abstract |
The invention provides compounds of formula (I): wherein: R1-R4 and A have any of the values defined in the specification, and their pharmaceutically acceptable salts, are useful for inhibiting beta-lactamase enzymes, for enhancing the activity of beta-lactam antibiotics, and for treating beta-lactam resistant bacterial infections in a mammal. The invention also provides pharmaceutical compositions, processes for preparing compounds of formula (I), and intermediates useful for the synthesis of compounds of formula (I). |