A compound of the formula :
wherein R¹ is hydrogen, halogen, hydroxy, lower alkoxy, lower alkyl or mono(or di or tri)halo(lower)alkyl, and
(in which R² and R³ are each lower alkyl),
and a pharmaceutically acceptable salt thereof, processes for their preparation and pharmaceutical compositions comprising them as an active ingredient in admixture with pharmaceutically acceptable carriers. The invention also relates to intermediates of the formula
式中的化合物
其中 R¹ 是
氢、卤素、羟基、低级烷
氧基、低级烷基或单(或二或三)卤代(低级)烷基,以及
(其中 R² 和 R³ 各为低级烷基)、
及其药学上可接受的盐、它们的制备工艺以及将它们作为活性成分与药学上可接受的载体混合的药物组合物。本发明还涉及式如下的
中间体