Compounds of the general formula: ##STR1## wherein R.sup.1 is heterocyclic group other than pyridyl and which is unsubstituted or substituted with lower alkyl or lower alkoxycarbonyl, R.sup.2 is hydrogen, halogen, or nitro, and R.sup.3 is carboxy group or its functional derivative, with the proviso that when R.sup.1 is an unsubstituted furyl, or furyl mono- or polysubstituted with alkyl and R.sup.2 is hydrogen, then R.sup.3 is functional derivative of carboxy and, where applicable, pharmaceutically acceptable salts thereof are hyaluronidase inhibitors and useful as anti-allergic agent.