| abstract |
Compounds of formula (I): <IMAGE> (I) wherein W represents an oxygen atom and X represents a group of formula -N(R1)-; R1 is hydrogen, alkyl or aralkyl; R2 and R3 are each hydrogen, alkyl, aralkyl, aryl or aromatic heterocyclic; R4 is hydrogen, alkyl or aralkyl; and A is alkylene which is optionally substituted by carboxy; and pharmaceutically acceptable salts and esters thereof, have a valuable vasodilatory activity. |