The present invention relates to compounds of the formula I, wherein Ht, G, R10, R30, R40, R50 and R60 have the meanings indicated in the claims, which are valuable pharmaceutical active compounds. They are inhibitors of the protease cathepsin A, and are useful for the treatment of diseases such as atherosclerosis, heart failure, renal diseases, liver diseases or inflammatory diseases, for example. The invention furthermore relates to processes for the preparation of the compounds of the formula I, their use and pharmaceutical compositions comprising them.