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Title: Syntheses of L-dopa glycosides using glucosidases
Authors: Vadivelan, Ganesan
Divakar, Soundar
Keywords: L-Dopa;Glycosides;Glycosylation;Amyloglucosidase;Immobilized;-glucosidase;Regioselectivity
Issue Date: Dec-2011
Publisher: NISCAIR-CSIR, India
Abstract: Syntheses of l-dopa 1 glycosides 13-22 with d-glucose 2, d-galactose 3, d-mannose 4, d-fructose 5, d-ribose 6, d-arabinose 7, lactose 8, maltose 9, sucrose 10, and d-mannitol 11 have been carried out using amyloglucosidase from Rhizopus mold and b-glucosidase isolated from sweet almond and entrapped onto calcium alginate beads. Invariably, l-dopa gives very low to moderate yields of glycosides 13-22 at 3.3 – 57.6% range. Only mono glycosylated products are detected through glycosylation/arylation at the 3rd or 4th OH positions of l-dopa 1. Arylation occurs at 6-O-positions with d-glucose 2 and d-galactose 3. Amyloglucosidase catalyzes the reaction with all ten carbohydrate molecules employed with the exception of d-sorbitol. Regio-selectivity is observed in case of d-mannose 4 to give 4-O-C1α, d-fructose 5 to give 4-O-2-O, ribose 6 to give 4-O-C1α, maltose 9 to give 4-O-C1α, sucrose 10 to give 4-O-6--O, and d-mannitol 11 to give 4-O-1-O. Immobilised b-glucosidase does not show any selectivity and catalyzed reactions with d-glucose 2, d-galactose 3, d-ribose 6 and lactose 8.
Page(s): 1779-1785
ISSN: 0975-0983(Online); 0376-4699(Print)
Appears in Collections:IJC-B Vol.50B(12) December 2011]

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