Method for producing 8-methoxy-quinolinecarboxylic acids
View Patent ↗The present invention relates to a novel process for preparing 8-methoxy-3-quinolonecarboxylic acids which are antibiotics having potent antibacterial action.
1. A process for preparing
comprising reacting
with methanol and potassium tert-butoxide in tetrahydrofuran as solvent and further comprising (a) adding dilute hydrochloric acid to the reaction mixture or adding the reaction mixture to dilute hydrochloric acid; and (b) isolating the precipitated hydrochloride by filtration to obtain
2. The process of claim 1 , further comprising recrystallizing the product of the process of claim 1 from water or a mixture of water/C 1 –C 3 -alkanol to obtain.
3. The process according to claim 2 , where the recrystallization is carried out from water or a water/ethanol mixture.
4. The process of claim 2 , further comprising drying the product of the process of claim 2
at from 40 to 60° C. and from 80 to 120 mbar.
5. The process according to claim 4 , wherein said drying is carried out at approximately 50° C. and approximately 100 mbar.