The invention provides a process for producing a compound of formula (I), wherein Y is selected from the group consisting of CH3, CH2OH, CH2CH2OH, CH2Br and Br; comprising the steps of: (i) reacting a compound of formula (II), wherein OX represents hydroxy or O−M+, in which M+ is a cation selected from Li+, Na+ and K+, and Y is as defined above; with trans-cinnamaldehyde (III), in the presence of a secondary amine compound; then (ii) treating the product of the preceding step with acid to afford the compound of formula (I). The above process may also be used in the production of tolterodine and fesoterodine, which are useful in the treatment of overactive bladder.