Reductive Cleavage of S-S Bond by Samarium Diiodide: Synthesis of β-Thioesters and β-Thionitriles

The reduction of disulfides by samarium diiodide led to sa arium thiolates (ArSSml2).This new thiolate anion species reacted smoothly with α, β -unsaturated esters (nitriles) to give 1,4-addition products β -thioesters and β -thionitriles in good yields under mild and neutralcondition.

SYNTHESIS OF LIQUID CRYSTALLINE POLYACRYLATES WITH THIOESTER AS BRIDGE-BOND

A new series of acrylates with the same mesogens containing thioester as bridge-bond were synthesized, and the acrylates were characterized by H-1 NMR, IR and MS. The polymers were obtained by radical polymerization using AIBN as initiator. The monomers and polymers exhibit thermotropic-enantiotropic Liquid crystalline behavior.

Recent Progress of Thioester Method

Introduction The availability of site-specifically modified peptides is of vital importance for biochemical and biophysical studies. Biological methods, such as expression using bacteria, are useful. They are, however, not always applicable to the synthesis of peptides with sitespecific modifications. Chemical methods can be viable alternatives to those biological approaches. Peptides obtained by chemical and biological means,

Improvement of Thioester Method by Using Pac Ester for Synthesis of Cyclopentapeptides

Thioester method was improved by using Pac (phenacyl group) ester as protecting group of 3-mercaptopropionic acid. Two cyclopentapeptides c(Ala-Tyr-Leu-Ala-Gly) and c(Pro-Tyr-Leu- Ala-Gly) were synthesized successfully by this method.

A Stereoselective Approach to S-Vinyl Thioesters from Alkynes,Elemental Sulfur and Acyl Chlorides

A facile, stereoselective synthesis of S-vinyl thioesters from easily available starting compounds and reagents is showed.

Effect of the Position of Reaction-Site in Amphipathic-Type Thioester in Aqueous Amidation Reaction

Amphipathic-type thioesters CH3(CH2)mCOS(CH2)nCOONa (m + n = 12) were synthesized and their reaction with various alkylamines was examined. Compounds having thioester moiety close to carboxylate (m = 10, n = 2) afforded the corresponding amides in good yields, while the substrate having thioester moiety distant from carboxylate (m = 2, n = 10) afforded the amides in relatively low yield. In all cases, the difference in yield due to the chain length of amine was not observed. The results indicated that the reaction took place effectively near the surface of micelle. However, the reaction was found to occur not only on micelle surface but also in solution.

New Synthetic Route to Copoly(Ester-Thioester)s by Direct Polycondensation of Thio-Acids with Diols of Cycloketones Derivatives

A new series of copoly(ester-thioester)s had been synthesized using direct polycondensation technique. These copolythioesters were synthesized by direct polycondensation of 4,4'-(tereph-thaloyIdithio) diacetic acid I, 3,3'(isophthaloyl-dithio) diacetic acid II, or 1,8 (sebacoyldithio) diacetic acid III, with 2,6-bis(p-hydroxybenzylidene) tert. butyl cyclohexanone IV and 2,6-divanyli-dene tert. butyl cyclohexanone V, using a condensing agent consisting of pyridine-thionyl clhloride complex. The resulting copolymers were characterized by elemental and spectral analyses, solubility, viscometery, electronic spectra and thermogravimietric analyses. The crystallinity of some copolymers was examined by X-ray diffraction analyses. Furthermore, the morphology of selec ted examples of the copolymers was examined by scanning electron microscopy.

Encouraging Solution to the Problem of Synthesizing Protein α-Thioester

Expressed protein ligation(EPL)provides a powerful tool to access large-size proteins with precise structures.Existing methods for constructing the critical protein thioester for EPL have predominantly relied on the recombinant intein fusion expressed in Escherichia coli(E.coli).Despite its powerful applications,the expression of thioester derived from eukaryotic protein in E.coli inherently suffers from its limited solubility,the inactivity of intein,premature hydrolysis and low yields.To overcome these obstacles,we present herein the facile one-flask synthesis of inaccessible proteinα-thioester via a SUMO-protein-intein(SPI)sandwich model.The utility of SUMO enhances the protein fusion yield and solubility,prevents premature hydrolysis and simplifies the purification process.The inaccessible protein thioester with internal Cys residues can be readily produced and is compatible with the EPL-desulfurization protocol used to prepare complex proteins,which is otherwise difficult to obtain using traditional methods.Its utility has been highlighted through the synthesis of human granulocyte colony-stimulating factor(G-CSF).

Improvement in the synthesis of 2-(5-amino-1,2,4-thiadiazol-3- yl)-2-(Z)-methoxyiminoacetic acid 2-benzothiazolyl thioester

2-(5-Amino-1,2,4-thiadiazol-3-yl)-2-(Z)-meth-oxyiminoacetic acid 2-benzothiazolyl thioester(III),an important intermediate of the fourth generation cephalos-porins,was efficiently synthesized by reacting 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid(I)with 2,29-dibenzothiazole disulfide(II)in the presence of triphenylphosphine.Effects of reaction time,temperature,solvents,catalysts and feeding molar ratio on the yield and quality of products were investigated,and an im-proved procedure suitable for industrial production was established.Using 1,2-dichloroethane as solvent,triphe-nylphosphine as reducer,and triethylamine as catalyst,n(I):n(II):n(triphenylphosphine)51.0:1.0:1.0,the product was obtained at room temperature in 98.1%yield.The purity of the product without further purification is 98.7%determined by HPLC method.This procedure could be a suitable alternative to the traditional processes because of its easy handling,high yield and low cost.

具有抗紫外线功能的光固化涂料组合物的制备与性能研究

以羟基二苯甲酮、2-巯基苯并噁唑、芳基酰氯为原料,采用简单、温和的方法合成了新型二苯甲酮衍生物和含苯并噁唑的硫酯类衍生物,采用核磁氢谱1H NMR、核磁碳谱13C NMR和高分辨质谱HRMS等测试手段对目标化合物进行表征,并对其进行了光学性能测试,并用其制备了具有抗紫外线功能的光固化涂料。结果表明:两类衍生物能有效吸收220~350 nm的紫外光,与低聚物、单体相容性好,无气味。新合成的二苯甲酮衍生物作为光引发剂可使涂层固化时间大幅缩短到9 s,固化膜的外观、附着力和凝胶率相较于市售光引发剂BP有明显提高;硫酯类衍生物作为紫外吸收剂不仅能够增加光固化涂层的抗紫外线功能,且易于光固化涂料的制造、贮存。该组合物在罩面剂、油墨、胶黏剂等领域也有良好的应用前景。

S-(2-羟乙基)-2,2-二甲基丙硫酸酯的合成研究

研究了S-(2-羟乙基)-2,2-二甲基丙硫酸酯的合成,采用三甲基乙酰氯和β-巯基乙醇作为反应物完成了硫酯键的构建,并对该反应条件进行了方法学研究。该化合物的合成工艺是在-78℃条件下,将β-巯基乙醇和三乙胺分别加入装有干燥DCM的圆底烧瓶中,缓慢滴加三甲基乙酰氯于反应体系中,允许反应升温至室温继续反应2h,该工艺方法得到82%左右的收率,且反应条件简单温和,工艺设备成本廉价,可进行大量合成,实现了操作简单、经济实惠和绿色环保的目的。

FeCl3-6H2O-Catalyzed Synthesis of β-Ketothioesters from Chain α-Oxo Ketene Dithioactals

A FeCl3-6H2O-catalyzed synthesis of β-ketothioesters from the hydrolysis reaction of chain α-oxoketene dithioacetals was carried out. Subsequently, we explored the FeCl3-6H2O-catalyzed Friedel-Crafts alkylation of the synthesized fl-ketothioesters with alcohols in CH3CN at 25 ℃, affording the desired α-alkylated fl-ketothioesters in excellent yields. Wide scope of the substrates, use of inexpensive reagents, high yields under mild reaction conditions are notable features of these reactions.

Theoretical study on formation of thioesters via O-to-S acyl transfer

Peptide thioester preparation via intramolecular O-to-S acyl transfer is a recently developed method for protein chemical synthesis through Fmoc chemistry. Theoretical calculations have been carried out to study the mechanism for the formation of thioesters via O-to-S acyl transfer. It is found that the O-to-S acyl transfer occurs via an anionic stepwise mechanism in which the cleavage of the C-O bond is the rate-limiting step. The side reaction of hydrolysis also proceeds through an anionic stepwise process, and its rate-limiting step is the attack of the hydroxide ion on the carbonyl carbon. Increase of the chain length between the ester O atom and the S atom can increase the energy barrier of the O-to-S acyl transfer. On the other hand, substituents at the α-position of the ester can reduce the energy barrier.

Recent advances in the preparation of Fmoc-SPPS-based peptide thioester and its surrogates for NCL-type reactions

Solid phase peptide synthesis(SPPS)based on Fmoc chemistry has become a commonly used technique in peptide chemistry,as it can be easily conducted using automated machine,and not requiring highly toxic HF in comparison to Boc-SPPS.With the fast development in the emerging field of protein chemical synthesis,many efforts have been endeavored aiming to find more efficient methods for preparing peptide fragments required in ligation reactions.This review briefly summarizes recent advances in the engineering and modification of Fmoc-SPPS-derived peptides,which can be used as the N-terminal fragments in a native chemical ligation(NCL)or NCL-type ligation reactions.

水相中烷基硫代酯的绿色合成

发展了一种无需任何添加剂,在水相中合成烷基硫代酯的绿色方法.以卤代烃与硫代酰胺为原料,在水相中反应4 h,即可以较高收率得到预期产物,并可兼容多种官能团.与传统方法相比,该方法具有实验操作简单、反应绿色高效及原子经济等优点,并且可以实现克级制备,具有较高的应用价值.

高效液相色谱法测定注射用盐酸石蒜碱硫酯含量

目的:基于高效液相色谱(HPLC)法开发一种注射用盐酸石蒜碱硫酯的含量测定方法。方法:色谱柱Kromasil(C18,4.6 mm×250 mm,5μm);流动相为甲醇-0.01 mol/L磷酸二氢钾(氢氧化钾调节pH至8.0)(80∶20);流速1.0 mL/min;检测波长290 nm;进样量10μL;柱温25℃。结果:经实验研究结果证明在该方法下,盐酸石蒜碱硫酯在0.08~0.32 mg/mL浓度范围内呈良好的线性关系(r=0.9998),平均回收率为99.7%,相对标准偏差(RSD)为0.9%(n=9)。用该方法对10个批次的自制品进行含量测定,结果均在98.0%~102.0%范围内。结论:本研究建立的方法具有简便、准确且重现性好等优点,可实现快速测定注射用盐酸石蒜碱硫脂的含量,以满足制剂大批量样品质量控制需求。

氮苯基丙二硫酯化合物的合成与表征

详细介绍了一种探究性的有机化学综合实验的设计,一种氮苯基丙二硫酯化合物的设计合成与表征。实验利用苯胺,甲醛水溶液与硫代乙酸为原料,在乙醇溶液中,通过“一锅法”得到氮苯基丙二硫酯化合物,并对产物结构进行简要的分析归纳。本实验主要针对化学化工专业类学生在有机化学实验中理论联系实践不足的问题,让学生从探究性的有机化学实验中提高分析与总结的综合能力。

Synthesis of c-Myb Protein(38-89)-NH_2 Using a Partially Protected Peptide Thioester

The method of selective modification of eysteine SH group with 4-methylbenzylchloride is developed,c-Myb protein (38-89)-NH_2 is synthesized by using a partially protected peptide thioester.The 4-methylbenzyl (MeBzl) protecting group of cysteine in the building block is stable during the segment cou- pling.The method can be used in the chemical synthesis of some protein containing cysteine.

Application of Pac Ester in Thioester Method for the Synthesis of Cyclopentapeptides

Thioester method for the synthesis of cyclopeptides is improved by using Pac (Pac = phenacyl, CH2COC6H5) ester as a protecting group of 3-mercaptopropionic acid. The Pac group is easy to be removed from C-terminal with zinc in acetic acid. The protected glycine thioester and peptide thioesters synthesized by the unproved method, are easy to be purified, so the final linear peptides are pure enough for the following cyclization. Furthermore, this method is flexible for peptide chain elongation, either from C-terminal or from N-terminal. So it is an efficient and practical method for synthesis of bioactive peptides. Two N-protected pentapeptide thioesters, Boc-Pro-Tyr-Leu-Ala-GlySCH2CH2COOPac and Boc-Ala-Tyr-Leu-Ala-Gly-SCH2CH2-COOPac were synthesized by the improved thioester method. After deprotecting Pac ester with zinc in aqueous acetic acid and Boc group with trifluoroacetic acid in CH2C12, two free pentapeptide thioesters were obtained. Ag+ -assisted cyclization in acetate buffered solution afforded two cyclic pentapeptides c(Pro-Tyr-Leu-Ala-Gly) and c(Ala-Tyr-Leu-Ala-Gly). Effects of different buffer pH, different Ag+ concentrations, etc. on the cyclization were studied.

Structure of Cyclic Aryl Thioester Dimer Based on o-Phthaloyl Dichloride and Bis(4-mercaptophenyl) Sulfide

A cyclic aryl thioester dimer was prepared by the reaction of o phthaloyl dichloride and bis(4 mercaptophenyl) sulfide in good yield under pseudo high dilution conditions via interfacial polycondensation. The structure of the cyclic dimer was confirmed by a combination of MALDI TOF MS, FTIR, gel permeation chromatography and NMR analyses. The X ray diffraction study of the single crystal of cyclic thioester dimer obtained from two solutions reveals no severe internal strain on the cyclic structure.