Air- and heat-stable planar tri-p-quinodimethane with distinct biradical characteristics.

A heptacyclic carbocycle possessing three p-quinodimethane units conjugated in one plane has been synthesized and shown to exhibit distinct biradical characteristics. The molecule has a HOMO/LUMO band gap of ca. 1 eV and a S(0)-T(1) energy gap of 2.12 kcal/mol, and it absorbs and emits near-IR light at room temperature. It is air-stable under ambient light for several months and thermally stable up to 160 °C under nitrogen, and it undergoes reversible two-electron oxidation and reduction. The synthetic approach is such that a smaller and larger oligo-p-quinodimethane can be synthesized.

Synthesis and antibacterial activity of 1-(2-fluorovinyl)-7-substituted-4-quinolone-3-carboxylic acid derivatives, conformationally restricted analogues of fleroxacin.

The novel 1-(2-fluorovinyl)-4-quinolone-3-carboxylic acid derivatives Z-15a-c, E-15a-c, Z-16a-c, and E-16a-c, conformationally restricted analogues of fleroxacin (5), were synthesized, and their in vitro antibacterial activity was evaluated. A dehydrosulfenylation of a 2-fluoro-2-[(4-methoxyphenyl)sulfinyl]ethyl group was employed as a key step for the construction of a 2-fluorovinyl group at the N-1 position. It appeared evident that the Z-isomers Z-15a-c and Z-16a-c exhibited 2- to 32-fold more potent in vitro antibacterial activity than the corresponding E-isomers E-15a-c and E-16a-c. Furthermore, since Z-15b showed in vitro antibacterial activity and DNA gyrase inhibition comparable to that of 5, it was hypothesized that the conformation of Z-15b would be equivalent to the active conformer of 5. The results revealed that the antibacterial Z-1-(2-fluorovinyl)quinolone derivatives carry the novel N-1 substituent of the fluoroquinolones.

Synthesis and biodistribution of 18F-labeled fleroxacin.

[18F]Fleroxacin (6,8-difluoro-1,4-dihydro-1-(2-[18F]fluoroethyl)-4- oxo-7-(4-methyl-1-piperazinyl)-3-quinolinecarboxylic acid) was synthesized from its methylsulfonyl ester precursor. 6,7,8-Trifluoro-4-hydroxyquinoline-3-carboxylic acid ethyl ester (Ro 19-7423) was alkylated with 2-bromoethanol to produce 6,7,8-trifluoro-1,4-dihydro-1-(2-hydroxyethyl)-4-oxo-3-quinolinecarboxyl ic acid ethyl ester in 76% yield which was then condensed with 1-methyl-piperazine to produce 6,8-difluoro-1,4-dihydro-1-(2-hydroxyethyl)-7-(4-methyl-1-piperazinyl)4- oxo-3- quinolinecarboxylic acid ethyl ester in 67% yield. This product was reacted with methanesulfonyl chloride to produce the mesylate precursor of fleroxacin in 66% yield. Nucleophilic substitution of the mesylate with 18F- in the presence of Kryptofix 2.2.2 followed by basic hydrolysis produced [18F]fleroxacin with a radiochemical yield of 5-8% [EOS] within 90 min. The pattern of biodistribution of [18F]fleroxacin was similar to the 14C-labeled drug.