取代基对涉及阿维菌素相关自由基的环己基向环戊基自由基重排的影响。
Substituent effects on the rearrangements of cyclohexyl to cyclopentyl radicals involving avermectin-related radicals.
作者信息
Luft Jennifer A R, Winkler Tammo, Kessabi Fiona M, Houk K N
机构信息
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
出版信息
J Org Chem. 2008 Nov 7;73(21):8175-81. doi: 10.1021/jo800923a. Epub 2008 Oct 9.
The rearrangement of a substituted cyclohexyl radical to a cyclopentylmethyl radical on the skeleton of avermectin B1 has been investigated using density functional (UB3LYP/6-31G(d)) and G3MP2B3 computational methods. The rearrangement is preferred when highly radical stabilizing groups are present at the 2- and 3-positions of the cyclohexyl radical. A substituent on the 3-position of the cyclohexyl radical enables ring-cleavage of the cyclohexyl radical, while a radical stabilizing substituent on the 2-position of the cyclohexyl radical stabilizes the final cyclopentylmethyl radical, enabling the overall rearrangement and reversing the normal thermodynamic preference for the hexenyl radical ring closure.
已使用密度泛函（UB3LYP/6-31G(d)）和G3MP2B3计算方法研究了阿维菌素B1骨架上取代环己基自由基重排为环戊基甲基自由基的过程。当环己基自由基的2位和3位存在高度稳定自由基的基团时，重排更易发生。环己基自由基3位上的取代基能使环己基自由基发生开环，而环己基自由基2位上的稳定自由基取代基则能稳定最终的环戊基甲基自由基，从而实现整体重排，并逆转己烯基自由基环化的正常热力学偏好。
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