An alternative synthesis of temafloxacin, a potent antibacterial agent

1992 ◽  
Vol 70 (5) ◽  
pp. 1323-1327 ◽  
Author(s):  
Daniel T. W. Chu ◽  
Isabella M. Lico ◽  
Akiyo K. Claiborne ◽  
Hermann Faubl
Keyword(s):  
Carboxylic Acid ◽  
Antibacterial Agent ◽  
Cyclization Reaction ◽  
Alternative Synthesis ◽  
Nucleophilic Displacement ◽  
Acid Hydrochloride

An alternative synthesis of (±)-7-(3-methylpiperazin-1-yl)-6-fluoro-1-(2,4-difluorophenyl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid hydrochloride 4, a potent antibacterial agent, was developed. The method was characterized by regiospecific displacement of the 4-fluoro of the 2,4,5-trifluoroacetophenone by 2-methylpiperazine to produce the key intermediate, 2,5-difluoro-4-(3-methylpiperazin-1-yl)acetophenone 12, which was subsequently converted to 4 via an intramolecular nucleophilic displacement cyclization reaction.

Thienoisothiazoles. III. The Synthesis and Reactions of 3-Phenyl-5-alkylthioisothiazole-4-carbonitriles and 3-Phenylthieno[3,2-d]isothiazoles

1989 ◽  
Vol 42 (8) ◽  
pp. 1291 ◽  
Author(s):  
HD Krebs
Keyword(s):  
Hydrogen Sulfide ◽  
Carboxylic Acid ◽  
Condensation Product ◽  
Nitro Derivative ◽  
Ring Closure ◽  
Hypophosphorous Acid ◽  
Alternative Synthesis ◽  
Nucleophilic Displacement ◽  
Mild Reduction ◽  
One Step

Oxidation of the alkyl 3-amino-4-cyano-3-phenylpropenedithioates (1), obtained by alkylation of the condensation product of 3-amino-3-phenylpropenenitrile and carbon disulfide, produced 3-phenyl-5-alkylthioisothiazole-4-carbonitriles (2a-d). The ease of nucleophilic displacement of the S-alkyl group in the isothiazole (2a) was utilized to synthesize the isothiazoles (2f-j). 3-Phenylthieno[3,2-d] isothiazole (3e) was prepared by deamination, hydrolysis and decarboxylation of the intermediate ethyl 4-amino-3-phenylthieno[3,2-d]isothiazole-5-carboxylate (3a), which was obtained by ring-closure of ethyl 2-(4-cyano-3-phenylisothiazol-5-ylthio)acetate (2d). 3-Phenylthieno[3,2-d] isothiazole was unreactive towards weaker electrophiles , but undergoes bromination and nitration in the α-position of the thiophen ring. The position of substituents in 5-bromo- (3w) and 5-nitro-3-phenylthieno[3,2-d] isothiazole (4a) was verified by alternative synthesis. The attempted deamination of 4-amino-5-bromo-3-phenylthieno[3,2-d] isothiazoe (30) and 4-amino-S-nitro-3-phenylthieno[3,2-d] isothiazole (3r) yielded 3-phenyl-S-nitrothieno[3,2-d]isothiazol-4-ol (3s) only, but the isomeric 4-bromo-3-phenyithieno[3,2-d] isothiazole (3v) was obtained by decarboxylation of 4-bromo-3-phenylthieno[3,2-d]isothiazole-5-carboxylic acid (3u). An alternative synthesis of the 5-nitro derivative was achieved by decarboxylation of 5-nitro-3-phenylthieno[3,2-d]isothiazole-4-carboxylic acid (32). Mild reduction of 3-phenylthieno[3,2-dlisothiazole derivatives, (3a,b) and (4c), with hydrogen sulfide or hypophosphorous acid afforded the substituted 3-(α-aminobenzylidene )-2,3-dihydrothiophen-2-thiones (5a-c), and the 3-benzoyl-2-alkylthiothiophen derivatives (6a,b) were obtained by a one-step synthesis, which avoided the isolation of the air-sensitive intermediates.

scholarly journals Functional Aromatic Poly(1,3,4-Oxadiazole-Ether)s with Benzimidazole Pendants: Synthesis, Thermal and Dielectric Studies

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Shimoga D. Ganesh ◽  
Vasantakumar K. Pai ◽  
Mahadevappa Y. Kariduraganavar ◽  
Madhu B. Jayanna
Keyword(s):  
Carboxylic Acid ◽  
Average Molecular Weight ◽  
Analytical Techniques ◽  
Gel Permeation Chromatography ◽  
Electrical Contacts ◽  
Dielectric Studies ◽  
Weight Average Molecular Weight ◽  
Nucleophilic Displacement ◽  
Ft Ir

Poly(1,3,4-oxadiazole-ether) with reactive carboxylic acid pendants was synthesized from solution polymerization via nucleophilic displacement polycondensation among 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole (BFPOx) and 4,4′-bis(4-hydroxyphenyl) valeric acid (BHPA). Without altering the polymeric segments, benzimidazole modified poly(1,3,4-oxadiazole-ether)s were prepared by varying stoichiometric ratios of 1,2-phenylenediamine. The molecular structural characterization of these polymers was achieved by, FT-IR, NMR, TGA, elemental analysis, and analytical techniques. The weight-average molecular weight of virgin polymer with carboxylic acid functionality was determined by gel permeation chromatography (GPC) and was found to be 22400 (Mw/Mn=2.07). All the synthesized polyethers were compressed into pellets and electrical contacts were established to perform dielectric properties.

scholarly journals The use of 3-bromopropionic acid for the determination of protein thiol groups

1973 ◽  
Vol 131 (4) ◽  
pp. 637-642 ◽  
Author(s):  
A. F. Bradbury ◽  
D. G. Smyth
Keyword(s):  
Carboxylic Acid ◽  
Intramolecular Cyclization ◽  
Iodoacetic Acid ◽  
Cyclization Reaction ◽  
Thiol Groups ◽  
Protein Thiol

S-Carboxymethylcysteine, formed by the reaction of iodoacetic acid with cysteine, was found to undergo intramolecular cyclization to yield 3-oxo-(2H,3H,5H,6H-1,4-thiazine)-5-carboxylic acid. The cyclization was studied under various conditions and the product was isolated and characterized. S-Carboxyethylcysteine, formed by the reaction of 3-bromopropionic acid with cysteine, did not undergo the cyclization reaction. The use of 3-bromopropionic acid was examined as an alternative to iodoacetic acid for the protection and determination of protein thiol groups.

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