Stereocontrolled Synthesis of the C21–C38 Fragment of the Unnatural Enantiomer of the Antibiotic Nystatin A1
作者:Thilo Berkenbusch、Reinhard Brückner
DOI:10.1002/chem.200305540
日期:2004.3.19
The C(21)-C(38) fragment all-trans-41 of the unnaturalenantiomer 1 of nystatin A(1) was prepared starting from the N-propionyl oxazolidinone 9. Aldol adduct ent-8 (ee > 96 %) derived in two steps was hydroborated with (thexyl)BH(2). Oxidative work-up and treatment with acid furnished delta-lactone 4. It contains the complete stereotetrade of the target molecule. The alpha,beta-unsaturated ester 28
Kinetics of proton transfer from phosphonium ions to electrogenerated bases: polar, steric and structural influences on kinetic acidity and basicity
作者:Ana-Paula Bettencourt、Ana Maria Freitas、M. Irene Montenegro、Merete Folmer Nielsen、James H. P. Utley
DOI:10.1039/a708086g
日期:——
linear sweep voltammetry (LSV) have been used to measure rates of protontransfer in DMSO solution between different types of electrogeneratedbase (EGB) and a series of phosphonium ions of relevance to ylide formation for synthetic reactions. Although the electrochemical methods are convenient for the measurement of rates of protontransfer in these systems a major conclusion of the study is that considerable
导数循环伏安法(DCV)和线性扫描伏安法(LSV)已用于测量DMSO溶液中质子在不同类型的电生成碱(EGB)与一系列与叶立德形成有关的合成反应之间的transfer离子转移速率。尽管电化学方法可方便地测量这些系统中的质子转移速率,但这项研究的主要结论是,在应用这些方法并从结果中得出一般结论时必须格外小心。尤其是将动酸度与热力学p K进行比较DMSO中的值表明,一系列Br离子不满足单个布朗斯台德关系。动酸度受到以下因素的严重影响:EGB是碳还是氮碱;一些the离子的烯醇化倾向;和空间因素。在酸性亚甲基上的其他电子需求量度(13 C和1 H化学位移,还原电位)与p K(DMSO)值一致。动力学结果证实,对于不可烯醇化的salts盐,Ph 3 P +基团比Bu 3 P +更具活化性。
Synthesis and characterization of analogues of glycine-betaine surface-active ionic liquids
作者:Inês S. Cardoso、Emanuelle L.P. de Faria、Armando J.D. Silvestre、Mara G. Freire、Aminou Mohamadou
DOI:10.1016/j.molliq.2021.117440
日期:2021.11
imidazolium-based, which may raise some environmental and health-related concerns. Aiming the development of ILs with surfactant properties and low ecotoxicity, in this work, novel surface-active analogues of glycine-betaine ILs (AGB-SAILs) combined with the dodecylbenzenesulfonate ([DBS]-) anion have been synthesized and characterized. The synthesized AGB-SAILs were characterized chemically by elemental
为了寻找可持续溶剂,具有低生态毒性特征的新型离子液体 (IL) 已成为研究的目标。其中,具有表面活性特性的离子液体在食品、化妆品、制药、家庭清洁和其他洗涤剂行业中发挥着重要作用。迄今为止报道的大多数表面活性 IL 都是基于咪唑的,这可能会引起一些与环境和健康相关的问题。为了开发具有表面活性剂特性和低生态毒性的 ILs,在这项工作中,甘氨酸-甜菜碱 ILs 的新型表面活性类似物 (AGB-SAILs) 与十二烷基苯磺酸盐 ([DBS] -) 阴离子已被合成和表征。通过元素分析和光谱方法对合成的 AGB-SAIL 进行化学表征。测定了它们的热特性、临界胶束浓度、胶束直径和对费氏弧菌的生态毒性,并将这些特性与商业表面活性剂十二烷基苯磺酸钠 (SDBS) 进行比较。结果表明,所有研究的 AGB-SAIL 在室温下都是液体并且热稳定。此外,它们中的大多数显示出比 SDBS更低的临界胶束浓度和对费氏弧
Preparation of Substituted Enol Derivatives From Terminal Alkynes and Their Synthetic Utility
作者:John R. DeBergh、Kathleen M. Spivey、Joseph M. Ready
DOI:10.1021/ja803480b
日期:2008.6.1
trapping with carboxylic anydrides or silyl triflates yields trisubstituted enol esters or silanes, respectively. The tandem carbometalation/oxygenation tolerates free and protected alcohols, heterocycles, olefins, and nitriles. Stereodefined enol esters can undergo asymmetric dihydroxylation to yield optically active alpha-hydroxy aldehydes. Reduction with NaBH4 provides the diols of 1,1-disubstituted olefins
醛的立体定义的烯醇衍生物由末端炔烃制备。具体而言,已知末端炔烃会经历 Cp2ZrCl2 催化的甲基铝化。在这里,我们表明所得的乙烯丙烷可以用过氧锌物质氧化以生成三取代的烯醇化物。用羧酸酐或甲硅烷基三氟甲磺酸酯进行亲电捕获分别产生三取代的烯醇酯或硅烷。串联碳金属化/氧化耐受游离和受保护的醇、杂环、烯烃和腈。立体定义的烯醇酯可以进行不对称二羟基化以产生光学活性的 α-羟基醛。用 NaBH4 还原以优异的 ee 提供 1,1-二取代烯烃的二醇。介绍了这种方法在昆虫信息素额蛋白的对映选择性合成中的应用。最后,显示 α-羟基醛经过同系化到末端炔、还原胺化、氧化和烯化。初步结果表明串联碳金属化/胺化可以用偶氮二羧酸盐完成。以这种方式,以极好的收率形成烯-肼。
An Olefin Cross-Metathesis Approach to Depudecin and Stereoisomeric Analogues
作者:Iván Cheng-Sánchez、Cristina García-Ruiz、Guillermo A. Guerrero-Vásquez、Francisco Sarabia
DOI:10.1021/acs.joc.7b00424
日期:2017.5.5
synthesis. Featured by its brevity and convergency, our developed synthetic strategy was applied to the preparation of the 10-epi derivative and the enantiomer of depudecin, which represent interesting stereoisomeric analogues for structure–activity relationship studies.