Synthesis of 9-cis-Retinyl Acetate.

All-trans-retinyl acetate (400 g) was dissolved in a solution of hexanes (800 ml) and trimethylamine (0.22 ml). After addition of 0.4 mg of bis(benzonitrile)palladium chloride, the mixture was stirred overnight in the dark at 65°C under nitrogen (Supplemental Fig. 1). The resulting solution was cooled to room temperature for 1 hour and then further cooled to −80°C. The all-trans-retinyl acetate that crystallized was filtered by suction using a filter precooled with dry ice. The filtrate was concentrated and further crystallized. This process was repeated to obtain a 70:30 mixture of 9-cis-/all-trans-retinyl acetate, which was used for the next steps without further purification.