Carbon‐13 NMR spectra of retinal1 and its related compounds

Carbon-13 NMR spectra of all-trans retinal1 and vitamin A1 were measured by the pulse Fourier transform method in CCl4. All peaks in these spectra were assigned from considerations of chemical shifts, half proton-decoupled spectra, spin-lattice relaxation times and induced chemical shift by the addition of shift reagent. The carbon-13 NMR spectrum was also measured for all-trans retinal1 which had been exposed to the sunlight for three hours, and the induced isomer was proposed to be 11-s-cis retinal1.