A compound of formula I, wherein the groups R1, R2, R3, X, m, and n are defined as in claim 1, which have valuable pharmacological properties, in particular bind to the GPR40 receptor and modulate its activity. The compounds are suitable for treatment and prevention of diseases which can be influenced by this receptor, such as metabolic diseases, in particular diabetes type 2. Furthermore, the invention relates to novel intermediates, useful for the synthesis of compounds of formula I.