Synthesis of retinals isotopically labelled at positions 11, 12, 14 and 20

Five retinals, having different combinations of 2H, with one having 2H and 13C labels at positions 11, 12, 14 and 20, were obtained with a chemical purity of above 98%, a level of 2H enrichment greater than 95% and with 13C enrichment of 99%. The retinals concerned are (20,20,20-2H3)-, (12,20,20,20-2H4)-, (12,14,20,20,20-2H5)-, (11,14-2H2)-, (12,14-2H2)- and (12,14-2H2,20-13C)retinal.