发布时间 : 星期四 文章常见的羟基的保护与脱保护方法更新完毕开始阅读e1d404af7f21af45b307e87101f69e314232fa0b
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Ac2O/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)
Compound 1 g, 10 mmol) and Ac2O mL, 10 mmol) in CH2Cl2 (30 mL) were treated with Et3N (2 mL, 10 mmol) and DMAP (122 mg, 1 mmol) at 20oC, and the mixture was stirred for 4 d. The mixture was diluted with CH2Cl2 and washed with 2M HCl, NaHCO3, H2O, 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（克，10毫摩尔）和乙酸酐（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，Ac2O, J. Org. Chem. 1998, 2342) Compound 1 g, 10 mmol) in CH2Cl2 (10 mL) and Ac2O mL, 10 mmol) were treated with TMSOTf in CH2Cl2 (1M, mL,) at 20oC. 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 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) mg, 88%).
化合物1（克，10毫摩尔）在二氯甲烷（10毫升）和乙酸酐（毫升，10毫摩尔）进行处理（TMSOTf在二氯甲烷中1m， 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 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）（毫克，88%）。 5.2.3 苯甲酰化保护羟基示例( 1981, 46, 5252)
To a solution of 1 g. mmol) in pyridine (20 ml), benzoyl chloride 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 g), which was triturated with i-PrOH to form crystals. These were recrystallized from i-PrOH to give colourless plates, . , yield g (85%). 在1的溶液（克，毫摩尔）吡啶（20毫升），苯甲酰氯（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（ 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℃，产量克（85%）。
5.2.4 特戊酰基保护羟基示例(. 1980,102,7962)
The triol 1 g, 20 mmol) is dissolved in pyridine (20 mL) and dry didhloromethane (20 mL) is added. To the cold (0oC) and stirred solution under argon is added dropwise over a period of 30 min., pivaloyl chloride 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 , (90%).
三醇1（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（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，（90%） 5.2.5 乙酸酯脱保护示例 (1972,94,8613)
A mixture of 1 g, mmol) and K2CO3 (2 g, 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 mL and extracted with CH2Cl2 (25 mL ? 3). The extract was dried over MgSO4 and concentrated in vacuo to afford 2 g (85%).
1的混合物（克，6毫摩尔）和碳酸钾（2克，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 ml提取，二氯甲烷（25毫升×?3）。提取MgSO4干燥和真空浓缩起2 克（85%）。
5.2.6 苯甲酸酯脱保示例( 1981, 46, 5252)
Dibenzoate 1 (500 mg, 09 mmol) was added to a solution of NaOH (250 mg, 62 mmol) in MeOH (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(. 1990,112,3693)
A solution of 136 mg mmol) of 1 in 20 mL of MeOH was hydrogenated at atmospheric pressure 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 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（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（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。