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排序方式: 共有191条查询结果,搜索用时 46 毫秒
31.
Boyd DR Sharma ND Llamas NM Coen GP McGeehin PK Allen CC 《Organic & biomolecular chemistry》2007,5(3):514-522
Enantiopure trans-dihydrodiols have been obtained by a chemoenzymatic synthesis from the corresponding cis-dihydrodiol metabolites, obtained by dioxygenase-catalysed arene cis-dihydroxylation at the 2,3-bond of monosubstituted benzene substrates. This generally applicable, seven-step synthetic route to trans-dihydrodiols involves a regioselective hydrogenation and a Mitsunobu inversion of configuration at C-2, followed by benzylic bromination and dehydrobromination steps. The method has also been extended to the synthesis of both enantiomers of the trans-dihydrodiol derivatives of toluene, through substitution of a vinyl bromine atom of the corresponding trans-dihydrodiol enantiomers derived from bromobenzene. Through incorporation of hydrogenolysis and diMTPA ester diastereoisomer resolution steps into the synthetic route, both trans-dihydrodiol enantiomers of monohalobenzenes were obtained from the cis-dihydrodiols of 4-haloiodobenzenes. 相似文献
32.
This paper studies four n-job, m-machine flowshop problems when processing times of jobs on various machines follow certain
conditions. The objective is to obtain a sequence, which minimizes total elapsed time under no-idle constraint. Under no-idle
constraint, the machines work continuously without idle-interval. We prove two theorems. We introduce simple algorithms without
using branch and bound technique. Numerical examples are also given to demonstrate the algorithms. 相似文献
33.
For each n 4 there exists a finite 2-group Gn such that itsnth dimension subgroup does not coincide with its nth lowercentral subgroup. This settles the dimension subgroup conjecturenegatively for all n4. 相似文献
34.
The sphingolipid backbone is readily assembled by E-selective olefin cross metathesis of a suitable building block. 相似文献
35.
Derek R. Boyd Peter B. Coulter Narain D. Sharma W.Brian Jennings Valerie E. Wilson 《Tetrahedron letters》1985,26(13):1673-1676
Steric and mesomeric effects have a marked influence upon the formation of oxaziridine (normal pathway) or nitrone (abnormal pathway) products from the imine-peroxyacid reaction; n.m.r. studies of the thermal isomerization of oxaziridines to nitrones provide evidence of a pseudo-abnormal oxidation pathway. 相似文献
36.
Summary A thin-layer Chromatographic investigation was carried out on Silica Gel-G plates for metal dithizonates and the technique was applied for detecting metals present in autopsy tissues in cases of suspected suicide and homicide. Rf values of the common metal complexes in four Chromatographic solvents and the colour of their respective spots on the TLC plate are reported.
Zusammenfassung Die Dünnschichtchromatographie von Metalldithizonaten auf Silicagel G-Platten wurde mit dem Ziel untersucht, Metalle in Leichenteilen nach Selbstmord oder Mord nachweisen zu können. Die Rf-Werte der Dithizonate üblicher Metalle in vier zur Chromatographie verwendeten Lösungsmitteln und die Farbe der Chromatogrammflecken wurden angegeben.相似文献
37.
Swarup Narain Tewari 《Mikrochimica acta》1961,49(1):37-40
Summary The separation by paper chromatography and identification of reducing sugars in urine is described.
Zusammenfassung Die papierchromatographische Trennung und Identifizierung reduzierender Zucker im Harn wird beschrieben.
Résumé On décrit la séparation par Chromatographie sur papier et l'identification des sucres réducteurs dans l'urine.相似文献
38.
Hao Liu Jian Xu Jiali Jiang Jun Yin Ravin Narain Yuanli Cai Shiyong Liu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(8):1446-1462
Well‐defined amphiphilic PCL‐b‐(PDMA)2 and (PCL)2‐b‐PDMA Y‐shaped miktoarm star copolymers and PCL‐b‐PDMA linear diblock copolymer were synthesized via a combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP), where PCL is poly (ε‐caprolactone) and PDMA is poly(2‐(dimethylamino)ethyl methacrylate). All of these three types of copolymers have comparable PCL contents and overall molecular weights. The PCL block is hydrophobic while the PDMA block is hydrophilic, and they behave like polymeric surfactants and self‐assemble into PCL‐core micelles in aqueous media. The chain architectural effects on the micellization properties, including the aggregation number, size, polydispersity, and micelle densities of (PCL29)2‐b‐PDMA45, PCL61‐b‐(PDMA24)2, and PCL56‐b‐PDMA49 in dilute aqueous solution, were then explored by dynamic and static laser light scattering (LLS). The intensity–average hydrodynamic radius, 〈Rh〉, the aggregation number per micelle, Nagg, and the core radius, Rcore, of the PCL‐core micelles all increased in the order PCL61‐b‐(PDMA24)2 < (PCL29)2‐b‐PDMA45 < PCL56‐b‐PDMA49. The surface area occupied per soluble PDMA block at the core/corona interface increased in the order PCL61‐b‐(PDMA24)2 < PCL56‐b‐PDMA49 < (PCL29)2‐b‐PDMA45. PCL61‐b‐(PDMA24)2 micelles had the largest overall micelle density, possibly because of that the presence of two soluble PDMA arms at the junction point favors the bending of the core–corona interface and thus the formation of densely‐packed core‐shell nanostructures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1446–1462, 2007 相似文献
39.
Mehta Aarti Srivastava A. K. Gupta Govind Chand Suresh Sharma Shailesh Narain 《Journal of Sol-Gel Science and Technology》2021,99(2):295-314
Journal of Sol-Gel Science and Technology - In this article, the beneficial effect of surface passivation rendered by the amalgamation of co-ordinating tri-n-octylphophine (TOP), oleylamine (OLA),... 相似文献
40.
In polar, nonhydrogen-bonding solvents, cocaine's phosphorescence differs from that of its model compound, methyl benzoate, in what can be attributed to an amine-benzoate charge transfer interaction and both compounds exhibit long wavelength bands not present in nonpolar media. 相似文献