三尖杉碱全合成研究的新进展

三尖杉碱是抗癌药物-三尖杉酯类尖化合物的母体。它的全合成研究一直受到众多学者的亲睐。近几年来，取得了三条新的合成路线。共同特点是:采用单环或二环小分子为原料，巧妙地合成了具有独特五环结构的三尖杉硷(1)。其中的Kuehne路线，产率达到41%。     

高三尖杉酯碱和三尖杉酯碱的合成研究

天然药物高三尖杉酯碱和三尖杉酯碱是从三尖杉植物的叶和茎中分离得到的微量生物碱,是手性化合物。结构上,二者不仅含有一个共同的母核三尖杉碱,酯基侧链的α位也均为手性叔醇。因母核三尖杉碱和酯基侧链较大的空间位阻,两个结构片段的酯化偶联具有较大的挑战性。设计合成位阻较小的侧链中间体是酯化反应发生的关键。因此,化学家们相继合成了结构多样的α-羰基羧酸侧链以及含有杂环的侧链中间体,如四元内酯杂环侧链、四氢呋喃杂环侧链、六氢吡喃杂环侧链、七元内酯杂环侧链,并成功地完成了高三尖杉酯碱、三尖杉酯碱和同属其他活性生物碱的合成。本文基于本课题组的相关研究,根据侧链片段的构建策略和方法,综述了天然药物高三尖杉酯碱、三尖杉酯碱以及其他天然产物的合成研究。不仅总结了近几年来的新进展,还对我国老一辈的科学家们在此方面作出的贡献进行了回顾。     

高异三尖杉酯碱的合成及其立体异构体的分离鉴定

2-氧代-6-甲基庚酰基三尖杉碱(3)与0-(1-甲氧基异丙基)羟基乙酸甲酯(4)在强碱性试剂二异丙胺锂(LDA)存在下,起亲核加成反应,反应中间体5在室温用酸性丙酮水解,得到一种新的三尖杉酯类生物碱一一高异三尖杉酯碱(6c)及其立体异构体(6a、6b、6d)的混合物,产率56%、通过制备薄层层析分得这四个立体异构体,它们的1H NMR和异三尖杉酯碱及其立体异构体的1H NMR类似,推定了它们的绝对构型。初步药理试验表明,高异三尖杉酯碱及其立体异构体的混合物对白血病L7712的DNA合成有明显的抑制作用。     

三尖杉碱全合成研究的新进展

三尖杉碱是抗癌药物——三尖杉酯类化合物的母体。它的全合成研究一直受到众多学者的亲睐。近几年来,取得了三条新的合成路线。共同特点是:采用单环或二环小分子为原料,巧妙地合成了具有独特五环结构的三尖杉硷(1)。其中的 Kuehne 路线,产率达到41%。     

异三尖杉酯碱侧链酸的合成

本文报道了异三尖杉酯碱侧链酸(3)的立体选择性合成。(R,R)-(+)-酒石酸先制成酒石酸二甲酯缩丙酮(8), 然后经烷基化、构型转换、催化加氢、碱性水解、部分酯化和酸性水解, 首次成功地得到了预期产物3。     

福建三尖杉碱及其类似物的半合成研究: 一个立体选择性反应的发现

从表台湾三尖杉碱(epiwilsonine)(3)合成福建三尖杉碱(cephalofortunaine)(4)时, 发现3在稀醋酸中子0℃加1:10溴-四氯化碳混合试剂能直接生成2-O-乙酰基福建三尖杉碱的一对2-C差向异构体1与2(9:1), 产率及两个产物比例随着温度而变化。同时报道了类似物5, 6, 10和11的半合成与这类化合物^1H NMR中质子的归属。     

异三尖杉酯碱类似物-酒石酸甲酯三尖杉碱酯的合成

异三尖杉酯碱系三尖杉属植物中所含具有抗肿瘤活性的四种生物碱之一,其本身的合成已有三种不同的方法^[1-3]先后获得成功。但是,在这些合成中,生成的异三尖杉酯碱都是立体异构体的混合物。据报导^[4.5]异三尖杉酯碱及其某些类似物对癌细胞具有明显的抑制作用。为了考察这类化合物的结构与抗癌活性之间的关系,并为异三尖杉酯碱立体异构体构型的确定提供依据,我们进行了(2R,3R)-酒石酸甲酯三尖杉碱酯Ⅵ和(2S,3S)-酒石酸甲酯三尖杉碱酯Ⅶ的合成。     

全合成三尖杉碱的研究近况

三尖杉碱具有五元稠环结构，围绕着五环组建的先后顺序不同，产生各种拼合策略和设计。本文简要介绍近几年全合成三尖杉碱的新路线。参考文献１９篇。     

高脱氧三尖杉酯碱的合成及其差向异构体的分离鉴定

由2′-氧-6′-甲基-庚酰基-三尖杉碱(简称α-酮酰基三尖杉碱)(4)与α-溴代乙酸甲酯进行Reformatsky反应,得到一种新的三尖杉酯类生物碱——高脱氧三尖杉酯碱(5)及其差向异构体表高脱氧三尖杉酯碱(6)的混合物,产率67％.两者通过苦味酸盐分级结晶得纯品,它们的结构由IR、~1H NMR和MS推定.同法,由外消旋α-酮酰基三尖杉碱(±4)制得外消旋高脱氧三尖杉酯碱(±5)及外消旋表高脱氧三尖杉酯碱(±6),它们的IR、~1H NMR和MS分别与5和6一致.同时,还得到了少量副产物3-氧-(甲氧羰甲基)-三尖杉碱(7)及其外消旋体±7,它们的结构也由IR、~1H NMR和MS证明.     

三尖彬属植物中生物碱的研究:VI.三尖杉中两种高刺桐类型的新生物碱的结构

本文报导从安徽产三尖杉弱碱部份分得五种高刺桐类型生物碱, 其中两种新生物碱经UV, IR光谱分析分鉴定为:2-O-乙基表福建三尖杉碱(2-O-ethglepicephalofortuneine)和2-O-乙基福建三尖杉碱(2-O-ethylcephalofortuneine)。     

Ca2+离子掺杂对γ-Ce2S3合成温度及热稳定性的影响

以CeCl₃·7H₂O、CaCl₂·2H₂O和C₂H₂O₄·2H₂O为原料,在制备钙铈氧化物前驱体基础上,再以Ar气为载气、CS₂为硫源对钙铈氧化物前驱体进行硫化合成Ca²⁺掺杂的γ-Ce₂S₃色料。 通过X射线衍射(XRD)、紫外-可见漫反射光谱(UV-Vis)及差热-热重分析(TG-DTA)等技术手段表征了色料的结构和性能。 结果表明,Ca²⁺掺杂能够明显降低γ-Ce₂S₃的合成温度,当n(Ca²⁺):n(Ce³⁺)≥0.16时,在900 ℃硫化150 min即可获得纯相的γ-Ce₂S₃,与不掺杂时合成γ-Ce₂S₃的温度相比降低了300 ℃左右。 同时,Ca²⁺掺杂能够提升γ-Ce₂S₃的抗氧化能力,当n(Ca²⁺):n(Ce³⁺)=0.64时,氧化放热峰的温度由不掺杂时的490.6 ℃提高至541.0 ℃。     

Synthesis and characterization of mesoporous ceria with hierarchical nanoarchitecture controlled by amino acids

In this work, we report the synthesis and characterization of mesoporous ceria with hierarchical nanoarchitectures controlled by amino acids. During the synthesis procedure, cerium oxalate precipitate was treated hydrothermally with different amino acids as crystallization modifiers, and hierarchically structured cerium oxalate precursors were obtained. Ceria can be produced after thermal decomposition of the cerium oxalate precursors. Structure and properties of the product were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, N2 adsorption analysis, and X-ray photoelectron spectroscopy (XPS) methods. The results indicate that the mesoporous ceria with hierarchical nanoarchitectures are composed of nanosized ceria crystallites as building units and possess high surface area and high concentration of oxygen vacancy. Depending on different amino acids as the crystallization modifiers, the ceria exhibit different morphologies, such as dendritic aggregation of rods, dumbbells of nanorod arrays, or aggregated spheres. It is proposed that both the type of functional side groups and the length of the side groups of the amino acids influence the morphologies of the ceria. Meanwhile, the solvent and hydrothermal treatment temperatures also play important roles in the morphological control. The method reported in this work would be regarded as a general way to fabricate mesoporous metal oxides with hierarchical nanoarchitectures.     

Synthesis of 1,3,4,6-tetraoxo compounds

The two-step method of synthesis of 1,3,4,6-tetraoxocompounds with different terminal substituents is developed. By condensation of alkyl methyl ketones with dimethyl oxalate new 1,6-dialkyl-substituted 1,3,4,6-tetraoxohexanes are obtained. The esters of 3,4,6-trioxoalkanoic acids are synthesized by the condensation reaction of alkyl acetates with dialkyl oxalates and alkyl methyl ketones. By the reaction of ethyl acetate with diethyl oxalate and methyl acetate the mixed diester of 3,4-dioxo-1,6-hexanedioic (ketipic) acid has been first prepared. Specific structural features of the synthesized compounds are discussed basing on the data of the IR, NMR, and XRD diffraction (XRD) analysis.     

Pressureless and Low-Pressure Synthesis of Microporous Carbon Spheres Applied to CO2 Adsorption

In this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO₂ adsorption properties was studied. The properties of materials produced at pressureless (atmospheric) conditions were compared with those synthesized under higher pressures. The results of this work show that enhanced pressure treatment is not necessary to produce high-quality carbon spheres, and the morphology and porosity of the spheres produced without an activation step at pressureless conditions are not significantly different from those obtained at higher pressures. In addition, CO₂ uptake was not affected by elevated pressure synthesis. It was also demonstrated that addition of the activator (potassium oxalate) had much more effect on key properties than the applied pressure treatment. The use of potassium oxalate as an activator caused non-uniform size distribution of spherical particles. Simultaneously higher values of surface area and total pore volumes were reached. A pressure treatment of the carbon materials in the autoclave significantly enhanced the CO₂ uptake at 25 °C, but had no effect on it at 0 °C.     

Synthesis of oligoesters and polyesters from oxalic acid and ethylene glycol

High molecular weight poly(ethylene oxalate) with fiber-forming properties was obtained from oxalic acid and ethylene glycol. The process was carried out on two stages in the melt. A new method was used for aliphatic oligoester synthesis in the melt, because the decomposition of oxalic acid takes place in the presence of glycol. The process was carried out at low temperatures with azeotropic water removal. Investigations of the polycondensation of oxalic acid and ethylene glycol with a compound forming a heteroazeotrope with water showed that the process is subject to the general laws of the polycondensation in melt: it depends on the ratio of initial components, presence of accelerating compounds, etc. However, the reaction time of polycondensation was dependent on the stirring intensity. High molecular weight poly(ethylene oxalate) was obtained by oligomer polycondensation in the melt. Thorium carbonate and tin dichloride were used as catalysts.     

3-羟基-4-甲基-5-乙基-2(5H)-呋喃酮的合成

报道了以草酸二乙酯为原料,制备具有焦糖香味的香料化合物3-羟基-4-甲基-5-乙基-2(5H)-呋喃酮的方法:首先乙基溴化镁与草酸二乙酯通过格氏反应,以约50%产率生成2-氧代丁酸乙酯,然后其在碳酸钾的作用下发生缩合反应,以约94%产率得到3-羟基-4-甲基-5-乙基-5-乙氧羰基-2(5H)-呋喃酮,再通过水解、脱羧反应,得到3-羟基-4-甲基-5-乙基-2(5H)-呋喃酮.路线总收率约36%.     

Synthesis of 2(3)-ethoxycarbonyl-5,6,7,8-tetrafluorochromones

The hitherto unknown ethyl pentafluorobenzoylpiruvate was prepared by condensing pentafluoroacetophenone with diethyl oxalate. Intramolecular cyclization of this ester or of its copper(II) chelate, as well as of ethyl 2-(ethoxymethylene)pentafluorobenzoylacetate affords 2- and 3-ethoxycarbonyl-5,6,7,8-tetrafluorochromones. Hydrolysis of the latter followed by decarboxylation gives 5,6,7,8-tetrafluorochromone.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 362–364, February, 1993.     

Synthesis of Diethyl Oxalate by a Coupling—Regeneration Reaction of Carbon Monoxide

This article describes a process for the synthesis of diethyl oxalate by a copling reaction of carbon monoxide,catalyzed by palladium in the presence of ethyl nitrite ,The kinetics and mechanism of the coupling and regeneration reaction are also discussed ,This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation.     

Synthesis of Diethyl Oxalate by a Coupling-Regeneration Reaction of Carbon Monoxide

This article describes a process for the synthesis of diethyl oxalate by a coupling reaction of carbon monoxide, catalyzed by palladium in the presence of ethyl nitrite. The kinetics and mechanism of the coupling and regeneration reaction are also discussed. This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation.     

Synthesis of calcium metaniobate by thermal decomposition of a coprecipitation product

The paper presents a new, nonconventional method, based upon coprecipitation, for the synthesis of niobium oxidic compounds. The coprecipitation product of niobic acid with calcium oxalate was used as precursor. Calcium metaniobate was obtained by appropriate thermal treatment of the coprecipitate. The coprecipitation mechanism was studied and the optimal conditions for quantitative precipitation of niobium and calcium were established. The mechanism of thermal decomposition of the coprecipitate was investigated by means of differential thermal analysis and X-ray powder diagrams. The final product of thermal decomposition, calcium metaniobate, is formed at 730°C.