The invention relates to compounds of formula (I): ##STR00001## wherein: G.sub.1 represents an alkylene chain as defined in the description, A represents ##STR00002## R.sup.2 and R.sup.3 represent hydrogen, alkyl, alkoxy or hydroxy or together form oxo, R.sup.4 and R.sup.5 represent hydrogen, R.sup.1 is as defined in the description, and medicinal products containing the same which are useful in treating or preventing melatoninergic disorders.