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

Dopamine–HCl and l-DOPA-α-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 β-amylase to produce α-glucosyl- and α-maltosyl-glycosides, respectively. The glucoamylase- or β-amylase-treated dopamine- and l-DOPA-α-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-α-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-α-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.

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