Theoretical calculation of electronic circular dichroism of the rotationally restricted 3,8"-biflavonoid morelloflavone
Theoretical calculation of electronic circular dichroism of the rotationally restricted 3,8"-biflavonoid morelloflavone
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DOI：
10.1021/jo071134z
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发表时间：
2007-11-23
影响因子：
3.6
通讯作者：
Ferreira, Daneel
中科院分区：
文献类型：
--
作者：
Ding, Yuanqing;Li, Xing-Cong;Ferreira, Daneel
[图形]使用时间相关密度泛函理论 (TDDFT) 对旋转限制的 3,8''-双黄酮 (+)-莫雷洛黄酮的电子圆二色性 (ECD) 进行理论计算，在 298 K 下使用 COSMO 模型在 B3LYP-SCRF/6-31G*/B3LYP/6-31G* 水平上进行，允许明确分配其 2R,3S 绝对构型。实验观察到的 290 nm 左右的棉花效应 (CE) 是由 ABC-黄烷酮部分的苯乙酮 pi -> pi* 跃迁和 DEF-黄酮部分内的电子跃迁造成的，而 350 nm 左右的另一个诊断阳性 CE 归因于 ABC-黄烷酮部分和 DEF-黄酮部分之间的电子相互作用以及 DEF-黄酮部分内的电子跃迁部分。其两种旋转异构体计算的 ECD 的显着差异表明旋转限制显着影响 3,8"-双黄酮类化合物的 ECD。源自单体黄酮类化合物的经验 ECD 规则可能不适用于复杂 3,8"-双黄酮类化合物的构型分配。这项研究为解释此类化合物的实验观察到的 ECD 光谱提供了新的见解。
[Graphics]Theoretical calculation of electronic circular dichroism (ECD) of the rotationally restricted 3,8 ''-biflavonoid (+)-morelloflavone using time dependent density functional theory (TDDFT), performed at 298 K at B3LYP-SCRF/6-31G*/B3LYP/6-31G* level with COSMO model, permitted unequivocal assignment of its 2R,3S absolute configuration. The experimentally observed Cotton effect (CE) around 290 nm is contributed by the acetophenone pi -> pi* transition of the ABC-flavanone moiety and the electronic transition within the DEF-flavone moiety, while another diagnostic positive CE around 350 nm is attributable to the electronic interaction between the ABC-flavanone moiety and the DEF-flavone moiety, as well as the electronic transition within the DEF-flavone moiety. The remarkable differences of the calculated ECD of its two rotamers indicate that the rotational restrictions significantly affect the ECD of 3,8"-biflavonoids. Empirical ECD rules derived from monomeric flavonoids may not be applicable to configurational assignment of complex 3,8"-biflavonoids. This study has provided new insights in interpreting the experimentally observed ECD spectra of this class of compounds.