There is provided compounds of formula I, R.sup.1O(O)C--CH.sub.2--(R)Cgl-Aze-Pab-R.sup.2I wherein R.sup.1 and R.sup.2 have meanings given in the description, which are useful as prodrugs of inhibitors of trypsin-like proteases, such as thrombin, and in particular in the treatment of conditions where inhibition of thrombin is required (eg thrombosis) or as anticoagulants.