The invention provides compounds of formula (I):
##STR1##
wherein: R1-R4 and A have any of the values defined
in the specification, and their pharmaceutically acceptable salts, are useful for
inhibiting -lactamase enzymes, for enhancing the activity of -lactam
antibiotics, and for treating -lactam resistant bacterial infections in
a mammal. The invention also provides pharmaceutical compositions, processes for
preparing compounds of formula (I), wherein R1 and R2 are
each independently hydrogen, (C1-C10)alkyl, (C2-C10)alkenyl,
(C2-C10)alkenyl, (C3-C8)cycloalkyl,
(C1-C10)alkoxy, (C1-C10)alkanoyl, (C1-C10)alkanoyloxy,
(C1-C10)alkoxycarbonyl, aryl, heterocycle, halo, cyano, nitro,
-COORe, -C(O)NRfRg, -OC(O)NRfRg,
NRfRg, or -S(O)nRh; R3 is
hydrogen, halo, aryl, heteroaryl, -S(O)nRh, or -CHCHC(O)NRmRp;
R4 is hydrogen; A is thio, sulfinyl, or sulfonyl; and intermediates
useful for the synthesis of compounds of formula (I).
