The present invention relates to compounds of formula (I) ##STR00001## wherein Ar, Ar.sub.2, R.sup.2, R.sup.3, R.sup.4, m, p and s are as defined in the description and claims, and pharmaceutically acceptable salts thereof. The compounds are useful for the treatment and/or prophylaxis of diseases that are associated with the activation of the glycogen synthase enzyme, such as diabetes.