Showing papers on "Xanthene published in 1995"

Transfer Hydrogenation of Nitro‐, Nitroso‐ and Azoarenes by Homolytic Retrodisproportionation

Abstract: Nitro-, nitroso- and azobenzene are reduced almost quantitatively to aniline when heated to 230–300°C with 9,10-dihydroanthracene (DHA), xanthene or tetralin. From the effect of polar substituents and polar solvents on the reactivity and from the isotope effect kH/kD ≈ 2.4 (280°C), a hydrogen-atom transfer from the H donor to the acceptor (retrodisproportionation) is proposed as the rate-determining step. The lower reactivity of xanthene compared with 9,10-dihydroanthracene eliminates the possibility of a rate-determining hydride transfer. The observation of an intense ESR signal of 9-xanthyl radicals during the reaction in diphenyl ether and the typical products support the proposed homolytic mechanism.

Conformation of xanthene dyes in the sulfhydryl 1 binding site of myosin. 2.

Abstract: The fluorescent dyes 5'-(iodoacetamido)tetramethylrhodamine (5'IATR) and 5'-(iodoacetamido)-fluorescein (5'IAF) bind covalently to the reactive sulfhydryl (SH1) of myosin subfragment 1 (S1), the 5'IATR as a dimer and the 5'IAF as a monomer. The conformation of the dimer and the dye-protein complex was investigated by comparison of several spectroscopic signals of the molecules before and after their association into a complex and interpretation of any changes using a coupled dipole oscillator model adapted for this problem [Burghardt & Ajtai (1995) Biophys. Chem. (submitted for publication)]. Absorption and fluorescence spectroscopies were performed on 5'IAF, 5'IATR, and rhodamine 6G (R6G) and rhodamine B (RB) as models of dimer conformation. Absorption, fluorescence, and circular dichroism (CD) spectroscopies were performed on 5'IATR-modified S1 (5'R-S1) and 5'IAF-modified S1 (5'F-S1). Combined spectroscopic and 2-D NMR data from rhodamines in solution determined the conformations of the dimers. Xanthene rings from dimers of identical dyes (homodimers) stacked in two structures having very different spectroscopic signatures. Xanthene rings from the heterodimer of R6G and RB stacked in one conformation. The two homodimer conformations of 5'IATR are equally likely to form in solution. The other rhodamine homodimers have one dominant, but not exclusive, structure. Both conformations of the 5'IATR dimer were coupled to a tryptophan as a model of the dye-protein interaction at SH1. The calculated CD from one dimer conformer (dimer A) coupled to tryptophan is negative for the lowest energy CD absorption band. The other dimer (dimer B) gives positive CD on the two lowest energy CD absorption bands. Both dimer structures of 5'IATR contributed to the early time-dependent CD signal from 5'IATR binding to SH1, but at equilibrium the CD signal indicated only dimer B, suggesting that the SH1 binding pocket converts dimer A into dimer B. The time-dependent CD signal from 5'IAF changes amplitude but not shape during the reaction with SH1. The model calculation accounting for the spectroscopic signals of 5'R-S1 and 5'F-S1 indicates several likely conformations of the 5'IATR dimer-tryptophan and 5'IAF-tryptophan complexes embedded in S1. These structures fit to the alpha-carbon structure of the SH1 binding pocket when the 5'IATR dimer and 5'IAF interact closely with Trp510 [Rayment et al. (1993) Science 261, 50-58].(ABSTRACT TRUNCATED AT 400 WORDS)

Echo FT-EPR Study of the Photochemical Reduction and Oxidation Reactions of 2,5-Di-t-butyl-1,4-benzoquinone and 2,5-Di-t-butylhydroquinone by Xanthene Dyes.

Abstract: Electron spin polarization has been studied in order to clarify the character of the short-lived radical-pair (RP) intermediates generated from the photosensitized reduction of 2,5-di-t-butyl-1,4-benzoquinone and the oxidation of 2,5-di-t-butylhydroquinone by xanthene dyes using FT-EPR spectroscopy. Unusual absorptive electron spin polarization and heavy atom effects were observed in a former photoreduction system, indicating the production of contact RP as the reaction intermediate. Absorptive polarization is created by sublevel selective back electron transfer in the triplet contact RP due to the spin-orbit coupling interaction. On the other hand, it has also been shown that for the photooxidation system a pure RP mechanism is operative to create spin polarization, suggesting the generation of a solvent separated RP as an intermediate. The reaction rate constants for electron transfer and hydrogen abstraction reactions were also determined by analyses of the time profile of the chemically induced electr...

Photochemical hydrogen evolution from alkaline solutions of xanthene dyes

Abstract: The effect of the composition of five xanthene dyes (photoabsorber and photosensitizer) on the hydrogen photoproduction from aqueous solutions was investigated. It is suggested that triethanolamine (TEOA) can quench the excited singlet state of fluorescein in aqueous solution (1 × 10−4 mol l−1, pH 12.5). As a result, a reduced form of fluorescein is produced, which can further reduce H+ to H2 in the presence of K2PtCl6 (5 × 10−5 mol l−1). The quantum yield of H2 photoproduction (ΦH2) is 0.024. For tetraiodofluorescein (erythrosin) in aqueous solution (1 × 10−4 mol l−1), pH 12.5; K2PtCl6, 5 × 10−5 mol l−1), ΦH2 is as high as 0.30 owing to the inner molecular heavy atom effect. The quantum yields of fluorescence and intersystem crossing, ΦF and ΦISC, were measured and compared with ΦH2 for all the investigated dyes. The results show an important ability of xanthene dyes to enhance hydrogen photoproduction from alkaline aqueous solutions.

Process for making xanthene or cubane based compounds, and protease inhibitors

Abstract: Methods for forming combinatorial libraries and the libraries produced thereby are provided. According to a preferred aspect of the invention, a plurality of core molecules, the core molecule being a xanthene or cubane derivative, are reacted with a plurality of different tool molecules to form a library of molecules having non-naturally occurring molecular diversity. The libraries are useful for identifying lead compounds which modulate the functional activity of a biological molecule. Protease inhibitors that have been isolated from the libraries also are disclosed.

Polymeric dye having xanthene skeleton and water-base ink composition containing this dye

Abstract: PURPOSE:To obtain the dye which shows a magenta color of high color tone when dissolved in water and is improved in solubility, storage stability and light resistance by chloro-sulfonating a xanthene dye and bonding the product of chloro-sulfonation with polyallylamine. CONSTITUTION:Acid Red of formula I is reacted with thionyl chloride in dimethylformamide to obtain a brown product of formula II. This product is reacted with a polyallylamine of formula III to obtain a polymeric dye comprising xanthene structural units of formula IV [wherein x is -(CH3)p- or -(CH3)p- CO-; R to R are each H or (un)substituted 1-4C alkyl; X and X are each sulfo or sulfonate; Y is carboxyl or carboxylate; k is 0-2; l+m=0-2; n is 20-300; and p is 0-5, provided that k and l are numbers which must not be 0 simultaneously].

9H‐xanthene‐2,7‐diols as antioxidants for autoxidation of linoleic acid

Abstract: The antioxidant activities of 9H-xanthene-2,7-diols and α-tocopherol were studied during the oxidation of linoleic acid in a homogeneous solution and in an aqueous micelle dispersion. The antioxidant activities of 9H-xanthene-2,7-diols for both systems were 1.0–2.4 times greater relative to α-tocopherol. In addition, the 1,3,4,5,6,8-hexamethylxanthene-2,7-diol showed less cytotoxicity toward human fibroblasts than did 2,6-di-t-butyl-4-methylphenol.

Antioxidant Activity of the Fused Heterocyclic Compounds, 9H-Xanthene-2, 7-diols

Abstract: 9H-Xanthene-2, 7-diols were shown to function well as hydrogen donor and suppress the oxidation of linoleic acid in homogeneous solution. In contrast to most other phenolic antioxidants these 9H-xanthene-2, 7-diols react with 26 peroxyl radicals per molecule and their antioxidant activities were close to that of α-tocopherol. The relationship of the antioxidant activity and electronic effects on stabilization of derived phenoxyl radicals were discussed.

Preparation of 1-Hydroxyxanthen-9(9H)-ones and 1-Hydroxyacridin-9(10H)-ones via Corresponding 3,4-Dihydro-1,9(2H)-diones

Abstract: Target 10-cyclopropyl-7-fluoro-1-hydroxy-6-(4-methyl-1-piperazinyl)acridin-9(10 H )-one ( IVc ) and 7-fluoro-1-hydroxy-6-(4-methyl-1-piperazinyl)-9 H -xanthen-9-one ( IVd ) were obtained from corresponding difluoro derivatives IVa and IVb , respectively. These intermediates were synthesized via respective 3,4-dihydro-1,9(2 H )-diones Va and Vb . Acridine derivative (10-cyclopropyl-6,7-difluoro-3,4-dihydro-1H-acridine-1,9(2H,10H)-dione, Va) was synthesized from 1-cyclopropyl-6,7-difluoroisatoic anhydride ( XI ) and xanthene derivative (6,7-difluoro-3,4-dihydro-1 H -xanthen-1,9(2 H )-dione, Vb ) from cyclohexenone derivative VIb . Several unsuccessful attempts to prepare hydroxyacridone IVc and/or some useful intermediates of its synthesis are also described.

Method for recovering phenol and xanthene values from waste polycarbonate

Abstract: Organic values are salvaged from scrap polycarbonate by heating in the presence of an acid catalyst and a C1-4 alkyl phenol such as m- or p-cresol. Among the compounds which can be salvaged are polyalkylated xanthenes, phenol and diaryl carbonate.

6'-Diethylamino-2'-nitrospiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one

Abstract: The title molecule, C 24 H 20 N 2 O 5 , is composed of two parts, namely, a butterfly-like xanthene moiety and an almost planar isobenzofuran fragment. The isobenzofuran plane is almost perpendicular to the two xanthene planes. The C−O bond length in the five-membered lactone ring is 1.487 (5) A, which is longer than the usual lactone C−O single-bond length

Fluorescence spectroscopy of monoclonal antibodies produced against the fluorescyl hapten conjugated through the xanthene ring.

Abstract: Two mouse anti-fluorescyl monoclonal antibodies (mAb), clones FL43.1 and FL55.3, were produced to the fluorescein hapten, which was conjugated to the carrier protein through the 4′ position of the xanthene ring. Association constants (K A) and thermodynamic parameters for both mAb were ascertained by monitoring the steady-state intrinsic and fluorescein fluorescence. Both techniques were in good agreement and gaveK A values in the 109 M −1 range. Ligand-induced intrinsic fluorescence quenching showed a hypsochromic shift for mAb FL43.1, but not for FL55.3, suggesting that the ligand interacts with different tryptophan residues in each mAb. Because these mAb are directed toward the phenylcarboxylate portion of fluorescein, the different ionic and structural forms should be useful as indicators of antibody binding site pH and buffering capacity near the binding site.

Reactive dyes useful for dyeing and printing e.g. cellulose, polyamide or polyester

Abstract: Reactive dyes of formula (I) F-(G-E-A-NMCN)n (I) which contain cyanamido-alkyl-carbonyl or -sulphonyl gp(s). are new where F = the radical of a mono-, dis- or poly-azo dye or its heavy metal complex or of an anthraquinone, phthalocyanine, formazan, azomethine, dioxazine, phenazine, stilbene, triphenylmethane, xanthene, thioxanthene, nitroaryl, napthoquinone, pyrenequinone or perylenetetracarbimide dye; G = a chemical bond; -NR - where R = H or 1-4C alkyl, or 1-8C alkylene, in which the chain may contain 1 or 2 -O-, -NH- and/or -NH-C6H4- gps.; E = -SO2- or -CO-; A = -CH2CH2)-, -CH(Me)CH2-, -CHX-CH2- or -CHX-CH(Me)- (X = Cl or Br); M = H, n alkali(ne earth) metal or ammonium gp.; n = 1-4.

Aziridines, 66 [1]. Arene Hydrides. 12 [2]. Reactions of carbanions with two sterically demanding 1-benzoylaziridines: SET, SN2, carbonyl attack†

Abstract: Reactions of 2-phenyl (1a) and 2-benzyl (1b) 1-benzoyl-2-butylaziridines with carbanions X−, AH−, and Fl− of xanthene, dihydroanthracene and fluorene always form N-(2-butylethyl)-benzamides carrying phenyl (9a) or benzyl (9b). This reductive ring opening indicates an SET mechanism with aziridino ketyls 6a, b as intermediates. Nucleophilic ring opening (SNs) is found only with the carbanion of the lowest reducing power: Fl− 5a, b (62%, 14%). These two mechanisms cleave different bonds, a finding without precedence in SN2/SET competitions. Carbonyl addition resulting in benzoyl transfer to xanthene, dihydroanthracene or fluorene is usually also observed. It is the main reaction with X− and 1a. The highest yields of 9a, b are obtained with AH− since a special inner-sphere SET is available.

Water-color ink and recording by using the same

Abstract: PURPOSE: To obtain a water-color ink having excellent discharging reliability and useful for a water-based writing tool or a pen plotter, etc., by including a coloring agent dispersible or soluble in water, water, an wetting agent and a specific chitosan derivative. CONSTITUTION: The water-color ink mainly composed of (A) a coloring agent dispersible or soluble in water (especially an acidic dye or a direct dye, etc., is preferable), (B) water and (C) a wetting agent contains (D) a chitosan derivative of formula I [D is a dye skeleton, preferably a xanthene-based dye skeleton of formula II (A is -SO2 - or-CO-; X is -SO3 or -COO ; R1 and R2 are each H, an alkyl or a halogen; (m) and (n) are each 0 or 1 not simultaneously 0) or a phthalocyanine-based dye skeleton of formula III (M is an alkali metal or an alkanolamine, etc.; Z is H, Cu or Ni, etc.; (n) is a natural number, (q) is an integer except 0 and 0<(p+q)<5), etc.

Process for continuously reacting organic dyestuffs containing amino groups with trifluorotriazine.

Abstract: Continuous reaction of an amino gp-contg. organic dye of formula D-NH-R (II) with 2,4,6-trifluoro-S-triazine (TFTZ) is effected by: (a) treating a cooled, neutral aq. soln. or suspension of (II) with a 1.0-2.0 fold molar amt. of buffer; and (b) supplying the prod., continuously, and simultaneously with TFTZ, to a reactor in which the two components are intensively mixed, dwell time in the reactor being 1-30 secs. In (II), D = sulpho gp-contg. mono- or polyazo, azo metal complex, anthraquinone, phthalocyanine, formazan, azomethine, dioxazine, phenazine, stilbene, triphenylmethane, xanthene, thioxanthone, nitroaryl, naphthoquinone, pyrenequinone or perylenetetracarboxamide dye; R = H or opt. substd. 1-4C alkyl. Pref.(II) is the copper formazan dye of formula (IIa), 3,6,8-trisulpho-2-(4-amino-2-ureidophenylazo)naphthalene trisodium salt or 3,4,8- or 3,6,8- trisulpho-2-(2-acetamido-4- aminophenylazo)naphthalene trisodium salt.

Reactive dyestuffs their preparation and their use

Abstract: Novel reactive dyes of the formula have been found in which D is the radical of an organic dye from the monoazo, polyazo, metal complex azo, anthraquinone, phthalocyanine, formazan, azomethine, dioxazine, phenazine, stilbene, triphenylmethane, xanthene, thioxanthone or nitroaryl series, and the remaining substituents have the meanings given in the description; and also a process for their preparation, and their use for the dyeing of fibre materials containing OH and NH groups.

Fiber-reactive dye, and its production and use

Abstract: Novel reactive dyes of the formula have been found in which D is the radical of an organic dye from the monoazo, polyazo, metal complex azo, anthraquinone, phthalocyanine, formazan, azomethine, dioxazine, phenazine, stilbene, triphenylmethane, xanthene, thioxanthone or nitroaryl series, and the remaining substituents have the meanings given in the description; and also a process for their preparation, and their use for the dyeing of fibre materials containing OH and NH groups.

Production of 3-n-monoalkylaminophenols

Abstract: PURPOSE:To produce the compound useful as an intermediate for pigments, dyes, herbicides, etc., in high purity by only reducing 3-N-monoacylaminophenols with lithium aluminum hydride. CONSTITUTION:3-N-Monoalkylaminophenols of formula II (e.g., 3-N- propylaminophenol) are obtained by only reducing 3-N-monoacylaminophenols (e.g. 3-N-propionylaminophenol) expressed by formula I (R is 1-3C straight-chain alkyl) with lithium aluminum hydride. The compound of formula I is obtained by reacting 3-aminophenol with a carboxylic acid of formula III. Especially, the reaction of 3-aminophenol with the carboxylic acid of formula III is carried out by heating reaction without using other acylating agent. The compound of formula II is an industrially extremely important compound as an intermediate for pressure-sensitive and heat-sensitive pigments, xanthene-based dyes, aqueous hair dyes, herbicides and metal coloring reagents.