| abstract |
A compound of the formula: <IMAGE> wherein R<1> is carboxy, carboxy derivative, oxalo, or acylamino, R<2> is hydrogen, halogen, lower alkyl, lower alkoxy, aryl or acylamino, R3 is ar(lower) alkyl, X is A is lower alkylene, and <IMAGE> -O-, -S-, or -HNCO-, in which R<4> is hydrogen or acyl, and a pharmaceutically acceptable salt thereof. These derivatives and their pharmaceutically acceptable salts have anti-allergic activity. |