N-sulfonyl-4-methyleneamino-3-hydroxy-2-pyridones

A compound of formula (I):

• wherein:
• a. R1 is aryl, optionally substituted with one or more hydrogen, halo, cyano, hydroxy, carboxy, keto, thioketo, amino, acylamino, acyl, amido, phenyl, aryloxy, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, alkoxy, aryl, cycloalkyl, spirocycloalkyl or combinations thereof;
• b. each R2 is independently chosen from hydrogen, halo, cyano, hydroxy, carboxy, keto, thioketo, amino, acylamino, acyl, amido, phenyl, aryloxy, alkyl, alkenyl, alkynyl, beteroalkyl, haloalkyl, alkoxy, aryl, and cycloalkyl;
• c. R3 and R4, together with the nitrogen atom to which they are bonded, join to form a piperazine ring substituted with a pyridazine ring or one or more hydrogen, halo, cyano, hydroxy, carboxy, keto, thioketo, amino, acylamino, acyl, amido, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, alkoxy, or combinations thereof;
• and
• d. R5 and R6 are each independently chosen from hydrogen, halo, cyano, hydroxy, carboxy, keto, thioketo, amino, acylamino, acyl, amido, phenyl, aryloxy, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, alkoxy, aryl, and cycloalkyl;
• or
• optical isomers, diastereomers and enantiomers of the formula above, or a pharmaceutically-acceptable salt thereof.