Microbial Synthesis of Medium‐Chain α,ω‐Dicarboxylic Acids and ω‐Aminocarboxylic Acids from Renewable Long‐Chain Fatty Acids

Biotransformation of long‐chain fatty acids into medium‐chain α,ω‐dicarboxylic acids or ω‐aminocarboxylic acids could be achieved with biocatalysts. This study presents the production of α,ω‐dicarboxylic acids (e.g., C₉, C₁₁, C₁₂, C₁₃) and ω‐aminocarboxylic acids (e.g., C₁₁, C₁₂, C₁₃) directly from fatty acids (e.g., oleic acid, ricinoleic acid, lesquerolic acid) using recombinant Escherichia coli‐based biocatalysts. ω‐Hydroxycarboxylic acids, which were produced from oxidative cleavage of fatty acids via enzymatic reactions involving a fatty acid double bond hydratase, an alcohol dehydrogenase, a Baeyer–Villiger monooxygenase and an esterase, were then oxidized to α,ω‐dicarboxylic acids by alcohol dehydrogenase (ADH, AlkJ) from Pseudomonas putida GPo1 or converted into ω‐aminocarboxylic acids by a serial combination of ADH from P. putida GPo1 and an ω‐transaminase of Silicibacter pomeroyi. The double bonds present in the fatty acids such as ricinoleic acid and lesquerolic acid were reduced by E. coli‐native enzymes during the biotransformations. This study demonstrates that the industrially relevant building blocks (C₉ to C₁₃ saturated α,ω‐dicarboxylic acids and ω‐aminocarboxylic acids) can be produced from renewable fatty acids using biocatalysis.

     

Copper(II)‐Catalyzed Aerobic Oxidative Coupling between Chalcone and 2‐Aminopyridine via C?H Amination: An Expedient Synthesis of 3‐Aroylimidazo[1,2‐a]pyridines

A simple and efficient protocol has been developed for the synthesis of 3‐aroylimidazopyridines via copper(II) acetate‐catalyzed aerobic oxidative amination. A library of 3‐aroylimidazopyridines was synthesized from readily accessible chalcones and 2‐aminopyridines with high yields and regioselectivity. The reaction proceeds through a tandem Michael addition followed by an intramolecular oxidative amination. The successful application of this methodology for a gram‐scale reaction indicates its potential for bulk synthesis.

     

Covalent Linkage of an R-ω-Transaminase to a d-Amino Acid Oxidase through Protein Splicing to Enhance Enzymatic Catalysis of Transamination

R-ω-Transaminases (RTAs) catalyse the conversion of R-configured amines [e.g., (R)-1-phenylethylamine] into the corresponding ketones (e.g., acetophenone), by transferring an amino group from an amino donor [e.g., (R)-1-phenylethylamine] onto an amino acceptor (e.g., pyruvate), resulting in a co-product (e.g., d -alanine). d -Alanine can be deaminated back to pyruvate by d -amino acid oxidase (DAAOs). Here, through in vivo subunit splicing, the N terminus of an RTA subunit (RTA^S) was specifically ligated to the C terminus of a DAAO subunit (DAAO^S) through native peptide bonds (RTA&DAAO). RTA^S is in close proximity to DAAO^S, at a molecular-scale distance. Thus the transfer of pyruvate and d -alanine between RTA and DAAO can be directional and efficient. Pyruvate→d -alanine→pyruvate cycles are efficiently formed, thus promoting the forward transamination reaction. In a different, in vitro noncovalent approach, based on coiled-coil association, the RTA^S N terminus was specifically associated with the DAAO^S C terminus (RTA#DAAO). In addition, the two mixed individual enzymes (RTA+DAAO) were also studied. RTA&DAAO has a shorter distance between the paired subunits (RTA^S–DAAO^S) than RTA#DAAO, and the number of the paired subunits is higher than in the case of RTA#DAAO, whereas RTA+DAAO cannot form the paired subunits. RTA&DAAO exhibited a transamination catalysis efficiency higher than that of RTA#DAAO and much higher than that of RTA+DAAO.     

Pd2(dba)3-catalyzed amination of C5-bromo-imidazo[2,1-b][1,3,4] thiadiazole with substituted anilines at conventional heating in Schlenk tube

ABSTRACT

An efficient Pd₂(dba)₃-catalyzed amination of C5-bromo-imidazo[2,1-b][1,3,4]thiadiazole using conventional heating is reported. The C5-bromoimidazo[2,1-b][1,3,4]thiadiazole was synthesized using a multistep approach which started by cyclization of thiosemicarbazide with a carboxylic acid to give 2-amino[1,3,4]thiadiazoles which were further treated with 2-haloketones to give imidazo[2,1-b][1,3,4]thiadiazoles. Then, the bromination of imidazothiadiazole was done using N-bromosuccinimide to give the C5-bromo-imidazo[2,1-b][1,3,4]thiadiazole. Afterward, various C-N bond-forming approaches were attempted such as S_NAr, Cu(I), Cu(II), Pd(OAc)_2, Pd₂(dba)₃ catalyst with different ligand, additive, base, solvent and temperature conditions. Out of various approaches used, only Buchwald Hartwig amination, performed with conventional heating, gave N-arylamine-5-imidazothiadiazoles. Then, 10 different anilines with different electron-withdrawing and donating groups at different positions were employed to examine the scope and limitations of the method. Salient features of this method include conventional heating in a Schlenk tube as the reaction condition, the absence of the use of toxic isocyanides, the wide nature of substituent tolerance with anilines, and moderately good product yields.     

乙酸铜促进的吲哚衍生物的分子内C-H活化/胺化反应

利用简单易得的原料设计并合成了新型的N-芳基取代的吲哚衍生物;通过C-H活化反应策略,发展了乙酸铜促进的吲哚衍生物的分子内C-H活化/胺化反应,获得了具有潜在生物活性的新型吲哚稠杂环化合物。研究了反应的底物适用范围,通过X-射线单晶衍射确定了化合物的晶体结构,提出了可能的反应机理。     

邻甲苯甲腈与对甲苯甲腈合成工艺的进展

简要叙述了邻甲苯甲腈与对甲苯甲腈的性质和用途。综述了邻甲苯甲腈与对甲苯甲腈四大类合成路线：甲基苯胺重氮化法,二甲苯氨氧化法,甲基苯甲酸氨化法和甲基苯甲醛肟化脱水法。各大类中又根据其它原料和方法的不同细分出几种方法,给出了具体的邻甲苯甲腈与对甲苯甲腈的合成步骤,并对其合成工艺的特点进行了分析。     

Copper(I)‐Catalyzed Dehydrogenative Amidation of Arenes Using Air as the Oxidant

The copper(I) bromide‐catalyzed intermolecular dehydrogenative amidation of arenes via C H bond activation assisted by a 2‐pyridyl or 1‐pyrazolyl chelating group using air as the terminal oxidant has been achieved at 140 °C. N‐Aryl amides, N‐alkyl amides, benzamide derivatives, imides, and lactams all are good coupling partners to obtain moderate to excellent yields. The amount of solvent is critical for the transformation: both increasing and decreasing the amount of solvent decreased the yield. Notably, the amidation of bimolecular 2‐phenylpyridine with the dual N H bonds of a primary amide proceeded smoothly in one‐pot to afford a good yield under the same conditions. The amidation can be performed with a good yield at the gram scale.

     

改性聚丁二烯胺化物的合成

由液体聚丁二烯合成改性聚丁二烯胺化物,研究在常压下胺化反应中反应温度、反应时间、催化剂用量及胺化剂用量对胺化产物胺值的影响规律,发现催化剂的存在可以大大促进胺化反应的速率,并找到了合成不同胺值的配方及反应条件;还研究了在加压胺化反应中各因素对胺值的影响规律,并通过加压胺化合成法合成出胺值大小适宜的改性聚丁二烯的胺化物,用作阳离子电泳涂料的基体树脂成分。     

新一代的计算机

本文简要地介绍了超导计算机,光计算机和量子计算机的原理和优点。并介绍了量子计算机的一些基本概念：量子叠加,量子纠缠,量子位和量子逻辑门。     

Single Nucleotide‐Catalyzed Biomimetic Reductive Amination

We have successfully developed a single nucleotide (adenosine 5′‐diphosphate)‐catalyzed enantioselective direct reductive amination of aldehydes and ketones using a Hantzsch ester as reducing agent. The process is a simple, efficient and a real mimic of the NADH reduction approach for the synthesis of structurally diverse amines. This reaction is the first report demonstrating the ability of a single nucleotide as catalyst and one of the most genuine biomimetic reactions of organic chemistry.