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131.
A. Paul Krapcho Martin J. Maresch Cynthia E. Gallagher Miles P. Hacker Ernesto Menta Ambrogio Oliva Roberto Di Domenico Giovanni Da Re Silvano Spinelli 《Journal of heterocyclic chemistry》1995,32(6):1693-1702
Synthetic procedures have been developed which lead to 4-hydroxy-6,9-difluorobenz[g]isoquinoline-5,10-dione ( 4a ) and its 3-methyl analogue 4b . Attempts to displace the fluorides from 4a with N,N-dimethylethylenediamine were unsuccessful. Analogue 4a on treatment with N-(t-butoxycarbonyl)ethylene diamine led to 15 , formed from addition of the nucleophilic amine to C-3. On the other hand, analogue 4b , on treatment with N,N-dimethylethylenediamine led to the anticipated difluoride displacement product 3c . The protection of the hydroxy group of 4a by benzylation with phenyldiazomethane led to 4c which on treatment with N-(t-butoxycarbonyl)ethylene diamine or N,N-dimethylethylenediamine led to the corresponding 6,9-bis-substituted analogues 18a and 18b , respectively. Reductive debenzylations of 18a and 18b by hydrogenation over Pearlman's catalyst also effected partial reductions of the quinone. However, air oxidation of the over reduced products led to 3a and 3b , respectively. Treatment of 3a with hydrogen chloride gas led to the hydrochloride salt of 3d . Addition of O-p-Methoxybenzyl-N,N'-diisopropylurea to 4a led to the p-methoxybenzyl analogue 4d . Treatment of 4d with N,N-dimethylethylene diamine or N-(t-butoxycarbonyl)ethylene diamine led to displacements of the fluorides to yield 18c and 18d , respectively. Deprotection of 18c to 3b was accomplished using methanesulfonic acid. Treatment of 18d with trifluoroacetic acid followed by addition of maleic acid led to dimaleate salt of 3d . 相似文献
132.
A. Paul Krapcho Cynthia E. Gallagher Abdelhakim Hammach Michael Ellis Ernesto Menta Ambrogio Oliva 《Journal of heterocyclic chemistry》1997,34(1):27-32
Treatment of difluoro or chloro fluoro-substituted benzyl bromides 5a-c with zinc dust in tetrahydro-furan leads to the corresponding benzylic zinc bromides 6a-c. These organometallics on treatment with chlorosubstituted heterocyclic esters 4A and 4B mediated by nickel catalysis undergo couplings to yield dihalobenzyl substituted heterocyclic esters 7Aa-c and 7Ba-c. Treatment of 4c with 6c under Pd catalysis leads to 7Cc. The acids 8, prepared by hydrolysis of these esters, with treatment of fuming sulfuric acid undergo cyclizations and oxidations to yield the desired regioisomeric dihalo-substituted heterocyclic quinones 2. 相似文献
133.
Ilaria Paolini Maria de la Cruz Pozo-Carrero Francesca Barbetti Zbigniew J. Kaminski Anna M. Papini 《Tetrahedron letters》2007,48(16):2901-2904
Optimization of coupling reactions of glycosylamines with Fmoc-protected aspartic acid, by microwave approach, is described. Different reaction conditions, quantities of substrates and solvents were tested to develop simple and reproducible methodologies. The best results were obtained using new triazine-based coupling reagents with a monomode microwave Discover® BenchMate™ instrument (CEM). The N-glycosyl amino acids were then deprotected to achieve final products for SPPS. 相似文献
134.
Francesco Paolo Invidiata Giancarlo Furn Ilaria Lampronti Daniele Simoni 《Journal of heterocyclic chemistry》1997,34(4):1255-1258
The reaction of thiocarbohydrazide with carboxylic acids at the melting temperature allows an improved preparation of the S-substituted 4-amino-3-mercapto-1,2,4-triazole heterocycles. The crude 4-amino-5-mercapto-1,2,4-triazoles react easily with carboxylic acids or carboxylic acid chlorides to afford the 1,2,4-triazolo[3,4-fc][1,3,4]thiadiazole ring system. 相似文献
135.
Mannelli I Minunni M Tombelli S Wang R Michela Spiriti M Mascini M 《Bioelectrochemistry (Amsterdam, Netherlands)》2005,66(1-2):129-138
An immobilisation procedure based on the direct coupling of thiolated probes (Probe-C6-SH) to bare gold sensor surfaces has been compared with a reference immobilisation method, based on the coupling of biotinylated probes onto a streptavidin-coated dextran-modified surface. The instrumentations used were a quartz crystal microbalance (QCM) and the optical instruments Biacore X and Spreeta based on surface plasmon resonance (SPR). The performances of the DNA-based sensors resulting from direct coupling of thiolated DNA probes onto electrodes of quartz crystals or gold SPR-chips have been studied in terms of the main analytical parameters, i.e. selectivity, sensitivity, reproducibility, etc. In particular, the two immobilisation approaches have been applied to the analysis of oligonucleotides, DNA amplified by polymerase chain reaction (PCR) and genomic DNA enzymatically digested. 相似文献
136.
Ilaria Fragalà 《Journal of Differential Equations》2008,245(5):1299-1322
We consider semilinear elliptic Dirichlet problems in bounded domains, overdetermined with a Neumann condition on a proper part of the boundary. Under different kinds of assumptions, we show that these problems admit a solution only if the domain is a ball. When these assumptions are not fulfilled, we discuss possible counterexamples to symmetry. We also consider Neumann problems overdetermined with a Dirichlet condition on a proper part of the boundary, and the case of partially overdetermined problems on exterior domains. 相似文献
137.
Concentrations of inhalable particulate matter (PM10), Pb, Zn, Pt, Ce, Cd, Se and of Benzo(a)pyrene (BaP) were determined in three locations near Venice from September 2000 to September 2001. Meteorological conditions were considered during the sampling period. All components showed higher concentrations during winter, except for Cd and Se in the two sites at Mestre. Spatial and temporal variations were observed. There were correlations between Pb and Zn and PM10, Cd and Se, Pb and BaP and, in the main street sampling site, also between BaP and Pt. Their possible sources of emission are discussed on the basis of correlations among elements. 相似文献
138.
Daniela?IchimEmail author Ilaria?Peroni Fernando?Sparasci 《Journal of Mathematical Modelling and Algorithms》2005,4(3):253-264
In a linear regression framework, structural change models are proposed for the detection of abrupt changes in parameter values.
Two models are discussed: 1) the pure structural change model, where all the components of the parameter are allowed to change and are tested all together, and 2) the partial structural change model, where only some of the parameter
β components might change. For an on-line implementation, a sliding window algorithm is introduced. The procedure was successfully
applied to phase transition identification in cryogenic thermometry.
*Work partially funded under EU SofTools_MetroNet Contact N. G6RT-CT-2001-05061. 相似文献
139.
The Workshop on "New Trends in Nucleic Acids Based Biosensors" was held at the University of Florence (Italy), from 25th to 28th October 2003. The workshop was funded by the European Science Foundation (ESF) within the programme "Functional Genomics" (Programme Area: DNA arrays and chips). This report describes the main arguments discussed during the workshop considering the state of art and the future trends in the field of nucleic acid-based biosensors, with particular attention on the aptamer field. 相似文献
140.
Santabarbara S Cazzalini I Rivadossi A Garlaschi FM Zucchelli G Jennings RC 《Photochemistry and photobiology》2002,75(6):613-618
In the present study the analysis of the relation between the excited state population in the photosystem II (PSII) antenna and photoinactivation has been extended from an in vitro system, isolated thylakoids, to an in vivo system, Chlamydomonas reinhardtii cells. The results indicate that the excited state quenching by an added singlet quencher induces maximal protection against photoinhibition of about 30% of that expected on the basis of the observed light intensity-treatment time reciprocity rule. Similar results, obtained previously with thylakoids, have been interpreted in terms of damaged or incorrectly assembled complexes that play an important role in photoinhibition in the thylakoid membranes (Santabarbara, S., K. Neverov, F. M. Garlaschi, G. Zucchelli and R. C. Jennings [2001] Involvement of uncoupled antenna chlorophylls in photoinhibition in thylakoids. FEBS Lett. 491, 109-113.). In an attempt to better define this aspect, the photoinhibition action spectra were determined for mutant barley thylakoids, lacking the chlorophyll (Chl) a-b complexes of the outer antenna, and for its wild type. The results indicate that in both systems the action spectra are significantly blueshifted (2-4 nm) and are broader than the PSII absorption in the membranes. These data are interpreted in terms of a heterogeneous population of outer and inner antenna pigment-protein complexes that contain significant levels of uncoupled Chl. 相似文献