Boron trifluoride → Dibenzyl 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl phosphate

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Reaction Steps

A solution of 2,3,4-tri-O-benzyl-L-fucopyranose (prepared, for example, according to Wegmann et al., supra.) (0.50 g, 0.86 mmol) in 20 ml of dry dichloromethane and commercially available dibenzyl phosphate which is not further purified (0.24 g, 0.86 mmol) is stirred under a nitrogen atmosphere at room temperature for about 2 h. In the case of very pure dibenzyl phosphate, a catalytic amount of boron trifluoride is added to the mixture. The solution is then concentrated and purified by chromatography (toluene/acetone 9:1). Dibenzyl 2,3,4-tri-O-benzyl-α-L-fucopyranosyl phosphate (4) is obtained in a yield of 90% as a colorless oil (0.54 g). TLC (toluene/acetone 7:1) gives an Rf of 0.60, [α]578 =-68.2 (c=1, chloroform).

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