A regiospecific synthesis of 1-methylamino-6-fluoro-7-(4-methylpiperazin-1-yl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid

An efficient and regiospecific synthesis of 1-methylamino-6-fluoro-7-(4-methylpiperizin-1-yl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid ( 3 ) via an intramolecular nucleophilic displacement cyclization reaction is reported.     

Synthesis and antibacterial activity of some 7-substituted 1-ethyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acids: Ethers,secondary amines and sulfides as c-7 substituents

A series of 7-substituted 1-ethyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acids were prepared from 1-ethyl-6,7-difluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid 8 . Those derivatives reported contain acyclic and heterocyclic substituents linked to the quinolone C-7 position via O, NH or S. The in vitro antibacterial data of some of these derivatives against 4 Gram positive and 4 Gram negative organisms are reported.     

Synthesis and antibacterial activity of new 5-substituted 1-cyclopropyl-6-fluoro-7-piperazinyl-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids

The 5-hydroxymethyl and the 5-formyl-1-cyclopropyl-6-fluoro-7-piperazinyl-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids have been prepared via a 5-trimethylsilyl group and were tested in vitro as potential antibacterials.     

Synthesis of 7-thio-substituted 4-oxoquinoline-3-carboxylic acids with antibacterial activity

A series of C-7 thio-substituted 1-cyclopropyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids were prepared and tested for their antibacterial activity. Structure-activity relationships associated with the C-5 and C-7 substituents were discussed. Among the C-7 substituents including alkylthio, arylthio, heteroarylthio, and cyclic aminothio groups, a 2-aminoethylthio group was the best for enhancing in vitro antibacterial activity. The C-5 variants increased activity in the order OH less than F less than H less than NH2. Of compounds prepared in this work, 5-amino-7-(2-aminoethyl)thio-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4 -oxo-quinoline-3-carboxylic acid (18) was the most active.     

Synthesis and reactions of 7-substituted 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids as an antibacterial agent

1-Cyclopropyl- and 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid derivatives having a sulfinyl or sulfonyl group at C-7 were synthesized from 2,6-dichloro-5-fluoronicotinic acid derivatives by the route involving the Dieckmann-type cyclization. The displacement reactions of these compounds with pyrrolidine and piperidine gave mainly the 7-(1-pyrrolidinyl)- and 7-(1-piperidinyl)-1,8-naphthyridine derivatives 24-27 , respectively. Enoxacin, a potent antibacterial agent, was also synthesized with the analogous route.     

Studies on antibacterial agents. III. Synthesis and antibacterial activities of substituted 1,4-dihydro-8-methyl-4-oxoquinoline-3-carboxylic acids

A series of substituted 4-oxoquinoline-3-carboxylic acids having a methyl group at the 8-position was prepared and tested for their antibacterial activity. 7-(trans-3-Amino-4-methyl-1-pyrrolidinyl)-1-cyclopropyl-1,4-dihydro-6- fluoro-8-methyl-4-oxoquinoline-3-carboxylic acid (21) exhibited highly potent antibacterial activity against both gram-positive and gram-negative bacteria, including Pseudomonas aeruginosa.     

1-环丙基-6-氟-7-(4-酰基-1-哌嗪基)-1,4-二氢-4-氧代喹啉-3-羧酸的合成及其抗菌活性研究

以1-环丙基-6-氟-7-氯-1, 4-二氢-4-氧代喹啉-3-羧酸为原料经过两步反应合成出了16个新的1-环丙基-6-氟-7-(4-酰基-1-哌嗪基)-1, 4-二氢-4-氧代喹啉-3-羧酸, 并利用IR, ¹H NMR, ¹³C NMR, MS谱及元素分析对其结构进行了表征. 初步体外抗菌活性研究表明, 大部分目标化合物对大肠杆菌有一定的抑菌活性, MIC值在0.312～20 g/mL之间, 但活性低于对照物环丙沙星和氧氟沙星; 目标化合物对绿脓杆菌无抑菌活性, 最低抑菌浓度(MIC)均大于20 g/mL.     

1-环丙基-6-氟-7-取代喹诺酮抗HIV活性的定量构效关系

用量子化学AM1法对一系列1-环丙基-6-氟-7-取代-1,4-二氢-4-氧-喹啉-3-羧酸的定量构效关系进行了研究,结果表明该类化合物在对HIV的抑制过程中是一很好的电子给予体,给电子的部位主要是7-位哌嗪基末端氮原子,并进一步提出从抗C^+和G^-菌活性差的喹诺酮中有望筛选出好的抗HIV化合物。     

Fluorocinnoline derivatives. II. Synthesis and antibacterial activity of fluorinated 1-alkyl-1,4-dihydro-4-oxocinnoline-3-carboxylic acids

Chemical modification of cinoxacin was studied with the aim of improving its antibacterial activity and spectrum. Alkylation of ethyl 6,7,8-trifluoro- and 6,7-difluoro-4-hydroxycinnoline-3-carboxylates (1 and 7) with alkyl iodide or dialkyl sulfate gave ethyl 1-alkyl-6,7,8-trifluoro- and 6,7-difluoro-1,4-dihydro-4-oxocinnoline-3-carboxylates (2 and 8), together with the isomeric anhydro-bases 3 and 9 of 2-alkyl-3-ethoxycarbonyl-6,7,8-trifluoro- and 6,7-difluoro-4-hydroxycinnolinium hydroxides, respectively. Acid-catalyzed hydrolysis of the 1-alkyl derivatives 2 and 8 gave the corresponding carboxylic acids 4 and 10. The same treatment of 3 and 9, accompanied with decarboxylation of the inner salts 5 and 11, afforded the anhydro-bases 6 and 12 of 2-alkyl-4-hydroxycinnolinium hydroxides, respectively. Displacement reactions of 4 and 10 with nucleophiles such as amine, alkoxide and thiolate gave 7-substituted 1-alkyl-6,8-difluoro- and 6-fluoro-1,4-dihydro-4-oxocinnoline-3-carboxylic acids (13 and 17-35). Antibacterial activities of these compounds were evaluated and compared with those of cinoxacin and norfloxacin. Some compounds showed a broader spectrum and more potent activity than cinoxacin, but were considerably inferior in activity to norfloxacin.     

A new synthetic route to 7-halo-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid,an intermediate for the synthesis of quinolone antibacterial agents

Starting from m-fluorotoluene, 7-chloro-6-fluoro- and 6,7-difluoro-1-cyclopropyl-1,4-dihydro-4-oxoquino-line-3-carboxylic acids, 3 and 16 were synthesized. Compounds 3 and 16 are useful intermediates for the synthesis of a class of quinolone antibacterial agents. The synthetic route involves two processes; i) construction of the quinoline ring by an intramolecular cyclization accompanied by the elimination of a nitro group and ii) introduction of fluorine atom by replacement of a nitro group with potassium fluoride. 7-(3-Amino-1-pyrroli-dinyl)-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (18) was prepared from 3 or 16. The antibacterial activity of 18 compares favorably with that of ciprofloxacin (2) .     

Synthesis of 1,4-dihydro-4-oxopyrrolo[1,2-b]pyridazine-3-carboxylic acids and 1,4-dihydro-4-oxoimidazo[1,5-b]pyridazine-3-carboxylic acids as potential antibacterial agents

To check the antibacterial potential of two families of aza analogues of the quinolones, 1,4-dihydro-4-oxopyrrolo[1,2-b]pyridazine-3-carboxylic acids and 1,4-dihydro-4-oxoimidazo[1,5-b]pyridazine-3-carboxylic acids, we have prepared a few derivatives in theses families using N-aminopyrrole and N-aminoimidazole derivatives as starting building blocks and the classical pathways of the quinolone series. The compounds showed no interesting antibacterial activity.     

Synthesis and Characterization of 8-Chloro-7-(4-(3-chloropropanoyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic Acid

A new compound 8-chloro-7-(4-(3-chloropropanoyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid(II, C_(20)H_(20)Cl_2FN_3O_4, Mr = 456.08) was synthesized and characterized by 1H NMR, 13 C NMR, HR MS and single-crystal X-ray diffraction. X-ray powder diffraction(XRPD), thermal stabilities, UV-Vis spectrum, photoluminescent properties and absolute quantum yield of compound II were also investigated. The structure demonstrates that the crystal belongs to the triclinic system, space group P1 with a = 7.7339(3), b = 10.2396(5), c = 15.9076(8) ?, α = 76.517(4), β = 77.609(4), γ = 80.320(4)°, V = 1187.22(9) ?3, Z = 2, Dc = 1.514 g/mm3, μ = 4.901 mm-1, F(000) = 556.0, R = 0.0534 and w R = 0.1447(I 2σ(I)). The result reveals that fluoroquionolone moiety in this structure stacks with π×××π interactions to generate an infinite 1D chain, which can stabilize the whole framework of compound II. Delightfully, preliminary antibacterial activity in vitro against 4 cell strains uncovers that compound II has almost equal strong activity in comparison with Clinafloxacin, but stronger than Norfloxacin. These outcomes provide important information for further exploration of the structure-activity relationship(SAR) of compound II derivatives or analogs.     

The synthesis of a series of 7-amino-1-cyclopropyl-8-fluoro-1,4-dihydro-4-oxo-1,6-naphthyridine-3-carboxylic acids as potential antibacterial agents

A series of 7-amino-1-cyclopropyl-1,4-dihydro-8-fluoro-4-oxo-1,6-naphthyridine-3-carboxylic acids has been prepared and evaluated for antibacterial activity. These compounds were prepared by the displacement of the chloro substituent from 7-chloro-1-cyclopropyl-1,4-dihydro-8-fluoro-4-oxo-1,6-naphthyridine-3-carboxylic acid employing the requisite nitrogen nucleophile to produce the title compounds. The naphthyridine acid was synthesized in ten steps from ethyl 2,4-dihydroxy-3-nitro-5-pyridinecarboxylate. The key step in the sequence was a Schiemann reaction carried out using the hexafluorophosphate salt of the diazonium ion derived from ethyl 3-amino-2,4-dichloro-5-pyridinecarboxylate.     

Polymorphism and stability of norfloxacin, (1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinil)-3-quinolinocarboxylic acid

Norfloxacin was studied by thermal methods (TG and DSC), X-ray powder diffraction, and by FT-IR, UV-VIS and NMR spectroscopy. The drug substance can be prepared in two different crystalline forms and in amorphous state, depending on the experimental conditions of preparation. DSC examinations were carried out at various heating rates and by cycling the samples in the temperature range 50°–250°C. The unstable crystalline form undergoes two irreversible solid-solid phase transitions at 176.5° and 197.6°C. The polymorph melts in the temperature range 218.5°–220.0°C.

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Zusammenfassung Norfloxacin wurde mittels thermischer Methoden (TG und DSC), weiterhin mittels der Debye-Scherrer-Methode und FTIR-, UV-VIS-und NMR-Spektroskopie untersucht. Je nach den experimentellen Bedingungen bei der Herstellung kann die Wirkstoffsubstanz in zwei verschiedenen kristallinen und in einer amorphen Form hergestellt werden. Die DSC-Untersuchungen wurden bei zahlreichen Aufheizgeschwindigkeiten und durch abwechselnden Temperaturwechsel zwischen Raum- und Schmelztemperatur durchgeführt. Die unstabile kristalline Form unterliegt zwei irreversiblen Feststoff-Feststoff-Umwandlungen bei 176.5° und bei 195.6°C. Das polymorphe Material schmilzt im Temperaturbereich 218.5°–220.0°C.

     

Synthesis and properties of 1-aryl-1,4-dihydro-2,7-dimethyl-4-oxopyrido[2,3-d]pyrimidine-6-carboxylic acids and their derivatives

Acetylation of 2-arylamino-5-carbethoxy-6-methylnicotinonitriles gave N-acetyl-2-arylamino-5-carbethoxy-6-methylnicotinonitriles, which, under the influence of hydrogen chloride, are cyclized to 1-aryl-1,4-dihydro-6-carbethoxy-2,7-dimethyl-4-oxopyrido[2,3-d]pyrimidines. The latter can be converted to the corresponding carboxylic and hydroxamic acids, as well as to acetylation products 1-aryl-2-acetonyl-1,4-dihydro-6-carbethoxy-7-methyl-4-oxopyrido [2,3-d]pyrimidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 535–539, April, 1992.     

Synthesis,structure elucidation and chemotherapeutic activity of 6-substituted 1-ethyl-1,4-dihydro-7-[(1-imidazolyl)phenylmethyl]- 4-oxo-3-quinolinecarboxylic acids

The synthesis, structure elucidation and chemotherapeutic activity of novel 3-quinolinecarboxylic acid derivatives are reported. These derivatives are characterized by a group (1-imidazolyl)phenylmethyl attached to the 7-position and chloro 10a , fluoro 10b or methoxy 10c appended to the 6-position.     

4H-1-benzothiopyran-4-one-3-carboxylic acids and 3,4-dihydro-2H-isothiazolo[5,4-bbenzothiopyran-3,4-diones as quinolone antibacterial analogs

The endocyclic replacement of a nitrogen atom at the 1-position of quinolone antibacterial nucleus with a sulfur atom was investigated. A series of 1-benzothiopyran-4-one-3-carboxylic acids 14–16 and isothiazolo-[5,4-b][1]benzothiopyran-3,4-diones 22–24 , suitably functionalized with a fluorine atom at C-6 and heterocyclic base at C-7, were prepared. The antibacterial evaluation of the target compounds showed an activity comparable to that of nalidixic acid for compounds 14–16 , while an increased activity against gram-positive bacteria was observed for compounds 22–24 .     

Synthesis of 6-sulfamoyl-4-oxoquinoline-3-carboxylic acid derivatives as integrase antagonists with anti-HIV activity

A series of novel 6-sulfamoyl-4-oxoquinoline-3-carboxylic acids derivatives have been synthesized and screened for HIV integrase inhibition activity.Their structures were confirmed by ESI-MS,~1H NMR and ~(13)C NMR.