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Bogert D Burnstein R Fisk R Fuess S Morfin J Ohska Stutte L Walker JK Bofill J Busza W Eldridge T Friedman JI Goodman MC Kendall HW Kostoulas IG Lyons T Magahiz R Mattison T Mukherjee A Osborne L Pitt R Rosenson L Sandacz A Tartaglia M Taylor FE Verdier R Whitaker S Yeh GP Abolins M Brock R Cohen A Ernwein J Owen D Slate J Weerts H 《Physical review letters》1985,55(6):574-577
3.
[formula: see text] The bakers' yeast reduction of 3-(1,3-benzodioxol-5-yl)-6-propoxy-1H-inden-1-one 4 has been shown to give (S)-3-(1,3-benzodioxol-5-yl)-2,3-dihydro-6-propoxy-1H-indan-1-one 6 in 65% yield with high enantioselectivity (> 99.0% ee), a key intermediate for the synthesis of the endothelin receptor antagonist SB 217242. In addition, the substituted 3-arylinden-1-ones 10a-e gave equally high enantioselectivity for the 3-arylindan-1-one products 13a-e. Mechanistic studies of the reaction indicate the operative pathway to be an asymmetric conjugate reduction, wherein the hydride transfer from NAD(P)H occurs from the Re-face of the indenone substrate. 相似文献
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Franzen S Wallace-Williams SE Shreve AP 《Journal of the American Chemical Society》2002,124(24):7146-7155
A complete resonance Raman excitation profile of the heme charge-transfer band known as band III is presented. The data obtained throughout the near-infrared region show preresonance with the Q-band, but the data also clearly show the enhancement of a number of modes in the spectral region of band III. Only nontotally symmetric modes are observed to have resonance enhancement in the band III region. The observed resonance enhancements in modes of B(1g) symmetry are compared with the enhancements of those same modes in the excitation profiles of the Q-band of deoxy myoglobin, also presented here for this first time. The Q-band data agree well with the theory of vibronic coupling in metalloporphyrins (Shelnutt, J. A. J. Chem. Phys. 1981, 74, 6644-6657). The strong vibronic coupling of the Q-band of the deoxy form of hemes is discussed in terms of the enhancement of modes with both B(1g) and A(2g) symmetry. The comparison between the Q-band and band III reveals that, consistent with the theory, only modes of B(1g) symmetry are enhanced in the vicinity of band III. These results show that band III is vibronically coupled to the Soret band. The coupling of band III to modes with strong rhombic distortion of the heme macrocycle calls into question the hypothesis that the axial iron out-of-plane displacement is primarily responsible for the structure-dynamics correlations observed in myoglobin. 相似文献
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Wu R Marta RA Martens JK Eldridge KR McMahon TB 《Journal of the American Society for Mass Spectrometry》2011,22(9):1651-1659
The structure of the proton-bound lysine dimer has been investigated by infrared multiple photon dissociation (IRMPD) spectroscopy
and electronic structure calculations. The structures of different possible isomers of the proton-bound lysine dimer have
been optimized at the B3LYP/6-31 + G(d) level of theory and IR spectra calculated using the same computational method. Based
on relative Gibbs free energies (298 K) calculated at the MP2/aug-cc-pVTZ//B3LYP/6-31 + G(d) level of theory, LL-CS01, and
followed closely (1.1 kJ mol–1) by LL-CS02 are the most stable non-zwitterionic isomers. At the MP2/aug-cc-pVTZ//6-31 + G(d) and MP2/aug-cc-pVTZ//6-31 + (d,p)
levels of theory, isomer LL-CS02 is favored by 3.0 and 2.3 kJ mol–1, respectively. The relative Gibbs free energies calculated by the aforementioned levels of theory for LL-CS01 and LL-CS02
are very close and strongly suggest that diagnostic vibrational signatures found in the IRMPD spectrum of the proton-bound
dimer of lysine can be attributed to the existence of both isomers. LL-ZW01 is the most stable zwitterionic isomer, in which
the zwitterionic structure of the neutral lysine is well stabilized by the protonated lysine moiety via a very strong intermolecular
hydrogen bond. At the MP2/aug-cc-pVTZ//B3LYP/6-31 + G(d), MP2/aug-cc-pVTZ//6-31 + G(d) and MP2/aug-cc-pVTZ//6-31 + G(d,p)
levels of theory, the most stable zwitterionic isomer (LL-ZW01) is less favored than LL-CS01 by 7.3, 4.1 and 2.3 kJ mol–1, respectively. The experimental IRMPD spectrum also confirms that the proton-bound dimer of lysine largely exists as charge-solvated
isomers. Investigation of zwitterionic and charge-solvated species of amino acids in the gas phase will aid in a further understanding
of structure, property, and function of biological molecules. 相似文献
8.
Douglas R. Robello Teresa D. Eldridge Michael T. Swanson 《Journal of polymer science. Part A, Polymer chemistry》1999,37(24):4570-4581
Polycyanoacrylates were found to be inherently unstable. Even in the absence of a deliberately added strong base, their molecular weights decreased drastically on standing in solution in accord with observations by Ryan and McCann (Makromol Chem Rapid Commun 1996, 17, 217). The initial high molecular weight polymer disappeared over the course of a few hours in solution and was replaced by a much lower molecular weight material. For polymers made by anionic polymerization, the entire sample degraded, but for polymers made by free-radical polymerization, only a portion of the sample was affected. This behavior was consistent with the mechanism proposed by Ryan and McCann, in which the polymer chains are in dynamic equilibrium with their monomers and the polymer degrades from its chain terminus. Surprisingly, the degradation in molecular weight even occurred slowly in the solid state. The degradation was inhibited by acids and could be prevented by free-radical copolymerization with small amounts of more stable monomers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4570–4581, 1999 相似文献
9.
Cecily Eldridge Gracia Quek Michael Sako John H. Ryan Simon Saubern Mary Chebib James M. Macdonald 《Tetrahedron》2018,74(12):1245-1252
Four histrionicotoxin analogues were prepared in an efficient manner utilizing a nitrone dipolar cycloaddition reaction as the key step in forming tricyclic intermediate 13. The nitrile in intermediate 13 was reduced with DIBAL to an aldehyde which then underwent Z-selective Wittig reactions to produce intermediates containing the Z-alkene side-chain. Hydrogenation of the Z-alkenes produced saturated histrionicotoxin analogues whereas reduction with SmI2 afforded the unsaturated histrionicotoxin analogues. The histrionicotoxin analogues were shown to be potent non-competitive antagonists of the α4β2 and α7 nAChR's with the most potent analogue 3 displaying IC50's of 0.10 μM and 0.45 μM against the α4β2 and α7 nAChR's, respectively. The unsaturated analogues 15 and 18 displayed Hill slope (nH) of approximately 1 whilst the saturated analogues 16 and 3 had a nH of approximately 0.5, which may indicate that the saturated analogues are binding to more than one binding site. 相似文献
10.
Christopher W. Murray Timothy R. Auton Matthew D. Eldridge 《Journal of computer-aided molecular design》1998,12(5):503-519
This paper tests the performance of a simple empirical scoring function on a set of candidate designs produced by a de novo design package. The scoring function calculates approximate ligand-receptor binding affinities given a putative binding geometry. To our knowledge this is the first substantial test of an empirical scoring function of this type on a set of molecular designs which were then subsequently synthesised and assayed. The performance illustrates that the methods used to construct the scoring function and the reliance on plausible, yet potentially false, binding modes can lead to significant over-prediction of binding affinity in bad cases. This is anticipated on theoretical grounds and provides caveats on the reliance which can be placed when using the scoring function as a screen in the choice of molecular designs. To improve the predictability of the scoring function and to understand experimental results, it is important to perform subsequent Quantitative Structure-Activity Relationship (QSAR) studies. In this paper, Bayesian regression is performed to improve the predictability of the scoring function in the light of the assay results. Bayesian regression provides a rigorous mathematical framework for the incorporation of prior information, in this case information from the original training set, into a regression on the assay results of the candidate molecular designs. The results indicate that Bayesian regression is a useful and practical technique when relevant prior knowledge is available and that the constraints embodied in the prior information can be used to improve the robustness and accuracy of regression models. We believe this to be the first application of Bayesian regression to QSAR analysis in chemistry. 相似文献