Piperazine derivatives

摘要

Piperazine derivatives of the following formula <IMAGE> wherein A and B are a carbon atom or a nitrogen atom except the case where both A and B are nitrogen atoms, R1 is hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a benzyl group or acetyl group; R2 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a benzyl group or a vinyl group; and R3 is hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and pharmaceutically acceptable salts thereof.