Synthesis of a piperidone model compound and revision of the structures of jenamidines A to C

Reaction of 2,3-dihydro-4-pyridone (4) with isatoic anhydride (5) provided the unstable product 6, for which the NMR spectral data are quite different from those reported for the ring system of jenamidine A. This suggests that the proposed structures 1 to 3 of jenamidines A to C should be revised to 8 to 10.