Synthesis of the muscle relaxant [14C]L-637,510

The synthesis of (E)‐3‐(9‐chloro‐5,6‐dihydro‐1 1 H‐pyrrolo(2,1‐b)(3)‐benzazepin‐11‐ylidene)‐N, N‐dimethyl‐1‐[3‐14C]‐propanamine (Z)‐2‐butenedioate(1:1) (11, [14C]L‐637,510), a potential muscle relaxant product for which 14C‐labeling was required for metabolism studies, is described. Introduction of the label in the 3‐position of the propanamine side chain was accomplished in eight steps from sodium [14C]cyanide with an overall radiochemical yield of 4.8%.