The present invention relates to novel compounds of the general formula (I) ##STR00001## wherein R.sup.1, R.sup.4, R.sup.5 and X are as defined,having a positive allosteric GABA.sub.B receptor (GBR) modulator effect, methods for the preparation of said compounds and to their use, optionally in combination with a GABA.sub.B agonist, for the inhibition of transient lower esophageal sphincter relaxations, for the treatment of gastroesophageal reflux disease, as well as for the treatment of functional gastrointestinal disorders and irritable bowel syndrome (IBS).