Compounds of formula (I) wherein R1 is a phenylcarbonylmethyl group wherein the phenyl moiety is substituted by R10 and R11 and R2 to R4 and R10 and R1l are defined as in the claims, or the prodrugs or salts thereof, particularly the physiologically acceptable salts thereof, pharmaceutical compositions containing these compounds, and methods of treating type II diabetes mellitus and obesity using these compounds.