Method for making 2-azabicyclo-[3.3.0]-octane-3-carboxylic acids

A method for making a compound of the formula ##STR11## or a salt thereof with an acid or a base, wherein the hydrogen atoms on the bridge-head carbon atoms in the 1- and 5-positions are in the cis-configuration relative to one another and the carboxyl group on the carbon atom in the 3-position is orientated in the endo-position relative to the bicyclic ring system, and wherein W is hydrogen, alkyl having 1-6 carbon atoms, or aralkyl having 7 or 8 carbon atoms, which method comprises cyclizing a compound of the formula ##STR12## wherein Y.sup.1 is alkanoyl having 1 to 5 carbon atoms or aroyl having 7 to 9 carbon atoms and

• R.sup.2 is alkyl having 1 to 5 carbon atoms or aralkyl having 7 to 9 carbon atoms,
• with a strong acid, with acylamide and ester cleavage, to give an intermediate compound of the formula ##STR13## catalytically hydrogenating this intermediate compound to form the desired compound wherein W is hydrogen in the presence of a transition metal catalyst or by reducing said intermediate with a borane-amine complex or a complex borohydride in a lower alcohol, and then optionally esterifying the acid product to give a compound wherein W is alkyl having 1 to 6 carbon atoms or aralkyl having 7 or 8 carbon atoms.