Complex Thermal Behavior of 11-cis-Retinal, the Ligand of the Visual Pigments

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• 作者：Carlos Silva Lpez ; Rosana lvarez ; Marta Domnguez ; Olalla Nieto Faza ; ngel R. de Lera
• 刊名：Journal of Organic Chemistry
• 出版年：2009
• 出版时间：February 6, 2009
• 年：2009
• 卷：74
• 期：3
• 页码：1007-1013
• 全文大小：339K
• 年卷期：v.74,no.3(February 6, 2009)
• ISSN：1520-6904

文摘

Upon heating to 80 °C, 11-cis-retinal yields a mixture of all-trans-retinal and 13-cis-retinal. This isomerization has been studied by means of density functional theory methods, and the computational results suggest a close competition between two mechanisms of very different nature. A classical internal rotation around the C11−C12 cis double bond, via a diradical transition state, accounts for the formation of the all-trans isomer. An intricate sequence of pericyclic reactions, namely a reversible [1,7]-H sigmatropic shift and a reversible 6-π-oxa-electrocyclic reaction, is responsible for the formation of 13-cis-retinal. Experiments using 11-cis-retinal labeled with deuterium at C19 confirmed the mechanistic proposal and also revealed an unprecedented outcome on the product composition of isotopologues.