Chemiluminescence Determination of Gossypol by Oxidation with N‐Bromosuccinimide

A chemiluminescence (CL) phenomenon was observed when gossypol was injected into a reaction mixture of N‐bromosuccinimide (NBS) and alkaline dichlorofluorescein (DCF). Based on this phenomenon, a rapid and sensitive method for the determination of gossypol was established. Under the optimum conditions, the linear range was from 1.0 × 10^?9 to 1.0 × 10^?6 M. The detection limit was 1.0 × 10^?10 M. The method has been applied to the determination of gossypol in cottonseed, cottonseed oil, pharmaceutical and biological fluids with satisfactory results. The possible CL reaction mechanism was discussed briefly.     

Oxidation of 2‐Phenylethylamine with N‐Bromosuccinimide in Acid and Alkaline Media: A Kinetic and Mechanistic Study

A kinetic study of oxidation of 2‐phenylethylamine (PEA), a bioactive compound, with potent oxidant, N‐bromosuccinimide (NBS) has been carried out in HCl and NaOH media at 313 K. The experimental rate laws obtained are: ‐d [NBS] /dt = k[NBS][PEA][H⁺] in hydrochloric acid medium and ‐d [NBS]/dt = k[NBS][PEA]^x[OH^?]^y in alkaline medium where x and y are less than unity. Accelerating effect of [Cl^?], and retardation of the added succinimide on the reaction rate have been observed in acid medium. Variation of ionic strength of the medium shows negligible effect on rate of reaction in both media. Decrease in dielectric permittivity of the medium decreased the rate in both media. The stoichiometry of the reaction was found to be 1:1 in acid medium and 1:2 in the case of alkaline medium. The oxidation products of PEA were identified as the corresponding aldehyde and nitrile in acid and alkaline medium, respectively. The reactions were studied at different temperatures and the activation parameters have been evaluated. The reaction constants involved in the proposed mechanisms were computed. The reaction was found to be faster in alkaline medium in comparison with the acid medium, which is attributed to the involvement of different oxidizing species. The proposed mechanisms and the derived rate laws are consistent with the observed experimental results.     

磺基水杨酸紫外导数分光光度法测定微量铁

在不同ｐＨ下铁－磺基水杨酸形成组成比不同的配合物，其紫外吸收光谱也不同，在ｐＨ５～７的六次甲基四胺－盐酸介质中形成１：２配合物，最大吸收波长λｍａｘ２４８ｎｍ表观摩尔吸光系数ε＝２．９×１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１比可见光区的灵敏度高１０倍，用三阶导数光谱法测定化学试剂中微量铁，结果与邻二氮菲法一致，相对标准偏差１．２％。     

N‐Bromosuccinimide (NBS): A Mild and Efficient Catalyst for Tetrahydropyranylation of Alcohols and Phenols under Solvent‐Free Conditions

Different types of alcohols and phenols are tetrahydropyranylated in the presence of NBS catalyst in good to excellent yields under mild, neutral and solvent‐free conditions.     

Preconcentration and Quantitative Determination of Esomeprazole Magnesium Present in Water

A simple, accurate, and sensitive preconcentration method for determination of esomeprazole magnesium in treated sewage water was developed based on HPLC. A preconcentration method was developed for aqueous solution containing pure drug using solid phase extraction. Macroporous beads of polystyrene divinyl benzene (PSDVB) polymer were used for preconcentration followed by chromatographic determination. Experimental parameters were optimized. This optimized method can detect esomeprazole magnesium concentration up to 0.003 mg L^?1 after preconcentration. This method was used for determination of esomeprazole magnesium in water collected from a sewage treatment facility. Esomeprazole magnesium could not be detected in the treated sewage water sample collected for the study.     

N‐Bromosuccinimide (NBS): A Novel and Efficient Catalyst for the Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐Free Conditions

A novel procedure for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes through one‐pot condensation of naphthalen‐2‐ol with arenecarbaldehydes in the presence of N‐bromosuccinimide (NBS) as catalyst under solvent‐free conditions is described.     

1,8‐Diazabicyclo[5.4.0]undec‐7‐ene: A Remarkable Base in the Debromination of 4‐ or 5‐Substituted N‐Benzyl α‐Bromo‐α‐p‐Toluenesulfonylglutarimide

Debromination of N‐benzyl 4‐ or 5‐substituted α‐bromo‐α‐p‐toluenesulfonylglutarimides is achieved with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) to give the N‐benzyl 4‐ or 5‐substituted α‐p‐toluenesulfonylglutarimides. The DBU/THF system is applied to a new methodology for the synthesis of bicyclic glutarimide skeleton in moderate yields.     

NBS‐Promoted Rearrangement of 1,1‐Diarylmethylenecyclopentane

The 1‐aroyl‐1‐aryl‐2‐bromocyclopentanes 3a , 3b , 3c and 3d (Ar = C₆H₅, 2‐FC₆H₄, 3‐FC₆H₄, 4‐FC₆H₄) were prepared from N‐bromosuccinimide (NBS)‐promoted rearrangement of 1,1‐diarylmethylenecyclopentane 2 . The possible mechanism was proposed. Two 1‐phenyl‐cyclopentane carbamides 5a and 5b with the anti‐influenza effect were also accomplished from compound 3a .     

The Synthesis of Some New N‐[1‐(2,5‐Dichlorophenyl)‐5‐Methyl‐1,2,3‐Triazol‐4‐yl]‐Carbamic Acid Ester Derivatives

The synthesis of some new N‐[1‐(2,5‐dichlorophenyl)‐5‐methyl‐1,2,3‐triazol‐4‐yl]‐carbamic acid ester derivatives are reported in this paper. The yielded products 6a‐l were confirmed by Elemental analyses, NMR, MS, and IR spectra.     

紫外光谱法同时测定强力霉素废水中磺基水杨酸与对甲基苯磺酸

强力霉素是以土霉素为原料经过氯代、脱水、氢化成盐、置换多步化学反应后,再经过净化、脱色、过滤、结晶、干燥而制成的一种广谱抗生素[1]。其生产原料品种多,工艺复杂,生产废水色度深、浓度高、毒性大、含盐量高[2]。磺基水杨酸与对甲基苯磺酸是强力霉素废水中两种主要污染物     

Kinetic Spectrophotometric Determination of Metoprolol Tartrate in Commercial Dosage Forms

A kinetic spectrophotometric method has been described for the determination of metoprolol tartrate in commercial dosage forms. The procedure is based on the reaction of the drug with 1‐chloro‐2, 4‐dinitrobenzene (CDNB) in dimethylsulfoxide (DMSO) at 100 ± 1 °C. The reaction is investigated by measuring the change in absorbance with time at 420 nm. Fixed‐time (ΔA) and equilibrium methods are chosen for obtaining the calibration curves. Both calibration curves were found to be linear over the concentration range of 5‐60 μg mL^?1. The regression analysis of calibration data resulted in the linear regression equations of ΔA = ?1.608 × 10^?4 + 3.96 × 10^?3 C and A = 7.31 × 10^?4 + 1.90 × 10^?2 C for fixed time (ΔA) and equilibrium methods, respectively. The limit of detection (LOD) for fixed time and equilibrium methods are 1.16 and 0.415 μg mL^?1, respectively. The method has been successfully applied to the quantitation of metoprolol tartrate in commercial dosage forms. Statistical comparison of the results shows that there is no significant difference between the proposed methods and El‐Ries's spectrophotometric method.     

Spectrophotometric Study of Isoniazid by Using 1,2‐Naphthoquinone‐4‐Sulfonic Acid Sodium as the Chemical Derivative Chromogenic Reagent

A new method for the determination of isoniazid by using 1,2‐naphthoquinone‐4‐sulfonic sodium as the chemical derivative chromogenic reagent is established. The method is based on a condensation reaction to measure the pink compound produced by the reaction of isoniazid with 1,2‐naphthoquinone‐4‐sulfonic sodium in pH 13.00 buffer solution. The stoichiometric ratio of the compound is 1:1, and its maximum absorption wavelength is at 460 nm, ? = 1.18 × 10⁴ L·mol^?1 cm^?1. Beer's law is perfectly obeyed in the range of 0.50?30 μg.mL^?1 of isoniazid. The linear regression equation is A = 0.0185 + 0.11056C (mol.L^?1), with 0.9994 of a linear regression correlation. The detection limit is 0.40 μg.mL^?1, RSD is 0.48%, and average recovery is over 99.3%. This paper further optimizes the determination of isoniazid compared to the previous methods, and the kinetic property and reaction mechanism are studied intensively. This proposed method has been successfully applied to the determination of isoniazid in tablets of isoniazid with satisfactory results.     

Preparation of N‐Fmoc‐Protected (S)‐5‐Amino‐4,4‐difluoro‐7‐methyloctanoic Acid,a Possible Dipeptide Isostere

The title compound 1 was prepared from L ‐leucine. The key steps include a Grignard addition to Bn₂‐leucinal, a CO/CF₂ replacement with Et₂NSF₃ (DAST) and use of a Ph group as synthetic equivalent of a COOH group. The difluoro‐δ‐amino acid 1 was incorporated into a peptide 8 ; tests with various proteases showed no inhibition by this particular peptide.     

A Spectrophotometric Investigation of the Interaction of Iodine with Dibenzyldiaza‐18‐crown‐6, Aza‐15‐crown‐5 and N‐phenylaza‐15‐crown‐5 in Chloroform Solution

The complex formation reactions between iodine and DBzDA18C6, A15C5 and N‐phenylA15C5 have been studied spectrophotometrically in chloroform solution. In the case of DBzDA18C6 is the resulting 1:2 (ligand…I⁺)I₃^?, while, in the case of A15C5 and N‐phenylA15C5 a 2:2 molecular complex of [(ligand)₂…I⁺]I₃^? type was formed. The spectrophotometric results indicate that gradual release of triiodide ion from its contact ion paired form in the molecular complex into the solution is the rate‐determining step of the reaction. The kinetic rate constants for the complexation reactions were determined at different temperatures, and activation parameters were calculated from Arrhenius and Eyring equations.     

2‐Aminocyclopentene‐1‐Dithiocarboxylic Acid‐Naphthalene Adsorbent for the Preconcentration and Determination of a Trace Copper in Real Samples by Spectrophotometric Method

A solid uncharged complex produced from 2‐aminocyclopentene‐1‐dithiocarboxylic acid (synthetic reagent) on naphthalene provides a very sensitive, selective and economical method for the preconcentration and determination of trace amounts of copper in drug and alloy samples. The 2‐aminocyclopentene‐1‐dithiocarboxylate of copper is retained quantitatively on microcrystalline naphthalene in the pH range 2.8–3.3. After filtration the solid mass consisting of copper complex‐naphthalene is dissolved with 4 mL of dimethylformamide (DMF). The absorbance is measured at 462 nm with a spectrophotometer against the reagent blank and molar absorptivity found to be 2.8 × 10⁵ liter mol^?1 cm^?1. Beer's law is obeyed over the concentration range of 0.1–16.0 μg of copper in 4 mL of the dimethylformamide solution. Detection limit is 3 ng mL^?1 [signal to noise ratio = 2]. Ten replicate determinations on a sample containing 1 μg of copper gave a relative standard deviation of 0.76%. The interference of a large number of anions and cations have been studied and the optimized conditions developed were utilized for determination of copper in various real samples.     

MALDI‐MS profiling of serum O‐glycosylation and N‐glycosylation in COG5‐CDG

Congenital disorders of glycosylation (CDG) are due to defective glycosylation of glycoconjugates. Conserved oligomeric Golgi (COG)‐CDG are genetic diseases due to defects of the COG complex subunits 1–8 causing N‐glycan and O‐glycan processing abnormalities. In COG‐CDG, isoelectric focusing separation of undersialylated glycoforms of serum transferrin and apolipoprotein C‐III (apoC‐III) allows to detect N‐glycosylation and O‐glycosylation defects, respectively. COG5‐CDG (COG5 subunit deficiency) is a multisystem disease with dysmorphic features, intellectual disability of variable degree, seizures, acquired microcephaly, sensory defects and autistic behavior. We applied matrix‐assisted laser desorption/ionization‐MS for a high‐throughput screening of differential serum O‐glycoform and N‐ glycoform in five patients with COG5‐CDG. When compared with age‐matched controls, COG5‐CDG showed a significant increase of apoC‐III_0a (aglycosylated glycoform), whereas apoC‐III₁ (mono‐sialylated glycoform) decreased significantly. Serum N‐glycome of COG5‐CDG patients was characterized by the relative abundance of undersialylated and undergalactosylated biantennary and triantennary glycans as well as slight increase of high‐mannose structures and hybrid glycans. Using advanced and well‐established MS‐based approaches, the present findings reveal novel aspects on O‐glycan and N‐glycan profiling in COG5‐CDG patients, thus providing an increase of current knowledge on glycosylation defects caused by impairment of COG subunits, in support of clinical diagnosis. Copyright © 2017 John Wiley & Sons, Ltd.     

Determination of 5‐Aminosalicylic Acid by Catalase‐Peroxidase Based Biosensor

5‐Aminosalicylic acid is an antiinflammatory drug used to treat inflammation of the digestive tract (Crohn's disease) and mild to moderate ulcerative‐colitis. 5‐Aminosalicylic acid is a bowel‐specific aminosalicylate drug. It was developed an amperometric biosensor for determination of 5‐aminosalicylic acid concentration and measurement technique is based on substrate‐competition. The biosensor is more suitable especially for routine 5‐aminosalicylic acid analysis because it is simple to construct and sensitive, specific and does not require any expensive apparatus. This enzyme based biosensor was made with a couple of enzymes which uses the same substrate. The electrode was developed to determine measurement conditions and also characterized.     

Polymerization of conjugated 5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine with rhodium and palladium complexes

The monomer 5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine was satisfactory obtained through the heterocoupling reaction of 5‐ethynyl‐N,N‐dimethylnaphthalen‐1‐amine and 4‐(5‐iodo‐1‐naphthyl)‐2‐methyl‐3‐butyn‐2‐ol catalyzed by a palladium–copper system, followed by acetone elimination. Poly{5‐[(5‐ethynyl‐1‐naphthyl)ethynyl]‐N,N‐dimethylnaphthalen‐1‐amine} was obtained through the reaction of the acetylene monomer with homogeneous rhodium and palladium catalyst complexes. The structure of the polymers always showed a trans–cisoidal chain configuration on the basis of IR and NMR spectra. Moreover, only for the rhodium catalyst complex in methanol was a dimeric product isolated in a very low yield, having a conjugated terminal ene–yne structure, which permitted the consideration of a metallated chain‐transfer intermediate in the polymer propagation. The mass determination of the polymers, by osmometry and gel permeation chromatography techniques, showed low average molecular weights. The kinetics of the catalyzed polymerization were analyzed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2038–2047, 2007     

Preparation of Silyl Ethers Using Hexamethyldisilazane in the Presence of N‐Bromosuccinimide under Mild and Solvent‐Free Conditions

A mild, simple, novel and highly efficient method for the rapid protection of various primary, secondary, tertiary aliphatic and aromatic alcohols using hexamethyldisilazane (HMDS) in the presence of N-bromosuccinimide (NBS) as an active, inexpensive, non-toxic and readily available catalyst under solvent-free conditions is described. Trimethylsilyl ethers were prepared in high to excellent yields with short reaction time under mild and almost neutral reaction conditions.     

Metal‐binding Sites of N‐Acetylneuraminic Acid

Sialic acid represents a group of thirty derivates of neuraminic acid with various substituents at the amino residue and the alcoholic hydroxy groups. We analysed the behaviour of the tetracoordinated metal ions palladium(II) and silicon(IV) against the most important derivative N‐acetylneuraminic acid (NANA). The molecular structures were assigned by a combined ¹H, ¹³C and ²⁹Si NMR‐spectroscopic approach. Despite the presence of many different functional groups, the coordination chemistry of NANA with Pd^II follows established rules. Coordination via the N‐acetyl‐group – sterically impossible with Pd^II – was realised with Si^IV.