Cycloadditions of nitrile oxides to 2,3-dihydrofuran are highly regioselective whereas the regioselectivity of the cycloadditions to 2,3-dihydrothiophen is only moderate. The directing effect of oxygen and sulfur in these cycloadditions could be evaluated at 2.8 and 1.1 Kcal mol-1 respectively. The related acyclic sulfur dipolarophiles, (E)-propenyl methyl and phenyl sulfides, similarly undergo cycloadditions
The preparation of optically active boronic ester substituted Δ2-isoxazolines
作者:Richard H Wallace、K.K Zong
DOI:10.1016/s0022-328x(99)00055-8
日期:1999.6
In this paper we report our recent results in the area of nitrile oxide cycloaddition to opticallyactive vinylboronic esters to afford opticallyactive boronic ester substituted Δ2-isoxazolines. In these studies, a number of opticallyactivediols were investigated and TADDOLs have been found to afford the best diastereoselectivity. The mixture of diastereomers obtained in these reactions can be readily
<i>N</i>-Vinyl-Nitroimidazole Cycloadditions: Potential Routes to Nucleoside Analogues
作者:Christopher Ramsden、Russell Clayton
DOI:10.1055/s-2005-872083
日期:——
Cycloaddition reactions of 4-nitro- and 5-nitro-1-vinylimidazoles have been investigated. The cycloadducts obtained are potential intermediates for synthesis of purine nucleoside analogues via reduction to the corresponding aminoimidazoles. A byproduct obtained using benzonitrile oxide as 1,3-dipolarophile has been identified as a novel tricyclic isomer 12 of the cycloadduct 11.
The Chemistry of Pseudomonic Acid. 18. Heterocyclic Replacement of the α,β-Unsaturated Ester: Synthesis, Molecular Modeling, and Antibacterial Activity
作者:Pamela Brown、Desmond J. Best、Nigel J. P. Broom、Robert Cassels、Peter J. O'Hanlon、Timothy J. Mitchell、Neal F. Osborne、Jennifer M. Wilson
DOI:10.1021/jm960738k
日期:1997.8.1
The electronic requirements around the C1-C3 region of pseudomonic acid analogues were investigated. Synthetic routes were developed to access a range of compounds where the alpha, beta-unsaturatedester moiety had been replaced by a 5-membered ring heterocycle. The inhibition of isoleucyl tRNA synthetase from Staphylococcus aureus NCTC 6571 was determined as was the minimum inhibitory concentration
研究了伪酸类似物的C1-C3区域周围的电子需求。已开发出合成路线以获取一系列化合物,其中α,β-不饱和酯部分已被5-元环杂环取代。确定了来自金黄色葡萄球菌NCTC 6571的异亮氨酰tRNA合成酶的抑制作用,以及测试化合物对该生物体的最小抑制浓度(MIC)。发现具有与α,β-不饱和酯中的羰基相对应的静电势区域以及与双键相对应的区域中的低能未占据分子轨道的化合物的IC50值为0.7-5.3 ng mL-1。但是,这些化合物的MIC值在2.0-8.0微克mL-1的范围内,