Hydrogen bonding and π-stacking in dipyrrinone acid dimers of xanthobilirubic acid and chiral analogs
作者:Stefan E. Boiadjiev、D.Timothy Anstine、Emily Maverick、David A. Lightner
DOI:10.1016/0957-4166(95)00301-5
日期:1995.9
Xanthobilirubic acid and its analogs self-associate strongly through intermolecular hydrogen bonding between their carboxylic acid and dipyrrinone components, forming π-stacked dimers. In contrast, their methyl esters form planar dimers conjoined by dipyrrinone to dipyrrinone intermolecular hydrogen bonding. When a stereogenic center is present in the propionic side acid chain, unusually large optical
黄胆红酸及其类似物通过其羧酸和二吡啶酮组分之间的分子间氢键强烈自缔合,形成π堆积的二聚体。相反,它们的甲酯形成平面二聚体,该二聚体由二吡啶酮连接至二吡啶酮分子间氢键。当一个立体异构中心存在于丙酸侧酸链,异常大的旋光和激子耦合圆二色性可为光学活性的酸可以观察到:βS -methylxanthobilirubic酸(1)具有[ α ] d 20 = -314°和Δ ∈ 434最大= -10.9,Δ ∈ 388最大= 5.7(氯仿3)。相比之下,甲基酯显示较弱的旋转和微乎其微CD:的(甲基酯1)具有[ α ] d 20 + 62°和Δ∈ 435 ⪡0.5,Δ∈⪡0.5。