Synthesis and some characteristics of [13C]-specially enriched tetragastrin and the related compound

[13C]-enriched tetragastrin and the related compound were synthesized in solution. Conversion of S-[13C]methylated tetragastrin to the enriched tetragastrin gave 10.5 ppm upfield chemical shift of Cepsilon resonance. The potency of the synthetic tetragastrin to stimulate gastric acid secretion was virtually identical with that of pentagastrin (ICI).