Synthesis of S‐benzyl‐DL‐[1‐¹³C]cysteine and its incorporation into oxytocin and [8‐arginlne]vasopressin and related compounds by total synthesis. Separation of diastekeoisomers by partition chromatography and HPLC

S‐Benzyl‐DL‐[1‐¹³C]cysteine was prepared from Na¹³CN by a three step synthesis and converted to the t‐butyloxycarbonyl derivative which was suitable for use in peptide synthesis. This compound was incorporated into the 1 and 6 positions of a variety of oxytocin and [8‐arginine]vasopressin derivatives and analogues via total synthesis using the solid phase method. The compounds were separated and purified by partition chromatography on Sephadex and their purity was checked by high pressure liquid chromatography. The compounds synthesized include [1‐hemi‐[1‐¹³C]cystine]oxytocin, [1‐hemi‐D‐[1‐¹³C]‐cystine]oxytocin, [1‐hemi‐[1‐¹³C]cystine, 8‐arginine]vasopressin, [1‐hemi‐D[1‐¹³C]cystine, 8‐arginine]vasopressin, [6‐hemi‐[1‐¹³C]cystine]oxytocin, [6‐hemi‐D‐[1‐¹³C]cystine]oxytocin, [1‐hemi‐D‐[1‐¹³C]cystine, 3‐D‐leucine]‐oxytocin, and [1‐hemi‐[1‐¹³C]cystine, 3‐D‐leucine]oxytocin.