Disclosed are compounds of the formula (I) and pharmaceutically acceptable salts thereof: wherein R1 is a halogen, or an oxygen linked leaving group including an aromatic ether, an alkyl sulfonate, an aryl sulfonate, an alkyl phosphonate, an aryl phosphonate, an alkyl phosphate or aryl phosphate; R2 is COOR5, C(═O)NH(CHR5)m—COOR5, NH(CHR5)mCON(R5)R6, C(═O)N(R5)R6 or NH(CHR5)mOH; R3 is H or alkyl; R4 is H, substituted or unsubstituted aryl, heteroaryl or alkyl; R5 and R6 are independently H, lower alkyl, aryl, hydroxy alkyl, amino alkyl, heteroaryl, lower alkylene-aryl, lower alkylene-heteroaryl or lower cycloalkyl; and m=0–6; pharmaceutical compositions containing the compounds; and a method for inhibiting interleukin-1β protease activity in a mammal utilizing the compounds and compositions.