The present invention provides novel compounds of formula I wherein W1, W2, W3, W4, W5, B, X1, X2, X3, X4, X5, E and L are as defined herein； invention compounds are gamma amino butyrique acid receptor-subtype B ("GABAB") positive allosteric modulators (enhancers), which are useful to provide methods of treating or preventing diseases or disorders, including treatment of anxiety, depression, epilepsy, schizophrenia, cognitive disorders, spasticity and skeletal muscle rigidity, spinal cord injury, multiple sclerosis, amyotrophic lateral sclerosis, cerebral palsy, neuropathic pain and craving associated with cocaine and nicotine, panic disorder, posttraumatic stress disorders, urge urinary incontinence, gastroesophageal reflux disease, transient lower oesophageal sphincter relaxations, functional gastrointestinal disorders and irritable bowel syndrome.
