Synthesis of dopamine and L-DOPA-α-glycosides by reaction with cyclomaltohexaose catalyzed by cyclomaltodextrin glucanyltransferase

Dopamine-HCl and L-DOPA-alpha-glycosides were prepared by reaction with cyclomaltohexaose, catalyzed by Bacillus macerans cyclomaltodextrin glucanyltransferase. The reaction gave maltodextrins attached to dopamine and L-DOPA; the maltodextrins were trimmed by reactions with glucoamylase and beta-amylase to produce alpha-glucosyl- and alpha-maltosyl-glycosides, respectively. The glucoamylase- or beta-amylasetreated dopamine- and L-DOPA-alpha-glycosides were fractionated and purified by BioGel P-2 gel-filtration column chromatography and preparative descending paper chromatography. Analysis by MALDI-TOF mass spectrometry and one- and two-dimensional NMR showed that the purified glycosides of dopamine and L-DOPA were glycosylated at the hydroxyl groups of positions 3 and 4 of the catechol ring. The major product was found to be 4-O-alpha-glycopyranosyl L-DOPA, and it was shown to be more resistant to oxidative tolerance experiments, involving hydrogen peroxide and ferrous ion, than L-DOPA. L-DOPA-alpha-glycosides are possibly more effective substitutes for L-DOPA in treating Parkinson's disease in that they are more resistant to oxidation and methylation, which renders L-DOPA ineffective and deleterious. (C) 2009 Elsevier Ltd. All rights reserved.