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41.
The (13)C NMR spectrum of 2-butyl-1,2-(13)C(2) cation (1) is unchanged on heating the sample to -78 degrees C, indicating no isomerization to another isotopomer. In contrast, the spectrum of 2-butyl-2,3-(13)C(2) cation (2) shows rapid formation of all of the other isotopomers except 1. These results are consistent with a protonated cyclopropane intermediate in the rearrangement process. In this mechanism, either C(1) and C(2) or C(3) and C(4) interchange. Only the bond between C(2) and C(3) breaks. 相似文献
42.
Functionalized, hydrogen-bonding ionic liquids have been successfully evaluated as media for the performance of cofactor-dependent enzyme catalysed oxidations; the effects of incorporating hydroxyl groups into both the cation and anion have been studied and the dependence of activity upon water content has been evaluated. 相似文献
43.
A. Stanley Jones Michael J. McClean Hironichi Tanaka Richard T. Walker Jan Balzarini Erik De Clercq 《Tetrahedron》1985,41(24):5965-5972
Reaction of 2',3'-secouridine with acetone gave the 3',5'--isopropylidene derivative (1) which upon treatment with mesylchloride gave the 2'--mesyl compound (2). Replacement of the mesyl group of 2 with halide could be effected by reaction with a metal halide in DMF. The 3',5'--isopropylidene group was removed simultaneously to give a 2'-halogeno-2'-deoxy-2',3'-secouridine. 2',3'-Dichloro-2',3'-dideoxy-2',3'-secouridine upon treatment with base gave 6()-chloromethyl-2()-(uracil-1-yl)-1,4-dioxane in addition to O2,2'-anhydro-3'-chloro-3'-deoxy-2',3'-secouridine, as previously reported. 2',3'-Dichloro-2',3'-dideoxy-5'-0-trityl-2',3'-secouridine was converted to 2',3'-dichloro-2',3'-dideoxy-2',3'-secocytidine (16) a triazole derivative. Compound 16 was unstable and appeared to form O2,2'-anhydro-3'-chloro-3'-deoxy-2,3'-secocytidine upon standing at room temperature. 5-Vinyl- and 5-() (2-bromovinyl) uridine dialdehydes have been made, as well as a number of other 5-substituted 2',3'-secouridine derivatives. None of the compounds obtained showed significant activity against a number of virus strains or tumor cell lines, except for 5-()(2-bromovinyl) uridine dialdehyde, which was inhibitory to the growth of human lymphoblast (Raji, Namalva) cells at a concentration of 28 μ/ml. 相似文献
44.
The synthesis of -5(2-bromovinyl)-2′-deoxyuridine in good yield from deoxyuridine an intermediate organopalladium derivative is described. The corresponding chloro and iodo compounds have also been made as have the corresponding bromo and iodo 2′-deoxycytidines. 相似文献
45.
Synthesis of amides from coupling esters with a range of primary amines can be conveniently achieved in moderate to excellent yields (69-99%) using an air-stable adduct of trimethylaluminium (AlMe3)2·DABCO (DABCO is 1,4-diazobicyclo[2.2.2]octane), referred to as DABAL-Me3. Reactions can be run without requiring the exclusion of atmospheric oxygen or the drying of solvents. 相似文献
46.
2,5-Divinyltetrahydropyran (1) can be isomerized using a ruthenium trichloride- triphenylphosphine catalyst to give 3,4-dihydro-3-vinyl-6-ethyl-2H-pyran (2) and 3,4-dihydro-3- ethylidene-6-ethyl-2H-pyran (3). These products give a variety of rearranged products on treatment with acid. The course of the reactions can be controlled by reaction conditions to give 4-ethyltoluene (5) or 3-hydroxymethyl-1-octen-6-one (4) from 2, and 3,4-dihydro-2-methyl-3-methylene-(6-ethyl-2H- pyran (7), 2,3,4-trimethyl-2-cyclohexen-1-one (8), or 3-hydroxymethyl-2-octen-6-one (6) from 3. All of these products (4–8) can be explained as arising by the initial opening of the dihydropyran to generate an unsaturated hydroxy ketone which then cyclizes to carbocyclic products. 相似文献
47.
Ronald F. Walker 《Analytical and bioanalytical chemistry》1998,360(3-4):325-326
This paper discusses some of the work of ISO-REMCO’s Task Group 4 (TG4) – the Accreditation TG, giving firstly a brief account of the recently published ISO Guide 34 – which gives guidance on the type of quality system a reference material producer should have in place. Secondly, work on the future development of Guide 34 to produce a document against which it will be possible for producers to be accredited without reference to ISO Guide 25 is discussed, and thirdly, the possible formation of an international register of CRM producers, which will provide users with information about the quality status of different producers, is considered. 相似文献
48.
Edward F. Hayes Zareh Darakjian Robert B. Walker 《Theoretical chemistry accounts》1991,79(3-4):199-213
Summary The Bending Corrected Rotating Linear Model (BCRLM), developed by Hayes and Walker, is a simple approximation to the true multidimensional scattering problem for reactions of the type: A + BC AB + C. While the BCRLM method is simpler than methods designed to obtain accurate three-dimensional quantum scattering results, this turns out to be a major advantage in terms of our benchmarking studies. The computer code used to obtain BCRLM scattering results is written for the most part in standard FORTRAN and has been ported to several scalar, vector, and parallel architecture computers including the IBM 3090-600J, the Cray XMP and YMP, the Ardent Titan, IBM RISC System/6000, Convex C-1 and the MIPS 2000. Benchmark results will be reported for each of these machines with an emphasis on comparing the scalar, vector, and parallel performance for the standard code with minimum modifications. Detailed analysis of the mapping of the BCRLM approach onto both shared and distributed memory parallel architecture machines indicates the importance of introducing several key changes in the basic strategy and algorithms used to calculate scattering results. This analysis of the BCRLM approach provides some insights into optimal strategies for mapping three-dimensional quantum scattering methods, such as the Parker-Pack method, onto shared or distributed memory parallel computers. 相似文献
49.
Chen JP Meziani ZE Beck D Boyd G Chinitz LM Day DB Dennis LC Dodge G Filippone BW Giovanetti KL Jourdan J Kemper KW Koh T Lorenzon W McCarthy JS McKeown RD Milner RG Minehart RC Morgenstern J Mougey J Potterveld DH Rondon-Aramayo OA Sealock RM Smith LC Thornton ST Walker RC Woodward C 《Physical review letters》1991,66(10):1283-1286
50.