Identification of the syn and anti geometric isomers of retinalmethoxime

Methoxime derivatization of all-trans retinal afforded two reaction products (I) and (II) as demonstrated by gas-liquid and thin-layer chromatography. Preparative thin-layer chromatography followed by elution allowed isolation of both substances in a pure form. Spectroscopic examination identified compounds (I) and (II) as the retinalmethoxime geometric isomers. Full structural assignment was performed by nuclear magnetic resonance spectroscopy: (I) possesses the syn and (II) the anti configuration.