Unequivocal synthesis and characterisation of dopamine 3- and 4-O-sulphates

The major metabolic products of the endogeneous catecholamine dopamine are its 3- and 4-O-sulphates which have also been implicated as intermediates in noradrenaline biosynthesis. Because of the unsatisfactory status of the literature concerning the synthesis, isolation, purity and characterisation of the dopamine O-sulphates we describe both a one-step synthesis and definitive separation and characterisation procedures for these metabolites. High-performance liquid chromatography (HPLC) combined with high-field nuclear magnetic resonance techniques were employed. The chemical sulphonation of dopamine gave three synthetic products, whose relative amounts depended critically upon the reaction conditions employed. Dopamine 3- and 4-O-sulphates together with dopamine 6-sulphonic acid, a hitherto undescribed derivative of dopamine, were for the first time isolated and characterised unequivocally. It should now prove possible to reappraise critically the biological significance of the major metabolite products of dopamine.