Methods of treating developmental disorders such as Angelman syndrome, Fragile X syndrome, Fragile X-associated tremor/ataxia syndrome (FXTAS), Autistic Spectrum Disorder, Autism, Aspergers syndrome, pervasive developmental disorder, Childhood Disintegrative Disorder, Rett syndrome, Landau-Kleffner Syndrome, Prader-Willi Syndrome, Tardive Dyskinesia, a seizure disorder and/or Williams Syndrome with a compound of formula 1 or a pharmaceutically acceptable salt thereof,wherein X, R1, R2, m and n have the meanings set forth in the specification, are provided. The methods provide therapeutic compositions that may be used to improve one or more symptoms of the developmental disorder.
