The present invention discloses and claims compounds of formula (I) ##STR00001## wherein M is N, and K and L are each C with the remaining substituents further defined herein. These compounds are effective as inhibitors of human casein kinase I.epsilon., and as such are useful in the treatment of central nervous system diseases and disorders including mood disorders and sleep disorders. Pharmaceutical compositions comprising compounds of formula (I) and methods for the preparation of compounds of formula (I) are also disclosed and claimed.