Synthesis of specifically deuteriated 9‐ and 13‐demethylretinals

Abstract

Abstract(13–2H) 13‐Demethylretinal, (11,12,13‐2H,) 13‐demethylretinal, (9‐2H)9‐demethylretinal and (9,10‐2H2)9‐demethylretinal were prepared in all‐E, 9Z, 11Z and 13Z isomeric form with high deuterium incorporation. In the synthesis of (9,10‐2H2)9‐demethylretinal, a Horner‐Emmons reaction with deuteriated diethyl (cyanomethyl)phosphonate was used. This synthon was subsequently used for the synthesis of (10‐2H)‐ and (14‐2H)retinal in high yield and with high deuterium incorporation. From the 13C NMR spectra of the demethylretinals (all‐E, 9Z and 13Z), he effect of a methyl group on the 13CNMR parameters of polyene‐chain carbons was determined.