| 摘要 |
A compound of formula (I), or a pharmaceutically acceptable salt thereof, wherein R1 is a carboxylic acid group, a derivative thereof, or hydroxymethyl; R2 is optionally substituted C1-8 alkoxy; and R3 is an amino group or a derivative thereof; with the proviso that when R1 is hydroxymethyl, R2 is not an unsubstituted C1-8 alkoxy group. |
