Synthesis and tritium labeling of the highly potent mast cell-degranulating substance P analog H-Arg-Pro-Lys-Pro-NH-C12H25

Tritium labeling of the mast cell degranulating substance P analog H‐Arg‐Pro‐Lys(3,4‐3H‐Pro)‐NH‐C12H25 by catalytic saturation of the dehydroproline (Dhp Abbreviations: Ac, acetyl; Dhp, L‐3,4‐dehydroproline; DMA, dimethyl‐acetamide; DMF, dimethylformamide; HOBt, 1‐hydroxybenzotriazole; MA, mixed anhydride coupling; NMM, N‐methylmorpholine; ONSu, N‐hydroxysuccinimide ester; TEA, triethylamine. ) double bond is described. Catalytic tritiation in water afforded the radioactive analog with a specific activity of 1.07 TBq/mmol. Tenfold enhancement of the catalyst‐to‐substrate ratio resulted in a reduced specific activity of 0.74 TBq/mmol.