The syntheses of the optical isomers of O3,O4-dimethyl-noradrenaline, O3,O4-dimethyl-fl-methyl-dopamine, 0304-dimethyl-fl-methoxy-dopamine as well as their Nmethylated analogues are described. ORD and NMR measurements of these compounds are performed in acidic and alkaline solutions. It is concluded that the conformation of the side chain of the catecholamine derivatives is only influenced by the charge-charge interaction between the protonated amino group and the electronegative floxygen atom, Internal hydrogen bonding is excluded as a factor influencing the conformational equilibrium of the side chain. (Pharm. Weekblad Sci. Ed. 2,