Retinoids and related compounds. X. Synthesis of geometrical isomers of (.+-.)-2- and (.+-.)-3-Hydroxyretinals and identification of the cromophore of the fly visual pigment.
The geometrical isomers of (±)-3-hydroxyretinals were synthesized and characterized. Subsequently, simultaneous separation of eight isomers of 2- and 3-hydroxyretinals by high-performance liquid chromatography (HPLC) was accomplished and, in addition, complete separation of eight syn-anti isomers of 3-hydroxyretinaloximes by HPLC was achieved. Under these analytical conditions, the chromophore of the fly (Drosphila melanogaster) visual pigment was identified as 11-cis-3-hydroxyretinal (10).