常见的羟基的保护与脱保护方法

目 录

1. 简介…………………………………………………………2 2. 硅醚……………………………………………………………2

2. 1 三甲基硅醚 (T M S -O R ) …………………………………………3 2. 2 叔丁基二甲基硅醚 (T B D M S -O R ) ………………………………4 2. 3叔丁基二苯基硅醚(T B D P S -O R ) ………………………………4

3. 苄醚…………………………………………………………6 4. 取代苄醚……………………………………………7 5. 取代甲基醚……………………………………………8 6. 四氢吡喃醚……………………………………………………………9 7. 烯丙基醚…………………………………………………………10

1. 前言

羟基广泛存在于许多在生理上和合成上有意义的化合物中，如核苷，碳水化合物、甾族化合物、大环内酯类化合物、聚醚、某些氨基酸的侧链。。另外，羟基也是有机合成中一个很重要的官能基，其可转变为卤素、氨基、羰基、酸基等多种官能团。在化合物的氧化、酰基化、用卤代磷或卤化氢的卤化、脱水的反应或许多官能团的转化过程中，我们常常需要将羟基保护起来。 在含有多官能团复杂分子的合成中，如何选择性保护羟基和脱保护往往是许多新化合物开发时的关键所在，如紫杉醇的全合成。羟基保护主要将其转变为相应的醚或酯，以醚更为常见。一般用于羟基保护醚主要有硅醚、甲基醚、烯丙基醚、苄基醚、烷氧甲基醚、烷巯基甲基醚、三甲基硅乙基甲基醚等等。羟基的酯保护一般用的不多，但在糖及核糖化学中较为多见。

2. 羟基硅醚保护及脱除

硅醚是最常见的保护羟基的方法之一。随着硅原子上的取代基的不同，保护和去保护的反应活性均有较大的变化。当分子中有多官能团时，空间效应及电子效应是影响反应的主要因素。在进行选择性去保护反应时，硅原子周围的空间效应，以及被保护分子的结构环境均需考虑。例如，一般情况下，在TBDMS 基团存在时，断裂DEIPS( 二乙基异丙基硅基) 基团是较容易的，但实际得出的一些结果是相反的。在这些例子中，分子结构中空间阻碍是产生相反选择性的原因。电子效应的不同也会影响反应的选择性。对于两种空间结构相似的醇来说，电子云密度不同造成酸催化去保护速率不同，因此可以选择性去保护。这一点对酚基和烷基硅醚特别有效：烷基硅醚在酸中容易去保护，而酚基醚在碱性条件下更容易去保护。降低硅的碱性还可以用于改变Lewis 酸催化反应的结果，并且有助于选择性去保护。在硅原子上引入吸电子取代基可以提高碱性条下水解反应的灵敏性，而对酸的敏感性降低。对大多数醚来说，在酸中的稳定性为TMS (1)

任何羟基硅醚的都可以通过四烷基氟化胺如TBAF 脱除，其主要硅原子对氟原子的亲和性远远大于硅-氧之间的亲和性。在用TBAF 裂解硅醚后，分解产生的四丁铵离子有时通过柱层析或HPLC 很难除干净，而季铵盐的质谱丰度(Bu4N +: 242) 又特别的强有

时会干扰质谱，因此这时需要使用四甲基氟化铵或四乙基氟化铵来脱除。

使用硅醚保护的另一个好处是可以在分子中游离伯胺或仲胺基的存在下，对羟基进行保护，其主要由于硅-氮键的结合远比硅-氧键来的弱，硅原子优先与羟基上的氧原子结合，这正是与其他保护基不同之处。顺便提一句，一般而言，决大部分的硅-氮键的结合是不稳定的，其很容易被水解掉。

2.1 三甲基硅醚的保护 (TMS-OR)

许多硅基化试剂均可用于在各种醇中引入三甲基硅基。一般来说，空间位阻较小的醇最容易硅基化，但同时在酸或碱中也非常不稳定易水解, 三甲基硅基化广泛用于多官能团化合物，生成的衍生物具有较高的挥发度而利于其相色谱和质谱分析。 2.1.1 三甲基硅醚羟基保护示例 (J. Org.Chem. 1996, 61, 2065)

TMSO

1

Me 2

HO

Compound 1 (3.00g, 4.286mmol) was dissolved in dry DMF (17 mL). To this solution at 0o C was added imidazole (874.3 mg, 12.86mmol), followed by TMSCl (1.63 mL, 12.86 mmol). After stirring at 0o C for 1.5 h, the reaction mixture was diluted with EtOAc (300 mL) and washed with water (3 20 mL) and then brine (30 mL). The organic layer was dried and concentrated in vacuo. The resulting material was then dissolved in dry DMF (20 mL) and treated at 0o C with imidazole (816 mg, 12.00 mmol), followed by chlorodimethylsilane (1.135g, 12.00mmol). The reaction mixture was stirred for 1h at 0o C and then diluted with EtOAc (200mL). The organic layer was washed with water and brine. Upon silica gel chromatography (10% ethyl acetate in hexane), 3.197 g (90%) of the desired product 2 was obtained.

Cleavage (J. Org.Chem. 1996, 61, 2065)

Hydrolysis was carried out under aprotic condition-anhydrous tetrabutylammonium fluoride in THF solution.

2.2 t-Butyldimethylsilyl ether (TBDMS-OR)

在化学合成中，采用硅基化进行羟基保护生成叔丁基甲基硅基醚是应用较多的方法之一。一般来说，在分子中羟基位阻不大时主要通过TBSCl 对羟基进行保护。 但当羟基位阻较大时则采用较强的硅醚化试剂TBSOTf 来实现。生成的叔丁基二甲基醚在多种有机反应中是相当稳定的，在一定条件下去保护时一般不会影响其他官能团。它在碱性水解时的稳定性约为三甲基硅醚的104倍。它对碱稳定。相对来说对酸敏感些。TBS 醚的生成和断裂的难易取决于空间因素，因此常常用于对多官能团，位阻不同的分子进行选择性保护。在伯、仲醇中，TBS 基相对来说较易于与伯醇反应。TBS 醚的断裂除了常用的四烷基氟化胺外，许多情况下也可用酸来断。当分子内没有对强酸敏感的官能基存在时，可用 HCl-MeOH, HCl-Dioxane 体系去除TBS ，若有对强酸敏感的官能基存在时，则可选用AcOH-THF 体系去除。

2.2.1 通过TBSCl 进行羟基的叔丁基二甲基硅醚保护示例 (J. Am. Chem. Soc. 1972, 94, 6190)

O

O

O

1

2OBn

2

2OBn

The hydroxyl lactone 1, upon treatment with TBDMSCl (1.2 equiv) and imidazole (2.5 equiv.) in DMF (2 mL/g of 1) at 35o C for 10 h, produced the silyl ether-lactone 2 in 96% yield.

2.2.2 通过TBSOTf 进行羟基的叔丁基二甲基硅醚保护示例(J.Org.Chem. 1987, 52, 622)

3

1

32

To an ice-cold solution of 4.8 g of pyridine (2.0 equiv) and 4.20 g of 1 in 30 mL of dry acetonitrile was added slowly 9.6 g of tert-butyldimethylsilyl triflate (36.2 mmol, 1.2 equiv). The reaction mixture was stirred for 5 h at room temperature and then poured into 200 mL of saturated sodium bicarbonate solution at 0o C. The solution was extracted thoroughly with hexane, and the organic extracts were dried over anhydrous potassium carbonate and filtered. Removal of the solvent under reduced pressure followed by distillation of the residue gave

6.29 g (82% yield).

2.2.3 通过TBAF 脱TBDPS 示例 (Can. J. Chem. 1975, 53, 2975)

Ph Ph

1

+-C C C 6H 5

HO

2

C C C 6H 5

To a solution of THP ether 1 (1.7 g, 3.3 mmol) in THF (10 mL) was added a 1 M solution of tetrabutylammonium fluoride in THF (5 mL, 5 mmol) at 22-24o C. The solution was stirred for 2 h and diluted with 100 mL (1:1) of Et2O/EtOAc solution. The organic layer was separated and washed with H 2O (3 ⨯ 100 mL). The water extract was washed with 2:1 Et 2O/EtOAc solution (2 ⨯ 50 mL), and the organic

layers were combined and dried over MgSO 4. The solvent was evaporated in vacuo, and the residue was chromatographed over silica gel using (5:1) hexanes/ethyl acetate solution to give 2 (0.75 g, 82%).

2.2.4 通过AcOH-THF 脱TBS

示例(Tetrahedron Lett. 1988, 29, 6331)

1

AcOh/H2O/THF

2

Selective removal of one of the TBDMS groups of 1 was accomplished by treatment with acetic acid-water-THF (13:7:3) (30°C, 15h) to give the monohydroxy compound 2 in 79% yield.

2.3 t-Butyldiphenylsilyl ether (TBDPS-OR)

在酸性水解条件下TBDPS 保护基比TBDMS 更加稳定（约100倍），而TBDPS 保护基对碱的稳定性比TBDMS 要差。 另外，由于该保护基的分子量较大，容易使底物固化而易于分离。 TBDPS 保护基对许多与TBDMS 保护基不相容的试剂显出比TBDMS 基团更好的稳定性。TBDMS 基团在酸性条件下不易迁移。TBDPS 醚对K 2CO 3 /CH3OH ，对9M 氨水、60℃、2h ；对MeONa （cat. ）/CH3OH 、25℃、24h 均稳定。该醚对80%乙酸稳定，后者可用于脱除醚中TBDMS ，三苯甲基，四氢吡喃保护基也对HBr /AcOH，12℃，2min ；对25%~75%甲酸，25℃，2h~6h；以及50%三氟乙酸，25℃，15min

稳定。

2.3.1 通过TBDPSCl 进行羟基的叔丁基二甲基硅醚保护示例(J.Org. Chem , 1992, 57, 1722)

HO

1

i-Pr NEt/t-BDPSiCl/CHCl t-BDPSiO

2

OH

To a solution of 1,4-butanediol (5 g, 55 mmol) in CH2Cl 2 (10 mL) containing i-Pr2NEt (10 mL) was added t-BDPSiCl (5 mL, 18 mmol) dropwise under N2 at 22-24o C. The solution was stirred at 22-24o C for 2 h, concentrated in vacuo and chromatographed, eluting with hexanes/ethyl acetate (10:1) to 2 (clear oil, 5.6 g, 95%).

2.4 三异丙基硅醚保护 (TIPS-OR)

酸性水解时，有较大体积的TIPS 醚比叔丁基二甲基硅醚要更稳定些。但稳定性比叔丁基二苯基硅基差。TIPS 基碱性水解时比TBDMS 基或TBDPS 基稳定。相对于仲羟基，TIPS 基对伯羟基有更好的选择性。

2.4.1通过TIPSCl 进行羟基的三异丙基硅醚保护示例(J. Org. Chem. 1995, 60, 7796)

31

3

2

To a stirred solution of (1)(1.5 g) in CH2Cl 2 (53 mL) cooled to 0o C were successively added 2,6-lutidine (6.2 mL, 53.3 mmol) and triisopropylsilyl triflate (7.90 mL, 29.5mmol). The mixture was allowed to warm to room temperature (30 min). Then excess triflate was consumed by addition of methanol (10 mL) and a saturated aqueous NH4Cl solution (60 mL). The phase was separated and the aqueous layer was extracted with CH2Cl 2 (4 ⨯ 50 Ml). The combined organic phases were washed with a saturated NaHCO3 (100 mL) a, 1M NaHSO4 (3 ⨯ 50 mL), and brine (50 mL), dried over Na2SO 4, filtered, and concentrated. Purification by flash chromatography (10% ethyl acetate in hexane) afforded silyl ether (2) (6.90 g, 89%).

3. 羟基苄醚保护及脱除

一般羟基的苄醚保护主要有苄基，对甲氧苄基及三苯甲基醚。

3.1苄基醚保护羟基 (Bn-OR)

一般烷基上的羟基在用苄基醚保护时需要用强碱，但酚羟基的苄基醚保护一般只要用碳酸钾在乙腈或丙酮中回流即可，回流情况下，这类烷基化在乙腈中速度比丙酮中要快四倍左右，因此一般用乙腈做溶剂居多。若反应速度慢可用DMF 做溶剂，提高反应温度，或加NaI,KI 催化反应。

苄基醚的裂解主要是通过催化加氢的方法，Pd 是理想的催化剂，用Pt 时会产生芳环上的氢化作用。在含色氨酸的肽中氢解苏氨酸常导致色氨酸还原成2，3-二氢衍生物。非芳性的胺可以使催化剂活性降低，阻碍O -脱苄；在氢化体系中加入Na 2CO 3可以防止苄基被裂解，但可使双键发生还原。孤立烯烃有可能影响苄基醚键的裂解（H 2，5% Pd-C，97%产率）。一般而言选择性的大小取决于取代的类型及空间位阻的情况。与酯共扼的三取代的烯烃存在时，苄基的水解也有相当好的选择性。对甲氧苄基基团存在时，苄基的水解（Pd-C ，EtOAc ，室温，18小时）有非常好的选择性。在反应体系中加入Pyridine 可使对甲氧苄基和苄基氢解产生区别。 苄基的氢解有溶剂的作用，如下列表： Effect of solvent on the hydrogenlysis of benzyl ether

3.1.1烷基羟基的苄基醚保护示例(Bull. Chem. Soc. Jpn. 1987, 60, 1529)

1

2

Compound 1 (12.1 g) in DMF (200 mL) was treated with 60% NaH (1.32 g), benzyl bromide (6.44 g) and tetrabutylammonium iodide (0.11 g). The reaction mixture was stirred at room temperature for 1.5 h. The product was purified by chromatography on silica gel with toluene-ethanol (20:1) to give 2 (14.0 g, 99%).

3.1.2 酚羟基的苄基醚保护示例

O

OH

K 2CO 3/EtOH

O

1

2

To a solution of 1 (37.65 g, 277 mmol) in EtOH (135 mL) was added benzyl chloride (36.5 g, 289 mmol), KI (1.75 g, 10 mmol) and K 2CO 3 (24.6 g, 178 mmol) with stirring. The resulting mixture was refluxed for 5 h. The mixture was allowed to cool to room temperature and the solvent was removed in vacuo. The residue was added water (100 mL) and extracted with Et 2O (80 mL 3). The extract was washed with saturated NaHCO 3, water and brine successively. The organic layer was dried over Na2SO 4 and concentrated in vacuo to give the crude product, which was distilled to afford 2 (49.1 g, 79%).

3.1.3苄基醚氢解脱保护示例(J. Am. Chem. Soc. 1971, 93, 1746)

310%Pd/C/H4

Compound 3 (105 mg) was hydrogenated in ethanol (10 mL) containing 1M hydrochloric acid (0.5 mL) in the presence of 10% palladium on charcoal (50 mg) in an initial hydrogen pressure of 3.4 MPa overnight. The product was purified by chromatography on silica gel with toluene-ethanol (3:1) to give 4 (90 mg, quant.)

3.2对甲氧基苄基醚保护羟基 (PMB-OR)

各种甲氧基苄醚已经合成得到并被用作保护基。实际上甲氧基取代的苄基醚较未取代的苄基醚更容易通过氧化去保护。下表给出了用二氯二氰苯醌去保护时的相对速率。

(OMe)n

i

CH 2Cl 2,H 2O (10:1), 20C

ii

OHC

iii

Cleavage of MPM, DMPM, and TMPM ethers with DDQ in CH2Cl 2/H2O at 20o C

一般而言，对甲氧基苄醚在合成中更为常用，羟基上对甲氧基苄基的方法和苄基类似，但脱除除了氢解的方法外，还可以氧化除去。

3.2.1对甲氧基苄基醚保护示例(Tetrahedron Lett. 1988, 29, 2459)

Bn

NaH, DMF

ClH 2C

OMe

Bn

To a stirred suspension of NaH (26 mg 1.09 mmol) in DMSO (1 mL) was added dropwise a THF solution (3 mL) of 1 (250 mg, 0.78 mmol) under Ar. After 45 min. at room temperature MPM chloride (158 mg, 1.01mmol) was added, and the stirring was continued for 3 h. the mixture was poured into sat. NH 4Cl aq. And then extracted with ether. The extract was washed with sat. NaCl aq., dried over MgSO 4, and concentrated in vacuo to leave an oil, which was chromatographed on a short silica gel column elution with EtOAc-n-hexane (1:1) gave a colorless oil of 2 296 mg, 86%.

3.2.2 在苄氧基存在下选择性脱去对甲氧基苄基示例(Tetrahedron Lett. 1988, 29, 2459)

Bn

Bn

CH 2Cl 2-H 2O

2

To a stirred solution of 2 (92 mg, 0.286 mmol) in CH2Cl 2 (2.9 mL) and water (0.17 mL) was added DDQ (97 mg, 0.427 mmol) at room temp. After 2.5 h precipitated DDQH was removed by decantation and washed with a small amount of CH2Cl 2. The combined CH2Cl 2 solution was washed with sat. NaHCO3 aq. And sat. NaCl aq. And dried over Na2SO 4. Evaporated of the solvent in vacuo gave an oil, which was chromatographed on a silica gel column with EtOAc-n-hexane (1:1) as eluant gave a colorless solid of 1 43.8 mg, 84%.

4. 烷氧基甲基醚或烷氧基取代甲基醚

烷氧基甲基醚或烷氧基取代甲基醚在羟基保护中也是较为多用的一类，常用的有THP (2-四氢吡喃) ，MOM （甲氧基甲机基），EE （2-乙氧基乙基），这类保护基都对酸不稳定，因此一般都是脱保护。它们对酸的稳定性是MOM>EE>THP。

4.1 THP (2-四氢吡喃) 保护羟基

THP 醚引入到一个手性分子的结果是形成了一个非对映体，因为在四氢吡喃环上新增了一个手性中心。（有时它会使NMR 谱的表达有点困难）。尽管如此， 它仍是有机合成中一个非常有用的保护基团，它的成本低，易于分离，对大多数非质子酸试剂有一定的稳定性，易于被出去。通常，几乎任何酸性试剂或任何可以在原位产生酸的试剂都可被用来引入THP 基团。

4.1.1 THP (2-四氢吡喃) 保护羟基示例(J.Org.Chem. 1977, 42,3772)

t-BDPSiO

1

C C C 6H 5

t-BDPSiO

2

C C C 6H 5

To a solution of 1 (1.5 g, 3.5mmol) in CH 2Cl 2 (10 mL) at 22-24o C was added 3,4- dihydro-2H-pyran (0.479 mL, 0.442 g, 5.25mmol) and PPTs (20 mg, 0.08mmol). The solution was stirred at 22-24o C for 1 h and diluted with a 100-mL solution of (1:1) diethyl ether and

ethyl acetate. The organic layer was separated, washed with H 2O (3 ⨯ 100mL), and the residue was chromatographed, eluting with hexane/ethyl acetate (20:1) to give the THP ether 2 as clear oil (1.75 g, 97%).

4.1.2 THP (2-四氢吡喃) 脱保护示例(J.Org.Chem. 1977, 42,3772) PPTS/EtOH/50o C

R C 1C C C 6H 5R C 2C C C 6H 5

To an ethanol solution (30 mL) of THP ether 1 (1.87 g, 5mmol) was added PPTS (20 mg, 0.08mmol) in one portion. The solution was refluxed for 1 h, cooled to 22-24o C, and diluted with a mixture of diethyl ether (100 mL) and H2O (200 mL). The organic layer was washed with H 2O (2 ⨯ 100mL), dried over Na 2SO 4 and concentrated in vacuo . The residue was purified by chromatography on silica gel, eluting with hexane/ethyl acetate (3:1) to give 2 (1.36 g, 94%) as clear oil.

4.2 MOM 保护羟基

MOM 是一般是通过MOMCl-DIEA 引入；其对酸还是较为稳定的，一般它的脱除需要在强酸条件下进行。

4.2.1 MOM (CH3OCH 2-OR) 羟基保护示例(J. Org. Chem. 1995,60,7796)

OPMB TBDPSO

OH

12OPMB TBDPSO MOM

To a stirred solution of (1) (51.0 g, 99 mmol) in CH2Cl 2 (1.0 L) at room temperature were successively added DIEA (51.5 mL, 0.297 mol) and MOMCl (15.0 mL, 0.198 mol) over a 10 min period. The solution was stirred 11 h at room temperature after which a saturated aqueous NH4Cl solution (200 mL) was added. The aqueous phase was segregated, and the organic one was washed with water (100 mL), brine (100 mL0, dried with anhydrous MgSO4, filtered, and concentrated to give pure MOM ether (2) (55.3 g, 100%) (slightly yellowish oil).

4.2.2 MOM 脱保护示例(ibid)

2CH 3

o 2CH 3

To a stirred solution (1) (1.00 g, 1.45 mmol) in dry isopropyl alcohol (10.0 mL) were added 12two drops (~0.06 mL) of concentrated aqueous hydrochloric acid. The solution was stirred at 55o C for 10 h and although incomplete as indicated by TLC analysis, was allowed to cool to room temperature (prolonged reaction times tend to give substantial decomposition). A saturated aqueous NaHCO 3 (20 mL) and diethyl ether (50 mL) were added to the mixture. The phase was separated and the aqueous layer was extracted with diethyl ether (5 50 mL). The combined organic layer was washed with brine (10 mL), dried over MgSO4, filtered, and concentrated. The crude product was purified by flash chromatography to give (2) (0.63 g, 65%).

4.3 EE （CH 3 CH2OCH 3CH-OR ）保护羟基

EE 的性质和THP 差的不是很多。

4.3.1 EE （CH 3 CH2OCH 3CH-OR ）羟基保护示例(J.Am.Chem.Soc. 1981,103,2427)

TsOH

12

Selective reaction of the primary hydroxyl group in 1 with ethyl vinyl ether at –22o C by using pyridinium tosylate as catalyst in CH2C12 was followed by formation of the methanesulfonate ester at C-6, to produce 2.

4.3.2 EE 脱保护示例(J.Am.Chem.Soc. 1986,108

,1035)

PPTS A solution of 19 mg (0.043 mmol) of ester 20 in 0.2 mL ether was treated at 0o C with 100 mL

of a 1 M solution of LAH in ether. After 5 min the solution was quenched with water and was extracted with ether. The solvent was evaporated and the residue was dissolved in 0.5 mL of methanol containing a few crystals of PPTS. The solution was stirred at 25o C for 2 h. The methanol was evaporated and the residue was dissolved in ether. The combined organic extract was washed with saturated aqueous sodium bicarbonate and the aqueous phase was back extracted with ether. The ether extracts were combined, washed with brine, dried (Na2SO 4,), and concentrated. The solid product was purified by HPLC (p-Porasil) to furnish 13 mg (90% overall) of desepoxyasperdiol as an oil.

4.4 SEM-Cl(TMSCH2CH 2OCH 2-) 保护羟基

SEM-作为羟基的保护基，其主要特点为最后脱保护可以通过四烷基氟化胺来脱去。SEM 醚对分解四氢吡喃基(THP) 和叔丁基二甲基硅醚（TBS ）的酸性条件（AcOH-H2O, THF, 45o C, 7小时）是稳定的。

4.4.1 SEM-Cl(TMSCH2CH 2OCH 2-) 保护羟基示例(TL , 1980,3343)

R 1+TMSOCH 2CH 2OCH 2Cl RO 2

Exposure of an alcohol 1 in CH2Cl 2 (ca, 2M) under an inert atmosphere containing 4-5 eq. of DIEA, to SEMCl (ca, 3 eq) at 25-40o C,affords the SEM ether in high yield.

在二氯甲烷中的酒精1曝光（CA ，2m ）在含有4-5平衡状态惰性气体下，以semcl （CA ，3eq ）在25-40℃，提供高产SEM 醚

4.4.2 SEM 保护基脱保护示例(ibid) RO 1ROH 2+CH 2O +H 2C CH 2+Me 3SiF

Removed of the SEM can be accomplished via reaction with Bu4NF (at concentration > 2M) in dry THF at 45o C. Standard extractive workup followed by rough SiO2 filtration give the desired product.

移除的SEM 可以通过反应bu4nf 完成（在浓度大于2m ）在无水THF45℃条件下。标准的萃取处理后粗糙的二氧化硅过滤得到所需的产品。

5. 其他保护基

5.1 烯丙基保护羟基

有关碳水化合物的文献中，烯丙醚用来保护醇是很常见的，原因在于烯丙醚通常可用各种方法形成糖苷。显然，烯丙醚不能与强的的亲电试剂共存，如溴、催化氢化的试剂。但它在中等强度的酸性条件（1N HCl ，回流，10小时）下稳定。易于生成，在大量其它保护基存在下有许多温和的脱保护方法，及其总体上的稳定性，使得烯丙醚成为许多反应系列中的主干。已有关于全氘代烯丙溴的合成及将它用作碳水化合物保护基方面的报道，全氘化合物的优点在于：烯丙基的NMR 中的共振不再掩蔽其它可供鉴定的共振吸收峰，如糖苷的导头碳的吸收峰。

5.1.1 烯丙基保护羟基示例(J.Org.Chem.C 1969, 2367) BnO HO OBn

OBn BnO AllylO 2OBn OBn 1

A mixture of 1 (50 g), powdered NaOH (50 g), benzene (500 mL), and allyl bromide (12 mL) was heated under reflux and the progress of the reaction was followed by TLC (ether: petroleum, 1:1). After 80 min. some starting material (Rf 0.15) remained and some diallyl derivatives present, but the major product was the monoallyl derivatives (Rf 0.56), the benzene solution was washed with water, dried (K2CO 3) and evaporated. The syrupy product was chromatographed on alumina, elution with benzene:ether removed the diallyl derivative (9 g) and elution with ether-methanol (25:1) gave the monoallyl derivatives (35 g ). Further elution with methanol gave unchanged starting material (8 g).

混合物1（50克）、NaOH （50克）、苯（500毫升），与烯丙基溴（12毫升）加热回流反应的进展是薄层色谱（乙醚：石油，1:1）。80分钟后，一些原料（RF 0.15）保持和二烯丙基衍生物的存在，但主要的产品是单烯丙基衍生物（RF 0.56）的苯溶液，用水洗涤，干燥（K2CO3）和蒸发。糖浆产品以氧化铝、洗脱苯醚的进程去除：二烯丙基衍生物（9 g ）和乙醚甲醇洗脱（25:1）给单烯丙基衍生物（35克）。甲醇进一步洗脱与不变起始原料（8克）。

5.1.2

烯丙基脱保护示例(J.Chem.Soc. Perkins Trans 1, 1980,738)

ROCH 2CH=CH2

1ROCH=CHCH32ROH + CH3CH 2CHO 3

A solution of menthyl allyl ether (0.114 g, 0.58 mmol) (prepared from menthol, sodium hydride, and allyl bromide), RhCl(PPh3) 3 (0.037 g, 0.040 mmol) and diazabicyclo[2,2,2]octane (0.013 g, 0.120 mmol) (added to inhibit premature hydrolysis of the intermediate enol ether. Free propionaldehyde reacts with RhCl(PPh3) 3 to form the catalytically much less active RhCl(PPh3) 2CO.) in 10% aqueous ethanol was heated at reflux for 3 h. An aliquot was injected into 1 N HCl and after a few minutes was assayed by vpc analysis which showed only menthol and menthyl allyl ether in 93% and 7% yield, respectively. Work up of a parallel reaction (by poured into water, extracting with ether, washing the ether with brine acidified to pH 2, drying over MgSO 4, concentrated, and separation on silica gel) gave menthol in 93% yield.

一份基烯丙基醚的溶液（0.114克，0.58毫摩尔）（由薄荷脑、氢化钠、烯丙基溴）RhCl （PPh3），3（0.037克，0.040毫摩尔）和二氮杂双环[2,2,2]辛烷（0.013克，0.120毫摩尔）（添加抑制中间体烯醚过早水解。自行RhCl （PPh3）丙醛反应3形成的催化活动更少RhCl （PPh3）2CO 。）在10%乙醇水溶液加热回流3 h.等分试样注入1 N HCl和几分钟后的VPC 分析仅表现在93%和7%薄荷脑和薄荷烯丙基醚产量分别测定。工作上的平行反应（被倒入水中，用乙醚提取，用盐水酸化至pH 2，洗醚干燥MgSO4、浓缩和硅胶分离）给了薄荷93%产量

5.2 酰基保护

醇通过酯的保护一般用在糖化学中较为多见，一般主要通过乙酰基、苯甲酰基和特戊酰基等。乙酰基保护也常常用于天然产物结构鉴定中羟基衍生化。一般上乙酰基方法较多，其中用乙酸酐在吡啶中引入乙酰基最为常用，由于该方法不能乙酰化位阻较大的叔醇，要想在叔醇引入乙酰基需要加入酰化催化剂（DMAP, 4-PPY）等，有时对位阻特别大的即使加入酰化催化剂（DMAP, 4-PPY）也无效时，可以考虑通过Lewis 酸催化，Procopiou P. A. 等人报道利用TMSOTf 催化位阻较大的叔醇的乙酰化，效果要比Ac 2O/DMAP体系更好（J. Org. Chem. 1998, 2342）。 苯甲酰化的常用方法是BzCl 或Bz2O/吡啶。特戊酰化的常用方法是PvCl /吡啶, 0-75℃。这些酰基化对伯醇选择性要大于仲醇，选择性特戊酰基>苯甲酰>乙酰基；有时特戊酰基可化学选择性的上在伯醇上。

5.2.1 乙酰化保护羟基示例 (DMAP: J. Org. Chem. 1993, 3791)

HO

1AcO 2+AcO 3OH +HO 4OAc

Compound 1 (1.38 g, 10 mmol) and Ac 2O (0.95 mL, 10 mmol) in CH 2Cl 2 (30 mL) were treated with Et3N (2 mL, 10 mmol) and DMAP (122 mg, 1 mmol) at 20o C, and the mixture was stirred for 4 d. The mixture was diluted with CH 2Cl 2 and washed with 2M HCl, NaHCO 3, H 2O, dried, and chromatographed on silica gel eluting with ethyl acetate-cyclohexane (1:3, 1:1 to give the diactate (2) (500 mg, 22%), the O-aryl acetate (3) (705 mg, 39%), and the O-alkyl acetate (4) (54 mg, 3%).

化合物1（1.38克，10毫摩尔）和乙酸酐（0.95毫升，10毫摩尔）在二氯甲烷（30毫升）分别用三乙胺（2毫升，10毫摩尔）和DMAP （122毫克，1毫摩尔）在20oC ，混合，搅拌4 D.混合稀释二氯甲烷和2M 盐酸，碳酸氢钠，H2O ，干洗，和硅胶柱色谱乙酸乙酯环己烷洗脱（1:3、1:1给定比例（2）（500毫克，22%），芳基乙酸（3）（705毫克，39%），和O-烷基酯（4）（54毫克，3%）。

5.2.2 Lewis 酸催化乙酰化保护叔羟基示例 (TMSOTf，Ac 2O, J. Org. Chem. 1998, 2342) HO

12OAc +AcO 3OH +HO 4OAc

Compound 1 (1.38 g, 10 mmol) in CH 2Cl 2 (10 mL) and Ac 2O (0.95 mL, 10 mmol) were treated with TMSOTf in CH2Cl 2 (1M, 0.25 mL,) at 20o C. The reaction mixture was checked by HPLC after 1 h and indicated a mixture (22:48:30). After stirring for 21 h, the starting material was consumed and the mixture of product was 88:12. After stirring for a total of

3.5 d the ratio improved to 93:7. The mixture was washed with water and brine, dried, and evaporated to give the O-alkyl acetate (4) (1.577 mg, 88%).

化合物1（1.38克，10毫摩尔）在二氯甲烷（10毫升）和乙酸酐（0.95毫升，10毫摩尔）进行处理（TMSOTf 在二氯甲烷中1m ，0.25 mL）在20℃下。反应混合物经HPLC 检查1 h后显示的混合物（22:48:30）。搅拌21 h后，原料消耗和产品混合88:12。搅拌共3.5 d的比例提高到93:7后。混合水和盐水，清洗干燥，蒸发给O-烷基酯（4）（1.577毫克，88%）。

5.2.3 苯甲酰化保护羟基示例( J.Org.Chem. 1981, 46, 5252)

OH

3

1N 3OBz 2

To a solution of 1 (0.94 g. 2.9 mmol) in pyridine (20 ml), benzoyl chloride (1.26 g, 9 mmole) was added with stirring and ice-cooling. Stirring was continued overnight at room

temperature. The mixture was poured into ice-water and extracted with benzene. The

benzene extract was washed with water, dried and evaporated to leave a faint yellow caramel (l.62 g), which was triturated with i-PrOH to form crystals. These were recrystallized from i-PrOH to give colourless plates, m.p. 106-107.5o C, yield 1.31 g (85%).

在1的溶液（0.94克，2.9毫摩尔）吡啶（20毫升），苯甲酰氯（1.26克，9毫摩尔）加入搅拌和冰冷却。在室温下继续搅拌。将混合物倒入冰水中，用苯萃取。苯提取液用水洗涤，干燥，蒸发，留下淡淡的黄色焦糖（l.62 G），这是与i-PrOH 中形成晶体的产物。这些结晶从i-PrOH 中给无色板，熔点106-107. 5℃，产量1.31克（85%）。

5.2.4 特戊酰基保护羟基示例(

J.Am.Chem.Soc . 1980,102,7962)

3

123

The triol 1 (3.24 g, 20 mmol) is dissolved in pyridine (20 mL) and dry didhloromethane (20 mL) is added. To the cold (0o C) and stirred solution under argon is added dropwise over a period of 30 min., pivaloyl chloride (2.48 mL, 20 mmol). The cooling is then removed and the mixture is stirred at room temperature for 14h. Concentrated followed by azeotropic removal of pyridine (toluene) gives a syrup which is purified by flash column chromatography on silica gel (50% ether in petroleum ether) yield 2 as a colorless oil, yield

4.43g, (90%).

三醇1（3.24克，20毫摩尔）溶于吡啶（20毫升）和干didhloromethane （20毫升）加入。在寒冷的（0℃）温度下搅拌下滴加液氩是超过30分钟的期间，特戊酰氯（2.48毫升，20毫摩尔）。冷却然后移除和在室温下搅拌14h 。集中由吡啶共沸除（甲苯）给出了糖浆，它是由硅胶柱层析纯化（50%乙醚石油醚）为无色油产量的2，产量4.43g ，（90%）

5.2.5 乙酸酯脱保护示例 (J.Am.Chem.Soc. 1972, 94, 8613)

K 2CO 3/MeOH

12CH 32CH 32

A mixture of 1 (1.59 g, 6.0 mmol) and K2CO 3 (2 g, 14.3 mmol) in MeOH (5 mL) and water (3 mL) was stirred at room temperature for 12 h. The mixture was concentrated in vacuo to a volume of 3.5 mL and extracted with CH 2Cl 2 (25 mL 3). The extract was dried over MgSO 4 and concentrated in vacuo to afford 2 1.13 g (85%).

1的混合物（1.59克，6毫摩尔）和碳酸钾（2克，14.3毫摩尔）甲醇（5毫升）和水（3毫升）在室温下搅拌12 h ，混合物在真空浓缩，体积3.5 ml 提取，二氯甲烷（25毫升× 3）。提取MgSO4干燥和真空浓缩起2 1.13克（85%）。

5.2.6 苯甲酸酯脱保示例( J.Org.Chem. 1981, 46, 5252) OBz

33OH

Dibenzoate 1 (500 mg, 09 mmol) was added to a solution of NaOH (250 mg, 62 mmol) in 12MeOH (35 mL) and the resulting mixture was stirred at room temp for 50 min. After

evaporation of MeOH in vacuo and addition of water, the solid separated was extracted with benzene-AcOEt. The organic extract was washed with water, dried and the solvent was

removed. The residue was chromatographed on silica gel to give a colorless caramel 2, yield 360 mg (90%).

二苯甲酸酯1（500毫克，9毫摩尔）的溶液中加入NaOH 溶液（250 mg，62毫摩尔）甲醇（35毫升）和由此产生的混合物在室温下搅拌50分钟在真空下加入水带甲醇蒸发后，以固体分离方式提取苯乙酸乙酯。有机提取物用水洗涤，干燥和溶剂后除去。残渣经硅胶为无色焦糖2，产率360毫克（90%）。

5.2.7 特戊酸酯脱保护示例(J.Am.Chem.Soc . 1990,112,3693)

PvO A N 3

1HO 1.Pd/BaCO, 2.NaOMe/MeOHH 2

A solution of 136 mg (0.3 mmol) of 1 in 20 mL of MeOH was hydrogenated at atmospheric 2pressure over 40 mg of 5% Pd/BaCO3 for 24 h at room temperature. The mixture was filtered using a Celite pad, and the filtrate was evaporated. The resulting colorless glass was dissolved in 10 mL of MeOH and stirred with 49 mg (0.9 mmol) of NaOMe for 20 h at room temperature, during which time white crystals separated. These were filtered and washed well with MeOH to give 66 mg of 2. The filtrate was neutralized with HOAc and concentrated, and the residue was purified by preparative TLC (developed using the upper phase of EtOAc/n-PrOH/H2O, 4:1:2). Recrystallization of this material from MeOH/95% EtOH gave an additional 18 mg for a total yield of 84 mg (80%) of 2. 136毫克的溶液（0.3毫摩尔）1甲醇20毫升氢化并在大气压力超过40毫克5%钯/碳酸钡室温下24h 。混合使用硅藻土垫过滤，与滤液的蒸发。由此产生的产物用甲醇10毫升和49毫克甲醇钠（0.9毫摩尔）在无色玻璃中搅拌20 h，在室温下，甲醇钠，其间有白色结晶分离。这些用66毫克甲醇洗涤两次过滤。滤液用乙酸中和、浓缩、和残渣制备TLC 纯化（采用乙酸乙酯/正丙醇/水，2上相）。从甲醇/ 95%乙醇给了一个额外的18毫克，总收率84毫克这种材料再结晶（80%）2。