Synthesis and spectroscopic characterization of the doubly locked 9E,11Z retinal model systems 7E,13E-11,19-10,29-dimethanoretinal and its 13Z isomer

Article abstract of DOI:10.1002/recl.19921110206

7E,13E-11,19-10,20-dimethanoretinal (1) and its 13Z isomer 2 were prepared from β-ionone, using the novel synthon 2-(diethoxyphosphinyl)-5,5-dimethoxyhexanenitrile.This synthon was also used to prepare 7E,9E,13E-10,20-methanoretinal (3) and its 13Z isomer 4 in high yield, starting from β-ionone.Spectroscopic analysis (mass, 1H and 13C NMR and UV/Vis) of these compounds is discussed.The introduction of the methano bridges leads to minimal steric and electronic changes.The photostationary state reached from 1 and 2 has the 13Z form 2 as the main constituent.This is one of the very few with a Z form as the main constituent of the photostationary state. 1 and 2 are very sensitive to acid-catalyzed isomerization of the 13-C=14-C double bond.The presence of the 11,19-methano bridge is responsible for this efficient Z-E isomerization.