The Bacterial Degradation of 5‐Amino‐4‐chloro‐2‐phenyl‐3(2H)‐pyridazinone

From the culture medium of bacteria, which utilize 5‐amino‐4‐chloro‐2‐phenyl‐3(2 H )‐pyridazinone (pyrazon) as sole source of carbon four metabolites could be isolated. These metabolites were identified as 5‐amino‐4‐chloro‐2‐(2,3‐ cis ‐dihydroxycyclohexa‐4, 6‐ diene ‐1‐yl)‐3(2 H )‐pyridazinone (compound I), as 2‐(5‐amino‐4‐chloro‐3‐oxo‐2,3‐dihydro‐2‐pyridazino)‐ cis , cis ‐muconic acid (compound II), as 2‐pyrone‐6‐carboxylic acid (compound III) and as 5‐amino‐4‐chloro‐3(2 H )‐pyridazinone (compound IV). Cell‐free extracts of the pyrazon‐degrading bacteria were shown to metabolize 2‐hydroxy‐muconic acid with a stoichiometric release of CO 2 . A pathway for the bacterial degradation of 5‐amino‐4‐chloro‐2‐phenyl‐3(2 H )‐pyridazinone is proposed.