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51.
The solid-phase synthesis of the octapeptide 1 AcGly-Ala-Lys-Arg-His-Arg-Lys-ValOMe, which represents the fragment 14-21 of the amino acid sequence of the chromosomal histone H4, as well as of the structurally related nonapeptide 2 AcGly-Ala-Lys-Leu-Arg-His-Arg-Lys-ValOMe, is described using a new polyacrylic resin containing a glycolamide ester linkage(resin-NHCO-CH2-OCO-peptide) acting as a labile anchoring moiety between the resin and the peptide.After elongation of the polypeptide chain using classical protecting groups, i.e. t-butyloxycarbonyl for the α-NH2 function, benzyloxycarbonyl, nitro and 2,4-dinitrophenyl groups for the side-chains of Lys, Arg and His respectively, both peptides 1 and 2 were obtained in good yields and with a high purity as shown by high-pressure liquid chromatography, by amino-acid analysis and by high-field proton NMR spectroscopy.This work demonstrates the ability of the newly introduced polyacrylic resin to act as a convenient support for solid-phase peptide synthesis. 相似文献
52.
Hydrazinoethyl phosphoric monoester has been prepared by reacting hydrazinoethanol with polyphosphoric acid, and isolated as di-sodium salt. Sodium hydrazinoethyl phosphate reacts with phenylisothiocyanate (in H2O+ethanol) to yield mainly the derivative thiocarbamoylated at the substituted nitrogen atom. This derivative, heated for one night at 100° in 0.5 N HCl, is cyclized to 3-amino-2-phenylimino-thiazolidine in 62% yield. Sodium hydrazinoethyl phosphate reacts with o-methoxycarbonylphenyl isothiocyanate (in H2O+dioxane) at the unsubstituted nitrogen atom to yield mainly the corresponding quinazoline derivative (IV, X = OPO3Na2). This derivative, heated for one night at 100° in 0.5 N HCl, is cyclized to 2-o-carboxyphenylamino-dihydro-δ2-1, 3, 4-thiadiazine (Va) in 55% yield (hydrolysis of the lactamic function as well). Aminoethyl phosphorous monoester (colaminephosphorous acid) reacted with phenylisocyanate (in H20+dioxane) in slightly alkaline medium (one equivalent of NaOH) yields sodium N-phenylcarbamoylaminoethyl phosphite. Refluxed for 20 minutes in 1N NaOH, this carbamoyl derivative is not cyclized but only hydrolyzed to the open-chained N-phenyl-N′-hydroxyethylurea (VII). 相似文献
53.
Terrence G. Vargo Joseph A. Gardella Lawrence Salvati 《Journal of polymer science. Part A, Polymer chemistry》1989,27(4):1267-1286
The surfaces of poly(methyl methacrylate) (PMMA) films modified by O2H2O and H2O radio-frequency glow discharge plasmas were studied using electron spectroscopy for chemical analysis (ESCA or XPS), low energy ion scattering (LEISS or ISS), Fourier transform IR spectroscopy (FTIR) with attenuated total reflectance (ATR) sampling, and critical surface energy from contact angle measurements. The extent and nature of modification with respect to promotion of a hydrophilic surface compared to the hydrophobic surface of the unmodified PMMA has been probed. Results show drastic decreases in C/O ratio at the near surface, which increases to that of the unmodified PMMA as deeper cross sections are analyzed. In addition peak fitting of ESCA data correlated with FTIR functional group information allows for the qualitative and quantitative analysis of the resulting bonding and structure of the modified layer. From these results combined with the polarity and surface energy differences obtained from contact angle measurements, the structural changes are discussed with respect to plasma reaction mechanisms and differences in the structure of the modified polymer films. 相似文献
54.
Charles B. de Koning Sunnyboy S. Manzini Joseph P. Michael Edwin M. Mmutlane Tefo R. Tshabidi Willem A.L. van Otterlo 《Tetrahedron》2005,61(3):555-564
The synthesis of substituted anthracenes from naphthalene precursors is described. The key step involved heating ortho-allyl substituted naphthalene-2-carbaldehydes and potassium t-butoxide in DMF with concomitant irradiation from a high pressure mercury lamp to afford anthracenes in yields of 76-98%. 相似文献
55.
Jacquelynn L. Savoca Robert P. Lattimer Joseph M. Richards Willem Windig Henk L.C. Meuzelaar 《Journal of Analytical and Applied Pyrolysis》1985,9(1):19-28
A set of twelve natural rubber vulcanizates was analyzed by Curie-point pyrolysis-mass spectrometry (Py-MS). Multivariate analysis successfully correlated the Py-MS data with either total or polysulfidic crosslink density measurements. (Polysulfidic means two or more sulfurs.) The principal correlation observed was an increase in the ratio of monomer to dimer pyrolyzate yield with an increase in crosslink density. The feasibility of using Py-MS for total crosslink density determination has thus been demonstrated. The Py-MS data, however, did not allow us to distinguish different types of crosslinks. 相似文献
56.
Joseph R. Lakowicz Ignacy Gryczynski Henryk Malak Zygmunt Gryczynski 《Photochemistry and photobiology》1996,64(4):632-635
Abstract— We report the observation of two-photon excitation of an organic fluorophore with two different wavelengths, a phenomenon we refer to as two-color two-photon (2C2P) excitation. Ultraviolet emission of p -Merphenyl at 340 nm was observed when the sample was illuminated with both 375 and 750 nm pulses from a picosecond dye laser. The emission of p -terphenyl was about 100-fold and more than 1000-fold less for illumination at only 375 or 750 nm, respectively. Observation of the 2C2P signal required temporal and spatial overlap of the 375 and 750 nm pulses. The amplitude of the signal depended on the polarization of each beam. 2C2P excitation can have applications in fluorescence microscopy and elsewhere when spatially localized excitation is desirable. 相似文献
57.
A procedure for synthesis of 2,4-diamino-6-substituted-5-deazapteridines (pyrido[2,3-d]pyrimidines) is described. Condensation of 1-piperidino-1-propene with ethoxymethylenemalononitrile afforded an enamino malononitrile adduct, which when treated with ammonia yielded 2-amino-3-cyano-5-methylpyridine. Cyclization to 2,4-diamino-6-methyl-5-deazapteridine could be effected with guanidine. Similar condensation of piperidinopropene with ethyl methoxymethylenecyanoacetate followed by cyclization with hydroxylamine gave 2-amino-3-carbethoxy-6-methylpyridine 1-oxide. Reduction with phosphorus trichloride afforded the pyridine base, however, attempts to cyclize the amino ester to 2-amino-4-hydroxy-6-methyl-5-deazapteridine were unusccessful. 相似文献
58.
Mary E. Carter James L. Nash Joseph W. Drueke James W. Schwietert George B. Butler 《Journal of polymer science. Part A, Polymer chemistry》1978,16(5):937-959
β-Nitrostyrene and many of its derivatives have been shown to yield high polymers via anionic initiation with alkoxide ions in protic solvents, e.g., alcohols. A study was conducted to determine the effect of certain substituents on the polymerization characteristics of representative monomers of this series and the properties of their polymers. A kinetic study was conducted and the relative rates of propagation were unexpectedly found to correlate well with brown's σ+ values. The rates of initiation of two representative monomers, β-nitrostyrene and p-methoxy-β-nitrostyrene, with sodium ethoxide were found to be 3.51 and 2.86 liter/mole sec, respectively. The rate of chain transfer in ethanol was studied qualitatively by using gel-permeation chromatography (GPC) to obtain molecular weight distribution (MWD) curves. The low values of the M w/M n ratios indicated little chain transfer in the protic solvent. 相似文献
59.
The chance to prepare sterically and inductively stabilized arsa‐ and phosphaalkenes of the type PhE=C(CF3)2 (E = As, P) by reacting phenyl‐bis(trimethylsilyl)‐arsane ( 1 ) and ‐phosphane ( 5 ), respectively, with hexafluoroacetone (HFA) was investigated. The insertion of the carbonyl function in one of the Si–E bonds was found to occur at temperatures between ?78 and 20 °C. The elimination of hexamethyldisiloxane, which in case of acylamides and ketones spontaneously follows the insertion and in case of RE(SiMe3)–CR′2(OSiMe3) at least can be initiated by solid sodium hydroxide as catalyst, turned out to be impossible for the primary products PhE(SiMe3)–C(CF3)2‐OSiMe3 [E = As ( 2 ), P ( 6 )]. 2 and 6 were characterized by analytical (C, H) and spectroscopic methods (IR, NMR, MS). 相似文献
60.
The ligand, 1,2-bis(difluorophosphino)ethane, (PF2C2H4PF2), reacts with Ni(CO)4 in the gas phase and in solution to produce carbon monoxide and a polymer, [Ni(PF2C2H4PF2)2]x. PF2C2H4PF2 displaces norbornadiene from (C7H8)Mo(CO)4 to yield the relatively air-stable complex, Mo(CO)4-(PF2C2H4PF2). Analysis of the infrared spectrum of the monomeric complex indicates that the ligand exhibits π-acceptor strength equal to PF2C6H10PF2. 相似文献