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Ruohola AM Koissi N Andersson S Lepistö I Neuvonen K Mikkola S Lönnberg H 《Organic & biomolecular chemistry》2004,2(13):1943-1950
Reactions of 9-ethylguanine, 2'-deoxyguanosine and guanosine with bromomalondialdehyde in aqueous buffers over a wide pH-range were studied. The main products were isolated and characterized by (1)H and (13)C NMR and mass spectroscopy. The final products formed under acidic and basic conditions were different, but they shared the common feature of being derived from glyoxal. Among the 1 : 1 adducts, 1,N(2)-(trans-1,2-dihydroxyethano)guanine adduct (6) predominated at pH < 6 and N(2)-carboxymethylguanine adduct (10a,b) at pH > 7. In addition to these, an N(2)-(4,5-dihydroxy-1,3-dioxolan-2-yl)methylene adduct (11a,b) and an N(2)-carboxymethyl-1,N(2)-(trans-1,2-dihydroxyethano)guanine adduct (12) were obtained at pH 10. The results of kinetic experiments suggest that bromomalondialdehyde is significantly decomposed to formic acid and glycolaldehyde under the conditions required to obtain guanine adducts. Glycolaldehyde is oxidized to glyoxal, which then modifies the guanine base more readily than bromomalondialdehyde. Besides the glyoxal-derived adducts, 1,N(2)-ethenoguanine (5a-c) and N(2),3-ethenoguanine adducts (4a-c) were formed as minor products, and a transient accumulation of two unstable intermediates, tentatively identified as 1,N(2)-(1,2,2,3-tetrahydroxypropano)(8) and 1,N(2)-(2-formyl-1,2,3-trihydroxypropano)(9) adducts, was observed. 相似文献
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Bengt Karlsson Anne-Marie Pilotti Anne-Charlotte Söderholm Torbjörn Norin Stefen Sundin Masashi Sumimoto 《Tetrahedron》1978,34(15):2349-2354
The structure of verticillol diepoxide 4 has been established by direct single crystal X-ray analysis. The structure of verticillol 5 follows from the chemical correlation to the diepoxide 4 as well as from NMR-LIS studies on verticillol which also provide evidence for the conformation of this alcohol. The absolute configuration of verticillol 5 has been assigned on the basis of CD data for the verticillol norketodiepoxide 6a. 相似文献
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Lindh J Enquist PA Pilotti A Nilsson P Larhed M 《The Journal of organic chemistry》2007,72(21):7957-7962
Scope and limitations of the base-free oxidative Heck reaction with arylboronic acids have been explored. Under our conditions, the dmphen-palladium(II)-catalyzed arylation proceeded with air or p-benzoquinone as reoxidants of palladium(0). We found that ambient temperature and mild aerobic conditions allow for the use of substrates sensitive to palladium(II)-catalyzed oxidation. Oxidative Heck couplings, employing different arylboronic acids, were smoothly and regioselectively conducted with both electron-rich and electron-poor olefins, providing high yields even with disubstituted butyl methacrylate, sensitive acrolein, and a vinylboronate ester. Controlled microwave processing was used to reduce reaction times from hours to minutes both in small scale and in 50 mmol scale batch processes. 相似文献
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The complex [MoW(μ-CC6H4Me-4)(CO)2(η7-C7H7)(η5-C2B9H10Me)] reacts with diazomethane in Et2O containing EtOH to afford the dimetal compound [MoW(OEt)(μ-CH2){μ-C(C6H4Me-4)C(Me)O}(η7-C7H7)(η5-C2B9H10Me)]. The structure of this product was established by X-ray diffraction. The Mo---W bond [2.778(4) Å] is bridged by a CH2 group [μ-C---Mo 2.14(3), μ-C---W 2.02(3) Å] and by a C(C6H4Me-4)C(Me)O fragment [Mo---O 2.11(3), W---O 2.18(2), Mo---C(C6H4Me-4) 2.41(3), W---C(C6H4Me-4) 2.09(3), Mo---C(Me) 2.26(3) Å]. The molybdenum atom is η7-coordinated by the C7H7 ring and the tungsten atom is η5-coordinated by the open pentagonal face of the nido-icosahedral C2B9H10Me cage. The tungsten atom also carries a terminally bound OEt group [W---O 1.88(3) Å]. The 1H and 13C-{1H} NMR data for the dimetal compound are reported and discussed. 相似文献
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S. Antus M. Nógrádi E. Baitz-Gács L. Radics H.-D. Becker B. Karlsson A.-M. Pilotti 《Tetrahedron》1978,34(16):2573-2577
Oxidation of isovanillin, vanillin and o-vanillin with TI(NO3)3 in MeOH gave the dimethyl acetals of 6,6-dimethoxy-2,4-cyclohexadien-1-one aldehydes (4–6 which dimerized spontaneously to give a single product each (7–9) the structure of which was elucidated by 1H and 13C NMR, photocyclization to the cage compounds 12–14 and of 7 and 9 by X-ray diffraction as well. 相似文献