the invention relates to compounds of the following formula : and their pharmaceutically acceptable salts , pharmaceutical compositions containing this compounds , and methods of using this compound for the treatment of various diseases or conditions , including but not limited to diseases and / or conditions of , or involving , the central nervous system , including schizophrenia adrenoleukodystrophy , mitochondrial diseases , huntington &# 39 ; s disease , trichotillomania , hiv - associated neurocognitive disorder , hypoxic - ischemic encephalopathy , drug craving , and drug addiction .