Synthetic approach to 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides based on common β-keto amide precursors

β-Keto amides were used as convenient precursors to both 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides. The utility of this approach is demonstrated with the synthesis of fourteen novel and four known quinolone derivatives, including natural products of microbial origin such as HHQ and its C(5)-congener. Two compounds with high activity against S. aureus have been identified among the newly obtained quinolones, with MICs ≤ 3.12 and ≤ 6.25 µg/mL, respectively.