G. Englert, S. H. Weber, M. Klaus
Nov 1, 1978
Citations
0
Influential Citations
24
Citations
Journal
Helvetica Chimica Acta
Abstract
Photoisomerization of an aromatic analogue of retinoic acid, ethyl all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-nona-2,4,6, 8-tetraenoate 1 in dilute solutions of hexane, benzene, and ethanol yielded multi-component mixtures of cis isomers which were separated by HPLC. FT-1H-NMR. at 270 MHz and, in some cases, homonuclear decoupling and Overhauser experiments as well as 13C-NMR. were applied to establish the structures of 4 mono-cis, 4 (of 6 possible) di-cis, and 3 (of 4 possible) tri-cis isomers. The structures of 3 isomeric esters, namely (2Z, 4E, 6E, 8E) 6, (2Z, 4Z, 6E, 8E) 9, and (2Z, 4Z, 6Z, 8E) 7 were independently confirmed by direct syntheses. The 1H-NMR. data of all these compounds and the 13C-NMR. data of the all-trans and of 6 cis isomers available in sufficiently large quantities are discussed.