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11.
Antonio Da Settimo Giampaolo Primofiore Bertacchi Maria Cristina Federico Da Settimo Anna Maria Marini 《Journal of heterocyclic chemistry》1995,32(3):941-945
The Ullmann reaction of 8-aminotheophylline or 8-aminocaffeine with 2-chlorobenzoic acid and of 8-bromotheophylline with ethyl-2-aminobenzoate afforded derivatives of three new heterocyclic systems: purino[7,8-α]quinazoline-5,9,11(6H,8H,10H)-trione, purino[8,9-b]quinazoline-2,4,11(1H,3H,5H)-trione and purino[8,7-b]quinazoline-2,4,6(1H,3H,11H)-trione, respectively. 相似文献
12.
Glatz Z Marini MV Wimmerová M Damborský J Nagata Y 《Journal of chromatography. A》2000,895(1-2):219-225
A new sensitive method has been developed for the determination of haloalkane dehalogenase activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of product - bromide or chloride ions - was monitored by sequential capillary zone electrophoresis runs. The determinations were performed in a 75 microm fused-silica capillary using 5 mM chromate, 0.5 mM tetradecyltrimethylammonium bromide (pH 8.4) as a background electrolyte, separation voltage 15 kV (negative polarity) and indirect detection at sample wavelength 315 nm, reference wavelength 375 nm for brominated and chlorinated substrates, respectively 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, separation voltage 18 kV (negative polarity) and direct detection at 200 nm for brominated substrates. The temperature of capillary was in both cases 25 degrees C. The method is rapid, can be automated, and requires only small amount of enzyme preparation and substrate. 相似文献
13.
In spite of the higher reactivity of styrene with respect to ethene for the alternating copolymerization with carbon monoxide, catalyzed by chiral (dihydrooxazole)(phosphino)palladium complexes, ethene is preferentially (and randomly) enchained in terpolymerization experiments; enantioface selection for styrene is comparably high in both copolymerization and terpolymerization processes. 相似文献
14.
Anil Kumar PG Pregosin PS Schmid TM Consiglio G 《Magnetic resonance in chemistry : MRC》2004,42(9):795-800
Three new salts of Rh(I), [Rh(1,5-COD)(Biphemp)]X, Biphemp = (6,6'-dimethylbiphenyl-2,2'-diyl)bis(diphenylphosphine), X = BF4-, 2a, PF6-, 2b, and CF3SO3-, 2c, were prepared and studied using PGSE diffusion, 1H-19F HOESY and inverse 103Rh (amongst other) NMR methods. Although the immediate coordination sphere of the cation does not sense the change in the anion, the PGSE diffusion and 1H-19F HOESY data suggest that, in addition to some ion pairing, each of the anions in 2 demonstrates selectivity in its approach towards the cation. 相似文献
15.
Two families of mixed finite elements for second order elliptic problems 总被引:32,自引:2,他引:30
Summary Two families of mixed finite elements, one based on triangles and the other on rectangles, are introduced as alternatives to the usual Raviart-Thomas-Nedelec spaces. Error estimates inL
2
() andH
–5
() are derived for these elements. A hybrid version of the mixed method is also considered, and some superconvergence phenomena are discussed. 相似文献
16.
Fernandez E Ford WT Qi N Read AL Smith JG Camporesi T De Sangro R Marini A Peruzzi I Piccolo M Ronga F Blume HT Hurst RB Venuti JP Wald HB Weinstein R Band HR Gettner MW Goderre GP Meyer OA Moromisato JH Shambroom WD Sleeman JC von Goeler E Ash WW Chadwick GB Clearwater SH Coombes RW Kaye HS Lau KH Leedy RE Lynch HL Messner RL Moss LJ Muller F Nelson HN Ritson DM Rosenberg LJ Wiser DE Zdarko RW Groom DE Lee H Delfino MC Heltsley BK Johnson JR Lavine TL Maruyama T Prepost R 《Physical review letters》1985,54(15):1620-1623
17.
1H and 13C NMR spectra of cis- and trans-3-(2-[2-(4-methylphenyl)ethenyl]phenyl])sydnones, the first stilbene-substituted mezoionic oxadiazolium rings, were fully assigned combining the information in various solvents, such as deuterated benzene, acetone and chloroform, using 2D NMR techniques. 相似文献
18.
Capozzi G Delogu G Fabbri D Marini M Menichetti S Nativi C 《The Journal of organic chemistry》2002,67(7):2019-2026
Sulfenylation of 6,6'-dimethoxy-2,2'-dihydroxybiphenyl, used as a racemic mixture and single enantiomers, by phthalimidesulfenyl chloride afforded the corresponding 3,3'-N,N'-dithiophthalimide with complete regioselectivity. Simple manipulations of the latter compound allowed access to the corresponding bis-thiol or o-thioquinone as useful intermediates for the synthesis of new sulfur-containing open-chain and macrocyclic C(2) enantiopure ligands. The application of this methodology to the preparation of a biphenyl bearing two cysteine units as potential HIV-1 protease inhibitor is also described. 相似文献
19.
The robustness testing of a normal-phase liquid chromatographic (LC) method for the determination of R-timolol and other related substances in S-timolol maleate was performed applying a two-level Plackett-Burman design. Two qualitative and five quantitative factors were examined. Two types of responses were considered, qualitative, i.e. chromatographic performance criteria, and quantitative ones. The latter were taken into account to determine if the analytical procedure was robust. The quantitative responses were the contents of R-timolol in two S-timolol maleate samples. Even though some significant factor effects were observed on the qualitative responses, the R-timolol contents were not significantly different from those observed at nominal conditions, which demonstrated the robustness of the procedure.Since the experiments of the Plackett-Burman design can be assimilated to laboratories in an interlaboratory study, uncertainty can be evaluated using the robustness test data. The robustness test was set-up in such a way that the required variances could be estimated. It was shown that the robustness set-up allows estimating the reproducibility uncertainty without performing an interlaboratory study. 相似文献
20.
F. Giordano G. P. Bettinetti A. La Manna A. Marini V. Berbenni 《Journal of Thermal Analysis and Calorimetry》1988,34(2):531-536
Differential scanning calorimetry has been applied to the study of the solid system cross-linked polyvinylpyrrolidone/trimethoprim.Different results have been systematically obtained on co-ground and not co-ground mixtures, suggesting some type of interaction to take place between components as a consequence of co-grinding.A simple phenomenological model of the interaction is proposed, which quite satisfactorily agrees with thermal data.
This work has been partially supported by Ministero Pubblica Istruzione (Fondi 60%). 相似文献
Zusammenfassung Das feste System von vernetztem Polyvinyl-pyrolidin/Trimethoprim wurde mittels DSC untersucht. Unterschiedliche Ergebnisse wurden systematisch für zusammen und nicht zusammen verriebene Mischungen gefunden, was auf eine Wechselwirkung zwischen Komponenten beim Verreiben hindeutet. Ein einfaches phänomenologisches Modell dieser Wechselwirkung wird vorgeschlagen, das mit thermischen Daten befriedigend übereinstimmt.
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This work has been partially supported by Ministero Pubblica Istruzione (Fondi 60%). 相似文献