| abstract |
A penicillin derivative represented by the following formula, and a pharmaceutically acceptable salt thereof and ester thereof: <CHEM> wherein R1 and R2 are each the same of different and represent hydrogen atom, trialkylsilyl group, carboxyl group, carboxyl group forming a pharmaceutically acceptable salt or esterified carboxyl group, and a process for preparing the same and a beta -lactamase inhibitor. |