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

A compound of formula (I):

• wherein:
• a) each R1 is 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;
• b) each R2 is 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;
• c) R3 and R4, together with the nitrogen atom to which they are bonded, join to form a pyrrolidine ring, optionally substituted with one or more hydrogen, halo, cyano, hydroxy, carboxy, keto, thioketo, amino, acylamino, acyl, amido, alkyl, alkenyl, alkynyl, heteroalkyl, haloalkyl, alkoxy, and 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.