The light sensitivity and unstable nature of 11-cis-retinoids makes them ideal visual chromophores in nature. The synthesis of 11-cis-retinal analogues is of paramount importance in bioorganic studies of rhodopsin, the photoreceptor of the visual transduction pathway, but the instability of 11-cis-retinoids complicates their synthesis and there is no general synthetic route. Common strategies to the cis geometry have failed in the case of 11-cis-retinoids, and most often low yields and complex isomeric mixtures are obtained. Herein we report an efficient, general, and mild preparation of 11-cis-retinoids by semi-hydrogenation of 11-yne-retinoid precursors with Cu/Ag-activated zinc dust.
The light sensitivity and unstable nature of 11-cis-retinoids makes them ideal visual chromophores in nature. The synthesis of 11-cis-retinal analogues is of paramount importance in bioorganic studies of rhodopsin, the photoreceptor of the visual transduction pathway, but the instability of 11-cis-retinoids complicates their synthesis and there is no general synthetic route. Common strategies to the cis geometry have failed in the case of 11-cis-retinoids, and most often low yields and complex isomeric mixtures are obtained. Herein we report an efficient, general, and mild preparation of 11-cis-retinoids by semi-hydrogenation of 11-yne-retinoid precursors with Cu/Ag-activated zinc dust.