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71.
Krishna C. Joshi Renuka Jain Anshu Dandia Vandana Sharma 《Journal of heterocyclic chemistry》1986,23(1):97-99
A novel system 2-oxo-1′,2′,4′,5′-tetrahydrospiro[3H-indole-3,3′-1,2,4,5-tetrazine]-6′-thione has been synthesized by the treatment of fluorinated isatins with thiocarbohydrazide in aqueous ethanolic medium. Under exactly similar conditions, N-acetylisatin gave exclusively thiocarbohydrazone. The spiro product, on treatment with acetic acid, gave fluorinated isoindigo. Characterization of these products have been done by elemental analyses, ir, pmr and mass spectral studies. 相似文献
72.
Kailash C. Malhotra Brij Bala Neeraj Sharma Subhash C. Chaudhry 《Transition Metal Chemistry》1995,20(4):388-390
Summary Complexes of composition [VOCl2(OC6H4Bu-t-4)] (1) and [VOCl(OC6H4Bu-t-4)2] (2) have been synthesized by the reaction of VOCl3 with equimolar and bimolar amounts, respectively, of 4-t-BuC6H4OSiMe3 in CCl4 and characterized by physio-chemical techniques. The complexes react with -hydroxyaldehydes and ketones such as 2-hydroxybenzaldehyde (salicylaldehyde, salH), and 2-hydroxy-2-phenylacetophenone (benzoin, benzH), 2-hydroxyacetophenone (hapH) and also with the potassium salt of p-chlorobenzohydroxamic acid (KBHACl) in 11 and 12 molar ratios, to yield five- and six-coordinate complexes. 相似文献
73.
Manoj P. Samant 《Tetrahedron letters》2007,48(29):5107-5110
We report the synthesis of racemic Alloc-Ncy(Tmob)-OH, the resolution of its methyl ester and demonstrate its application to form a norcystine bridge in octreotide-amide using the Fmoc strategy on solid phase. N-Alloc and S-Tmob protections of norcysteine (Ncy) were found to be a preferred choice for Fmoc strategy over three other protected norcysteines synthesized, that is, Fmoc-Ncy(tBu)-OH, Alloc-Ncy(tBu)-OH, and Alloc-Ncy(Trt)-OH. 相似文献
74.
Schmidt DL Brady RF Lam K Schmidt DC Chaudhury MK 《Langmuir : the ACS journal of surfaces and colloids》2004,20(7):2830-2836
Adhesive and marine biofouling release properties of coatings containing surface-oriented perfluoroalkyl groups were investigated. These coatings were prepared by cross-linking a copolymer of 1H,1H,2H,2H-heptadecafluorodecyl acrylate and acrylic acid with a copolymer of poly(2-isopropenyl-2-oxazoline) and methyl methacrylate at different molar ratios. The relationships between contact angle, contact angle hysteresis, adhesion, and marine biofouling were studied. Adhesion was determined by peel tests using pressure-sensitive adhesives. The chemical nature of the surfaces was studied by using X-ray photoelectron spectroscopy. Resistance to marine biofouling of an optimized coating was studied by immersion in seawater and compared to previous, less optimized coatings. The adhesive release properties of the coatings did not correlate well with the surface energies of the coatings estimated from the static and advancing contact angles nor with the amount of fluorine present on the surface. The adhesive properties of the surfaces, however, show a correlation with water receding contact angles and contact angle hysteresis (or wetting hysteresis) resulting from surface penetration and surface reconstruction. Coatings having the best release properties had both the highest cross-link density and the lowest contact angle hysteresis. An optimized coating exhibited unprecedented resistance to marine biofouling. Water contact angle hysteresis appears to correlate with marine biofouling resistance. 相似文献
75.
Densities and apparent molar volumes of aqueous 2-chloroethanol were determined at temperatures from 15.0 to 34.4°C using digital densimetry. The results of the volumetric measurements have been used to calculate the following thermodynamic quantites at 25°C: V
2
o = 55.05 ± 0.02 cm3-mol–1, (V
2
o/T)p = 0.01486 ± 0.00318 cm3-K–1-mol–1, and (2
V
2
o/T
2)p = 0.02972 ± 0.00318 cm3-K–2-mol–1. Partial molar volumes of transfer from water to 1 mol-dm–3 2-chloroethanol have also been determined for L-glycine, L-alanine, L-serine, L-glutamic acid, and L-aspartic acid at 35.0°C. The transfer results have been explained in terms of the nature of the interactions of the groups in the solute and solvent. Hydration numbers of L-glycine and L-alanine have also been calculated in aqueous 2-chloroethanol. 相似文献
76.
It is shown that the long-lived transient absorption which is observed when solutions of cryptocyanine and DDI (1, 1′-diethyl-2, 2′-dicarbocyanine iodide) in methanol and other alcohols are exposed to nanosecond ruby laser pulses arises from a photoproduct whose formation requires consecutive absorption of two photons. 相似文献
77.
We have used fluorescence quenching of tryptophan-containing trans-membrane peptides by bromine-containing phospholipids to study the specificity of peptide-lipid interactions. We have synthesized peptides Ac-K2GLm WLnK2A-amide where m = 7 and n = 9 (L16) and m = 10 and n = 12 (L22). Binding constants of L22 for dioleoylphosphatidylserine [di(C18 : 1)PS] or dioleoylphosphatidic acid [di(C18 : 1)PA] relative to dieoleoylphosphatidylcholine [di(C18 : 1)PC] were close to 1. However, for L16, whilst the bulk of the di(C18 : 1)PA molecules bound with a binding constant relative to di(C18 : 1)PC close to 1, a small number of di(C18 : 1)PA molecules bound much more strongly. Assuming just one high affinity binding site on L16 for anionic lipid, the affinity of the site for di(C18 : 1)PS was calculated to be ca. 8 times that for di (C18 : 1)PC. The relative binding constant was little affected by ionic strength and close contact between the anionic headgroup of di(C18 : 1)PS and a lysine residue on the peptide was suggested. The relative binding constant for di(C18 : 1)PS at this high affinity site was less than for di(C18 : 1)PA. Cholesterol interacts with L22 with an affinity about 0.7 of that of di(C18 : 1)PC. The structure of the peptide itself is important. The peptide Ac-KKGYL6WL8YKKA-amide (Y2L14) incorporated into bilayers of dinervonylphosphatidylcholine [di(C24 : 1)PC] whereas L16 did not incorporate into this lipid. It is suggested that thinning of a lipid bilayer around a peptide to give optimal hydrophobic matching is less energetically unfavourable when a Tyr residue is located in the lipid/water interfacial region. 相似文献
78.
Bozlee BJ Misra AK Sharma SK Ingram M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(10):2342-2348
In the present study, we investigated remote laser-induced fluorescence (LIF), at a distance of 4.8 m, of a variety of natural minerals and rocks, and Hawaiian Ti (Cordyline terminalis) plant leaves. These minerals included calcite cleavage, calcite onex and calcite travertine, gypsum, fluorapatite, Dover flint and chalk, chalcedony and nephelene syenite, and rubies containing rock. Pulsed laser excitation of the samples at 355 and 266 nm often resulted in strong fluorescence. The LIF bands in the violet-blue region at approximately 413 and approximately 437 nm were observed only in the spectrum of calcite cleavage. The green LIF bands with band maxima in the narrow range of approximately 501-504 nm were observed in the spectra of all the minerals with the exception of the nephelene syenite and ruby rocks. The LIF red bands were observed in the range approximately 685-711 nm in all samples. Excitation with 532 nm wavelength laser gave broad but relatively low fluorescence background in the low-frequency region of the Raman spectra of these minerals. One microsecond signal gating was effective in removing nearly all background fluorescence (with peak at approximately 610 nm) from calcite cleavage Raman spectra, indicating that the fluorescence was probably from long-lifetime inorganic phosphorescence. 相似文献
79.
Ajay K. Bose Subhendu N. Ganguly Maghar S. Manhas Vaidyanathan Srirajan Ashoke Bhattacharjee Sochanchingwung Rumthao Anju H. Sharma 《Tetrahedron letters》2004,45(6):1179-1181
A novel dinitro secondary metabolite, 2-nitro-4-(2′-nitroethenyl)phenol from a marine source, has been prepared via highly accelerated, microwave assisted, nitration reactions using mild reagents. ipso-Substitution of a carboxy group by a nitro group is discussed. 相似文献
80.
Solubilities and the solvolytic behaviour of various inorganic compounds, Lewis acids and bases in fused monobromoacetic acid at 60 ± 0.5°C are discussed. Ionic compounds are fairly soluble, iodides and thiocyanates being comparatively more soluble than chlorides and bromides. Tetraalkyl ammonium halides are highly soluble in this solvent. Conductometric and spectroscopic studies of various Lewis acids and bases in fused monobromoacetic acid indicate their solvolytic behaviour and their subsequent ionization. The solvolyses products BBr3·CH2BrCOOH and SbCl5·CH2BrCOOH have been observed to be the strongest Bronsted acids. Auto-ionization of this solvent has been supported by acid/base titrations. 相似文献