| abstract |
Compounds of formula (I):n [in which R 1 and R 2 is each -R 5 , -CH=CH-R 5 or -C≡C-R 5 , in which R 5 is optionally substituted aryl or aromatic heterocyclic; R 3 is hydrogen, alkyl, cyano or -R 5 ; X is oxygen or sulphur; A is 1,4-piperazin-1.4-diyl or a 1,4-homopiperazin-1,4-diyl; B is alkylene, carbonyl, thiocarbonyl, sulphinyl or sulphonyl; and R 4 is optionally substituted phenyl] and pharmaceutically acceptable salts thereof have valuable PAF antagonist activity, and may be prepared by reacting a compound containing the piperazine or homopiperazine part of the molecule with a compound containing the other part of the molecule. |