Studies on 6-aminoquinolones: Synthesis and antibacterial evaluation of 6-amino-8-ethyl- and 6-amino-8-methoxyquinolones

From our quantitative structure-activity relationship (QSAR) study on a lar ge set of 6-aminoquinolones, which indicated that a group larger than methy l could be allocated at C-8 position, we have synthesized two new series of 6-aminoquinolones characterized by the presence of an ethyl or a methoxy g roup at C-8 position. The antibacterial evaluation shows that, while the 8- ethyl derivatives were devoid of any antibacterial activity, the introducti on of methoxy group gave compounds with good antibacterial activity, especi ally against Gram-positive bacteria. A tentative explanation of the differe nt behaviours among the 8-substituted analogues is given taking into accoun t both the length and electronic properties of the C-8 groups. (C) 1999 Els evier Science Ltd. All rights reserved.