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) esterStandard Protection ProcedureTo 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.RemovalThe 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.ORThe 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. ReferencesJ. 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) esterStandard Protection ProcedureTo 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. RemovalThe 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.ReferencesTetrahedron, 1970, 26, 803-812.Carb. Res., 1993, 244, 237-246.Piv - (pivaloate) esterStandard ProcedureThe glycoside is dissolved in pyridine:DCM 2:1 and cooled to -20°. PivCl (1.2 eq per -OH) is then added drop wise under an inert atmosphere and the result is stirred at 0° until complete by TLC (usually 8 h). The mixture is then diluted with DCM and extracted with 5% HCl twice and once with water. The organic layer is then dried (sodium sulfate) and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in MeOH, and a solution of sodium methoxide in methanol (10 eq per -OH) is added drop wise at room temperature under an inert atmosphere and stirred until the reaction is complete by TLC (usually 24 h). Aqueous HCl (10%) is added to the solution until neutral and theresulting mixture is concentrated in vacuo. The residue is purified by flash chromatography (SiO2) if necessary.ReferencesTet. Asym. 2000, 295-303.J. Am. Chem. Soc. 1990, 112, 3693-3695.Lev - (levulinate) esterStandard Protection ProcedureTo a solution of the glycoside in dry pyridine at room temperature under an inert atmosphere, levulinic anhydride (2 eq) is added drop wise. The reaction was stirred until complete by TLC (usually 24 h) and ice water is added. The mixture is extracted with chloroform and then the organic layer is back extracted with brine, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in pyridine and hydrazine hydrate (1M in pyridine:acetic acid 3:2) is added at room temperature under an inert atmosphere. After addition of hydrazine is sufficient to consume starting material completely by TLC (usually a few minutes),pentane-2,4-dione is added with cooling to quench the reaction. The mixture is diluted with chloroform and extracted once with water and once with brine. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The residue is purified by flash chromatography (SiO2) if necessary.ReferencesJACS, 1975, 97, 1614-1615.Tet. Lett., 1976, 52, 4875-4878.[Benzyl] [Trityl] [PMP] [Allyl] [pMB] [Back to Carb. Synthesis] Bn - (benzyl) etherStandard Protection ProcedureTo a solution of sodium hydride (1.3 eq per -OH) in DMF, the glycoside (dissolved in DMF) is added drop wise at 0° under an inert atmosphere. The mixture is stirred for 30 minutes at 0° and benzyl bromide (1.3 eq per -OH) is added drop wise. *Note - a catalytic amount of TBAI or crown ether can be added. The reaction is stirred at room temperature until complete by TLC (usually 16 h) and methanol is added slowly to quench the reaction. The solution is then diluted with chloroform and water, extracted 3 times with water and once with brine. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.ORTo a solution of the glycoside in DCM, benzyl trichloroacetimidate (2 eq per -OH) is added drop wise (as a solution in cyclohexane - see third reference) with TfOH (catalytic - >1mol%). The result is stirred at room temperature under inert atmosphere until complete by TLC (usually overnight). Saturated aqueous sodium bicarbonate is added and the mixture is diluted with DCM. The organic layer is extracted once with water, once with brine, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in 1:1 MeOH:tBuOH and palladium hydroxide (0.1 eq) is added at room temperature. A hydrogen atmosphere is added (balloon pressure) and the reaction is stirred until complete by TLC (usually 16 h). The mixture is then filtered and concentrated. *Note - catalytic glacial acidic acid may be added if the reaction isn't complete. The resulting residue is purified by flash chromatography (SiO2) if necessary.ReferencesJ. Org. Chem., 1979, 44, 3442.J. Am. Chem. Soc., 1971, 93, 1746.Tr - (triphenyl methyl) or trityl etherStandard Protection ProcedureTo a solution of the glycoside, trityl chloride (1.1 eq for primary over secondary, 1.5 eq for each -OH otherwise), and triethylamine (1.5 eq for primary over secondary, 2 eq for each -OH otherwise) stirring in DMF under an inert atmosphere at room temperature, DMAP (0.05 eq) is added. The reaction is stirred until complete by TLC (usually overnight)and then poured into ice-water. The mixture is extracted with chloroform and the organic layer is washed with saturated aqueous ammonium chloride and water, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in ethanol and 5% palladium on charcoal is added under a hydrogen atmosphere. The reaction is stirred until complete by TLC (usually overnight) and filtered. The solution is concentrated and the residue is purified by flash chromatography (SiO2) if necessary. ReferencesTet. Lett., 1979, 2, 95-98.JOC, 1978, 18, 2877-2881.pMB - (para-methoxy benzyl) etherStandard Protection ProcedureTo a solution of sodium hydride (1.3 eq per -OH) in DMF, the glycoside (dissolved in DMF) is added drop wise at 0° under an inertatmosphere. The mixture is stirred for 30 minutes at 0° andpara-methoxybenzyl bromide (1.3 eq per -OH) is added drop wise. *Note - a catalytic amount of TBAI or crown ether can be added. The reaction is stirred at room temperature until complete by TLC (usually 16 h) and methanol is added slowly to quench the reaction. The solution is then diluted with chloroform and water, extracted 3 times with water and once with brine. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in DCM/H2O 20:1 and DDQ (up to 10 eq) is added at room temperature under an inert atmosphere. The reaction is stirred until complete by TLC (usually 24 h, may require heat) and diluted with DCM. The solution is extracted with saturated aqueous sodium bicarbonate, dried (sodium sulfate), and concentrated in vacuo. Product can then be purified by column chromatography if necessary. The resulting residue is purified by flash chromatography (SiO2) if necessary. ReferencesJACS, 1992, 114, 2524-2536.JACS, 1996, 118, 9265-9270.Allyl - (allyl) etherStandard Protection ProcedureTo a solution of sodium hydride (1.3 eq per -OH) in DMF, the glycoside (dissolved in DMF) is added drop wise at 0° under an inert atmosphere. The mixture is stirred for 30 minutes at 0° and ally bromide (1.3 eq per -OH) is added drop wise. *Note - a catalytic amount of TBAI or crown ether can be added. The reaction is stirred at room temperature until complete by TLC (usually 16 h) and methanol is added slowly to quench the reaction. The solution is then diluted with chloroform and water, extracted 3 times with water and once with brine. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.ORTo a solution of the glycoside in DCM, benzyl trichloroacetimidate (2 eq per -OH) is added drop wise (as a solution in cyclohexane - see third reference) with TfOH (catalytic - >1mol%). The result is stirred at room temperature under inert atmosphere until complete by TLC (usually overnight). Saturated aqueous sodium bicarbonate is added and the mixture is diluted with DCM. The organic layer is extracted once withwater, once with brine, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in AcOH:water 20:1 and Palladium chloride (1.5 eq) followed by sodium acetate (5 eq) is added. The mixture is stirred under an inert atmosphere at room temperature until complete by TLC (usually overnight). Ethyl acetate is added and the mixture is extracted 2 times with saturated aqueous sodium bicarbonate. The organic layer is then extracted once with brine, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.ReferencesTet. Lett., 1997, 40, 13,509-13,556.JOC, 1973, 18, 3224.J. Chem. Soc. Perkin Trans. I, 1985, 2247-2250.JACS, 1991, 113, 2092-2112.PMP - (p-methoxyphenyl) etherStandard Protection ProcedureTo a solution of the glycoside in THF under an inert atmosphere is added triphenylphosphine (1.3 eq), diethylazocarboxylate (1.3 eq), andp-methoxyphenol (3 eq). The resulting solution is heated to 80° and stirred until complete by TLC (usually 2 h). The mixture is concentrated in vacuo and purified by flash chromatography (SiO2).RemovalThe glycoside is dissolved in acetonitrile:water 4:1 at room temperature under an inert atmosphere and CAN (5 eq) is added. The mixture is stirred until complete by TLC (usually less than 1 h) and diluted with chloroform. The resulting solution is washed with water and saturated sodium chloride solution. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The residue can then be purified by flash chromatography (SiO2) if necessary.ReferencesTet. Lett., 1988, 29, 1389-1390.Heterocycles, 1990, 31, 1555-1563.[TMS] [TES] [TIPS] [TBS] [TBDPS] [Back to Carb. Synthesis] TMS - (trimethyl silyl) etherStandard Protection ProcedureTo a solution of the glycoside and triethylamine (2 eq) stirring in THF at 0° under an inert atmosphere, is added drop wise TMS-Cl (1.5 eq). The result was allowed to warm to room temperature and stirred until complete by TLC (usually 6 h). The solution is then concentrated in vacuo and the residue taken on directly to next step.RemovalThe glycoside is dissolved in THF (~2M) and TBAF (1M solution in THF) is added drop wise at 0° under inert atmosphere. The reaction is allowed to warm to room temperature and stirred until complete by TLC (usually a few hours - if not complete in this time more TBAF solution may be added). *Note - equal volumes of glacial acetic acid (compared to TBAF solution.) may be added to prevent removal of acetates or other sensitive protecting groups. The reaction mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary.ReferencesJACS, 1972, 94, 2549-2550.TES - (triethyl silyl) etherStandard Protection ProcedureTo a solution of the glycoside and imidazole (2 eq) stirring in DMF at 0° under an inert atmosphere, is added drop wise TES-Cl (2 eq). The result is allowed to warm to room temperature and stirred until complete by TLC (usually overnight). An equal volume of ether is added and the reaction mixture is extracted three times with water and once with brine. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The product can then be purified by flash chromatography (SiO2) if necessary. RemovalThe glycoside is dissolved in THF (~2M) and TBAF (1M solution in THF) was added drop wise at 0° under an inert atmosphere. The result is allowed to warm to room temperature and stirred until complete by TLC (usually a few hours - if not complete in this time more TBAF solution may be added). *Note - equal volume of glacial acetic acid (compared to TBAFsolution.) may be added to prevent removal of acetates or other sensitive protecting groups. The reaction mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary. ReferencesHelv. Chim. Acta, 1981, 64, 2002-2021.TIPS - (triisopropyl silyl) etherStandard Protection ProcedureTo a solution of the glycoside stirring in DMF at 0° under an inert atmosphere, TIPS-Cl (1.3 eq) and imidazole (1.5 eq) were added succinctly. The result was allowed to warm to room temperature and stirred until complete by TLC (usually overnight). The mixture is diluted with equal volume of chloroform and extracted three times with water and once with brine. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in THF (~2M) and TBAF (1M solution in THF) was added drop wise at 0° under an inert atmosphere. The result is allowed to warm to room temperature and stirred until complete by TLC (usually a few hours - if not complete in this time more TBAF solution may be added). *Note - equal volume of glacial acetic acid (compared to TBAF solution.) may be added to prevent removal of acetates or other sensitive protecting groups. The reaction mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary. ReferencesJOC, 1980, 45, 4797-4798.TBS - (tert-butyl dimethyl silyl) etherStandard ProcedureTo a solution of the glycoside in DMF at 0° under an inert atmosphere, TBS-Cl (1.1 eq for selective primary -OH protection, 1.3 eq otherwise) and imidazole (1.3 to 1.5 eq) were added succinctly. The result was allowed to warm to room temperature and stirred until complete by TLC (usually overnight). The mixture is diluted with equal volume of chloroform andextracted three times with water and once with brine. The organic layer is dried (sodium sulfate) and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.ORTo a solution of the glycoside and distilled 2,6-lutidine (2.1 eq) in dry DCM under an inert atmosphere at -78°, TBS-OTf is added drop wise over 30 minutes. The result is stirred until complete by TLC (usually 30 minutes - if not complete more TBS-OTf may be added) and methanol is added. The mixture is diluted with chloroform, washed with water and brine, dried over magnesium sulfate and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in THF (~2M) and TBAF (1M solution in THF) was added drop wise at 0° under an inert atmosphere. The result is allowed to warm to room temperature and stirred until complete by TLC (usually a few hours - if not complete in this time more TBAF solution may be added). *Note - equal volume of glacial acetic acid (compared to TBAF solution.) may be added to prevent removal of acetates or other sensitive protecting groups. The reaction mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary. ReferencesJACS, 1997, 119, 449-450.JACS, 1972, 94, 6190-6191.JOC, 1987, 52, 622-635.TBDPS - (tert-butyl diphenyl silyl) etherStandard ProcedureThe glycoside is dissolved in DMF at room temperature under an inert atmosphere and treated with imidazole (2 eq per -OH) followed by TBDPS-Cl (1.5 eq per -OH). The reaction mixture is stirred until complete by TLC (usually overnight), diluted with ether and washed with 1M HCl followed by brine. The organic layer is dried (magnesium sulfate) and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalTo a solution of the glycoside in THF at room temperature in a Nalgene container, commercially available 30% HF in pyridine is added drop wise under an inert atmosphere. The result is stirred until complete by TLC (usually 16 h) and diluted with slow addition of saturated sodium bicarbonate. Chloroform is added and the mixture is extractedsuccessively with water, saturated copper sulfate, and brine. The organic layer is then dried (sodium sulfate) and concentrated. The resulting residue is purified by flash chromatography (SiO2) if necessary. ReferencesJACS, 1997, 119, 449-450.Alcohol protection - [MOM] [MEM] [BOM] [SEM]Diol protection - [Acetonide] [Benzylidene][p-Methoxybenzylidene] [DTBS(OR)2] MOM - (methoxy methyl) etherStandard Protection ProcedureTo a solution of the glycoside in DCM (approx. 0.1M) and Hunig's base (N,N-diisopropylethyl amine, 2.0 eq) at 0°, MOM-Cl (1.5 eq) is added under an inert atmosphere. The reaction is warmed to room temperature and stirred until complete by TLC (usually >8 h). Ether is added and the mixture is washed 3 times with water and once with brine. The organic layer is dried (magnesium sulfate), filtered and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in 1:1 THF:6N HCl and heated to 55° with stirring until the reaction is complete by TLC (usually 8 h). Saturated sodium chloride solution is then added and the reaction mixture isextracted three times with ether. The combined organic layers are dried (sodium sulfate), filtered and concentrated in vacuo. The residue is purified by flash chromatography (SiO2) if necessary.ReferencesJACS, 1977, 99, 1275-1276.JOC, 1975, 40, 2025-2029.MEM - (methoxy ethoxy methyl) etherStandard Protection ProcedureTo a solution of the glycoside and MEM-Cl (1.5 eq) in dry DCM, diisopropylethylamine (1.5 eq) is added and stirred at room temperature under an inert atmosphere until complete by TLC (usually 5 h). The reaction is diluted with DCM and extracted twice with water, once with brine, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.ORTo a mixture of NaH (1.2 eq) stirring in THF at 0°, the glycoside is added drop wise (as solution in THF). After stirring for 30 minutes, MEM-Cl (1.5 eq) is added drop wise and reaction is allowed to warm to roomtemperature. The mixture is stirred until complete by TLC (usually overnight) and diluted with DCM. The mixture is then extracted twice with water, once with brine, dried (sodium sulfate), and concentrated in vacuo. The product is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in DCM and magnesium bromide etherate (excess) is added at room temperature under an inert atmosphere. The reaction is stirred until complete by TLC (usually >24 h), at which time water is added and stirred for 30 additional minutes. Aqueous HCl (1N) is added drop wise until the pH is 1-2 and the solution is clear. The resulting solution is extracted three times with ethyl acetate, dried (magnesium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.ReferencesTet. Lett., 1976, 11, 809-812.JOC, 1994, 59, 2314-2323.J. Chem. Soc. Perkin Trans. I, 1985, 2247-2250.BOM - (benzyloxy methyl) etherStandard Protection ProcedureTo a solution of the glycoside in DCM (approx. 0.1M) and Hunig's base (N,N-diisopropylethyl amine, 2.0 eq) at 0°, BOM-Cl (1.2 eq) is added under an inert atmosphere. The reaction is warmed to room temperature and stirred until complete by TLC (usually >24 h). Ether is then added and the mixture is washed 3 times with water and once with brine. The organic layer is dried (magnesium sulfate), filtered and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in EtOAc:Hex (1:2) and catalytic Pd(OH)2 is added (10mol%) under a hydrogen atmosphere. The reaction is stirred at room temperature until complete by TLC (usually a few hours). The mixture is then filtered and concentrated in vacuo. The residue is purified by flash chromatography (SiO2) if necessary.ReferencesJACS, 1975, 97, 6260.JACS, 1994, 116, 4674-4688.Tetrahedron, 1987, 43, 4395-4406.SEM - (trimethylsilyl) ethoxymethyl etherStandard ProcedureTo a solution of the glycoside under inert atmosphere at room temperature in DCM or THF (~2M), diisopropylethylamine (4 eq for each -OH) is added followed by the addition of SEM-Cl (3 eq for each -OH). The reaction is stirred until complete by TLC, at which time saturated ammonium chloride is added. The mixture is extracted with two portions of DCM and the combined organic layers are extracted twice with saturated bicarbonate and once with brine. The solution is then dried (magnesium sulfate), filtered, and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in a 0.5M solution of sulfuric acid in 2:1 MeOH:THF at 0° under inert atmosphere. The reaction is stirred untilcomplete by TLC (usually <3 h) and saturated sodium bicarbonate solution is added slowly. The mixture is then diluted with ethyl acetate and separated. The aqueous layer is back extracted twice with ethyl acetate and the combined organic layers are extracted with saturated sodium bicarbonate and brine. The organic solution is then dried (magnesium sulfate), filtered, and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.ReferencesTet. Lett, 1993, 12, 1991-1994Tet. Lett, 1980, 21, 3343-3346Acetonide - (isopropylidene) ketalStandard Protection ProcedureTo a solution of the glycoside stirring in DMF, p-toluenesulfonic acid (10mol%) and 2,2-dimethoxypropane are added. The result is stirred at room temperature under inert atmosphere until complete by TLC (usually >6 h). The reaction is neutralized with 5% aqueous sodium bicarbonate and concentrated in vacuo. The material is dissolved in ethylacetate, washed with water, saturated sodium chloride, dried (sodium sulfate), and concentrated in vacuo. The product is then purified by flash chromatography (SiO2) if necessary.RemovalThe glycoside is dissolved in 80-90% AcOH in water and stirred at 60-90° until complete by TLC (usually <3 h). The solution is then concentrated in vacuo and purified by flash chromatography (SiO2) if necessary. ReferencesChem. Pharm. Bull., 1990, 38, 3366-3372. Benzylidene AcetalStandard Protection ProcedureThe glycoside is dissolved in DMF and benzyaldehyde dimethyl acetal (5 eq) is added. To this solution stirring at room temperature under an inert atmosphere, toluene-p-sulfonic acid (0.3 eq) is added. After the reaction is complete by TLC (usually overnight), the mixture is neutralized with triethylamine. The solution is then concentrated in vacuo and purified by flash chromatography (SiO2) if necessary.ORThe glycoside is dissolved in acetonitrile and benzyaldehyde dimethyl acetal (5 eq) is added. To this solution stirring at room temperature under inert atmosphere, toluene-p-sulfonic acid (0.3 eq) is added. After the reaction is complete by TLC (usually overnight), the mixture is diluted with chloroform and extracted twice with water. The aqueous layer is then back extracted with chloroform. The combined organic layers are dried and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.Complete RemovalThe glycoside is dissolved in 50-80% AcOH in water and heated to 60-70° with stirring until complete by TLC (usually >4 h). The solution is then concentrated and coevaporated with toluene 3 times. The residue is purified by flash chromatography (SiO2) if necessary.ORTo a solution of the glycoside in methanol at room temperature under an inert atmosphere, toluene-p-sulfonic acid (0.3 eq) is added. The reaction is stirred until complete by TLC (usually overnight) and triethylamine is added to neutralize. The mixture is concentrated in vacuo and the residue is purified by flash chromatography (SiO2) if necessary.ORTo a solution of the glycoside in methanol:t-butanol 1:1 at roomtemperature under a hydrogen atmosphere, Pd(OH)2-C (20mol%) is added. The reaction is stirred until complete by TLC (usually overnight, if not complete up to one eq of HCl may be added) and filtered washing with methanol. The solution is concentrated in vacuo and the resulting residue is purified by flash chromatography (SiO2) if necessary.Partial RemovalFor primary benzyl and secondary -OH - To a solution of the glycoside in DCM under inert atmosphere at 0°, triethylsilane (5 eq) isadded. Trifluoroacetic acid (5 eq) is then added drop wise and the reaction mixture is allowed to warm to room temperature. The reaction is stirred until complete by TLC (usually <3 h) and diluted with DCM. The organic solution is then extracted twice with saturated aqueous sodium bicarbonate solution, dried (sodium sulfate), and concentrated in vacuo. The resulting residue is purified by flash chromatography (SiO2) if necessary.For secondary benzyl and primary -OH - To a solution of the glycoside dissolved in DCM under an inert atmosphere at room temperature, 4A molecular sieves are added and stirred for one hour. The mixture is then cooled to -78° and triethylsilane (3 eq) is added followed by PhBCl2 (3.4 eq). After stirring for one hour, triethylamine and methanol are added and the mixture is diluted with chloroform. The organic solution is washed with saturated aqueous sodium bicarbonate solution, dried (sodium。