Prodrugs of imidazopyridine derivatives

A compound of the formula 1

• 7
• in which
• R1 is hydrogen, 1-4C-alkyl or hydroxy-1-4C-alkyl,
• R2 is hydrogen, 1-4C-alkyl, hydroxy-1-4C-alkyl, halogen, 2-4C-alkenyl or 2-4C-alkynyl,
• R3 is hydrogen, halogen, trifluoromethyl, 1-4C-alkyl, 2-4C-alkenyl, 2-4C-alkynyl, carboxyl, —CO-1-4C-alkoxy, hydroxy-1-4C-alkyl, 1-4C-alkoxy-1-4C-alkyl, fluoro-1-4C-alkoxy-1-4C-alkyl or the radical —CO—NR3aR3b,
• one of the substitutents R4a and R4b is hydrogen and the other is hydroxyl, 1-4C-alkoxy, 1-4C-alkoxy-1-4C-alkoxy, 1-4C-alkylcarbonyloxy or the radical R4′, or in which R4a and R4b together are O (oxygen),
• where R4′ is a radical from which a hydroxyl group is formed under physiological conditions,
• one of the substitutents R5a and R5b is hydrogen and the other is hydrogen, hydroxyl, 1-4C-alkoxy, 1-4C-alkoxy-1-4C-alkoxy, 1-4C-alkylcarbonyloxy or the radical R5′, or in which R5a and R5b together are O (oxygen),
• where R5′ is a radical from which a hydroxyl group is formed under physiological conditions,
• where
• one of the substituents R4a and R4b must have the meaning R4′ and/or one of the substituents R5a and R5b must have the meaning R5′,
• R6 is hydrogen, halogen, 1-4C-alkyl, 1-4C-alkoxy, 1-4C-alkoxycarbonylamino, 1-4C-alkoxy-1-4C-alkoxycarbonylamino or trifluoromethyl,
• R7 is hydrogen, halogen, 1-4C-alkyl or 1-4C-alkoxy and
• X is O (oxygen) or NH,
• where
• R3a is hydrogen, 1-7C-alkyl, hydroxy-1-4C-alkyl or 1-4C-alkoxy-1-4C-alkyl and
• R3b is hydrogen, 1-7C-alkyl, hydroxy-1-4C-alkyl or 1-4C-alkoxy-1-4C-alkyl,
• or where
• R3a and R3b together, including the nitrogen atom to which both are bonded, are a pyrrolidino, piperidino or morpholino radical,
• or its salts.