Method of treating disorders of the melatoninergic system and a certain benzofuran containing compound

A method-of-treating a mammal afflicted with a disorder of the melatoninergic system comprising the step of administering to the said mammal an amount of a compound selected from the group consisting of those of formula (I):

• ##STR44## in which R.sub.1 represents alkyl,
• A forms, with the benzene ring to which it is attached, a cyclic group selected from the group consisting of benzofuran and 2,3-dihydrobenzofuran,
• R.sub.2 represents hydrogen,
• R.sub.3 represents ##STR45## with X representing oxygen and R.sub.4 representing alkyl, it being understood that, in the description of formula (I),
• the term "alkyl" denotes a linear or branched group containing 1 to 6 carbon atoms, inclusive, and the enantiomers and diastereoisomers thereof, which is effective for alleviating the said disorder.