Trichloroacetonitrile → O-(2,3,4-tri-O-acetyl-beta-L-fucopyranosyl) trichloroacetimidate

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Reaction Steps

A mixture of 2,3,4-tri-O-acetyl-L-fucopyranose (anomer mixture) (0.85 g, 2.93 mmol), trichloroacetonitrile (3 ml, 30 mmol) and potassium carbonate (2.73 g, 19.7 mmol) in dry dichloromethane (12 ml) is stirred under nitrogen at room temperature for about 4 h. After filtration through kieselguhr, the solvent is removed. After chromatographic purification (petroleum ether/diethyl ether 2:5), a mixture of O-(2,3,4-tri-O-acetyl-α-L-fucopyranosyl) trichloroacetimidate (3) and O-(2,3,4-tri-O-acetyl-β-L-fucopyranosyl) trichloroacetimidate (2) is obtained in a yield of 76% (α:β=1:1.3). α-Anomer: [α]D =-116.0 (c=1, chloroform), Rf =0.54 (petroleum ether/ethyl acetate 2:1), m.p. 107°-109° C. β-Anomer: [α]D =-24.5 (c=1, chloroform), Rf =0.34 (petroleum ether/ethyl acetate 2:1), m.p. 60°-63° C.

Provenance & Evidence