Synthesis of (+)-(4S)- and (−)-(4R)-11Z-4-hydroxyretinals and determination of the absolute stereochemistry of a visual pigment chromophore in the bioluminescent squid, Watasenia scintillans

Abstract Synthesis of (+)-(4S)- and (−)-(4R)-11Z-4-hydroxyretinals (4-OH-RALs) 1a and 1b was accomplished from (4S)- and (4R)-4-hydroxy-β-ionones, respectively, to determine the absolute configuration of a visual pigment chromophore in Watasenia scintillans. The CD spectra of the native chromophore and its anti-oxime agreed with those of synthetic (4R)-compounds. The CD exciton chirality method as applied to the p-dimethylaminocinnamate of (4R)-4-OH-RAL also establishes the absolute configuration of the native chromophore as 1b .