Hydrogen Bromide → HCID 54446585, compound

Participants

Reaction Steps

A solution of 1,2,3,4-tetra-O-acetyl-6-O-methyl-β-D-mannopyranose (2.8 g) in dry dichloromethane (2 ml) at 0°-5° C. is treated with 30% hydrobromic acid in glacial acetic acid (25 ml) for 2 hours. The reaction mixture is worked-up in the normal manner to give 2,3,4-tri-O-acetyl-6-O-methyl-α-D-mannopyranosyl bromide (2.8 g), which is reacted with thiourea (0.76 g) in dry acetone (5 ml) at reflux temperature for 2 hours. The solution is evaporated in vacuo to a syrup, which is partitioned between ethyl ether (25 ml) and water (25 ml). The aqueous layer is extracted three times with ethyl ether. A solution of cinnamyl bromide (1.44 g) in acetone (30 ml) is added to the aqueous solution containing 2-S-(2,3,4-tri-O-acetyl-6-O-methyl-α-D-mannopyranosyl)-2-thiopseudourea hydrobromide. This is followed by the addition of potassium carbonate (1.26 g) and potassium metabisulfite (1.77 g) and the reaction mixture is stirred vigorously for 2 hours at room temperature. Acetone is evaporated in vacuo and the product is extracted with chloroform and washed twice with water. The solution is dried and evaporated to an oil, which is put on a column of silica gel and eluted with CHCl3 --EtOAc (98:2, v/v). The desired fractions are combined and evaporated in vacuo to give 19 as an oil (1.15 g, 33% overall yield): [α]D27 +147° (C 2.08, chloroform).

Provenance & Evidence