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1.
Dr. Lidia A. Maslovskaya Dr. Andrei I. Savchenko Prof. Elizabeth H. Krenske Dr. Sharon Chow Tina Holt Dr. Victoria A. Gordon Dr. Paul W. Reddell Carly J. Pierce Prof. Peter G. Parsons Prof. Glen M. Boyle Prof. Andrei G. Kutateladze Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11862-11867
Structurally unique halimanes EBC-232 and EBC-323, isolated from the Australian rainforest plant Croton insularis, proved considerably difficult to elucidate. The two diastereomers, which consist an unusual oxo-6,7-spiro ring system fused to a dihydrofuran, were solved by unification and consultation of five in silico NMR elucidation and prediction methods [i.e., ACDLabs, olefin strain energy (OSE), DP4, DU8+ and TD DFT CD]. Structure elucidation challenges of this nature are prime test case examples for empowering future AI learning in structure elucidation. 相似文献
2.
Prof. Polly L. Arnold Dr. Alessandro Prescimone Dr. Joy H. Farnaby Dr. Stephen M. Mansell Prof. Simon Parsons Prof. Nikolas Kaltsoyannis 《Angewandte Chemie (International ed. in English)》2015,54(23):6735-6739
The diuranium(III) compound [UN′′2]2(μ‐η6:η6‐C6H6) (N′′=N(SiMe3)2) has been studied using variable, high‐pressure single‐crystal X‐ray crystallography, and density functional theory . In this compound, the low‐coordinate metal cations are coupled through π‐ and δ‐symmetric arene overlap and show close metal? CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic‐type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms‐in‐molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa. 相似文献
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The reductive rearrangement, by lithium a-luminum hydride, of 1-silyl-enyne-Ketones or esters affords the corresponding 1-siRyl-β-allenylalcohols, useful synthetic intermediates. 相似文献
5.
David John Parsons Andrew Angus Martyn Brawn Joe Morris 《The Journal of the Operational Research Society》2014,65(9):1387-1395
Local Government Authorities (LGA) in England and Wales have statutory responsibility for the maintenance of Public Rights of Way (PROW), such as pathways and byways open to non-motorised traffic. The departments responsible have to compete for budgets and justify their expenditure in terms of councils’ priorities, such as well-being and environment. A need was identified for a simple decision support tool to provide a consistent and transparent framework for assessing the range of possible social and economic benefits from expenditure on PROW. The tool uses the Analytic Hierarchy Process to elicit weights forming the links from path attributes to users and usage to benefits, with a final stage to combine the benefits according to LGA priorities. It was successfully tested through case studies, where improving signage was generally found to be the most cost effective option, giving moderate benefits at low cost, whereas improving the physical conditions of the surface gave greater benefits at relatively high cost. 相似文献
6.
Simon Parsons 《Tetrahedron: Asymmetry》2017,28(10):1304-1313
Methods for determination of absolute structure using X-ray crystallography are described, with an emphasis on applications for absolute configuration assignment of enantiopure light-atom organic compounds. The ability to distinguish between alternative absolute structures by X-ray crystallography is the result of a physical phenomenon called resonant scattering, which introduces small deviations from the inherent inversion symmetry of single-crystal X-ray diffraction patterns. The magnitude of the effect depends on the elements present in the crystal and the wavelength of the X-rays used to collect the diffraction data, but it is always very weak for crystals of compounds containing no element heavier than oxygen. The precision of absolute structure determination by conventional least squares refinement appears to be unduly pessimistic for light-atom materials. Recent developments based on Bijvoet differences, quotients and Bayesian statistics enable better and more realistic precision to be obtained. The new methods are sensitive to statistical outliers, and techniques for identifying these are summarised. 相似文献
7.
Unprecedented 1,14‐seco‐Crotofolanes from Croton insularis: Oxidative Cleavage of Crotofolin C by a Putative Homo‐Baeyer–Villiger Rearrangement 下载免费PDF全文
Dr. Lidiya A. Maslovskaya Dr. Andrei I. Savchenko Carly J. Pierce Dr. Victoria A. Gordon Dr. Paul W. Reddell Prof. Peter G. Parsons Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(44):14226-14230
EBC‐162 isolated from Croton insularis, obtained from the northern rainforest of Australia, was structurally affirmed as crotofolin C ( 4 ). Novel oxidative degradation products, EBC‐233 and EBC‐300, which are the first crotofolane endoperoxides, were also isolated. Both endoperoxides were found to be stable intermediates, which are proposed to undergo an unprecedented homo‐Baeyer–Villiger biosynthetic rearrangement to give a new class of 1,14‐seco‐crotofolane diterpenes. Prolonged storage of all isolates assisted in authenticating their natural product status. Anticancer activities of reported compounds are presented. 相似文献
8.
Josiane Arnaud Isabelle Coté Patrick J. Parsons Marina Patriarca Andrew Taylor Cas Weykamp 《Accreditation and quality assurance》2014,19(3):169-174
Proficiency testing schemes monitor laboratory performance and provide a stimulus for improvement in accuracy. Where several schemes operate in the same analytical sector, there are risks that assessments of performance may be in conflict. Performance assessment for the determination of trace elements such as aluminum in serum is particularly important due to the high risk of contamination and therefore erroneous results. The objectives of this work were (1) to compare several mathematical models to establish a predefined standard deviation for proficiency assessment and (2) to evaluate the influence of instrumental methods and proficiency testing scheme on the assessment of performance for serum aluminum measurements. For this purpose, three samples were sent to the participants of four proficiency testing schemes. Assigned values were calculated according to algorithm A according to ISO 13528 and standard deviation for proficiency assessment according to three methods based on individual variability, state of the art or previous proficiency testing results. The method based on individual variability produced a more stringent standard deviation compared to analytical imprecision based on the state of the art. The instrumental methods gave similar results, whereas significant differences were observed between the four proficiency testing schemes indicating that harmonization of the standard deviation for proficiency assessment fails to allow transferability from one proficiency testing scheme to another and that additional factor(s) contribute to variability in performance assessment. 相似文献
9.
Samuel Piña Jr. Diana M. Cedillo Carlos Tamez Nezhueyotl Izquierdo Jason G. Parsons Jose J. Gutierrez 《Tetrahedron letters》2014
Reported here is the reduction of aromatic nitro compounds using sodium borohydride and transition metal sulfides as catalysts. The reaction conditions were optimized using the reduction of nitrobenzene as a model reaction. The catalysts studied were iron sulfide (Fe3S4), copper sulfide (CuS), zinc sulfide (ZnS), cobalt sulfide (Co3S4), and nickel sulfide (NiS). The reduction was monitored using gas chromatography. Quantitative conversions were achieved using Co3S4 and NiS, representing a ten-fold increase in reactivity compared to the non-catalyzed reaction. Fe3S4 and ZnS had no apparent effect on the reduction of nitrobenzene while the reduction using CuS showed a marginal increase. The reduction method was applied to several aryl-nitro derivatives containing either electron-withdrawing or electron-donating groups. Halogen containing aryl-nitro compounds were reduced without dehalogenation. The reduction had no effect on other functional groups such as carboxylic acids, esters, amides, or alkenes, indicating that the reduction is highly chemoselective. 相似文献
10.
The selective and efficient acetylation of the hemiacetal hydroxyl in the equilibrium mixture between RCl2C(OAll)OH and AllOH/RCl2CHO was achieved using the acylating system Ac2O/Et3N/dimethylaminopyridine (DMAP).