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排序方式: 共有93条查询结果,搜索用时 15 毫秒
61.
Radomir N. Saicic 《合成通讯》2013,43(17):2559-2562
Addition of 2.5 mol% DBU to a mixture of isomeric 2,4‐dimethylglutaric anhydrides in ethyl acetate promotes crystallization‐induced transformation, affording the pure cis‐2,4‐dimethylglutaric anhydride in 87% yield. 相似文献
62.
Radomir Jasiński Magda Ziółkowska Oleh M. Demchuk Agata Maziarka 《Central European Journal of Chemistry》2014,12(5):586-593
[2+3] Cycloaddition reactions of the highly reactive (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone with (E)-2-R-nitroethenes proceed under mild conditions and yield mixtures of stereoisomeric 2-methyl-3-(3,4,5-trimethoxyphenyl)-4-nitro-5-R-isoxazolidines. The effect of regiospecificity of the cycloadditions may be accounted for by the theory of electrophilicity indexes. Stereoselectivity, however, is determined by a compilation of steric and secondary orbital effects. 相似文献
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The enynol 2 was transformed into D -erythro-sphingosine 11 (7 steps, 46%) and into ceramide 1 (8 steps, 41% overall yield). The key steps were the mono-epoxidation of the enynol 5 (Ti(t-BuO)4, (?)-D -diethyl tartrate, t-BuOOH) to 6 (86%, ≥ 98% ee), the regioselective intramolecular opening of the oxirane 6 via the benzylurethane 7 , and the reductive tranformation of the acetylene 9 into the oxazolidinone 10 (Li, EtNH2, 88%). 相似文献
67.
A C,D-seco-paclitaxel derivative 12 was prepared and tested for biological activity. The key step in the synthesis was a free radical fragmentation of the bicyclic tertiary alcohol 7 under the conditions of the hypobromite reaction. The compound 12 showed no activity in the tubulin test. 相似文献
68.
Agnieszka Kącka Luis R. Domingo Radomir Jasiński 《Research on Chemical Intermediates》2018,44(1):325-337
The molecular mechanism of the decomposition reaction of nitroethyl benzoates catalyzed by Lewis acids based on boron element—BH3 and BF3—was studied using density functional theory methods. These reactions take place much faster than the uncatalyzed process. However, the presence of fluorinated Lewis acids has a unique influence on the molecular mechanism. In the case of BF3, a change from a one-step mechanism to a two-step one involving a zwitterionic intermediate is observed. 相似文献
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Radomir Konjevi† Jitendra P. Khurana Kenneth L. Poff† 《Photochemistry and photobiology》1984,39(6):789-792
Abstract
The shape of the fluence-response relationship for the phototropic response of the JK224 strain of Arabidopsis thaliana depends on the fluence rate and wavelength of the actinic light. At low fluence rate (0.1 μmol m-2 s-1 ), the response to 450-nm light is characterized by a single maximum at about 9 μmol m-2 . At higher fluence rate (0.4 μmol m-2 s-1 ), the response shows two maxima, at 4.5 and 9 μmol m-2 . The response to 510-nm light shows a single maximum at 4.5 μmol m-2 . Unilateral preirradiation with high fluence rate (25 μmol m-2 s-1 ) 510-nm light eliminates the maximum at 4.5 μmol m-2 in the fluence response curve to a subsequent unilateral 450-nm irradiation, while the second maximum at 9 μmol m-2 is unaffected. Based on these results, it is concluded that a single photoreceptor pigment has been altered in the JK224 strain of Arabidopsis thaliana. 相似文献
The shape of the fluence-response relationship for the phototropic response of the JK224 strain of Arabidopsis thaliana depends on the fluence rate and wavelength of the actinic light. At low fluence rate (0.1 μmol m