One embodiment of the invention relates to compounds of the formula I, ##STR00001## in which R1, R2, R3, R4, R5 and R6 have the meanings given in the specification. Other embodiments of the invention relate to physiologically acceptable salts of compounds of formula I, to processes for their preparation and to medicaments comprising these compounds. The compounds of the invention are suitable for use, for example, as hypolipidemics.