Highly fluorescent and stable 6,7-dimethoxy-2-oxoquinoline-4-carbonitriles (11) were synthesized starting from appropriate 4-hydroxyquinolones 3 via reactive 4-chloroquinolones 8 by using toluenesulfinates as catalysts. In contrast to the well-described 4-trifluoromethyl-substituted analogues 18, N-substituted derivatives 11 fluoresce in water, polar, and apolar solvents in a narrow 430-440-nm window with almost constant quantum yield of 0.5. Equal excitation is possible in the broad double maximum between 385 and 410 nm yield-

Reactions of 2,4‐dichloroquinolines (2a–f) with sodium azide in DMF lead either regioselectively to 4‐azido‐2‐chloroquinolines (3a–f) or with excess of sodium azide and catalysts to 5‐azido‐tetrazolo[1,5‐a]quinolines (4a–f). 2,4‐Dichloroquinolines (2g–i) having electron donating substituents in 3‐position react with sodium azide in DMF to a mixture of 4‐azido‐2‐chloroquinolines (3g–i) and 5‐chlorotetrazolo[1,5‐a]quinolines (5g–i). When the reaction of the 2,4‐dichloroquinolines (2a–i) with sodium azide is carried out in ethanol with addition of methanesulfonic acid, regioselectively 5‐chloro‐tetrazolo[1,5‐a]quinolines (5a–i) are obtained. Structural assignments of 3 and 5 have been carried out by 13C‐NMR spectra, IR spectra and degradation reactions of the azido‐ and tetrazolo group to aminoquinolines (7 and 10) via iminophosphoranes (8 and 9). It could be shown that in 2‐azido/tetrazolo‐quinolines (4 and 5) the tetrazole ring structure is the dominant species.

4‐Azido‐2(1H)‐quinolones 1 are thermolyzed in the presence of carboxylic acids and polyphosphoric acid to yield oxazolo[4,5‐c]quinolones 3. Formation of other possible isomeric ring closure products such as oxazolo[5,4‐c]quinolones 2 or isoxazolo[4,3‐c]quinolones 4 could be excluded by independent syntheses.

Thus, the determination of the percent of IgG1 by itself and/or in combination with conventional markers may provide relevant information regarding the noninvasive detection of early stages of gynecologic carcinoma.

A reactive disulfide bond (SS)* was detected and characterized in IgG of humans, rats and mice by virtue of disulfide interchange with dithionitrobenzoate. (SS)* was found exclusively in human IgG1 and rat IgG2b. In human IgG1 (SS)* was identified as the upper one of the two interheavy bridges in the hinge, where it appears to take part in complement activation. The biological significance of (SS)* in IgG was underlined by the fact that no other serum proteins were found to exhibit a similar reactivity.