A short synthesis and its application to the preparation of radio labelled leukotriene inhibitor Sch 37224

A new, short synthesis of 1‐(1,2‐dihydro‐4‐hydroxy‐1‐phenyl‐2‐oxo‐1,8‐naphthyridin‐3‐yl)‐pyrrolidinium hydroxide, inner salt, 1, was achieved by condensing methyl 2‐phenylamino‐3‐pyridine carboxylate 2 with ethyl 1‐pyrrolidine acetate 4. This gave highly pure product in 60% yield. This synthesis was applied to the preparation of 14C labelled 1. Radiolabelled 1 was synthesized from u‐[14C]‐aniline in three steps at 97% radiochemical purity and 27.3% radiochemical yield.