Compounds of the formula
##STR1##
wherein X1 is C(O), -S(O)-, or -S(O)2-;
X2 is CR3 or N; X3 is -NH-, -O-, or -S-;
X4 is CR4 or N; X5 is CR5 or
N; and X6 is CR6 or N are useful as inhibitors of IMPDH enzyme.
Thus, these compounds can be used as therapeutic agents for IMPDH-associated disorders.
