| abstract |
The invention provides compounds of formula (I): n n n wherein: R 1 -R 4 and A have any of the values defined in the specification, and their pharmaceutically acceptable salts, are useful for inhibiting β-lactamase enzymes, for enhancing the activity of β-lactam antibiotics, and for treating β-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). |