This invention relates to a novel class of compounds, represented by theformula below, wherein the meanings of R1 , R2 and R3 are indicated therein,which are cysteine protease inhibitors, including but not limited to,inhibitors of cathepsms K, L, S and B These compounds are useful for treatingdiseases in which inhibition of bone resorption is indicated, such asosteoporosis, osteoarthritis and rheumatoid arthritis.