摘要:
A compound of the formula or its pharmaceutically acceptable salt: wherein
R 1 $ is hydrogen, lower alkyl or lower alkoxy-phenyl, R 2 is hydrogen or lower alkyl, R 3 and R 5 are each hydrogen, or together to form a bond for getting a group of the formula: wherein R 4 and R 6 are each as defined below, R 4 is lower alkyl, R 6 is hydrogen or lower alkyl, R 7 is hydrogen or a certain group, and R 10 is hydrogen or lower alkyl which may have carboxy or esterified carboxy, processes for its preparation and pharmaceutical compositions containing it as an effective ingredient.