There are provided pharmaceutically-acceptable acid addition salts of compounds of formula I, wherein R 1 represents C 1-2 alkyl substituted by one or more fluoro substituents； R 2 represents G 1-2 alkyl； n represents 0, 1 or 2； and wherein the acid addition salt is an inorganic acid addition salt, an organic acid addition salt, a carboxylic acid addition salt, a hydroxy acid addition salt or an amino acid addition salt； which salts are useful as prodrugs of competitive inhibitors of trypsin-like proteases, such as thrombin, and thus, in particular, in the treatment of conditions where inhibition of thrombin is required (e.g. thrombosis) or as anticoagulants.本發明提供一種醫藥上可接受的式I化合物的酸加成鹽，其中R1代表一或多個氟取代基取代的C1－2烷基；R2代表C1－2烷基；及n代表0，1或2，此種鹽可用作胰蛋白酶樣蛋白酶，如凝血酶，競爭抑制劑的藥前體，所以特別適用於需抑制凝血酶的疾病(例如血栓)的治療或用作抗凝血劑。
