abstract |
Compounds of formula (I): <IMAGE> (I) wherein R1 and R2 is each -R5, -CH=CH-R5 or -C 3BOND C-R5, wherein R5 is optionally substituted aryl or aromatic heterocyclic; R3 is hydrogen, alkyl, cyano or -R5; X is oxygen or sulfur A is 1,4-piperazin-1,4-diyl or a 1,4-homopiperazin-1,4-diyl; B' is alkylene, carbonyl, thiocarbonyl, sulfinyl or sulfonyl: and R4 is optionally substituted phenyl and pharmaceutically acceptable salts thereof have valuable PAF antagonist activity. |