Pyridonylmethylaminomethylcephemcarboxylates I [R = Me, CH2CH2OH, CHMe2, CH2CH:CH2, CH2(CH2)3Me] were prepared by substitution of the iodomethylcephem with alkylaminomethylpyridones.CP6232 (I; R = Me) showed extremely potent antibacterial activity against Gram-neg. bacteria.Although CP6232 showed weak activity against Gram-pos. bacteria the present results also demonstrated that the 1,5-dihydroxy-4-pyridone entity is a potent substituent in the 3-position of cephalosporin.