Retinoids and Related Compounds. Part 15. Synthesis and Spectral Characterization of Bicyclic Retinals Involving the 8‐18 or 8‐16 Bonded Structure.

In order to investigate both the chromophore conformation around the trimethylcyclohexene ring and the origin of the induced β-circular dichroism (CD) band in rhodopsin, two C(6)–C(7) singlebond fixed retinal analogues, 6s-cis- and 6s-trans-locked bicyclic retinals 5 and 6, have been synthesized. Their spectral characterization is described.