Synthesis of some new 4-imino-3,5,7-trisubstituted-pyrido[2,3-d]pyrimidine-2(1H)-thiones

The synthesis of 4-imino-3,5,7-trisubstituted-pyrido[2,3-d]pyrimidine-2(1H)-thiones is described. The elemental analysis, ir and nmr spectral data confirm the structure of the products.     

Analysis of certain mixtures ofα-Amino acids

Summary -Amino acids are determined by reaction with perinaphthindan-2,3,4-trione hydrate to form dihydroxyperinaphthindenone which is titrated with chloramine-T in the presence of acidified bromide and methyl red. The thiol group of cysteine is blocked by cyano-ethylation before determination. Some amino acids can be directly titrated with chloramine-T in the presence of bromide and methyl red, e. g., cysteine (after cyanoethylation), methionine and lanthionine, or in the presence of iodide and starch, e. g., cysteine (after tetrathionate reaction) when concomitant amino acids do not interfere. These methods are used to analyze model mixtures of cysteine with serine, methionine with glycine and cysteine with methionine.

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Analyse bestimmter Gemische von -Aminosäuren

Zusammenfassung -Aminosäuren werden mit Peri-Naphthindan-2,3,4-trion-hydrat umgesetzt, wobei sich Dihydroxyperinaphthindenon bildet, das mit Chloramin T in der Gegenwart von angesäuertem Bromid und Methylrot titriert wird. Die Thiolgruppe des Cysteins wird vor der Bestimmung durch Cyanoäthylierung blockiert. Manche Aminosäuren können unmittelbar mit Chloramin T in der Gegenwart von Bromid und Methylrot titriert werden, z. B. Cystein (nach Cyanoäthylierung), Methionin und Lanthionin, oder in Gegenwart von Jodid und Stärke Cystein (nach Umsetzung mit Tetrathionat), wenn die begleitende Aminosäure nicht stört. Diese Verfahren wurden benutzt, um Modellgemische von Cystein mit Serin, Methionin mit Glycin und Cystein mit Methionin zu analysieren.

     

Alkalimetric determination of mercaptans through trithiocarbonic acid formation

A simple and rapid alkalimetric method for the determination of mercaptans through trithiocarbonic acid formation is described. The mercaptans are titrated in tert.-butanol in the presence of carbon disulphide with standard aqueous sodium hydroxide, with phenolphthalein as indicator. The -SH group is smoothly, rapidly and quantitatively transformed into the group under the specified conditions. The method has been extended to the analysis of mercaptan-carboxylic acid and mercaptan-trithiocarbonate mixtures.     

Use of HPTLC,HPLC, and Densitometry for Qualitative Separation of Indole Alkaloids from Rauvolfia serpentina Roots

JPC – Journal of Planar Chromatography – Modern TLC - High-performance thin-layer chromatography (HPTLC) has been used for normal-phase separation of the components of hexane,...     

Zirconium(IV) fluorosulphates : Preparation and characterization

Zr(SO₃F)₄, (A); ZrO(SO₃F)₂, (B); Zr(O₂CCH₃)₂, (SO₃F)₂, (C); and Zr(O₂CCH₃)₃SO₃F, (D) have been prepared and characterized (elemental analysis,i.r. Spectra and thermal analysis). The SO₃F groups are bidentate in (A) – (C) but have C_3V symmetry in D where all the three oxygen atoms of SO₃F group are coordinated in an equivalent manner. (A) – (D) are good Lewis acids and form coordination complexes with pyridine, triphenylphosphine oxide and 2,2′-bipyridyl. The thermal decomposition of the fluorosulphates is complex.     

ENERGETICS OF DNA REPAIR IN UV-IRRADIATED PERIPHERAL BLOOD LEUKOCYTES FROM CHRONIC MYELOID LEUKAEMIA PATIENTS

Abstract— The relationship between energy metabolism and UV-induced (251 nm) DNA repair has been investigated in leukocytes obtained from peripheral blood of chronic myeloid leukaemia patients. Energy supply was modulated by using inhibitors of respiratory (antimvcin-A) and glycolytic (2-deoxy-o-glucose and other glucose analogues) pathways for adenosine-triphosphatc (ATP) production. DNA repair was measured by the unscheduled DNA synthesis technique. Parameters of energy metabolism like glucose utilization. lactate production and ATP content of cells. were measured under similar experimental conditions. The observations made indicate the following results: (1) ATP for DNA repair can be supplied by the respiratory and/or by the glycolytic pathway. (2) In the absence of respiration, the rate of glycolysis bears a linear correlation with DNA repair. (3) A minimum threshold rate of ATP-production is necessary for DNA repair.     

A simple and reliable semipreparative high-performance liquid chromatography technique for the isolation of marker-grade hyperforin from Hypericum perforatum L extract

The present work describes isolation of bioactive lipophilic constituent [namely, hyperforin from St. John's wort (Hypericum perforatum L.)], of approximately 98% purity by semipreparative high-performance liquid chromatography (LC). The extraction, isolation, and analysis of the collected compound is performed without the use of antioxidants and inert gas atmospheres at all the stages. Hyperforin, separated isocratically on a 12microm semiprep column, is obtained in high purity, lyophilized after the removal of the organic phase, and preserved at a low temperature. The purity of the collected marker compound is estimated by the use of LC-mass spectrometry and spectroscopic techniques.     

o-Iodosobenzoate as an oxidimetric titrant

o-Iodosobenzoate has been used as a titrant at pH 7 with potassium iodide and starch as indicator, under Andrews' titration conditions with iodine monochloride as preoxidant, and in acid medium with potassium bromide and Methyl Red as indicator. Methods are described for the determination of tetrathionate (through disulphide cleavage by cysteine), hydrogen sulphite, thiosulphate, xanthates, cysteine and glutathione in certain combinations (involving masking of sulphite and thiols with acrylonitrile). Hexacyanoferrate(II) is determined in the presence of arsenic(III), antimony(III) and thallium(I). Sulphathiazole, sulphadiazine and sulphamerazine consume six equivalents of bromine per mole, but phthalation or diazotization of the aromatic amino group prevents disubstitution of bromine in the benzene ring. Chloramphenicol is determined by reduction of its aromatic nitro group to an amino group, followed by bromination. Rutin and vitamin C react with eight and two equivalents of bromine per mole respectively.     

Determination of bromine in organic compounds by high-performance liquid chromatography

A method is proposed for the determination of bromine in organic compounds (which may also contain chlorine and iodine) by oxygen-flask combustion of the compound followed by pre-column reaction of bromide with acetanilide and 2-iodosobenzoic acid to form 4-bromoacetanilide which is then chromatographed on an ODS column with a mobile phase of methanol: water, 65:35 v/v, detection at 240 nm, and 4-N-acetylaminotoluene as internal standard. The method is rapid and precise (RSD 相似文献   

Determination of thiourea and its organic derivatives with iodine trichloride

Thiourea and its organic derivatives and thiosemicarbazide are determined in water, methanol or glacial acetic acid medium by reaction with an excess of iodine trichloride in the presence of mercuric chloride. The reaction is complete in 15 min. The excess of iodine trichloride is evaluated by adding potassium iodide and titrating the liberated iodine with thiosulphate. A variety of organic thioureas can be determined with an average accuracy and precision of 0.2%.