Abstract: A compound of the formula, ##STR1## wherein R represents a hydrogen atom, a naphthyl, indanyl, tetrahydronaphthyl or pyridyl group, or a phenyl group which may have 1 to 3 substituents selected from the group consisting of a halogen atom, and an alkyl, alkenyl, alkoxy, alkanoyl, cyano, formyl, trifluoromethyl, phenyl, phenylalkyl, alkanoyl-amino, aminosulfonyl, carboxyl, alkoxycarbonyl, benzyloxycarbonyl, benzoylvinyl, phenylvinylcarbonyl, carboxyvinyl, and diphenyl-methyloxycarobnylvinyl group, A represents an oxygen or sulfur atom, and n represents an integer of 0 to 3, with the proviso that when n is an integer of 0, R must not be a hydrogen atom, or a pharmaceutically acceptable salt thereof is effectively useful for inhibiting a complement reaction, inflammation caused by an allergic reaction, and platelet aggregation.