Simple preparation of 3I-O-substituted beta-cyclodextrin derivatives using cinnamyl bromide

[reaction: see text] A new method for preparation of 3(I)-O-substituted beta-cyclodextrin derivatives was developed. Cinnamyl bromide reacts with beta-cyclodextrin to form predominantly the 3(I)-O-cinnamyl derivative (30% isolated yield, >90% regioselectivity). After protection of the remaining cyclodextrin hydroxyls by acetylation, the cinnamyl group can be easily transformed to many other groups (exemplified by transformation to 3(I)-O-carboxymethyl derivative). Substitution pattern in singly modified CDs was unambiguously determined by a combination of 2D NMR techniques.     

Spectrofluorimetric determination of guanethidine sulphate, guanoxan sulphate and amiloride hydrochloride in tablets and in biological fluids using 9,10-phenanthraquinone

A highly sensitive spectrofluorimetric method for the determination of some drugs of the monosubstituted guanidine derivatives in laboratory made tablets, in spiked human serum and in urine samples is presented. The method is based on the reaction of guanethidine sulphate (I), guanoxan sulphate (II) and amiloride hydrochloride (III) with 9,10-phenanthraquinone (IV) to give highly fluorescent derivatives. The linearity ranges were found to be 0.06-0.96 mug/ml for (I) and (II) and 0.04-0.28 mug/ml for (III), with relative standard deviation less than 2%. Mean percentage recoveries for tablets were found to be 99.9 +/- 1.3, 100.5 +/- 1.1 and 100.0 +/- 1.6 for I, II and III, respectively. For I and III the results are highly correlated with the B.P. methods. Using the synchronous fluorimetry, differentiation between I and II was possible. Chloroform, dichloromethane and ethyl acetate have been used to extract I, II and III, respectively from serum and urine at basic pH, followed by applying the proposed fluorimetric method. Percentage recoveries were found to be 95.7-102.2%. The limit of detection is 0.04 mug/ml for I and II and 0.02 mug/ml for III.     

Computation of the amide I band of polypeptides and proteins using a partial Hessian approach

A partial Hessian approximation for the computation of the amide I band of polypeptides and proteins is introduced. This approximation exploits the nature of the amide I band, which is largely localized on the carbonyl groups of the backbone amide residues. For a set of model peptides, harmonic frequencies computed from the Hessian comprising only derivatives of the energy with respect to the displacement of the carbon, oxygen, and nitrogen atoms of the backbone amide groups introduce mean absolute errors of 15 and 10 cm(-1) from the full Hessian values at the Hartree-Fock/STO-3G and density functional theory EDF16-31G(*) levels of theory, respectively. Limiting the partial Hessian to include only derivatives with respect to the displacement of the backbone carbon and oxygen atoms yields corresponding errors of 24 and 22 cm(-1). Both approximations reproduce the full Hessian band profiles well with only a small shift to lower wave number. Computationally, the partial Hessian approximation is used in the solution of the coupled perturbed Hartree-Fock/Kohn-Sham equations and the evaluation of the second derivatives of the electron repulsion integrals. The resulting computational savings are substantial and grow with the size of the polypeptide. At the HF/STO-3G level, the partial Hessian calculation for a polypeptide comprising five tryptophan residues takes approximately 10%-15% of the time for the full Hessian calculation. Using the partial Hessian method, the amide I bands of the constituent secondary structure elements of the protein agitoxin 2 (PDB code 1AGT) are calculated, and the amide I band of the full protein estimated.     

Gold(I)-catalyzed intramolecular tandem addition/Friedel-Crafts reactions between acyclic enamides and 1-arylalkynes

Electron-deficient acyclic enamine derivatives react with electron-rich 1-arylalkynes using cationic gold(I) species as catalysts in an intramolecular process to form annulated 1-amido-substituted indene derivatives as the major products. Yields for this process range between 21% and 98%. In some cases, a two-step process that includes a subsequent alkene isomerization is needed.     

Copper-catalyzed aminohalogenation using the 2-NsNCl(2)/2-NsNHNa combination as the nitrogen and halogen sources for the synthesis of anti-alkyl 3-chloro-2-(o-nitrobenzenesulfonamido)-3-arylpropionates

New regio- and stereoselective aminohalogenation of cinnamic esters has been developed using the combination of 2-NsNCl(2)/2-NsNHNa as the nitrogen and chlorine sources and copper(I) triflate as the catalyst. The new procedure provides an efficient synthesis of anti-alkyl 3-chloro-2-(o-nitrobenzenesulfonamido)-3-phenylpropionate derivatives. Nine examples are presented with good yields (62-82%) and stereoselectivity ((5:1)-(30:1)).     

Direct functionalization of nanodiamond particles using dopamine derivatives

The article reports on the strong linking of dopamine derivatives as a simple and a versatile strategy for the surface functionalization of hydroxyl-terminated nanodiamond (ND-OH) particles. Azide- (ND-N(3)) or poly-N-isopropylacrylamide-terminated (ND-PNIPAM) particles were obtained from ND-OH particles through the reaction with the corresponding dopamine derivatives. The azide-terminated ND particles were further derivatized with a fluorescent probe, alkynyl-pyrene, via copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition. The modified ND particles were characterized using transmission Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy, electrochemical measurements, thermogravimetric analysis (TGA), and particle size measurements. The surface loading of ND particles with dopamine was estimated from TGA and UV-vis spectroscopy and was found to be around 0.27 mmol g(-1). Because of its simple, gentle nature and versatility, the chemistry developed in this work can be used as an avenue for the preparation of functional nanodiamond particles for various applications.     

超声辅助合成喹喔啉类化合物

在超声辅助下,使用蒙脱土负载碘催化苯偶酰衍生物与邻苯二胺经缩合反应合成了4个喹喔啉类化合物,其结构经¹H NMR和IR确证。以苯偶酰（1a）和邻苯二胺（2）的反应为模板,对反应条件进行了优化。结果表明：最佳应条件为：1a 0.1 mmol, n(1a)：n(2)为1.0 ：1.2,催化剂蒙脱土负载碘用量为5 mol%,二氯甲烷为溶剂,于30 ℃超声反应5 min,收率97.2%。该催化体系回收利用3次后收率为82.0%,说明其具有一定的循环使用能力。     

Assessment of amination reactions via nucleophilic aromatic substitution using conventional and eco-friendly energies

The efficiency of conventional heating energy source compared with Infrared (IR), Ultrasound (US), Microwave and the simultaneous combination US–IR eco-friendly approaches for preparation of new N-(5-R¹ _-amino-2-nitrophenyl)acetamides and 5-R¹-amino-2-nitroaniline by Nucleophilic Aromatic Substitution (S_NAr) via addition–elimination reactions on the halogens F, Cl, Br, I, employing amines as nucleophiles were explored. Moreover, phenyldiazenyl derivatives in good yields by an oxidative one-pot S_NAr-based amination reaction from an unusual oxidation of 2-phenylhydrazinyl derivatives in DMSO was prepared.     

5-(2,4-二氯苯氧亚甲基)-2-芳酰胺基-1,3,4-噻二唑的合成

研究了对1-(2,4-二氯苯氧乙酰基)-4-芳酰基氨基硫脲的酸催化环化, 它在酸催化下的环化是定向进行的, 环化途径是生成中间体后脱水而得到5-(2,4-二氯苯氧亚甲基)-2-芳酰胺基-1,3,4-噻二唑, 产物的结构经元素分析, 红外, 核磁以及质谱方法确证。     

Efficient synthesis of piperidine derivatives using dendrimer based catalytical pockets

The synthesis of highly functionalized piperidine derivatives using amine functionalized maltitol-cored dendritic polymer (MAL-G0) in acetonitrile as the reaction medium is reported. A variety of piperidine derivatives were synthesized and the reaction gave an excellent yield of 89%–95%. The highly functionalized nature of the catalyst provided large number of active sites which resulted in good yield within a short period of time. Maltitol is a carbohydrate polyol system which was chosen here as the core for the synthesis of the dendritic catalyst; it was an effective approach for the preparation of piperidine like medicinal compounds. Maltitol-cored dendritic polymer was effectively synthesized and characterized using GPC, TG, UV–Visible, IR, and NMR techniques and also all the synthesized piperidine derivatives were characterized using LCMS, IR, and NMR techniques.     

Determination of some halogen osmium-carbonyl derivatives using ion-selective electrodes

Summary The concentrations of certain halogen derivatives of osmium carbonyls were determined potentiometrically by using a silver ion-selective electrode based potentiometric titration technique. In case of the series Os₃(CO)₁₂X₂, X= Cl, Br, I, inflections in the titration curves were at volumes of AgNO₃ corresponding to one halide ion. In contrast, the series Os₃(CO)₁₀X₂ gave inflections equivalent to two X^– ions. The concentrations of trans-Cl₂Os(CO)₄ as well as ClSnPh₃ were also determined by this technique. Standard deviations were in the range of 0.1%–0.37%, recoveries between 98% and 99.7%.

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Bestimmung einiger Halogenosmiumcarbonylverbindungen mit Hilfe von ionenselektiven Elektroden

     

Analysis of hydroquinone and some of its ethers by using capillary electrochromatography

Capillary electrochromatography (CEC) was used for the analysis of relevant compounds in cosmetic preparation. Hydroquinone (HQ) and some of its ethers (methyl-, dimethyl-, benzyl-, phenyl-, propyl-HQ derivatives) were analyzed by using an octadecylsilica (ODS) stationary phase packed in fused-silica capillary (100 microm I.D.; 30 cm and 21.5 cm total and effective lengths, respectively). 20 mM Ammonium acetate pH 6-acetonitrile (50-70%) were the mobile phases used for the experiments. The acetonitrile (ACN) content strongly influenced the resolution of the studied compounds as well as the efficiency and the retention factor. Baseline resolution for the studied analytes was achieved at both the lowest and the highest percentage of ACN, the last one providing the shortest analysis time. Mobile phase containing 70% of ACN was therefore used for the analysis of an extract of skin-toning cream declared to contain HQ. Good repeatability of both retention times, peak areas and peak areas ratio (Asample/Ainternational standard) was found. The calibration graphs were linear in the concentration range studied (5-90 microg/ml) with correlation coefficients between 0.9975 and 09991. The analysis of the cosmetic preparation revealed the presence of HQ (1.72%, w/w) and of two additional peaks (not identified).     

Assessment of the complexation degree of camptothecin derivatives and cyclodextrins using spectroscopic and separative methodologies

The complexation of camptothecin and homocamptothecin derivatives, topoisomerase I inhibitors, with two cyclodextrins (CDs) of pharmaceutical interest (native and hydroxypropylated β-CD) was studied at pH 3.5 and 6. In a first step, the affinity order of the six compounds studied for the β-CD and HP-β-CD was evaluated in HPLC using immobilized stationary phases [Cyclobond I 2000 (β-CD) and Cyclobond I 2000 RSP (HP-β-CD)]. In a second step, the apparent binding constants of the 12 complexes studied were determined at both pH by HPLC using Scott’s method with CD as a chiral additive. The 1:1 stoichiometry of the complex formed between HP-β-CD and the homocamptothecin derivative elomotecan (R)-6 was established by fluorescence spectroscopy using the continuous variation method developed by Job and ESI-MS. Complementary investigations were achieved for topotecan (S)-3 and elomotecan (R)-6 using CE. Further studies provided similar conclusions concerning affinity of all the derivatives studied for both CDs: that is, a slightly larger affinity was observed for HP-β-CD with respect to β-CD, except for (S)-3. For (S)-3, this affinity increase with pH, in the range studied.     

Enantioselective oxidative biaryl coupling reactions catalyzed by 1,5-diazadecalin metal complexes

[reaction: see text]. Chiral 1,5-diaza-cis-decalins have been examined as ligands in the enantioselective oxidative biaryl coupling of substituted 2-naphthol derivatives. Under the optimal conditions employing a 1,5-diaza-cis-decalin copper(I) iodide complex with oxygen as the oxidant, rapid and highly selective couplings could be achieved (90-93% ee, 85% yield).     

Novel one-pot synthesis of 4H-chromene derivatives using amino functionalized silica gel catalyst

A simple, efficient, and environmentally benign method for the synthesis of 4H-chromene derivatives was developed using well ordered and recoverable amino functionalized silica gel as a base catalyst. The 4H-chromene derivatives were obtained in short time and excellent yield(87%–96%) by three component reaction of aldehydes, malononitrile and cyclic 1,3-diketones in water at 70 8C.     

Oxytrifluoromethylation of multiple bonds using copper catalyst under mild conditions

Oxytrifluoromethylation reaction of styrene derivatives and alkynes with external and internal oxygen nucleophiles, catalyzed by copper (I) salts under mild conditions, was developed. Direct formation of a β-trifluoromethylstyrene derivative from a styrene derivative was also achieved by the reaction in the presence of a Brønsted acid. Further transformation of the oxytrifluoromethylated products was conducted to demonstrate their utility.     

Selective hydrogen transfer reactions from alcohols to ketones promoted by rhodium complexes with 1,10-phenanthroline and related ligands

Substituted cyclohexanones are effectively reduced to the corresponding alcohols using propan-2-ol as hydrogen source and Rh(I) complexes with 1,10-phenanthroline (phen) and substituted derivatives as catalyst precursors.Rh(I) derivatives with phen, 4,7-Ph₂phen and 4,7-Mc₂phen (chel/Rh ⩾ 2) promote the preferential formation of the axial alcohol (substrate = 4-t-butylcyclohexanone), while the 4,7-(MeO)₂phen derivative gives in higher yield the equatorial isomer. Hindered substrates such as 2-methylcyclohexanone and 3,3,5-Me₃cyclohexanone are reduced to the corresponding axial alcohol with a selectivity ⩾ 98% (chel = 4,7-Me₂phen).     

Amination of ethers using chloramine-T hydrate and a copper(I) catalyst

Amination of C-H bonds activated by ether oxygen atoms is facile with chloramine-T as nitrene source and copper(I) chloride in acetonitrile as catalyst. For cyclic ethers the hemiaminal products are generally stable and can be isolated pure. For acyclic ethers, the hemiaminal products, as expected, fragment with elimination of alcohol to yield imines. When activation of benzylic positions is remote through a conjugated system, stable benzylamine derivatives are isolated. Mechanistic studies are consistent with concerted insertion of an electrophilic nitrenoid into the C-H bond in the rate-determining step, though in an asynchronous manner with a more activated substrate.     

α-苯亚甲氨基苯甲基膦酸酯的1,3-偶极及其负离子的环加成反应

用α-苯亚甲氨基苯甲基膦酸酯与几种亲偶极物进行热及碱催化反应得到含磷酰基与不含磷酰基的加成产物,描述了产品的合成方法和立体化学测定,根据立体化学分析结果,可以认为反应是通过环加成的途径进行的.