Syntheses of dopa glycosides using glucosidases

Syntheses of L-dopa 1a glucoside 10a,b and DL-dopa 1b glycosides 10-18 with D-glucose 2, D-galactose 3, D-mannose 4, D-fructose 5, D-arabinose 6, lactose 7, D-sorbitol 8 and D-mannitol 9 were carried out using amyloglucosidase from Rhizopus mold, beta-glucosidase isolated from sweet almond and immobilized beta-glucosidase. Invariably, L-dopa and DL-dopa gave low to good yields of glycosides 10-18 at 12-49% range and only mono glycosylated products were detected through glycosylation/arylation at the third or fourth OH positions of L-dopa 1a and DL-dopa 1b. Amyloglucosidase showed selectivity with D-mannose 4 to give 4-O-C1 beta and D-sorbitol 8 to give 4-O-C6-O-arylated product. beta-Glucosidase exhibited selectivity with D-mannose 4 to give 4-O-C1 beta and lactose 7 to give 4-O-C1 beta product. Immobilized beta-glucosidase did not show any selectivity. Antioxidant and angiotensin converting enzyme inhibition (ACE) activities of the glycosides were evaluated glycosides, out of which L-3-hydroxy-4-O-(beta-D-galactopyranosyl-(1'-> 4) beta-D-glucopyranosyl) phenylalanine 16 at 0.9 +/- 0.05 mM and DL-3-hydroxy-4-O-(beta-D-glucopyranosyl) phenylalanine 11b,c at 0.98 +/- 0.05 mM showed the best IC50 values for antioxidant activity and DL-3-hydroxy-4-O-(6-D-sorbitol) phenylalanine 17 at 0.56 +/- 0.03 mM, L-dopa-D-glucoside 10a,b at 1.1 +/- 0.06 mM and DL-3-hydroxy-4-O-(D-glucopyranosyl)phenylalanine 11a-d at 1.2 +/- 0.06 mM exhibited the best IC50 values for ACE inhibition.