Compounds of general formula (I) wherein X is an oxygen or sulfur atom; Y is alkylene or cycloalkylene; A is hydroxy, alkoxy, acyloxy, mercapto, alkyl-sulfonyloxy, phenyl-sulfonyloxy, (a) or (b) wherein R3 is an alkyl or alkylene group φ-substituted by 2,3-dihydro-4H-1,3-benzoxazin-4-one-N-yl; R is hydrogen, alkyl or phenyl; R1 and R2 are independently hydrogen, halogen, alkoxy, trifluoromethyl or alkyl; and the pharmaceutically acceptable acid and base salts thereof, are useful as therapeutically active substances.