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511.
The sodium salt of heptakis(2-O-methyl-6-O-sulfo)cyclomaltoheptaose (HMS), the second single-isomer, sulfated beta-CD carrying nonidentical substituents at all of the C2, C3, and C6 positions, has been synthesized, analytically characterized, and used for the capillary electrophoretic separation of the enantiomers of a group of 23 weak base analytes in acidic aqueous and methanolic BGEs. HMS interacted strongly with only about half of the analytes studied. The good separation selectivities and favorable normalized EOF mobilities allowed for rapid, efficient separation of the enantiomers of 19 of the 23 weak base analytes in the aqueous BGEs, often with separation selectivity values complimentary to those obtained with other single-isomer sulfated CDs. HMS did not prove to be as good a resolving agent in acidic methanolic BGEs as its counterpart, heptakis(2-O-methyl-3-O-acetyl-6-O-sulfo)cyclomaltoheptaose. 相似文献
512.
Intermolecular couplings versus intramolecular ring closures were observed in the reaction of p-tert-butylthiacalix[4]arene and diethylene glycols affording dimers 2 and/or the inherently chiral 1,2-thiacalix[4]crown-3 derivatives 5 under the Mitsunobu protocol. The enantiomeric separation of 5a was achieved by chiral HPLC. The reaction of thiacalix[4]monocrowns 1 with diethylene glycols failed to give crowned thiacalix-tubes 7, instead biscrowns 8 were formed. Partially alkylated double thiacalix[4]arenes 10, 11 were obtained via the base promoted alkylations of a thiacalixarene dimer 2a containing diethyleneoxy linkers. 相似文献
513.
514.
Katalin E. Kvr Gyula Batta 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,170(2):341
Since the introduction of RDCs in high-resolution NMR studies of macromolecules, there is a growing interest in the development of accurate, and sensitive methods for determining coupling constants. Most methods for extracting these couplings are based on the measurement of the splitting between multiplet components in J-coupled spectra. However, these methods are often unreliable since undesired multiple-bond couplings can considerably broaden the multiplet components and consequently make accurate determination of their position difficult. To demonstrate one approach to this problem, G-BIRD(r) decoupled TROSY sequences are proposed for the measurement of 1JNH and 1JNC′ coupling constants. Resolved or unresolved splittings due to remote protons are removed by a G-BIRD(r) module employed during t1 and as a result, spectra with narrow, well-resolved peaks are obtained from which heteronuclear one-bond couplings can be accurately measured. Moreover, introduction of a spin-state-selective α/β-filter in the TROSY sequence allows the separation of the 1JNC′ doublet components into two subspectra which contain the same number of peaks as the regular TROSY spectrum. The 1JNC′ couplings are obtained from the displacement between the corresponding peaks in the subspectra. 相似文献
515.
T. Bartik B. Happ Anke Sieker Sylvia Stein Angela Sorken K.-H. Thiele Christian Kriebel Gyula Plyi 《无机化学与普通化学杂志》1992,608(2):173-183
Bimetallic and trimetallic compounds containing unsupported bonds of subgroup 4 metals (M = Ti, Zr, Hf) and Co were prepared by hydride elimination (A) from RM derivatives (R1 = PhCH2; RN; R2 = Me, Et)) and by salt elimination (B) from RMX (X = Cl, Br; R.1 = PhCH2, RN and R3O; R3= i-Pr, n-Bu)) by reaction with HCo(CO)4 and Na[Co(CO)4], respectively. Compounds RMCo(CO)4 with R1 = PhCH2, RM[Co(CO)4]2 R.1 = PhCH2, were prepared both by methods A and B, while (R3O)4-n Ti[Co(Co)4]n (n = 1, 2) compounds were obtained by reaction B. Several tertiary phosphine and phosphite derivatives of the former two types were obtained by substitution of a carbonyl group by PR ligand or by A type reaction of HCo(CO)3(PR with RM compounds. 相似文献
516.
In this paper we consider discrete time forward interest rate models. In our approach, unlike in the classical Heath–Jarrow–Morton
framework, the forward rate curves are driven by a random field. Hence we get a general interest rate structure. Our aim is
to give an overview of our results in such a model on the following questions: no-arbitrage conditions, maximum likelihood
estimation of the volatility, as well as the joint estimation of the parameters and the asymptotic behaviour of the estimators,
relationship with continuous models. Finally we give discussion on the practical problems of the estimation and we show several
numerical results on the statistics of such models.
This research has been supported by the Hungarian Scientific Research Fund under Grants No. OTKA–F046061/2004 and OTKA–T048544/2005. 相似文献
517.
Dr. Gyula Tircsó Dr. Martín Regueiro‐Figueroa Viktória Nagy Zoltán Garda Tamás Garai Dr. Ferenc Krisztián Kálmán Dr. David Esteban‐Gómez Dr. Éva Tóth Dr. Carlos Platas‐Iglesias 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):896-901
A highly rigid open‐chain octadentate ligand (H4cddadpa) containing a diaminocylohexane unit to replace the ethylenediamine bridge of 6,6′‐[(ethane‐1,2 diylbis{(carboxymethyl)azanediyl})bis(methylene)]dipicolinic acid (H4octapa) was synthesized. This structural modification improves the thermodynamic stability of the Gd3+ complex slightly (log KGdL=20.68 vs. 20.23 for [Gd(octapa)]?) while other MRI‐relevant parameters remain unaffected (one coordinated water molecule; relaxivity r1=5.73 mm ?1 s?1 at 20 MHz and 295 K). Kinetic inertness is improved by the rigidifying effect of the diaminocylohexane unit in the ligand skeleton (half‐life of dissociation for physiological conditions is 6 orders of magnitude higher for [Gd(cddadpa)]? (t1/2=1.49×105 h) than for [Gd(octapa)]?. The kinetic inertness of this novel chelate is superior by 2–3 orders of magnitude compared to non‐macrocyclic MRI contrast agents approved for clinical use. 相似文献
518.
György Keglevich János Kovács Tamás Körtvélyesi Gyula Parlagh Tímea Imre Krisztina Ludányi László Hegedűs Miklós Hanusz Kálmán Simon Andrea Márton György Marosi László Tőke 《Heteroatom Chemistry》2004,15(2):97-106
The [4 + 2] cycloaddition of the double-bond isomers ( A and B ) of dihydrophosphinine oxide 1 afforded novel phosphabicyclo[2.2.2]oct-5-ene derivates ( 2–4 ), formation of which was justified by PM3 semiempirical calculations. The compounds of dimer type ( 2–4 ) were utilized in the UV light-mediated fragmentation-related phosphinylation of nucleophiles, especially in that of alcohols. To explore the role of structural modifications on the fragmentation ability, disulfide 5 , phosphabicyclooctane 7 obtained by the hydrogenation of 2 , and the adduct of dihydrophosphinine oxide 1 with benzoquinone ( 7 ) were also synthesized and tested in fragmentation. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:97–106, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10221 相似文献
519.
The reaction of dialkylphosphinous chlorides ( 1 ) with arylmagnesium bromides carried out in the air atmosphere was found to afford aryl‐dialkylphosphine oxides ( 2 ) and aryl dialkylphosphinates ( 3 ) in a comparable quantity. Formation of the latter product ( 3 ) is the first example that an aryl‐dialkylphosphine, formed as an intermediate, is autooxidized to the corresponding phosphinate. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:38–41, 2001 相似文献
520.
Gyrgy Keglevich Attila Kovcs Lszl Tke Klmn Újszszy Gyula Argay Mtys Czugler Alajos Klmn 《Heteroatom Chemistry》1993,4(4):329-335
Preparation of P-amino-3-phosphabicyclo[3.1.0]-hexane 3-oxides either by addition of dichlorocarbene to the double bond of 1-amino-2,5-dihydro-1H-phosphole 1-oxides or by substitution of the P-chloro derivative of the bicyclic system was accomplished. Two different diastereomers are obtained by the two approaches; their 13C NMR spectra were interpreted on the basis of the P-ethoxy isomers, whose structures were confirmed by X-ray analysis. The P-hydroxy adduct was also prepared, and it was found that intermolecular O H … O hydrogen bonding connects the molecules together in the solid phase. This effect eliminates the possibility of diastereoisomerism, as was also observed in the case of P-hydroxy tetrahydrophosphinine oxides. Thermolysis of the P-hydroxy adduct is a better way to synthesize 1-hydroxy-1,2-dihydrophosphinine oxides than by hydrolysis of the phosphinic chlorides. 相似文献