Compounds of formula I: ##STR00001## wherein R.sup.1 is hydroxy or NHSO.sub.2R.sup.1A wherein R.sup.1A is (C.sub.1-8)alkyl, (C.sub.3-7)cycloalkyl or {(C.sub.1-6)alkyl-(C.sub.3-7)cycloalkyl}, which are all optionally substituted from 1 to 3 times with halo, cyano, nitro, O(C.sub.1-6)alkyl, amido, amino or phenyl, or R.sup.1A is C.sub.6 or C.sub.10 aryl which is optionally substituted from 1 to 3 times with halo, cyano, nitro, (C.sub.1-6)alkyl, O(C.sub.1-6)alkyl, amido, amino or phenyl; R.sup.2 is (C.sub.5-6)cycloalkyl and R.sup.3 is cyclopentyl; or a pharmaceutically acceptable salt thereof, useful as inhibitors of the HCV NS3 protease.