| abstract |
A compound of the formula :n in which R 1 is carboxy or protected carboxy,n R 2 is hydroxy(lower)alkyl or protected hydroxy(lower)alkyl, R 3 is hydrogen or lower alkyl, R 4 is heterocyclic group, which may have suitable substituent(s), and R 5 is hydrogen or imino-protective group, and pharmaceutically acceptable salts thereof, processes for their preparation and pharmaceutical compositions comprising them as an active ingredient. The invention further comprises intermediates of the formulan and process for the preparation thereof. |