Monoacylation of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid by protease in N,N-dimethylformamide with low water content

Recent biotechnological progress in enzymatic synthesis of glycosides

Glycosylation is one of the most important post-modification processes of small molecules and enables the parent molecule to have increased solubility, stability, and bioactivity. Enzyme-based glycosylation has achieved significant progress due to advances in protein engineering, DNA recombinant techniques, exploitation of biosynthetic gene clusters of natural products, and computer-based modeling programs. Our report summarizes glycosylation data that have been published within the past five years to provide an overall review of current progress. We also present the future trends and perspectives for glycosylation.

Intramolecular acyl migration and enzymatic hydrolysis of 2-O-α-D-glucopyranosyl-6-O-(2-pentylheptanoyl)-L-ascorbic acid

2-O-α-D-Glucopyranosyl-6-O-(2-pentylheptanoyl)-L-ascorbic acid (6-bDode-AA-2G) underwent an intramolecular acyl migration to yield approximately 12% of 2-O-α-D-glucopyranosyl-5-O-(2-pentylheptanoyl)-L-ascorbic acid (5-bDode-AA-2G) in neutral solutions for 3 days. In small intestine homogenate from guinea pigs for 12h, 6-bDode-AA-2G, which hardly underwent acyl migration to give 5-bDode-AA-2G, was predominantly hydrolyzed with α-glucosidase and then with esterase to ascorbic acid.

Regioselective monoacylation of 2-O-α-D-glucopyranosyl-L-ascorbic acid by a polymer catalyst in N,N-dimethylformamide

6-O-Dodecanoyl-2-O-α-D-glucopyranosyl-L-ascorbic acid (6-sDode-AA-2G) was synthesized from 2-O-α-D-glucopyranosyl-L-ascorbic acid and lauric anhydride with a polymer catalyst, poly(4-vinylpyridine), in N,N-dimethylformamide without the introduction of protecting groups. The optimum reaction conditions enabled 6-sDode-AA-2G to be synthesized in a yield of 49.7%. The yield and the regioselectivity in this method were far superior to those in our previous method by using an enzyme. The polymer catalyst could be recycled more than five times without any significant activity loss.

Protease-catalyzed monoacylation of 2-O-α-D-glucopyranosyl-L-ascorbic acid in three solvent systems

6-O-dodecanoyl-2-O-α-D-glucopyranosyl-L-ascorbic acid (6-sDode-AA-2G) was synthesized from 2-O-α-D-glucopyranosyl-L-ascorbic acid and vinyl laurate with a protease from Bacillus subtilis in 30% dimethylformamide (DMF)/dioxane with a low water content. The addition of 3% (v/v) water to DMF/dioxane dramatically enhanced the 6-sDode-AA-2G synthesis. The optimum reaction conditions enabled 6-sDode-AA-2G to be synthesized in a yield of 38.1%.