The present invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof;






or a pharmaceutically acceptable salt, tautomer, or stereoisomer thereof, wherein the variables are as defined herein. The present invention further provides pharmaceutical compositions comprising such compounds; and methods of using such compounds for treating joint damage or injury in a mammal, for inducing hyaline cartilage production or for inducing differentiation of chondrogenic progenitor cells into mature chondrocytes.