JPH0121151B

A compound of the formula:wherein R1 is lower alkyl,R2 is carboxy or a protected carboxy group,R3 is amino or a protected amino group andR4 is lower alkyl having halogen atom(s) or lower unsaturated aliphatic group,and pharmaceutically acceptable salt thereof, and process for their preparation.The invention also relates to the starting derivatives and their preparation and to a pharmaceutical composition comprising, as an effective ingredient, the above compound in association with a pharmaceutically acceptable, substantially non-toxic carrier or excipient, and to a method for treating an infectious disease caused by pathogenes, which comprises administering the above compound to infected human beings or animals.