光偶联催化系统中分子-电子-质子传递过程与机制（英文）

酶-光偶联催化系统(EPCS)集成了半导体的光吸收能力和酶的高活性/特异性,可模拟自然界光合作用实现太阳能驱动的有用化学品合成.作为EPCS中的“能量货币”,辅因子(如NAD(P)+和NAD(P)H)参与了约80%的酶促氧化还原反应,且在酶-光间充当物质/能量交换的枢纽.然而, EPCS涉及光催化和酶催化反应,涉及分子、电子和质子传递过程,属于典型的复杂多相反应,导致其光-化学转化效率与理论值差距较大.本文从微观尺度对EPCS中分子-电子-质子传递过程进行了理解和剖析,系统介绍了自然界光合作用和EPCS中的“新三传”(即质量传递、热量传递和动量传递)现象.与传统化工领域通过强化宏观尺度上“三传”提升单元操作过程效率的方法类似,本文总结并提出了通过协调优化“新三传”(即分子传递、电子传递和质子传递)来强化EPCS中物质-能量耦合关系,进而提升光-化学转化效率的新策略.其中,分子传递主要包括电子供体分子从反应液向催化剂传递以及辅因子分子在光催化模块和酶催化模块间穿梭;电子传递主要包括光生电子从其生成位点到光催化剂表面进而到电子媒介的传递;质子传递主要包括质子从溶液或催化剂表面向电子媒介的传...     

水／有机体系中漆酶酶促催化2,6-二甲氧基苯酚及产物表征

作为酶促催化底物之一的2,6-二甲氧基苯酚（DMP）经常用于测定漆酶活性．然而到目前为止,其酶促产物结构却仍不清楚．由此,研究了漆树漆酶对其催化氧化反应．在水,有机溶剂体系中,催化得到一种产物3,3′,5,5′-四甲氧基-1,1′-联苯-4-4′-二酚（TMBP）,对其用红外、核磁和色谱一质谱等系统测定,并简要探讨了酶促反应机理．     

表面活性剂在水-有机两相体系中对β-葡萄糖苷酶催化合成红景天苷的影响

采用缓冲液/正己烷为反应体系,比较了几类表面活性剂(CTAB,SDS,SDBS,Tween 20)对酶活的影响.并在该反应体系中,考察了表面活性剂对β-葡萄糖苷酶催化合成红景天苷的反应中底物转化率以及初始反应速率的影响,确定了反应混合体系的适宜含水量.结果表明,在水/有机两相体系中,HLB值较高的SDS对酶的失活体现出了一定的抑制作用,其余表面活性剂均对酶失活起了不同程度的加速作用.在几类表面活性剂各自最适添加浓度下,CTAB,SDS,Tween 20三组均将底物转化率从9.2%提高到11%左右.不添加表面活性剂所测得的初始反应速率最高,Tween 20组次之,离子型表面活性剂添加组最低.对于SDS添加组,当其含水量为10%时,底物转化率可以达到22.3%.     

Recent advances in the synthetic chemistry of 1,5-benzothiazepines: A minireview

Benzothiazepine, a prominent “drug prejudice core”, is a heterocyclic moiety of immense importance due to its presence in a wide range of bioactive compounds. They act as a primary “biolinker” in diverse synthetic routes to obtain bioactive molecules and serve as important templates in synthetic and medicinal chemistry. They are known to possess a plethora of pharmacological activities, which include Ca²⁺ channel blockers, CNS acting agents, anti-HIV, ACE inhibitors, antimicrobial, antifungal, anticancer. Their promising behaviour as drug molecules led the scientific community to develop novel, mild, green, and highly efficient synthetic routes for their synthesis. The conventional synthesis generally involved the condensation of chalcones with 2-aminothiophenol in the presence of acid/base with high-temperature heating, mostly resulting in poor yields or mixtures. However, recent trends are replacing these conditions with mild and green conditions through organocatalysis or other methodologies. In this review, an attempt has been made by authors to summarize (a) Recent developments in the synthetic strategies of 1,5-benzoathiazepines and its derivatives (b) Conventional methods for the synthesis of 1,5-benzothiazepines including progress in the green chemistry routes (c) Applications of various metals and organocatalysts to achieve the enantioselective synthesis of title compounds.     

Bioorthogonal chemistry:a covalent strategy for the study of biological systems

The development of genetically encoded,wavelength-tunable fluorescent proteins has provided a powerful imaging tool to the study of protein dynamics and functions in cellular and organismal biology.However,many biological functions are not directly encoded in the protein primary sequence,e.g.,dynamic regulation afforded by protein posttranslational modifications such as phosphorylation.To meet this challenge,an emerging field of bioorthogonal chemistry has promised to offer a versatile strategy to selective...     

Bioorthogonal chemistry: a covalent strategy for the study of biological systems

The development of genetically encoded, wavelength-tunable fluorescent proteins has provided a powerful imaging tool to the study of protein dynamics and functions in cellular and organismal biology. However, many biological functions are not directly encoded in the protein primary sequence, e.g., dynamic regulation afforded by protein posttranslational modifications such as phosphorylation. To meet this challenge, an emerging field of bioorthogonal chemistry has promised to offer a versatile strategy to selectively label a biomolecule of interest and track their dynamic regulations in its native habitat. This strategy has been successfully applied to the studies of all classes of biomolecules in living systems, including proteins, nucleic acids, carbohydrates, and lipids. Whereas the incorporation of a bioorthogonal reporter site-selectively into a biomolecule through either genetic or metabolic approaches has been well established, the development of bioorthogonal reactions that allow fast ligation of exogenous chemical probes with the bioorthogonal reporter in living systems remains in its early stage. Here, we review the recent development of bioorthogonal reactions and their applications in various biological systems, with a detailed discussion about our own work—the development of the tetrazole based, photoinducible 1,3-dipolar cycloaddition reaction.     

A mixed hard- and soft-modelling approach to study and monitor enzymatic systems in biological fluids

Mixed hard- and soft-modelling multivariate curve resolution (HS-MCR) is applied to study and to monitor complex enzymatic systems. Working under the basis of the soft-modelling technique multivariate curve resolution-alternating least squares (MCR-ALS), a hard constraint is introduced to force some or all concentration profiles to fulfil an enzymatic model. In this way, improvements to the application of pure hard- or pure soft-modelling are achieved.The enzymatic reactions of different mixtures of hypoxanthine, xanthine and uric acid with xanthine oxidase are studied. This is a complex enzymatic process, where uric acid acts as a linear competitive inhibitor. The reactions were monitored with UV-vis spectrophotometry coupled to a stopped-flow module.This work has two aims, both of them focusing on different aspects linked to modelling enzymatic systems using HS-MCR. The first goal is related to the elucidation of the real enzymatic mechanism when one of the chemical substances involved in the process apparently deviates from the mechanism found in the literature. The second one focuses on modelling the enzymatic reaction in the presence of a biological interference, such as human urine. The elucidation of the real mechanism of this enzymatic process and of the behaviour of the involved chemical species in a natural absorbing medium are good examples of situations that can benefit from mixed modelling approaches involving the best of hard- and soft-modelling methodologies.     

Organoboron chemistry comes to light: Recent advances in photoinduced synthetic approaches to organoboron compounds

Photoinduced synthetic approaches to organoboron compounds have attracted significant attention in the recent years. Photochemical activation of organic molecules enables generation of reactive intermediates from a variety of precursors, resulting in borylation methods with improved and broader substrate scopes. The review summarizes recent developments in the area of photoinduced reactions of organoboron compounds with an emphasis on borylation of haloarenes, amine derivatives, and redox-active esters of carboxylic acids, as well as photoinduced rearrangements of organoboron compounds and photoinduced synthesis of organoboron compounds from alkenes and alkynes.     

Stereocontrolled 1,2-cis glycosylation as the driving force of progress in synthetic carbohydrate chemistry

Recent developments in stereoselective 1,2-cis glycosylation that have emerged during the past decade are surveyed herein. For detailed coverage of the previous achievements in the field the reader is referred to our earlier reviews: A. V. Demchenko, Curr. Org. Chem., 2003, 7, 35–79 and Synlett, 2003, 1225–1240.