* All experimental methods are cited from the reference, please refer to the original source for details. We do not guarantee the accuracy of the content in the reference.
Reference：
[1] Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1995, # 22, p. 2883 - 2898
[2] Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1995, # 22, p. 2883 - 2898
3
[ 13242-53-0 ]
[ 22860-22-6 ]
[ 18968-05-3 ]
Reference：
[1] Journal of the American Chemical Society, 2010, vol. 132, # 21, p. 7405 - 7417
With trifluoroacetic acid; In water; acetonitrile; at 0℃;
The commercial peracetylated mannose 1 (i.e. 1,2,3,4,5-penta-O-acetyl-alpha-D-mannopyranose) is brominated in the anomeric position by the action of hydrogen bromide in acetic acid, as described by A. LEVENE et al. in J. Biol. Chem., 1931, 90, 89-98. The activated intermediate 2 is cyclized to the orthoester 3 in a 2,6-dimethylpyridine/methanol mixture. The regioselective opening of the orthoester by acid hydrolysis at 0 C. in a 10% aqueous trifluoroacetic acid/acetonitrile mixture produces 1,3,4,6-tetra-O-acetyl-beta-D-mannopyranose (5). The regioisomer 4 is also isolated.
With silver (II) carbonate; water In acetone at 0 - 25℃; for 20h;
With copper(ll) sulfate pentahydrate; acetic acid; zinc In water at 20℃; for 3h; diastereoselective reaction;
General procedure for the synthesis of 2,3,4-tri-Oacetyl-α-L-rhamnopyranose (3) and 2,3,4,6-tetra-O-acetyl-α-D-mannopyranose (6)
To a suspension of L-rhamnose/D-mannose (10.00 g) in acetic anhydride (7.0 mol equiv) wasadded 1 g of 33 wt % HBr/acetic acid at room temperature.The temperature of the reaction mixture was maintained at room temperature by adding ice occasionally in the water bath. Stirring was continued for 3 h during which time the suspended solid went into solution. This solution was then treated with an additional 9.5 g of 33 wt % HBr/acetic acid and the resulting solution was stirred overnight at room temperature. Anhydrous sodium acetate (8.0 g) was then added to neutralize the excess HBr. The resulting mixture was dried under vacuo and to thesyrup obtained was added CuSO4.5H2O (0.5 g) and zinc (2.0 g)in a solution of water (50 mL) and acetic acid (50 mL). Theresultant reaction mixture was stirred vigorously using mechanical stirrer at room temperature for 3 h. The solid was then removed by filtration and washed with ethyl acetate (500 mL)and water (200 mL). The organic layer of the filtrate was washed with saturated aqueous NaHCO3 then with brine and dried(Na2SO4). The solvent was removed under reduced pressure to afford 2,3,4-tri-O-acetyl-α-L-rhamnopyranose (3) (90 %yield) and 2,3,4,6-tetra-O-acetyl-α-D-mannopyranose (6) (87 %yield) as colorless syrups.
With copper(ll) sulfate pentahydrate; acetic acid; zinc In water at 20℃; for 3h;
General procedure for the synthesis of 2,3,4-tri-O-acetyl-α-L-rhamnopyranose (3) and 2,3,4,6-tetra-O-acetyl-α-D-mannopyranose (6):
General procedure: To a suspension of L-rhamnose/D-mannose (10.00 g) in acetic anhydride (7.0 mol equiv) was added 1 g of 33 wt % HBr/acetic acid at room temperature. The temperature of the reaction mixture was maintained at room temperature by adding ice occasionally in the water bath. Stirring was continued for 3 h during which time the suspended solid went into solution. This solution was then treated with an additional 9.5 g of 33 wt % HBr/acetic acid and the resulting solution was stirred overnight at room temperature. Anhydrous sodium acetate (8.0 g) was then added to neutralize the excess HBr. The resulting mixture was dried under vacuo and to the syrup obtained was added CuSO4.5H2O (0.5 g) and zinc (2.0 g) in a solution of water (50 mL) and acetic acid (50 mL). The resultant reaction mixture was stirred vigorously using mechanical stirrer at room temperature for 3 h. The solid was then removed by filtration and washed with ethyl acetate (500 mL) and water (200 mL). The organic layer of the filtrate was washed with saturated aqueous NaHCO3 then with brine and dried (Na2SO4). The solvent was removed under reduced pressure to afford 2,3,4-tri-O-acetyl-α-L-rhamnopyranose (3) (90 % yield) and 2,3,4,6-tetra-O-acetyl-α-D-mannopyranose (6) (87 % yield) as colorless syrups.
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