Fucopyranosyl bromide

Other syrupy, benzylated bromides bearing O-acetyl or O-p-nitro-benzoyl groups were also prepared and characterized,86-84 as well as a partially benzylated chloride.85 Acid hydrolysis of 22 gave crystalline 2-O-benzyl-a-L-fucose, which was acylated with p-nitrobenzoyl chloride-pyridine. Treatment84 of the resulting tris(p-nitrobenzoate) with hydrogen bromide-dichloromethane led to precipitation of p-nitrobenzoic acid and formation of syrupy 2-0-benzyl-3,4-di-0-(p-nitro-benzoyl)-a-L-fucopyranosyl bromide (33). 

M. Dejter-Juszinsky and H. M. Flowers, Koenigs-Knorr reaction. 11—synthesis of an oi-L-linked disaccharide from tri-O-benzyl-L-fucopyranosyl bromide, Carbohydr. Res. 18 219 (1971). 

A mixture of 2,3,4-tri-0-acetyl-a-L-fucopyranosyl bromide (1.4 g, 3.91 mmol), and silver 3-methoxy-2-pyridoxide in 75 mL (1.45 g, 6.25 mmol) of toluene was refluxed for 40 min. The mixture was cooled to room temperature, filtered over Celite, and washed with dichloromethane. The residue was washed with dichloromethane, the filtrate was evaporated and the product was purified by flash chromatography on silica gel (EtOAc-hexane, 2 3). First eluted was 3-methoxy-2-pyridyl 2,3,4-tri-O-acetyl-a-L-fucopyranoside (0.15 g, 10%), followed by 3-methoxy-2-pyridyl 2,3,4-tri-0-acetyl-0-L-fncopyranoside (1.02 g, 65%). 

Ceramides prepared in this way have been used for the partial synthesis of the a-L-fucopyranosyl ceramide (84) (a compound previously isolated from metastatic human carcinoma). Condensation [88] of 2,3,4-tri-Obenzyl-a-L-fucopyranosyl bromide (80) with an unprotected ceramide in the presence of tetraethylammonium bromide in di-chloromethane and subsequent chromatographic purification gave (81) which on catalytic hydrogenation gave the saturated fucosyl ceramide (84). The dichloroacetamido derivative (82) was prepared similarly and converted into the free sphingosine derivative (83) by the action of barium hydroxide. 

Khorlin and co-workers [194, 195] prepared the blood-group A (type 1) tetrasaccharide (267) from the chloroacetate (272). This was condensed with 2-O-benzyl-3,4-di-O-p-nitrobenzoyl-a-L-fucopyranosyl bromide to give the 2-O-a-L-fucosyl derivative and after removal of the chloroacetyl group with thiourea the product was... 

Tri-O-benzyl-a-L-fucopyranosyl bromide dissolved in methylene chloride containing tetraethylammonium bromide, stirred 0.5 hr. in the dark under dry Ng in the presence of molecular sieve 4 a soln. of benzyl 2-acetamido-3,6-di-0-benzyl-2-deoxy-a-D-glucopyranoside and diisopropylethylamine in anhydrous di-methylformamide added, and stirred 12 hrs. benzyl 2-acetamido-3,6-di-0-benzyl-2-deoxy-4-0-(2,3,4-tri-0-benzyl-a-L-fucopyranosyl)-a-D-glucopyranoside. Y 82%. Limitation s. J.-C. Jacquinet and P. Sinay, Carboh. Res. 42, 251 (1975). 

A free radical method which gives 2-deoxy-equatorially substituted products proceeds via 2,6-anhydroaldonic acid derivatives (Scheme 17). Trapping of the C-1 radical derived from tri-O-acetyl-a-L-fucopyranosyl bromide with acrylonitrile led to compound (137) which has been used to prepare an affinity adsorbent for porcine liver a-L-fucosidase. ... 

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