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11.
Huang F Switek KA Zakharov LN Fronczek FR Slebodnick C Lam M Golen JA Bryant WS Mason PE Rheingold AL Ashraf-Khorassani M Gibson HW 《The Journal of organic chemistry》2005,70(8):3231-3241
Four new bis(m-phenylene)-32-crown-10-based cryptands with different third bridges were prepared. Their complexes with paraquat derivatives were studied by proton NMR spectroscopy, mass spectrometry, and X-ray analysis. It was found that these cryptands bind paraquat derivatives very strongly. Specifically, a diester cryptand with a pyridyl nitrogen atom located at a site occupied by either water or a PF(6) anion in analogous complexes exhibited the highest association constant K(a) = 5.0 x 10(6) M(-1) in acetone with paraquat, 9000 times greater than the crown ether system. X-ray structures of this and analogous complexes demonstrate that improved complexation with this host is a consequence of preorganization, adequate ring size for occupation by the guest, and the proper location of the pyridyl N-atom for binding to the beta-pyridinium hydrogens of the paraquat guests. This readily accessible cryptand is one of the most powerful hosts reported for paraquats. 相似文献
12.
Li AC Alton D Bryant MS Shou WZ 《Rapid communications in mass spectrometry : RCM》2005,19(14):1943-1950
Bioanalytical support of plasma pharmacokinetic (PK) studies for drug discovery programs primarily involves the quantitative analysis of dosed compounds using liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/MS/MS) operated in selected reaction monitoring (SRM) mode. However, there is a growing need for information on the metabolism of new chemical entities (NCEs), in addition to the time-concentration profiles from these studies. In this paper, we present a novel approach to not only quantify parent drugs with SRM, but also simultaneously screen for metabolites using a hybrid triple quadrupole/linear ion trap (QqQ(LIT)) instrument. This was achieved by incorporating both the conventional SRM-only acquisition of parent compounds and the SRM-triggered information-dependent acquisition (IDA) of potential metabolites within the same scan cycle during the same LC/MS/MS run. Two test compounds were used to demonstrate the applicability of this approach. Plasma samples from PK studies were processed by simple protein precipitation and the supernatant was diluted with water before injection. The fast scanning capability of the linear ion trap allowed for the information-dependent acquisition of metabolite MS/MS spectra (<1 s/scan), in addition to the collection of adequate data points for SRM-only channels. The MS/MS spectra obtained from potential metabolites in post-dose samples correlated well with the spectra of the parent compounds studied, therefore providing additional confirmatory structure information without the need for repetitive analyses. Relative quantitative time-concentration profiles of identified metabolites were also obtained. Furthermore, this articulated SRM+SRM-IDA approach generated equivalent quantitative results for parent compounds to those obtained by conventional SRM-only analysis. This approach has been successfully used to support discovery PK screening programs. 相似文献
13.
M. S. Bryant J. O. Lay M. P. Chiarelli 《Journal of the American Society for Mass Spectrometry》1992,3(4):360-371
An analytical strategy using fast atom bombardment (FAB) ionization and tandem mass spectrometry has been developed to determine the molecular weight and major fragment ions, and to provide limited structural characterization of low picomole levels of carcinogen-nucleoside adducts. This strategy consists of three main components: (1) the sensitivity for analysis by FAB combined with mass spectrometry is increased via chemical derivatization; (2) the nucleoside adducts are selectively detected by using constant neutral loss scans; and (3) structurally characteristic fragments are obtained by using daughter ion scans. Trimethylsilyl derivatized arylamine-nucleoside adducts have been detected at levels as low as a few picomoles by using this approach. After experimental determination of the mass of the BH 2 + fragment ion, daughter ion spectra have been used to probe the structure specificity associated with collision-activated decomposition of this fragment. With model C-8 substituted arylamine adducts [N-(deoxyguanosin-8-yl)-4-aminobiphenyl, N-(deoxyadenosin--yl)-4-aminobiphenyl, and N-(deoxyguanosin-8-yl)-2-aminofluorene], nucleoside-specific and carcinogen-specific fragmentation have been observed in daughter ion spectra. 相似文献
14.
Highly selective and efficient separations of a wide range of acidic species in capillary electrophoresis employing non-aqueous media 总被引:2,自引:0,他引:2
Summary The novel application of CE using non-aqueous media has been studied for the separation of a range of acidic compound types.
This enabled the first quantitative assay by CE employing non-aqueous media to be performed. Separation selectivity manipulation
for closely related species was achieved through variation of organic solvent types and composition, ionic strength changes,
alteration of pH* values and the addition of cyclodextrin additives soluble in organic solvents. This offers a greater range of possibilities
during method development than use of aqueous buffer. The generation of low operating currents permitted rapid, highly efficient
and selective separations to be achieved by applying high field strengths across short capillaries.
Optimised rinsing and capillary regenerating procedures were devised which allowed highly repeatable separations to be achieved
with migration time repeatability below 1% RSD. Use of internal standards also allowed 1% RSD values to be obtained for injection
precision. Routine operating effects were assessed and it was observed that stacking effects remain important in non-aqueous
CE. Also, optimal separations are obtained when the samples are diluted in the pure solvent used to prepare the electrolyte.
The application range of non-aqueous CE was appreciably extended to include acidic drugs, dyes, surfactants and preservatives. 相似文献
15.
16.
Darryn E. Bryant 《Designs, Codes and Cryptography》1992,2(2):159-168
For m = 6 and for all odd composite integers m, as well as for all even integers m 10 that satisfy certain conditions, 2-perfect m-cycle systems are constructed whose quasigroups have a homomorphism onto quasigroups which do not correspond to a 2-perfect m-cycle systems. Thus it is shown that for these values of m the class of quasigroups arising from all 2-perfect m-cycle systems does not form a variety. 相似文献
17.
18.
J. Bryant Neilsen H. Smith Broadbent William J. Hennen 《Journal of heterocyclic chemistry》1987,24(6):1621-1628
Although 6-methyl- ( 1 ) and 6-phenylisoxanthopterin ( 2 ) have previously been synthesized, the requirement of high purity necessary for immunological testing has necessitated our development of the first reported synthesis of these compounds by unequivocal methods. In the process of so doing four new pyrazines, ethyl 3-amino-5-chloro-6-methyl-2-pyrazinecarboxylate ( 11 ), N,N-dimethyl-N'-(6-chloro-3-cyano-5-phenylpyrazin-2-yl)methanimidamide ( 16 ), 2-amino-3-ethoxycarbonyl-5-phenylpyrazine 1-oxide ( 19 ), and ethyl 3-amino-5-chloro-6-phenyl-2-pyrazinecarboxylate ( 20 ) were synthesized. Four new pteridines, 7-methoxy-6-methyl-2,4-pteridinediamine ( 7 ), 7-methoxy-6-phenyl-2,4-pteridinediamine ( 17 ), 2-amino-7-ethoxy-6-methyl-4(3H)-pteridinone ( 12 ), and 2-amino-7-ethoxy-6-phenyl-4(3H)-pteridinone ( 21 ) have also been synthesized enroute to these isoxanthopterins. 相似文献
19.
Miyazaki A Fujisawa Y Shiotani K Fujita Y Li T Tsuda Y Yokoi T Bryant SD Lazarus LH Okada Y 《Chemical & pharmaceutical bulletin》2005,53(9):1152-1158
1,2-Dihydropyrazin-2-one derivatives, which have two aminoalkyl groups at the positions 3 and 6, were found to be efficient tools for the construction of potent, selective and long-acting opioid mimetics. During the course of preparation, we found that the catalytic hydrogenation of 3,6-bis(benzyloxycarbonylaminomethyl)-5-methyl-1,2-dihydropyrazin-2-one to remove the benzyloxycarbonyl groups resulted in a side reaction. By MS and NMR studies and by preparation of additional 1,2-dihydropyrazin-2-one derivatives, the structure of the by-product was identified as 3-aminomethyl-5,6-dimethyl-1,2-dihydropyrazin-2-one. Preparation of additional compounds substituted with deuterium provided us with sufficient information to confirm the structure of the product and to support a cyclization mechanism in its formation. 相似文献
20.
W. G. Campbell J. C. Mc Gowan St. A. Bryant A. J. Bailey A. Orup R. I. Thieme H. Bergström K. G. Trobeck P. W. Moryganow J. I. Wlassjuk N. K. Koshewnikowa G. S. Ssurta G. Jayme H. Pfretzschner R. Steinmann M. G. van Beckum G. J. Ritter J. H. Barbour C. F. Cross und E. J. Bevan 《Fresenius' Journal of Analytical Chemistry》1940,119(1-2):67-71
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