Synthesis of [ 14 C]ABT‐418, a cholinergic channel activator labeled at two sites on the isoxazole ring

Abstract [ 14 C]ABT‐418, (S)‐3‐[ 14 C]methyl‐5‐[N‐methyl‐2‐pyrrolidinyl][4‐ 14 C]isoxazole hydrochloride, was labeled in two positions at maximum specific activity. Starting with 100 mCi of sodium [2‐ 14 C]acetate, 14.6 mCi at 105 mCi/mmol was obtained in 8 steps including the formation of [1,3‐ 14 C]acetone in the pyrolysis of barium [2‐ 14 C]acetate. The key step was the formation of the dianion of [1,3‐ 14 C]acetone oxime and its condensation with L‐proline methyl ester.