Synthesis of retinals labelled at positions 14 and 15 (with ¹³C and/or ²H)

Eight retinals labelled at positions 14 and 15 with 13 C and/or 2 H were obtained with >98% chemical purity, 92% 13 C incorporation, 95% 2 H incorporation at position 14 and 99% 2 H incorporation at position 15. (14‐ 13 C)retinal, (15‐ 13 C)retinal and (14,15‐ 13 C 2 )retinal were synthesized from (2‐ 13 C)‐, (1‐ 13 C)‐ and (1,2‐ 13 C 2 )acetonitrile, respectively, while for the synthesis of (14‐ 2 H)retinal, C 2 H 3 CN was used. Via a three‐step process these retinals were transformed into (14,15‐ 2 H 2 )retinal, (14‐ 13 C,15‐ 2 H)retinal, (15‐ 13 C,15‐ 2 H)retinal and (14,15‐ 13 C 2 ,15‐ 2 H)‐retinal. Their 13 C– 13 C, 13 C‐ 2 H and 13 C‐ 1 H NMR coupling constants were determined.