An ab initio study of the A Ac1 hydrolysis mechanism of formamide

Ab initio calculations have been used to examine the reaction profile for the A _wc1 hydrolysis mechanism for formamide, giving a value of 67.3 kcal/mole for H . Comparisons between computed and experimental proton affinities are used to assess the reliability of the calculations. Orbital energies are reported for formamide, N-protonated and O-protonated formamide, carbon monoxide and the formyl cation.     

The application of Nα-formyl amino acid esters in the enzyme-catalyzed peptide synthesis

The synthesis of N-formyl protected amino acid esters and their use in kinetically controlled -chymotrypsin-, trypsin- and carboxypeptidaseY-catalyzed peptide synthesis is described. Using the synthesis of H-Tyr-Ala-OH as example it is demonstrated that optically uniform products are obtained. Reaction yields are discussed with regard to the ester component employed. In comparison to commonly used -amino protecting groups in chemical peptide synthesis, N-formyl amino acid derivatives show improved solubilities in aqueous-alcoholic media.Die Synthese N-Formyl-geschützter Aminosäureester und deren Anwendung in der kinetisch kontrollierten -Chymotrypsin-, Trypsin- und CarboxypeptidaseY-katalysierten Peptidsynthese wird beschrieben. Man erhält hierbei optisch einheitliche Produkte, was anhand der Synthese von H-Tyr-Ala-OH gezeigt wurde. Reaktionsausbeuten bei Verwendung verschiedener Ester werden diskutiert. Im Verhältnis zu gängigen -Aminoschutzgruppen der chemischen Peptidsynthese weisen N-Formyl-geschützte Derivate in wäßrig-alkoholischen Medien verbesserte Löslichkeiten auf. Abbreviations: IUPAC-IUB rules for peptides are followed, see Pure Appl. Chem. (1984) 56:595.Boc=tert. butyloxycarbonyl,CT=-chymotrypsin,DCC=N,N-dicyclohexylcarbodiimide,DIPEA=diisopropylethylamine,Fmoc 9-fluorenylmethyloxycarbonyl,For=formyl, GC=gaschromatography, HOSu=N-hydroxysuccinimide, HPLC=high pressure liquid chromatography,MeCN=acetonitrile, —OMe=methyl ester, —OProp=n-propyl ester,PFPA=decafluoropropionic anhydride,T=trypsin,TBA=tetrabutylammonium hydrogen sulfate, TLC=thin layer chromatography,TMS=tetramethylsilane,Y=carboxypeptidaseY,Z=benzyloxycarbonyl.     

Solid-phase synthesis of pyrido[2,3-d]pyrimidin-7-ones

A novel solid-phase method for the synthesis of 4-methyl-pyrido[2,3-d]pyrimidin-7-one compounds with two diversity points is described. The polymer supported methylsulfonyl derivatives A₃, achieved by coupling compound G with different resin-bound amines A₁ followed by oxidation with MCPBA, are substituted with several amines R₁R₂NH. Final cleavage affords 126 compounds having formula H in good yield and purity.     

Photolysis of open-chain 1,2-diazidoalkenes: generation of 2-azido-2H-azirines, formyl cyanide, and formyl isocyanide

Solutions of several open-chain 1,2-diazidoethenes were photolyzed to yield 2-azido-2H-azirines, which were identified by NMR spectroscopy at low temperature. On prolonged irradiation or warm-up of the NMR solutions, these heterocycles lost a second molecule of nitrogen to be cleaved into two fragments of cyano compounds. In the case of (Z)-2,3-diazidocinnamaldehyde, the formation of formyl cyanide was detected by IR spectroscopy when the photolysis was performed in argon matrix. The latter substance was rearranged to formyl isocyanide on irradiation. This new species was characterized by comparison of its experimental and calculated (B3LYP/6-311+G^∗∗) IR spectrum.     

HOCl…HCOCl复合物的结构和电子性质

在DFT-B3LYP/6-311++G**水平上求得HOCl+HCOCl复合物势能面上的四种稳定构型(S1, S2, S3和S4). 其中, 在复合物S1和S3中, HOCl单体的5H原子作为质子供体, 与HCOCl单体中作为质子受体的1O原子相互作用, 形成红移氢键复合物; 在复合物S4中, HOCl单体的7Cl原子作为质子供体, 与HCOCl单体中作为质子受体的1O原子相互作用, 形成红移卤键复合物; 而在复合物S2中, 同时存在2C—3H…6O蓝移氢键和4Cl…5O相互作用. 在MP2/6-311++G**水平上计算的单体间的相互作用能考虑了基组重叠误差(BSSE)和零点振动能(ZPVE)校正, 其值在-5.05与-14.76 kJ·mol-1之间. 采用自然键轨道理论(NBO)对两种单体间相互作用的本质进行了考查, 并通过分子中原子理论(AIM)分析了复合物中氢键和卤键键鞍点处的电子密度拓扑性质.     

Synthesis of porphyrins bearing 1-4 hydroxymethyl groups and other one-carbon oxygenic substituents in distinct patterns

Porphyrins that bear one-carbon oxygenic substituents (hydroxymethyl, formyl, ester) directly attached to the macrocycle afford a compact architecture of utility for diverse applications. Routes to 9 porphyrins bearing such groups in distinct architectures (A₄-, trans-A₂-, trans-A₂B₂-, trans-AB-, and trans-AB₂C-porphyrins) have been explored (A=hydroxymethyl), including porphyrins bearing two one-carbon units in different oxidation states (hydroxymethyl/ester, formyl/ester). The hydroxymethyl group was introduced via TBDMS-protected dipyrromethane precursors.     

Biosourced 3-formyl chromenyl-azo dye as Michael acceptor type of chemodosimeter for cyanide in aqueous environment

A simple water-soluble aldehyde functionalized chromone 5 was utilized as a doubly activated Michael acceptor type of chemodosimeter for cyanide in water. The water solubility of the probe 5 is due to the incorporation of two glycerol units on the starting prepared chemodosimeter. This sensory system is able to selectively distinguish cyanide among fluoride and many other anions at micromolar concentrations and instantly detect cyanide in water at ambient temperatures with a detection limit down to 1.0 mM. Thus, the chemodosimeter 5 was applied to the quantitative determination of cyanide anion in drinking water sample (drinking water from commence).     

Formyl Radical Generation from α-Chloro N-Methoxyphthalimides Enables Selective Aldehyde Synthesis

The aldehydes installation by radical formylation constitutes an attractive synthetic strategy. However, the generation of formyl radicals for organic synthesis applications remains unknown. Herein we report the first formyl radical generation from α-chloro N-methoxyphthalimides, which selectively synthesize aldehydes by alkene hydroformylation under mild photoredox conditions. The aldehydes can be installed on acrylates, acrylamides, vinyl sulfones, vinyl ketones, and complex steroids by radical hydroformylation in excellent chemoselectivity and regioselectivity. The concerted hydrochloride elimination for the formyl radical generation from α-chloro methoxy radicals is established by experimental and computational approaches.     

气相中自由基OH在不同催化剂下对甲酰氟FCHO进行提氢反应的理论性研究

分别在水、甲酸和硫酸存在的情况下,通过CCSD(T)//M06-2X/6-311++G(3df,3pd)的理论方法,对大气中自由基OH提取甲酰氟FCHO上的氢进行了反应机理和动力学的研究.计算结果表明相对于反应物,加入催化剂的过渡态的能垒从3.64 kcal/mol分别下降到-2.89、-6.25和-7.76 kcal/mol,表明水、甲酸和硫酸在甲酰氟FCHO和自由基OH提氢反应中起了重要作用.通过运用具有Eckart隧道校正的传统过渡态理论计算出的动力学数据表明通道X...FCHO+OH(X=H₂O, HCOOH,或者H₂SO₄)要比通道X...OH+FCHO更有利于反应的发生.催化剂水、甲酸和硫酸的加入使甲酰氟FCHO 和自由基OH提氢反应的速率常数要比不加催化剂时小,说明了催化剂的加入不能促进大气中甲酰氟FCHO和自由基OH的反应.     

Structures and Electronic Properties of HOCl···HCOCl Complexes

B3LYP/6-311++G** and MP2/6-311++G** calculations were used to analyze the interaction between hypochlorous acid (HOCl) and formyl chloride (HCOCl). The results showed that there were four equilibrium geometries (S1, S2, S3, and S4) optimized at B3LYP/6-311++G** level, and all the equilibrium geometries were confirmed to be in stable states by analytical frequency calculations. Complexes S1 and S3 use the 5H atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift hydrogen bond systems. However, the blue-shifted hydrogen bond (2C-3H···6O) coexists with 4Cl···5O interaction in structures S2. As for S4, it uses the 7Cl atom of HOCl as proton donor and the terminal 1O atom of HCOCl as acceptor to form red shift halogen bond system. Interaction energies between monomers in the four complexes corrected with basis set superposition error (BSSE) and zero-point vibrational energy (ZPVE) lie in the range from −5.05 to −14.76 kJ·mol⁻¹ at MP2/6-311++G** level. The natural bond orbital (NBO) and atoms in molecules (AIM) theories have also been applied to explain the structures and the properties of the complexes.