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Carbon monoxide-releasing molecules (CORMs) that enable the delivery of controlled amounts of CO are of strong current interest for applications in biological systems. In this review, we examine the various conditions under which CO is released from 3-hydroxyflavones and 3-hydroxy-4-oxoquinolines to advance the understanding of how these molecules, or derivatives thereof, may be developed as CORMs. Enzymatic pathways from quercetin dioxygenases and 3-hydroxy-4-oxoquinoline dioxygenases leading to CO release are examined, along with model systems for these enzymes. Base-catalyzed and non-redox-metal promoted CO release, as well as UV and visible light-driven CO release from 3-hydroxyflavones and 3-hydroxy-4-oxoquinolines, are summarized. The visible light-induced CO release reactivity of recently developed extended 3-hydroxyflavones and a 3-hydroxybenzo[g]quinolone, and their uses as intracellular CORMs, are discussed. Overall, this review provides insight into the chemical factors that affect the thermal and photochemical dioxygenase-type CO release reactions of these heterocyclic compounds.

Quinolones (oxoquinolines) belong to the broad family of quinolines, bearing a carbonyl group at any position of the quinoline core [1]. The versatility of the quinolone chemo type attracted the interest of researchers for several decades, leading to a wealth of information that unravelled the potential of quinolones for applications in major fields, namely in medicinal chemistry. Quinolones are nowadays associated to several pharmacological properties, with quinolone derivatives being either used as drugs or under development as drug candidates, to target a variety of human diseases and disorders.

The quinolones are derivatives of oxoquinolines and mostly known for their antibacterial and antiviral activities. Many quinolones are chiral compounds having asymmetric centers and important due to their enantioselective biological activities. In order to study the biological activities of quinolone enantiomers, to control the manufacturing of homochiral drugs and to prepare necessary quantities of pure enantiomers for preclinical or clinical trials, respective chiral separation methods are urgently needed. In this context, the present review discusses chromatographic and electrophoretic methods for the enantioseparation of chiral quinolones and provides some useful information on their physical and pharmaceutical properties. The drawbacks of currently used techniques are revealed and ways to overcome them are outlined. Moreover, recommendations for an optimal choice of a separation protocol are given.

We have achieved the synthesis of 1-aryl-2-substituted 4-oxoquinoline and 4-oxo-1,8-naphthyridine derivatives, which cannot be synthesized by known methods, via two useful synthons, 2-formyl-4-oxoquinoline and 2-methylsulfonyl-4-oxo-1,8-naphthyridine. We also succeeded in the synthesis of 1-aryl-3-fluoro-4-oxoquinoline by fluorocyclization of N-arylenaminone with Select-fluor ® and potassium carbonate in DMF in a one-pot procedure. To the best of our knowledge, this is the first synthesis of 3-fluoro-4-oxoquinoline derivatives. We confirmed that these protocols were mutually applicable to the synthesis of 4-oxoquinoline and 4-oxo-1,8-naphthyridine derivatives.

Various 2-substituted 4-oxoquinoline and 4-oxo-1,8-naphthyridine derivatives are prepared from the key intermediates (I) and (VIII), respectively.

The synthesis of N-[p-(3'-(2'-aryl-4'-oxo-1',3'-thiazolyl)}diphcnylj-7-hydroxy-4-methyl-2-oxoquinolines 4 have been achieved starting from resorcinol. 7-hydroxy-4-methylcoumarin(4-methylumbelliferone) 1 is obtained by the reaction of resorcinol with ethylacetoacetate. 1 on treatment with benzidine gives N-(p-aminodiphenyl)-7-hydroxy-4-methyl-2-oxoquinoline 2. 2 on treatment with different aryl aldehydes in presence of glacial acetic acid furnishes N-(p-arylidinoamino-diphenyl-7-hydroxy-4-methyl-2-oxoquinolines 3a-e. The latter on treatment with thioglycollic acid in presence of anhydrous ZnCl 2 yields 4a-e. The in vitro anti-JEV activity of these compounds has also been evaluated.

It is shown that cyclization of Β-(2-carboxyaryl) aminopropionic acids to 1,2,3,4-tetrahydro-4-oxoquinolines in the presence of acetic anhydride and alkali metal acetates proceeds via the intermediate formation of the N-acetyl derivative of the monopotassium salt of the starting acid, which undergoes further conversion into the cyclic mixed anhydride. The latter decomposes with loss of CO2 to give the corresponding 1,2, 3,4-tetrahydro-4-oxoquinoline.