Photochemistry of some non zwitterionic fluoroquinolones

• Two non zwitterionic analogues of fluoroquinolone drugs have been synthesized.
• The photochemistry has been investigated.
• Both compound undergo photoheterolysis of the C8F bond generating a triplet cation.
• The quantum yield is low.
• Assistance to defluorination by the N+H bond has a determining role.

Two non zwitterionic analogues of fluoroquinolone drugs, viz. 1-ethyl-7-piperidino-8-fluoroquinol-4-one-3-carboxylic acid and 1-ethyl-7-piperidino-6,8-difluoroquinol-4-one-3-carboxylic acids have been synthesized and their photochemistry has been investigated. Both compound undergo photoheterolysis of the C8F bond generating a triplet cation that either inserts into the 1-alkyl chain or is trapped or reduced by external nucleophiles. The reaction is analogous to that observed with the corresponding (zwitterionic) 7-piperazino derivatives, but the quantum yield is ca five times lower. This supports the rationalization that in the latter case assistance to defluorination by the N+H bond has a determining role.

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