Quinolone chemical structures

Fig. 5.5 Chemical structures of commonly used quinolone derivatives.

Figure 1 P. aeruginosa QS system. Its mechanism, (a) Biosynthesis of acyl-homoserine lactone (AHL). Abbreviations SAM, 5-adenosyl methionine ACP, acyl carrier protein, (b) General chemical structure of AHL molecules, generally called autoinducer-1 (AI-1). (c) Chemical structure of V. fischeri AI-1. (d) Chemical structure of P. aeruginosa 3-oxo-C y-HSL and (e) C4-HSL. (f) Pseuodomonas quinolone signal, PQS.

The chemical structure at position 8 in the quinolone ring probably determines the phototoxic potential, since the introduction of a methoxy group at this position markedly reduces the phototoxicity of individual drugs (65). 

The family of colchicines-site binders includes compounds of diverse structure unified by interference with the colchicine binding epitope. The respective compounds can be clustered according to their chemical structure mainly into I) colchicines and compounds with colchicine like substructures, II) combretastatins and phenstatins, III) compounds having an indole core structure, IV) quinolones, V) sulphonamidcs and VI) naturally occurring as well as synthetic compounds. 

Recent Advances in the Chemistry of Quinolones 251 Table 1. Chemical structure of the most representative quinolone derivates... 

Looking back to the discovery of nalidixic acid almost 30 years ago, enormous efforts have been made and a huge number of analogs synthetized to improve overall properties. If one considers the relatively simple chemical structure of quinolones in comparison to other classes of antibacterials (macrolides, aminoglucosides, P-lactams), one can wonder if there is room for innovation or... 

Nowadays, antibiotics are primarily classified according to the mechanism of their action, with similarity of chemical structure as a secondary factor. Penicillin and its derivatives inhibit the formation of bacterial cell walls (Fig. 3.38). Cephalosporins have the same active mechanism. Other compounds are taken up into bacterial DNA to form unstable molecules (quinolones, metronidazole) or inhibit peptide synthesis (tetracychnes, aminoglycosides, macrolides). Some antibiotics (e.g. glycopeptides) exert a complex effect. 

TABLE 1.9 Common Quinolones, Their Molecular Structures, and Chemical Characteristics... 

Flindersine and a new quinolone alkaloid, 3-dimethylallyl-4-dimethyl-allyloxy-2-quinolone, C19H23O2N (mp 114°-115°) were isolated. Mass and NMR spectroscopy indicated structure LXVIIa for this base. Minor chemical reactions served to confirm this structure, particularly catalytic hydrogenation, which induced rapid hydrogenolysis of the ether linkage 102). 

All the principal alkaloids of both groups possess as a common structural feature the 4-methoxyquinoline unit, in consequence of which they undergo a typical isomerization to iV-methyl-4-quinolones on vigorous treatment with methyl iodide. This reaction, which has been of considerable assistance in the elucidation of the structures of the alkaloids, also provides a chemical relationship with the alkaloid of Eehinopa species (Compositae), which was shown to be W-methyl-4-quinolone itself. The isomeric lV-methyl-2-quinolone occurs in Angostura bark. 

Structure-activity relationships in both quinolone and naphthyridone series of compounds have shown that introduction of a C-6 substituent tends to enhance antibacterial activity [3, 5] and it is of particular interest that replacement of an hydrogen atom by an halogen atom especially fluorine results in an outstanding enhancement of the antibacterial activity. All the clinically useful new quinolones bear a fluorine at the C-6 position of the quinolone, naphthyridine, or benzoxazine ring system and consequently almost all the chemical modifications involved any position but C-6, the fluorine atom being always present. 

As was used in much of our earlier work on incorporation of antibiotic into existing polyester substrates, Cipro was the antibiotic chosen for this study. Antibiotics vary m structural type, spectrum of activity, and clinical usefidness. Cipro is one of the fluoroquinolones, a family of more than ten antibiotics and the drug of choice for many applications" . Quinolone antibiotics are chemically stable, and effective at low concentrations against the common clinically encountered organisms, particularly those bacteria responsible for biomaterial infection". These antibiotics also have structural features (solubility, molecular mass, and functional groups) that coincide with those of textile dyes and our previous wodc has shown that these similarities lead to the potential for dye-like interactions with polymeric materials " . 

Quinolones is the name given to a broad family of synthetic chemotherapeutic antibacterials chemically based on the 4-quinolone and 1,8-naphthyridine structures. The structures of these two quinolone nuclei and an example of a drug from each of these groups are shown in Fig. 6.17a, b. Cinoxacin is an example of a... 

Ishii H, Koyama K, Chen I-S, Lu ST et al. 1982 Studies on the chemical constituents of rutaceous plants. 46. The chemical constituents of Xanthoxylum integrifoliolum (Merr.) Merr. Fagara in-tegrifoliolum Merr.) 2. Structural establishment of integriquinolone a new phenolic quinolone. Chem Pharm Bull 30 1992-1997... 

Takahashi S, Kakinuma N, Iwai H, Yanagisawa T, Nagai K, Suzuki K, Tokunaga T, Nakagawa A. Quinolactacins A, B and C novel quinolone compounds from Penicillium sp. EPF-6. II. Physico-chemical properties and structure elucidation. J. Antibiot. 2000 53(11) 1252-1256. 

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