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TCI Practical Example: The Regioselective Koenigs-Knorr-Type Glycosylation of Carbohydrates Using a Borinic Acid Ester Catalyst

We are proud to present the regioselective Koenigs-Knorr-type glycosylation of carbohydrates catalyzed by a borinic acid ester.

Used Chemicals

• 2,3,4,6-Tetra-O-acetyl-α-D-glucopyranosyl Bromide [T1961]
• Methyl α-L-Fucopyranoside [M1051]
• 2-Aminoethyl Diphenylborinate [D0281]
• Silver(I) Oxide
• Acetonitrile

Procedure

To a solution of methyl α-L-fucopyranoside (392 mg, 2.2 mmol, 1.1 equiv), silver(I) oxide (463 mg, 2.0 mmol, 1.0 equiv) and 2-aminoethyl diphenylborinate (45 mg, 0.2 mmol, 10 mol%) in acetonitrile (23 mL) was added 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (822 mg, 2.0 mmol, 1 equiv) at r.t. and the mixture was stirred for 4 hours. The reaction mixture was filtered through celite pad and washed with dichloromethane (30 mL). The solvent was removed under reduced pressure and the residue was purified by column chromatography (ethyl acetate:hexane = 0:1 - 3:1 on silica gel), to give 1 as a white amorphous (914 mg, 90%).

Experimenter’s Comments

The reaction mixture was monitored by TLC (ethyl acetate, Rf = 0.51).
The color of the reaction mixture turned from black to gray as the reaction proceeds.

Analytical Data

Compound 1

¹H NMR (400 MHz, CDCl₃); δ 5.23 (t, J = 9.5 Hz, 1H), 5.07 (t, J = 9.5 Hz, 1H), 5.04 (dd, J =　9.5, 7.8 Hz, 1H), 4.83 (d, J = 3.8 Hz, 1H), 4.68 (d, J = 7.8 Hz, 1H), 4.25 (dd, J = 12.2, 2.7 Hz, 1H), 4.17 (dd, J = 12.2, 5.1 Hz, 1H), 3.99 (dd, J = 10.0, 3.8 Hz, 1H), 3.95 (brq, J = 6.8 Hz, 1H), 3.83 (dd, J = 10.0, 3.5 Hz, 1H), 3.76 (ddd, J = 10.0, 5.1, 2.7 Hz, 1H), 3.72 (m, 1H), 3.43 (s, 3H), 3.14 (d, J = 3.8 Hz, 1H), 2.27 (brs, 1H), 2.10 (s, 3H), 2.07 (s, 3H), 2.04 (s, 3H), 2.02 (s, 3H), 1.31 (d, J = 6.8 Hz, 3H).

Lead Reference

• Regioselective Activation of Glycosyl Acceptors by a Diarylborinic Acid-Derived Catalyst
• C. Gouliaras, D. Lee, L. Chan, M. S. Taylor, J. Am. Chem. Soc. 2011, 133, 13926.

Other References

• Boronic Acid-Catalyzed Regioselective Koenigs–Knorr-Type Glycosylation
• N. Shimada, T. Sugimoto, M. Noguchi, C. Ohira, Y. Kuwashima, N. Takahashi, N. Sato, K. Makino, J. Org. Chem. 2021, 86, 5973.