醚氨基及氨基酸的各种保护基及去保护方法大全

醚、氨基及氨基酸的各种保护基及去保护方法大全

（整理有详细操作）

[Acetate] [Benzoatel] [Pivaloate] [Levulinate] [Back to Carb.

Synthesis]

Ac - (acetate) ester

Standard Protection Procedure

To a solution of the glycoside in dry pyridine (25 eq) under an inert atmosphere at room temperature, acetic anhydride (10 eq) is added and stirred until complete by TLC (usually 16 h). The reaction mixture is then poured into ice/water and extracted three times with chloroform. The combined organic layers are extracted with 3% HCl, saturated aqueous sodium bicarbonate, and water. The organic layer is then dried and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.

Removal

The glycoside is dissolved in methanol and a solution of sodium methoxide in methanol (0.1 eq per -OAc) is added drop wise at 0°. The solution is warmed to room temperature and stirred under an inert atmosphere until complete by TLC (usually within a few hours). Amberlite cationic exchange resin is then added with vigorous stirring until the pH of the mixture is neutral. The mixture is then filtered and concentrated. The resulting residue is purified by flash chromatography (SiO2) if necessary.

OR

The Glycoside is dissolved in methanol and hydrazine hydrate (15 eq per -OAc) is added in two portions over 1.5 hours. The solution is stirred at room temperature under an inert atmosphere until complete by TLC (usually 6 hours). The solution is then neutralized with glacial acetic acid. The mixture is filtered through celite and concentrated. The resulting residue is purified by flash chromatography (SiO2) if necessary. References

J. Org. Chem., 1996, 61, 6442-6445.

"Synthetic Methods for Carbohydrates" Lemieux, Ch 6, pg. 90-115.

J. Chem. Soc., Perkin Trans. 1, 1996, 985-993.

Bz - (benzoate) ester

Standard Protection Procedure

To a solution of the glycoside dissolved in dry pyridine (0.3M), benzoyl chloride (4 eq per -OH) is added at room temperature under an inert atmosphere and stirred until complete by TLC (usually 16 h). Methanol is added and the solution was concentrated in vacuo. The residue was dissolved in DCM and washed with water, saturated copper sulfate, and brine. The organic layer is dried and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary. Removal

The glycoside is dissolved in MeOH and a solution of NaOH (2.5 eq per -OH) in MeOH is added slowly. The mixture is stirred at room temperature under an inert atmosphere till complete by TLC (usually 1 h) and then concentrated in vacuo. The residue is dissolved in ethyl acetate and the organic solution is washed twice with water, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.

References