An ether cleavage of (4) with pyridine hydrochloride leads to 1-(4'-hydroxyphenyl)-2-phenyl-n-butane-1-one (5) ##STR7## By reacting (5) with compounds of the general formula R1 R2 N--CH2 CH2 Cl (6) wherein R1 and R2 may be the same or different, provided that, when R1 and R2 are the same, each of them is a methyl or ethyl radical, and when R1 and R2 are different, one of them is a benzyl radical a