Prostanoid compounds are described having the formula: ##STR1## where A is a cyclopentane ring, which is substituted by oxo and/or hydroxy or etherified hydroxy and may be saturated or unsaturated; X is --CH.dbd.CH-- or --(CH.sub.2).sub.2 --; R is alkyl having a terminal --COOH or ester grup; and Y is amino or substituted amino, particularly heterocyclic amino. The compounds have bronchodilator activity and/or inhibit blood platelet aggregation. The preparation and pharmaceutical formulation of the compounds is also described.