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81.
Behforouz M Haddad J Cai W Arnold MB Mohammadi F Sousa AC Horn MA 《The Journal of organic chemistry》1996,61(19):6552-6555
The novel 7-(N-formyl-, 7-(N-acetyl-, and 7-(N-isobutyrylamino)-2-methylquinoline-5,8-diones were synthesized in excellent overall yields in three steps via the nitration of the commercially available 8-hydroxy-2-methylquinoline followed by a reduction-acylation step and then oxidation. Acid hydrolysis of 7-(N-acetylamino)-2-methylquinoline-5,8-dione (14a) afforded the novel 7-aminoquinoline-5,8-dione 7 in excellent yields. Due to our efficient preparation of dione 14a, we now report a short and practical method for the total synthesis of the potent antitumor agent lavendamycin methyl ester (1b) with an excellent overall yield. 相似文献
82.
Lung A Stuart LM Bosted PE Andivahis L Alster J Arnold RG Chang CC Dietrich FS Dodge WR Gearhart R Gomez J Griffioen KA Hicks RS Hyde-Wright CE Keppel C Kuhn SE Lichtenstadt J Miskimen RA Peterson GA Petratos GG Rock SE Rokni SH Sakumoto WK Spengos M Swartz K Szalata Z Tao LH 《Physical review letters》1993,70(6):718-721
83.
Results are presented for potentiometric ammonia gas-sensors which show that the response times increase significantly with age of the sensor when ammonium picrate is used as internal electrolyte and the samples have greater osmolarities than the internal electrolyte solution. A build-up of ammonium picrate crystals on the inner side of the gas-permeable membrane is responsible for this increasein response time. The use of ammonium chloride as internal electrolyte provides constant response times indepent of sample osmotic strength, and is recommended as a means of ensuring that optimal dynamic response characteristics are maintained. 相似文献
84.
Summary Most boundary element methods for two-dimensional boundary value problems are based on point collocation on the boundary and the use of splines as trial functions. Here we present a unified asymptotic error analysis for even as well as for odd degree splines subordinate to uniform or smoothly graded meshes and prove asymptotic convergence of optimal order. The equations are collocated at the breakpoints for odd degree and the internodal midpoints for even degree splines. The crucial assumption for the generalized boundary integral and integro-differential operators is strong ellipticity. Our analysis is based on simple Fourier expansions. In particular, we extend results by J. Saranen and W.L. Wendland from constant to variable coefficient equations. Our results include the first convergence proof of midpoint collocation with piecewise constant functions, i.e., the panel method for solving systems of Cauchy singular integral equations.Dedicated to Prof. Dr. Dr. h.c. mult. Lothar Collatz on the occasion of his 75th birthdayThis work was begun at the Technische Hochschule Darmstadt where Professor Arnold was supported by a North Atlantic Treaty Organization Postdoctoral Fellowship. The work of Professor Arnold is supported by NSF grant BMS-8313247. The work of Professor Wendland was supported by the Stiftung Volkswagenwerk 相似文献
85.
Dallas A. Connor Arnold M. Falick Mark C. Young Martin D. Shetlar 《Photochemistry and photobiology》1998,68(3):299-308
In recent years, there has been a significant number of studies in which UV light has been used as a reagent to induce cross-links in nucleic acid-protein complexes. An area of considerable interest among those interested in structural biology is the garnering of information about the sites of cross-linking within the protein and nucleic acid members of photolinked conjugates, under the assumption that such knowledge should lead to identification of contact regions or sites within the native complexes. In this paper, we present our results from a photocross-linking study of the complex of the single-stranded DNA-binding domain of rat DNA polymerase β (pol β-ss) with the oligonucleotide d(ATATATA). In this study, we have used single nanosecond laser pulses as the cross-linking reagent and matrix-assisted laser desorp-tion/ionization-time of flight mass spectrometry as an analytical tool to identify cross-linked peptides purified from proteolytic digests of the cross-linked complex. Six cross-linked peptides have been identified in tryptic digests of the protein-oligonucleotide conjugates that result from irradiation of the pol β-ss-d(ATATATA) complex with a single laser pulse. Comparisons with NMR data in the literature for the same complex show that each of the cross-linked peptides contains amino acids that are in contact with the nucleic acid component of the complex. 相似文献
86.
87.
H. W. Sarkas S. T. Arnold J. H. Hendricks L. H. Kidder C. A. Jones K. H. Bowen 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,26(1):46-50
We present preliminary evidence for catalytic activity by unsupported mixed metal oxide nanocrystalline materials. The results of this study show that a nanophase form of Li-MgO has begun to exhibit catalytic activity by 300 °C. This is at least 200 degrees below the temperature at which conventional Li-MgO catalysts exhibit comparable activity. Furthermore, at higher temperatures, the same nanophase composition shows enhanced activities and somewhat improved hydrocarbon selectivities over conventional Li-MgO catalysts. 相似文献
88.
The new monoterpenoid 5-isobutyl-3-methyl-2-furancarbaldehyde was isolated from Tagetes glandulifera Schrank and its structure confirmed by synthesis. 相似文献
89.
John T. Gupton John E. Gall Steve W. Riesinger Stanton Q. Smith Kathy M. Bevirt James A. Sikorski Maria L. Dahl Zdenek Arnold 《Journal of heterocyclic chemistry》1991,28(5):1281-1285
An alternative preparation of a 2-iminovinamidinium salt from phosphonoacetic acids is described along with its application to the synthesis of 5-formylpyrimidines and masked 4-formylpyrazoles. 相似文献
90.
54Mn is analyzed in complex food ash of high cationic environment. The initial step is an extraction atpH 2.7 with hexane containing di(2-ethylhexyl) phosphoric acid (HDEHP) to complex the54Mn and other nuclides. The manganese is reextracted into an alkaline EDTA buffer which is washed with 1% 8-hydroxyquinoline
in chloroform containing 5% isoamyl alcohol. The54Mn is determined by gamma spectrometry with recoveries ranging from 96.6 to 99.4%. 相似文献