Allyl bromide → (S)-3-(Allyloxy)-2-((tert-butoxycarbonyl)amino)propanoic acid

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Reaction Steps

A solution of Boc-Ser-OH (1, 2.05 g, 10 mmol) in DMF (30 ml) is added to a stirred suspension of sodium hydride (60 wt % in mineral oil, 880 mg, 22 mmol) in DMF (30 ml) at 0° C. After the evolution of hydrogen gas ceased, allyl bromide (0.95 ml, 11 mmol) is added to the milk-colored solution. The resulting mixture is stirred at room temperature for 5 h to give a clear solution. The solvent is removed in vacuo, water (50 ml) is added, and the aqueous solution is extracted with ether (2×20 ml.) The aqueous solution is then acidified to pH 3.0 with 1.0 N HCl and extracted further with ethyl acetate (5×20 ml.) The combined ethyl acetate extracts are washed with water (20 ml), brine (20 ml), dried over anhydrous magnesium sulfate, and concentrated to give crude Boc-Ser(allyl)-OH (1.96 g) as a light yellow oil. A solution of this oil in ether (30 ml) is treated with dicyclohexylamine (1.594 ml, 8.0 mmol), the solvent removed, and the residue triturated with 1:9 ethyl acetate/hexane to yield 2 (2.26 g) as a colorless solid. An additional amount of 2 (0.58 g) is isolated from the trituration solution also as a colorless solid. (b) Step 2:

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