| 摘要 |
The invention relates to a compound of formula (I) or a salt thereof, wherein R1 is carboxy, lower alkoxycarbonyl or tetrazol-5-yl; R2 is lower alkyl; R3 is lower alkyl; R4 is alkyl, C3-C7 cycloalkyl, aryl, alkoxy, C3-C7 cycloalkoxy or aryloxy; and R5 and R6 are each independently of the other hydrogen or lower alkyl; or R5 and R6 together are C2-C6 alkylene; to processes for their preparation, to pharmaceutical compositions comprising a compound of formula (I) or a pharmaceutically acceptable salt thereof, and to the use of a compound of formula (I) or of a salt thereof. |
