Patent ID: 7199248

Claim:
A process for preparing a compound of the formula (III): wherein R 2 is lower alkoxy or higher alkoxy, R 4 is carboxy A 1 is an aromatic bivalent group, heterocyclic bivalent group or cyclo(lower)alkane bivalent group, and A 2 is an aromatic bivalent group, heterocyclic bivalent group or cyclo(lower)alkane bivalent group, which comprises: hydrolyzing a compound of the general formula (II): wherein R 2 , A 1 and A 2 are each as defined above, and R 1 is protected carboxy, with aqueous potassium hydroxide to give a compound of the general formula (I): wherein R 2 , A 1 and A 2 are each as defined above, and R 3 is a potassium salt of carboxy, and reacting this compound (I) with hydrochloric acid to obtain the compound (III).