The present invention relates to broad spectrum β-lactamase inhibitors. More particularly, the invention relates to inhibitors of Class B metallo (MBL) and Class D (OXA) β-lactamases. A method of treating a bacterial infection is provided, wherein the method comprises administering to a mammalian patient in need of such treatment a compound of formula (I)
wherein
R
1
is selected from
R
2
is selected from
with certain provisos as herein defined;
in combination with a pharmaceutically acceptable β-lactam antibiotic in an amount which is effective for treating the bacterial infection.