| abstract |
A compound of the formula:n in whichn R 1 and R 2 are each hydrogen or lower alkyl, R 3 is aryl or heterocyclic group, each of which may be substituted by suitable substituent(s), R 4 is hydrogen, halogen or lower alkyl, A is methylene, methine, oxa, thia, sulfinyl or sulfonyl, Y is vinylene or ethylene, Z is a group of the formula: wherein R 5 is carboxy or protected carboxy, and R 6 is hydrogen or hydroxy-protective group, and the line of ---is a single or double bond, nor pharmaceutically acceptable salts thereof, processes for their preparation and pharmaceutical comoositions comprising them as an active ingredient in admixture with a pharmaceutically acceptable carrier or excipient. |