Abstract: The present invention discloses compounds of the formula wherein the dotted bonds are optional extra bonds allowing any tautomeric isomers compatible with substituents X and R3; R3 is non-existing, hydrogen, or alkyl; X is O, S, imino, alkoxy, alkylthio, or amino; R1 is hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, acyl, acylalkyl, alkoxyalkyl, dialkoxyalkyl, or phenylalkyl which may be substituted with alkyl, halogen, amino, nitro or cyano; and R4, R5, R6 and R7 independently of each other are hydrogen; halogen; amino; nitro; CN; CF3; COOH; COO-alkyl; alkyl; acyl; alkoxy; —(CH2)n,—OH wherein n is 0, 1, 2, or 3; —(CH2)m—O-alkyl wherein m is 0, 1,2, or 3; —(CH2)p—O-acyl wherein p is 0, 1,2, or 3; or a pharmaceutically acceptable addition salt thereof.