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

Five retinals, having different combinations of 2 H, with one having 2 H and 13 C labels at positions 11, 12, 14 and 20, were obtained with a chemical purity of above 98%, a level of 2 H enrichment greater than 95% and with 13 C enrichment of 99%. The retinals concerned are (20,20,20‐ 2 H 3 )‐, (12,20,20,20‐ 2 H 4 )‐, (12,14,20,20,20‐ 2 H 5 )‐, (11,14‐ 2 H 2 )‐, (12,14‐ 2 H 2 )‐ and (12,14‐ 2 H 2 ,20‐ 13 C)retinal.