Compounds of formula (I) and their use in therapy, particularly for the treatment of a disorder mediated by CB.sub.1 receptors such as obesity: Formula (I) wherein: R.sup.1 and R.sup.2 are independently selected from aryl; and R.sup.3 is hydrogen or alkyl; or a pharmaceutically acceptable salt or prodrug thereof, wherein at least one of R.sup.1 and R.sup.2 has a non-hydrogen substituent in the ortho-position(s) thereof relative to the point of attachment to the [--CH--O--] group. ##STR00001##