[Acetate] [Cbz] [Troc] [Fmoc] [Phth] [Azide] [Boc]
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Ac - (acetate) amide

Standard Protection Procedure

To a solution of the glycoside in pyridine stirring under an inert atmosphere at 0°, is added acetic anhydride (15 eq).  The solution is allowed to warm to room temperature and stir until complete by TLC (usually 16 h).  The reaction mixture is then concentrated in vacuo and 1:1 water:ethyl acetate is added.  The organic layer is isolated and extracted twice with 1N HCl, three times with saturated aqueous sodium bicarbonate, once with brine, dried with magnesium sulfate, and concentrated in vacuoThe resulting residue is purified by flash chromatography (SiO2) if necessary.
References
    JOC, 1996, 61, 6442-6445.
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Cbz - (benzyloxy) carbamate

Standard Protection Procedure

The amino-glycoside is dissolved in 7-10% aqueous sodium bicarbonate solution and, while stirring at 0°, benzyl chloroformate (1.5 eq) is added drop wise.  The result is stirred at 0° for one hour and allowed to warm to room temperature.  The reaction is stirred until complete by TLC (usually >2 h) and the precipitate (product) was filtered.  The solid was extracted with hot ethyl acetate and the organic solvent was dried (sodium sulfate) and concentrated.  The product can then be purified by crystallization from ethyl acetate.
OR
The amino-glycoside is dissolved in methanol and, while stirring at 0°, N-benzyloxycarbonyloxysuccinimide (1.5 eq) is added.  To the result, triethylamine (1.5 eq) is added drop wise.  The mixture is stirred at 0° for 1 h and allowed to warm to room temperature.  The reaction mixture is stirred until complete by TLC (usually overnight) and concentrated in vacuoThe residue is purified by flash chromatography (SiO2) if necessary.
Removal
The glycoside is dissolved in methanol and 10% Pd-C is added under a hydrogen atmosphere.  To this mixture, catalytic HCl (or acetic acid) is added and allowed to stir at room temperature until complete by TLC (usually greater than 3 hours).  The mixture is then filtered and concentrated in vacuo.  The resulting residue is purified by flash chromatography (SiO2) if necessary.
OR
The glycoside is dissolved in 1:1 methanol:tert-butanol and Pd(OH)2-C is added under a hydrogen atmosphere.  The mixture is  allowed to stir until complete by TLC (usually greater than 3 hours) then filtered and concentrated in vacuo.  The resulting residue is purified by flash chromatography (SiO2) if necessary.
References
    JOC, 1964, 29, 3654-3658.
    JACS, 1982, 104, 4446-4450.
    Tet. Lett., 1976, 5, 379-382.
    Tet. Lett., 1985, 26, 4759-4760.
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Fmoc - (9-fluorenylmethyl) carbamate

Standard Protection Procedure

To a solution of the glycoside in aqueous 9% potassium carbonate, Fmoc-OSu (0.95 eq) is added as a solution in DMF at 0°.  The reaction is allowed to warm to room temperature and stirred until complete by TLC (usually >1 h).  The reaction mixture is then diluted with ethyl acetate and water.  The aqueous layer is extracted three times with ethyl acetate and the combined organic layers are dried (sodium sulfate) and concentrated in vacuoThe product is purified by flash chromatography (SiO2) if necessary.
Removal
The glycoside is dissolved in a 20% solution of piperidine in DMF (or excess DBU in DMF) and stirred under an inert atmosphere at room temperature until complete by TLC (usually <3 h).  The mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary.
References
    Synlett, 2001, 3, 341-344.
    Tet. Lett., 1995, 36, 8645-8648.
    Synlett, 2001, 11, 1693-1698.
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Boc - (tert-butyloxy) carbamate

Standard Protection Procedure

To a solution of the glycoside stirring in dioxane:water 3:1, di-tert-butyl dicarbonate (1 eq) is added and stirred at room temperature overnight (or until complete by TLC).  The mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary.
OR
To a solution of the glycoside stirring in methanol with catalytic NaOMe, di-tert-butyl dicarbonate (1 eq) is added and stirred at room temperature overnight (or until complete by TLC).  The mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary.
Removal
The glycoside is dissolved in DCM:TFA 1:2 and stirred at room temperature under an inert atmosphere until complete by TLC (usually a few minutes).  The solution is then concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary.
References
    Tet. Lett., 1982, 16, 1705-1708.
    JACS, 1995, 117, 11060-11069.
    Tet. Lett., 1990, 31, 1253-1256.
    J. Med. Chem., 1991, 1468-1475.
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Troc - (trichloroethyl) carbamate

Standard Protection Procedure

The amino-glycoside is dissolved in a saturated aqueous sodium bicarbonate solution and, while stirring at 0°, trichloroethyl chloroformate (1.5 eq) is added drop wise.  The mixture is stirred at 0° for one hour and allowed to warm to room temperature.  The mixture is stirred until complete by TLC (usually >2 h) and the precipitate (product) was filtered.  The solid was extracted with hot ethyl acetate and the organic solvent was dried (sodium sulfate) and concentrated in vacuo.  The product can then be purified by crystallization.
Removal
The glycoside is dissolved in glacial acetic acid and zinc dust (excess) is added.  The resulting suspension is stirred at room until complete by TLC (usually <3 h).  The mixture is then filtered, concentrated in vacuo and redissolved in chloroform.  The organic solution is washed once with 5% aqueous sodium bicarbonate, dried (sodium sulfate), and concentrated in vacuo.  The product is purified by flash chromatography (SiO2) if necessary.
References
    Helv. Chim. Acta, 1990, 12, 3366-3372.
    Tet. Lett., 1988, 29, 2227-2230.
    Tet. Lett., 1985, 26, 909-912.
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Azide -

Removal (Reduction)

To a solution of the glycoside in methanol (containing 1 eq of HCl) stirring at room temperature under a hydrogen atmosphere, Pd-C (20mol%) is added and stirred until complete by TLC (usually overnight).  The mixture is then filtered through celite, washing with methanol, and concentrated in vacuo.  The product is purified by flash chromatography (SiO2) if necessary.
Removal (Reduction to Acetamide)
The glycoside is dissolved in THF:AcO2:AcOH 3:2:1 and zinc (excess, activated with 2% aq. copper sulfate) is added.  The mixture is stirred at room temperature under an inert atmosphere until complete by TLC (usually 2 h).  Dry THF is then added and the mixture is filtered through celite and concentrated in vacuo.  The resulting residue is purified by flash chromatography (SiO2) if necessary.
References
    Tet. Lett., 1985, 26, 4759-4760.
    J. Chem. Soc., Perkin Trans. 1, 1996, 985-993.
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Phth - phthalamide

Standard Protection Procedure

To the glycoside (as HCl salt), a sodium methoxide solution (1 eq of Na) is added and stirred for 10 minutes.  The mixture is filtered (to remove NaCl) and the salt is washed several times with methanol.  To the filtrate, phthalic anhydride is added (0.525 eq) and stirred for 10 minutes.  Distilled triethylamine (1 eq) and more phthalic anhydride (0.525 eq) are added and stirred for another 10 minutes.  The resulting mixture was heated to 50° for 20 minutes and then cooled to 0° for 1 h.  The mixture is then filtered (reserving the filtrate) and washed several times with methanol.  This material is air dried overnight to obtain expected product.  The filtrate is concentrated, suspended in ether, and filtered to obtain more of the expected product.  The material can then be further purified by flash chromatography (SiO2) or acetylated using standard procedures.
Removal
The glycoside is dissolved in 6:1 isopropanol:water and sodium borohydride (7.5 eq) is added in two portions over 1 h.  The solution is stirred at room temperature for approx. 8 hours (cloudy white precipitate should form) at which time the reaction is acidified to a pH of 4 with glacial AcOH and then heated to 80° for 8 hours.  The solution is then concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary.
References
    JOC, 1996, 61, 6442-6445.
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