The present invention relates to compounds of the general formula wherein R.sup.1 is cycloalkyl, substituted by OR or is 2-(7-oxa-bicyclo[2.2.1]he- pt-1-yl)-ethyl; R is hydrogen, lower alkyl or C(O)-lower alkyl; X is --CHR'--; and R' is hydrogen or lower alkyl; and pharmaceutically acceptable acid addition salts, optically pure enantiomeres, racemates or diastereomeric mixtures thereof for the treatment of Alzheimer's disease, Parkinson's disease, Huntington's disease, neuroprotection, schizophrenia, anxiety, pain, respiration deficits, depression, ADHD, drug addiction, such as amphetamine, cocaine, opioids, ethanol, nicotine, cannabinoids, or for the treatment of asthma, allergic responses, hypoxia, ischaemia, seizure and substance abuse, or for use as sedatives, muscle relaxants, antipsychotics, antiepileptics, anticonvulsants and cardiaprotective agents for coronary artery disease and heart failure.