The invention provides the substantially geometrically pure cis-stereoisomeric form of a compound of formula (I) and the substantially geometrically and optically pure cis-stereoisomeric form of a compound of formula (II): ##STR1## wherein R.sup.1 is H or C.sub.1 -C.sub.4 alkyl, together with processes for their preparation. The compounds are intermediates for the preparation of the antidepressant agent known as sertraline.