The present invention provides compounds of formula I:
1
or a pharmaceutically acceptable derivative thereof, wherein X is oxygen or sulfur; Y is —S—, —O—, or —NR
1
—; and R
2
, R
3
, and R
4
are as described in the specification. These compounds are inhibitors of protein kinase, particularly inhibitors of GSK-3 mammalian protein kinase. The invention also provides pharmaceutical compositions comprising the inhibitors of the invention and methods of utilizing those compositions in the treatment and prevention of various disorders, such as diabetes and Alzheimer's disease.