Synthesis of 5‐(2,3‐ditritiopropoxy)‐3‐(1,2,5,6‐tetrahydropyrid‐4‐yl)indole ([³H]CP‐96,501): A selective ligand for the serotonin (5‐HT1B) receptor

The synthesis of [ 3 H]CP‐96,501 [5‐(2,3‐ditritiopropoxy)‐3‐(1,2,5,6‐tetrahydropyrid‐4‐yl)indole], a selective radioligand for the serotonin (5‐HT 1B ) receptor and analog of RU‐24,969, is described. 5‐Hydroxyindole is converted in two steps to 5‐(2‐propenyloxy)‐3‐(N‐ t ‐butoxycarbonyl‐1,2,5,6‐tetrahydropyrid‐4‐yl)indole ( 3 ). Hydrogena‐tion or tritiation of 3 followed by removal of the t ‐butoxycarbonyl protecting group afforded CP‐96,501 ( 1a ) and [ 3 H] CP‐96,501 ( 1b ), respectively.