The synthesis of [2H], [3H], and [14C]-labeled 8β-[(methylthio)methyl]-6-propylergoline mesylate (pergolide mesylate), a potent, long-acting dopamine agonist

The [3H]‐ and two [14C]‐isotopomers of 8β‐[(methylthio)methyl]‐6‐propylergoline mesylate (pergolide mesylate) have been synthesized. The [3H]‐derivative was synthesized by the palladium catalyzed tritiation of the corresponding 6‐allyl derivative. Reaction of 8β‐[(methylthio)methyl]‐ergoline with 1‐[14C]‐1‐propyl bromide yielded pergolide labeled in the 6‐propyl group. Alternatively, reaction of 8β‐mesyloxy‐6‐propylergoline with [14C]‐sodium cyanide, followed by base hydrolysis, yielded 8β‐carboxy‐6‐propylergoline‐[14C], which was subsequently converted to pergolide mesylate radiolabeled in the 17‐position via a four step sequence.