氨基的保護(hù)及脫保護(hù)策略-060226

1、經(jīng)典合成反應(yīng)標(biāo)準(zhǔn)操作氨基的保護(hù)及脫保護(hù) 藥明康德新藥開(kāi)發(fā)有限公司經(jīng)典化學(xué)合成反應(yīng)標(biāo)準(zhǔn)操作氨基的保護(hù)及脫保護(hù)策略編者： 彭憲藥明康德新藥開(kāi)發(fā)有限公司化學(xué)合成部目 錄1 氨基的保護(hù)及脫保護(hù)概要22 烷氧羰基類(lèi)2-1. 芐氧羰基（Cbz） 42-2. 叔丁氧羰基（Boc） 162-3. 笏甲氧羰基（Fmoc） 282-4. 烯丙氧羰基（Alloc） 342-5. 三甲基硅乙氧羰基（Teoc） 362-6. 甲（或乙）氧羰基 403 ?；?lèi)3-1. 鄰苯二甲?；≒ht） 433-2. 對(duì)甲苯磺?；═os） 493-3. 三氟乙?；═fa） 534 烷基類(lèi)4-1. 三苯甲基（Trt） 574-2.

2、 2,4-二甲氧基芐基（Dmb） 634-3. 對(duì)甲氧基芐基（PMB） 654-4. 芐基（Bn） 701氨基的保護(hù)及脫保護(hù)概要選擇一個(gè)氨基保護(hù)基時(shí)，必須仔細(xì)考慮到所有的反應(yīng)物，反應(yīng)條件及所設(shè)計(jì)的反應(yīng)過(guò)程中會(huì)涉及的所有官能團(tuán)。首先，要對(duì)所有的反應(yīng)官能團(tuán)作出評(píng)估，確定哪些在所設(shè)定的反應(yīng)條件下是不穩(wěn)定并需要加以保護(hù)的，并在充分考慮保護(hù)基的性質(zhì)的基礎(chǔ)上，選擇能和反應(yīng)條件相匹配的氨基保護(hù)基。其次，當(dāng)幾個(gè)保護(hù)基需要同時(shí)被除去時(shí)，用相同的保護(hù)基來(lái)保護(hù)不同的官能團(tuán)是非常有效（如芐基可保護(hù)羥基為醚，保護(hù)羧酸為酯，保護(hù)氨基為氨基甲酸酯）。要選擇性去除保護(hù)基時(shí)，就只能采用不同種類(lèi)的保護(hù)基（如一個(gè)Cbz保護(hù)的氨基可

3、氫解除去，但對(duì)另一個(gè)Boc保護(hù)的氨基則是穩(wěn)定的）。此外，還要從電子和立體的因素去考慮對(duì)保護(hù)的生成和去除速率的影響（如羧酸叔醇酯遠(yuǎn)比伯醇酯難以生成或除去）。最后，如果難以找到合適的保護(hù)基，要么適當(dāng)調(diào)整反應(yīng)路線(xiàn)使官能團(tuán)不再需要保護(hù)或使原來(lái)在反應(yīng)中會(huì)起反應(yīng)的保護(hù)基成為穩(wěn)定的；要么重新設(shè)計(jì)路線(xiàn)，看是否有可能應(yīng)用前體官能團(tuán)（如硝基，亞胺等）；或者設(shè)計(jì)出新的不需要保護(hù)基的合成路線(xiàn)。在合成反應(yīng)中，伯胺、仲氨、咪唑、吡咯、吲哚和其他芳香氮雜環(huán)中的氨基往往是需要進(jìn)行保護(hù)的。已經(jīng)使用過(guò)的氨基保護(hù)基很多，但歸納起來(lái)，可以分為烷氧羰基、酰基和烷基三大類(lèi)。烷氧羰基使用最多，因?yàn)镹-烷氧羰基保護(hù)的氨基酸在接肽時(shí)不易發(fā)生消

4、旋化。伯胺、仲氨、咪唑、吡咯、吲哚和其他芳香氮?dú)涠伎梢赃x擇合適的保護(hù)基進(jìn)行保護(hù)。下表列舉了幾種代表性的常用的氨基保護(hù)基。幾種代表性的常用的氨基保護(hù)基結(jié)構(gòu)縮寫(xiě)應(yīng)用引入條件脫去條件Cbz伯胺、仲氨、咪唑、吡咯、吲哚等Cbz-Cl/Na2CO3/CHCl3/H2OH2/Pd-C，供氫體/Pd-C，BBr3/CH2Cl2 or TFA，HBr/HOAc等Boc伯胺、仲氨、咪唑、吡咯、吲哚等Boc2O/NaOH/diox/H2O, Boc2O/ /MeOH, Boc2O/Me4NOH/CH3CN3MHCl/EtOAc, HCl/MeOH or diox, TosOH/THF-CH2Cl2, Me3SiI

5、/CHCl3orCH3CNFmoc伯胺、仲氨等Fmoc-Cl/NaHCO3,/diox/H2O20%哌啶/DMF，50%哌啶/CH2Cl2等Alloc伯胺、仲氨、咪唑、吡咯、吲哚等Aloc-Cl/PyNi(CO)4/DMF/H2O;Pd(PPh3)4/Bu3SnH;Teoc伯胺、仲氨、咪唑、吡咯、吲哚等Teoc-Cl/堿/diox/H2OTBAF；TEAF-伯胺、仲氨、咪唑、吡咯、吲哚等ROCOCl/NaHCO3,/diox/H2OHBr/HOAc;Me3SiI;KOH/H2O/乙二醇Pht伯胺鄰苯二甲酸酐/CHCl3/70;鄰苯二甲酰亞胺-NCO2Et/aq. Na2CO3H2NNH2/Et

6、OH，NaBH4/i-PrOH-H2O（6：1）Tos伯胺、仲氨、咪唑、吡咯、吲哚等Tos-Cl/Et3NHBr/HOAc, 48%HBr/苯酚（cat）Tfa伯胺、仲氨、咪唑、吡咯、吲哚等TFAA/Py; 苯二甲酰亞胺-NCO2CF3/CH2Cl2K2CO3/MeOH/H2O;NH3/MeOH;HCl/MeOHTrt伯胺、仲氨、咪唑、吡咯、吲哚等Trt-Cl/Et3NHCl/MeOH, H2/Pd/EtOH, TFA/CH2Cl2Dmb伯胺、仲氨、咪唑、吡咯、吲哚等ArCHO/NaCNBH3/MeOHPMB伯胺、仲氨、咪唑、吡咯、吲哚等PMB-Br/ K2CO3/CH3CN;PhCHO/Na

7、CNBH3/MeOHHCO2H/Pd-C/MeOH; H2/Pd(OH)2/EtOH; TFA; CAN/ CH3CNBn伯胺、仲氨、咪唑、吡咯、吲哚等Bn-Br/Et3N or K2CO3/CH3CN;PhCHO/NaCNBH3/MeOHHCO2H/Pd-C/MeOH; H2/Pd(OH)2/EtOH; CCl3CH2OCOCl/CH3CN2烷氧羰基類(lèi)保護(hù)基烷氧羰基類(lèi)保護(hù)基可用于氨基酸，以在肽合成中減少外消旋化的程度。外消旋化發(fā)生在堿催化的N-保護(hù)的羧基活化的氨基酸的偶聯(lián)反應(yīng)中，也發(fā)生在易由N-?；Ｗo(hù)的氨基酸形成的中間體惡唑酮中。要使外消旋化程度減到最小，需使用非極性溶劑、最弱的堿、低的反

8、應(yīng)溫度，并使用烷氧羰基類(lèi)保護(hù)的氨基酸是有效的。其中常用的有易通過(guò)酸性水解去保護(hù)的Boc基、由催化氫解去保護(hù)的Cbz基、用堿經(jīng)-消除去保護(hù)的Fmoc基和易由鈀催化異構(gòu)化去保護(hù)的Alloc基。2.1芐氧羰基（Cbz）芐氧羰基（Cbz）是1932年Bergmann發(fā)現(xiàn)的一個(gè)很老的氨基保護(hù)基，但一直到今天還在應(yīng)用。其優(yōu)點(diǎn)在于：試劑的制備和保護(hù)基的導(dǎo)入都比較容易；N-芐氧羰基氨基酸和肽易于結(jié)晶而且比較穩(wěn)定；芐氧羰基氨基酸在活化時(shí)不易消旋；能用多種溫和的方法選擇性地脫去。2.1.1芐氧羰基的導(dǎo)入 芐氧羰基的導(dǎo)入，一般都是用Cbz-Cl。游離氨基在用NaOH 或NaHCO3 控制的堿性條件下可以很容易同Cb

9、z-Cl反應(yīng)得到N-芐氧羰基氨基化合物。,-二胺可用該試劑在pH= 3.5-4.5稍有選擇性地被保護(hù)，其選擇性隨碳鏈地增長(zhǎng)而減弱，如H2N(CH2)nNH2, n=2時(shí)71%被單保護(hù); n=7時(shí)29%被單保護(hù)1。 氨基酸酯同Cbz-Cl的反應(yīng)則是在有機(jī)溶劑中進(jìn)行，并用碳酸氫鹽或三乙胺來(lái)中和反應(yīng)所產(chǎn)生的HCl。此外，Cbz-ONB（4-O2NC6H4OCOOBn）等芐氧羰基活化酯也可用來(lái)作為芐氧羰基的導(dǎo)入試劑，該試劑使伯胺比仲胺易被保護(hù)，但苯胺由于親核性不足，與該試劑不反應(yīng)2。1G. J. Atwell, W. A. Denny., Synthesis, 1984, 10322D. R. Kel

10、ly, M. Gingell, Chem. Ind.(London), 1991, 888Cbz-Cl很容易用苯甲醇同光氣的反應(yīng)來(lái)制備（見(jiàn)下式），在低溫下可以保存半年以上而不發(fā)生顯著的分解。除Cbz-Leu為油狀物外，絕大多數(shù)氨基酸的芐氧羰基衍生物都可以得到結(jié)晶。有的N-芐氧羰基氨基酸能同它的鈉鹽按一定比例形成共晶，共晶產(chǎn)物的熔點(diǎn)較高，并難溶于有機(jī)溶劑。例如，苯丙氨酸經(jīng)芐氧羰基化后再加酸析出Cbz-Phe時(shí)往往得到共晶產(chǎn)物（熔點(diǎn)144），此共晶產(chǎn)物用乙酸乙酯和1M HCl一道震搖時(shí)可完全轉(zhuǎn)化為Cbz-Phe而溶于乙酸乙酯中。因此。除Cbz-Gly以外，一般都是采用酸化后用有機(jī)溶劑提取的方法來(lái)得

11、到純的N-芐氧羰基氨基酸。2.1.1.1 游離氨基酸的Cbz保護(hù)示例Konda-Yamada, Yaeko; Okada, Chiharu et al., Tetrahedrom; 2002, 58(39), 7851-7865 Cbz-Cl (18.5 l, 0.155 mmol) in diethyl ether (0.2 ml) was dropped to a solution of (R)-1 (36.4 mg, 0.129 mmol) in 10% aqueous Na2CO3 (1.8 ml) at 0°C, and stirred for 5 h. The react

12、ion mixture was acidified with 10% citric acid, extracted with CHCl3 (10 mlX3). The organic layer was washed with water, dried over Na2SO4, evaporated to give light yellow gels, which were purified by preparative TLC (CHCl3/MeOH=5:1) to afford (R)-6 (25.7 mg, 47.1%) as yellow amorphous solid. Rf = 0

13、.87 (n-BuOH/AcOH/H2O=4:1:5); aD23 = -27.270 (c = 0.99, CHCl3);2.1.1.2 氨基酸酯的Cbz保護(hù)示例M. Carrasco, R. J. Jones, S. Kamel et a1., Org. Syn., 70, 29A 3-L, three-necked, Morton flask equipped with an efficient mechanical stirrer, thermometer, and a dropping funnel is charged with L-methionine methyl ester

14、hydrochloride 1 (117.6 g, 0.56 mol), potassium bicarbonate (282.3 g, 2.82 mol, 5 eq.), water (750 mL), and ether(750 mL), and the solution is cooled to 0°C. Benzyl chloroformate (105 g, 88.6 mL, 0.62 mol, 1.1 eq.) is added dropwise over 1 hr, the cooling bath is removed, and the solution is sti

15、rred for 5 hr. Glycine (8.5 g, 0.11 mol, 0.2 eq.) is added (to scavenge excess chloroformate) and the solution is stirred for an additional 18 hr. The organic layer is separated, and the aqueous layer is extracted with ether (2 × 200 mL). The combined organic layers are washed with 0.01 M hydro

16、chloric acid (2 × 500 mL), water (2 × 500 mL), and saturated brine (500 mL), and then dried (Na2SO4), filtered, and evaporated on a rotary evaporator. The resulting oil is further dried in a Kugelrohr oven (50°C, 0.1 mm, 12 hr) to leave product 2 as a clear oil that solidifies upon co

17、oling: 165166 g (9899%), mp 4243°C.2.1.1.3 氨基醇的Cbz保護(hù)示例(1)Clariana, Jaume; Santiago, G. G. et al Tetrahedron: Asymmetry, 2000, 11(22), 4549-4558Benzyl chloroformate (0.95 ml, 6.7 mmol) was added via syringe into a stirred mixture of aminoalcohol 7 (0.989 g, 5.1 mmol) and sodium carbonate (0.683

18、g, 6.4 mmol) in the solvent system water (10 ml)THF (3 ml) maintained at 0°C. The mixture was stirred at room temperature for 18 h (TLC monitoring) and then partitioned between dichloromethane and water. The organic phase was dried and evaporated to afford a white solid which was passed through

19、 a column of silica gel with hexanesethyl acetate (v:v 2:1) to afford the desired product (1.198 g, 72%), mp 125127°C.2.1.1.4氨基醇的Cbz保護(hù)示例(2)Inaba, Takashi; Yamada, Yasuki et al J. Org. Chem., 2000, 65(6), 1623-1628To a mixture of toluene (3.85 L), water (3.85 L), and K2CO3 (470 g, 3.40 mol) were

20、 successively added 1a (770 g, 2.72 mol) and CbzCl (488 g, 2.72 mol) with vigorous stirring at a temperature below 25 °C. After stirring at room temperature for 3 h, triethylamine (27.5 g, 270 mmol) and NaCl (578 g) were successively added, and the mixture was stirred for a further 30 min. The

21、organic layer was separated and concentrated to give the desired product as oil, which was used for the next reaction without purification. The analytical sample was prepared by column chromatography;2.1.2芐氧羰基的脫去 芐氧羰基的脫除主要有以下幾種方法：1). 催化氫解；2). 酸解裂解；3). Na/NH3（液）還原。 一般而言目前實(shí)驗(yàn)室常用簡(jiǎn)潔的方法就是催化氫解， 但當(dāng)分子中存在對(duì)催化氫

22、解敏感或鈍化的基團(tuán)時(shí)，我們就必須采用化學(xué)方法如酸解裂解或Na/NH3（液）還原等。 催化氫解如下式所示。催化氫解的供氫體可以是H2、環(huán)己二烯1, 2、1，4-環(huán)己二烯2、甲酸銨3和甲酸4-6等，以后四個(gè)為供氫體的反應(yīng)又叫催化轉(zhuǎn)氫反應(yīng)，通常這比催化氫化反應(yīng)更迅速。催化劑主要用5-10%的鈀-碳、10-20%的氫氧化鈀-碳或鈀-聚乙烯亞胺，鈀-聚乙烯亞胺/甲酸對(duì)于除去Cbz要比前兩者要好7。當(dāng)HBr/HOAc脫去Cbz保護(hù)基時(shí)，產(chǎn)物往往帶又一點(diǎn)顏色，而且分解產(chǎn)生的溴化芐會(huì)產(chǎn)生一些副反應(yīng)并難以除盡，而催化氫解多數(shù)能得到無(wú)色得產(chǎn)物。由于硫能使催化劑中毒，因此，含有胱氨酸、半胱氨酸等含硫的肽等N-芐氧羰

23、基氨基衍生物一般不用催化氫解法脫除。一般溶劑可以用甲醇，乙醇，乙酸乙酯， 四氫呋喃等，在醇類(lèi)質(zhì)子溶劑中反應(yīng)速度要快的多。1. G. Briefer, T. T. Nesftrick., Chem. Rew., 1974, 74, 5672. A. E. Jackson, R. A. Johnstone., Synthesis., 1976, 685; G. M. Anantharamaiah, K. M. Sivanandaiah., J. Chem. Soc., Perkin Trans. 1, 1977, 4903. M. Makowski, B. Rzeszotarska, L. Sme

24、lka et al., Liebigs Ann. Chem., 1985, 14574. D. R. Coleman, G. P. Royer., J. Org. Chem., 1980, 45, 22685. B. Eiamin, G. M. Anantharamaiah, G. P. Royer et al., J. Org. Chem., 1979, 44, 34426. M, J. O. Anteunis, C. Becu, F. Becu et al., Bull. Soc. Chim. Belg., 1987, 96, 7757. D. R. Coleman, G. P. Roye

25、r., J. Org. Chem., 1980, 45, 2268 D. R. Coleman, G. P. Royer., J. Org. Chem., 1980, 45, 2268如果在Boc2O存在下用Pd/C進(jìn)行氫化，則釋放出的胺直接轉(zhuǎn)變成Boc衍生物1。而且這類(lèi)反應(yīng)往往要比不加Boc2O來(lái)的快，其主要由于氫解出來(lái)的胺往往會(huì)與貴金屬有一定的絡(luò)合，使催化劑的活性降低，和Boc2O反應(yīng)為酰胺后則去除了這一效果。另外有時(shí)在氫解時(shí)加入適當(dāng)?shù)乃岽龠M(jìn)反應(yīng)也是一樣的道理，避免了生成的胺降低反應(yīng)的活性。1. M. Sakaitani, K. Hori, Y. Ohfune., Tetrahedron

26、Lett., 1988, 29, 2983另外當(dāng)分子中有鹵原子(Cl, Br, I)存在時(shí)，一般直接用Pd/C會(huì)造成脫鹵的發(fā)生，一般這種情況下，使用PdCl2為催化劑，以乙酸乙酯或二氯甲烷為溶劑可較好的避免脫鹵的發(fā)生。用MeOH/DMF為溶劑時(shí)，在Cbz-賴(lài)氨酸衍生物氫化的過(guò)程中會(huì)生成N-甲基化的賴(lài)氨酸1。使用氨為溶劑時(shí)，H2/Pd-C在-33下氫化，肽中的半胱氨酸或蛋氨酸單元不使催化劑毒化，此外，氨還會(huì)阻止BnO醚的還原，所以對(duì)Cbz可得到一些選擇性2-3。1. D. R. Coleman, G. P. Royer., J. Org. Chem., 1980, 45, 22682. J. P

27、. Mazaleyrat, J. Xie, M. Wakselman., Tetrahedron Lett., 1992, 33, 43013. N. L. Benoiton., Int. J. Pept. Petein Res., 1993, 41, 6112.1.2.1 5-10%的鈀-碳催化氫解示例C. Jaume; G. G. Santiago et al., Tetrahedron: Asymmetry, 2000, 11(22), 4549-4458A solution of (R)-8 (0.170 g, 0.52 mmol) in absolute methanol (3 ml

28、) was hydrogenated in the presence of 15% Pd/C (0.026 g) at room temperature for 12 h. The mixture was filtered (Celite) and washed with methanol. Then, perchloric acid (0.050 ml, 0.83 mmol) was added and the mixture was stirred for 5 min. The solvent was evaporated to afford (R)-7·HClO4, mp 23

29、3235°C; aD23=15.6 (c=0.68, methanol).2.1.2.2 5-10%的鈀-碳催化氫解示例B. Pierfrancesco; C. silvia et al., Tetrahedron, 1999, 55(10), 3025A solution of N-Cbz arylglycinol (17) (1.02 mmol) in MeOH (10 mL) was stirred for 15 min in the presence of an excess of Pd(OH)2/C under a dihydrogen atmosphere. The so

30、lution was then filtered on a Celite pad and the solvent removed in vaccuo. Purification of the crude afforded the desired free 2-arylglycinols (S)-21 in 87% yield, white solid; aD20=+47.0 (c=0.78, CHCl3); mp 94-96°C (AcOEt)。2.1.2.3 Pd/C-甲酸銨催化氫解示例Alargov, D. K; Naydenova, Z; Monatsh. Chem., 199

31、7, 128(6-7), 725-732576.6 mg of compound 1 (1 mmol) was dissolved in 20 ml of methanol. Then 150 mg of ammonium formate (3 mmol) and 75 mg of 10% Pd-C was added and the reaction mixture was stirred at room temperature 10 min and then heated to reflux for 45 min. The mixture was filtered through celi

32、te and the filtrate was evaporate to dryness to give 430 mg of compound 2 (98%). This compound was used without further purification in the subsequent step.2.1.2.4 Pd/C-甲酸催化氫解示例Fyles, T. M.; Zeng, B.; J. Org. Chem., 1998, 63(23), 8337-8345Compound 1 (0.6 g, 0.8 mmol) was dissolved in 1:1 formic acid

33、/methanol (60 mL) and added to a round-bottom flask (100 mL) containing 1 equiv of palladium catalyst (10% Pd/C, 1.0 g, 0.9 mmol). The mixture was continuously stirred under reflux temperature for 24 h. The catalyst was removed by filtration and washed with an additional 10 mL of methanol. The combi

34、ned solvents were removed by evaporation under reduced pressure to give Compound 2 (0.34 g, 81%, a white solid, mp 96-98 °C). This compound was used without further purification in the subsequent step.2.1.2.5 Pd/C催化氫解脫Cbz上Boc示例WO200409216610%Pd-C was addede to a solution of compound 1 (596 mg ,

35、 1.77 mmol) and (Boc)2O (773 mg, 3.54 mmol) in etnyl acetate (30 ml). The reation vessel was evacuated and back-filled with nitrogen (three times), then back-filled with hydrogen (1 atm). After 2 h, the mixture was filtered and concentrated. Purification by silica gel chromatography (30% ethyl aceta

36、te/ hexanes - 50% ethyl acetate/ hexanes) gave compound 2 (289 mg, 54%).2.1.2.6 PdCl2催化氫解脫除帶鹵原子分子上的Cbz示例US20030144297To a solution o compound 1 (900 mg) in methylene chloride (16.5 ml) was addede PdCl2 (30 mg) and triethylamine (0.229 ml). Triethyl silane was added (2 x 0.395 ml) over 2 h. The react

37、ion mixture stirred 1 h and 2 ml of trifluoroacetic acid was added. After 30 min the reaction was basified with 2 N NaOH, extracted with methylene chloride, dried over MgSO4, filtered and concentrated. Chromatography was run on a biotage 40S column with 3-5% MeOH/CH2Cl2 with 0.5% NH4OH to provide co

38、mpound 2 as a oil (501 mg, 74%).2.1.2.7 Pd黑催化氫解，用氨為溶劑,半胱氨酸的Cbz脫除示例Arthur M. Felix, Manuel H. Jimenz et a1., Org. Syn., 59, 159A dry 1-L three-necked, round-bottomed flask is equipped with a dry ice reflux condenser, a gas-inlet tube, and a magnetic stirring bar as illustrated in the figure. The reac

39、tion vessel is immersed in an acetonedry ice bath, and a total of 300 mL of ammonia is passed through a drying tower containing potassium hydroxide pellets and collected in the flask. The bath is removed to permit the reaction to proceed at the boiling point of ammonia (33), and a gentle stream of d

40、ry nitrogen is bubbled into the flask. A solution of 0.708 g (0.80250 mole) of N-benzyloxycarbonyl-L-methionine in 10 ml. of N,N-dimethylacetamide 1.02 g (1.40 ml., 0.0101 mole) of triethylamine and 1.25 g of freshly prepared palladium black are added. The nitrogen stream is discontinued and replace

41、d by a stream of hydrogen that has been passed through a concentrated sulfuric acid scrubber. The mixture is stirred under reflux for 5.5 hours to effect hydrogenolysis. The hydrogen stream is discontinued, a flow of nitrogen is resumed, and the dry ice is removed from the reflux condenser, permitti

42、ng rapid evaporation of ammonia. The flask is attached to a rotary evaporator, and the mixture is evaporated to dryness under reduced pressure. The residue is dissolved in water and filtered through a sintered funnel of medium porosity to remove the catalyst. The filtrate is evaporated to dryness, a

43、nd the residue (354 mg, 95%) is crystallized from waterethanol. The white crystalline product, after drying under reduced pressure at 25°, weighs 272305 mg. (7382%), m.p. 280282° (dec.), 25D +23.1° (c = 1, aqueous 5 N hydrochloric acid). 酸解脫除 氨基甲酸芐酯在強(qiáng)酸性條件下容易去保護(hù)。HBr/HOAc 是酸解脫除芐氧羰基的最常用的

44、試劑1。脫除反應(yīng)主要按下式進(jìn)行2。反應(yīng)需要消耗2分子的HBr，Cbz的脫除速度隨HBr濃度的增大而增大，因此實(shí)際上都是采用高濃度的過(guò)量HBr/HOAc溶液（1.2M-3.3M）以保證反應(yīng)的完全。 1. D. Ben-Ishai, A. Berger., J. Org. Chem., 1952, 17, 1564; R. A. Boissonnas, J. Blodinger, A. D. Welcher., J. Am. Chem. Soc., 1952, 74, 53092. R. A. Boissonnas, J. Blodinger, A. D. Welcher., J. Am. Che

45、m. Soc., 1952, 74, 5309; J. Meienhofer, E. Schnabel., Z. Naturforsch., 1965, 20b, 661含有絲氨酸1和蘇氨酸2的肽或其它含羥基的氨基衍生物用HBr/HOAc脫除Cbz時(shí)會(huì)發(fā)生羥基的O-乙?；磻?yīng)。雖然O-乙酰基能用堿皂化或氨解脫去，但為了避免這個(gè)副反應(yīng)，可以改用HBr/二氧六環(huán)或HBr/三氟乙酸來(lái)代替HBr/HOAc3。由于HBr在三氟乙酸中的溶解度較小，因此不能預(yù)先制成HBr/三氟乙酸溶液，而只能將保護(hù)的肽或氨基衍生物溶于無(wú)水三氟乙酸中，先于0下通入干燥的HBr，待Cbz大部分脫除后，再室溫通短時(shí)間以求完全脫除

46、變化基。Cbz被HBr分解產(chǎn)生的溴化芐能同肽中的某種氨基酸反應(yīng)，也是需要加以注意的。如，甲硫氨酸的硫原子能同溴化芐反應(yīng)生成S-芐基甲硫氨酸4，防止的辦法是加入硫醚（CH3SC2H5）為捕捉劑5。色氨酸被HBr/HOAc分解產(chǎn)生有色物質(zhì)，防止的辦法是加入亞磷酸二乙酯。硝基精氨酸會(huì)發(fā)生硝基的部分脫落，改用液體HBr于-67處理可以避免。1. G. D. Fasman, E. R. Blout., J. Am. Chem. Soc., 1960, 82, 22622. S. Fujiwara, S. Moerinaga, K. Narita., Bull. Chem. Soc. Japan., 19

47、62, 35, 4383. J. Meienhofer, E. Schnabel., Z. Naturforsch., 1965, 20b, 661; 黃惟德等，生物化學(xué)與生物物理學(xué)報(bào), 1961, 984. N. F. Albertson, F. C. Mckay., J. Am. Chem. Soc., 1953, 73, 53235. S. Guttmann, R. A. Boissonnas, Helv. Chim. Acta., 1959, 42, 1257用液體HF在0處理10-30分鐘即可將Cbz完全脫去1。FSO3H2、CH3SO3H2, 3、CF3SO3H3, 4和C6H5S

48、CH3-TFA5也是較好的試劑。Me3SiI在氯仿、乙腈中能于幾分鐘內(nèi)選擇性脫去Cbz和Boc保護(hù)基6。對(duì)于BBr3/CH2Cl2而言，較大分子的肽的Cbz衍生物可在TFA中去除，因?yàn)殡脑谒嶂械娜芙舛缺仍贑H2Cl2中大7。從肽中脫去Cbz，可在TFA中添加0.5 M 4-（甲硫基）苯酚8或使用HF/Me2S/對(duì)甲苯酚9（25:65:10,v/v）來(lái)抑制Bn+對(duì)芳香氨基酸的加成。1. S. Sakakibara et a1., Bull. Chem. Soc. Japan., 1967, 40, 2164; S. Matsuura, C. H. Niu, J. S. Cohen., J. Ch

49、em. Soc. Chem. Commun., 1976, 4512. H. Yajima, H. Ogawa, H. Sakurai., J. Chem. Soc. Chem. Commun., 1977, 9093. H. Yajima et a1., J. Chem. Soc. Chem. Commun., 1974, 1074. H. Yajima et a1., Chem. Pharm. Bull., 1975, 23, 11645. Y. Kiso, K. Ukawa, T. Akita., J. Chem. Soc. Chem. Commun., 1980, 1016. R. S

50、.Lott, V. S. Chauham, C. H. Stammer., J. Chem. Soc. Chem. Commun., 1979, 4957. J. Pless, W. Bauer., Angew Chem., Int. Ed. Engl., 1973, 12, 147; A. M. Felix., J. Org. Chem., 1974, 39, 14278. M. Bodanszky, A. Bodanszky., Int. J. Pept. Protein Res., 1984, 23, 2879. J. P. Tam, W. F. Heath, R. B. Merrifi

51、eld., J. Am. Chem. Soc., 1983, 105, 6442此外，已經(jīng)報(bào)道過(guò)的還有以下的一些不常用的方法。如HCl/CHCl31、HCl/HOAc2、HBr/SO23、液體HBr4、TosOH5、HI/HOAc6、碘化磷7、Et3SiH8、沸騰的TFA9、8M HCl的乙醇液或6 M HCl回流1小時(shí)10或濃鹽酸于25-75加熱處理1-1.5小時(shí)11等。1. G. D. Fasman, M. Idelson, E. R. Blout., J. Am. Chem. Soc., 1961, 83, 7092. R. B. Merrifield., J. Am. Chem. So

52、c., 1963, 85, 21493. M. Idelson, E. R. Blout., J. Am. Chem. Soc., 1958, 80, 46314. M. Brenner, H. C. Curtius., Helv. Chim. Acta., 1963, 46, 21265. E. Taschner, B. Liberek, Abstr. Int. Cong. Biochemistry, Vienna 19586. E. Waldschmidt-Leitz, K. Kuhn., Chem. Ber., 1951, 84, 3817. E. Brand, B. F. Erlang

53、er, H. Sachs., J. Am. Chem. Soc., 1952, 74, 18498. Birkofer et al., Angew. Chem., Int. Ed., 1965, 4, 4179. F. Weygand, W. Steglich., Z. Naturforsch., 1959, 14b, 47210. A.E. Barkdoll, W. F. Ross., J. Am. Chem. Soc., 1944, 66, 567; G. Chelucci, M. Falorni, G. Giacomelli., Synthesis., 1990, 112111. J.

54、White., J. Biol. Chem., 1934, 106, 1412.1.2.8 HBr-AcOH脫除Cbz示例B. Anna; P. Gerald., Heterocycles, 2002, 58, 521A solution of the amine Cbz compund (208 mg, 0.44 mmol) in 33 % hydrobromic acid in acetic acid (1 mL) and glacial acetic acid (0.6 mL) was stirred at rt for 3 h under an atmosphere of nitrog

55、en. The volatiles were removed in vacuo to leave the free amine hydrobromide (168 mg, 91 %) as a brown, highly hygroscopic powder; D =-18.0° (c = 0.4, EtOH); 2.1.2.9 TMSI脫除Cbz示例1US20040204397Me3SiI (0.73 ml, 0.73 mmol) was added to a soluton of compound 1 (146 mg, 0.33 mmol) in acetonitrile (10

56、 ml) at room temperature, and the resulting mixture was stirred at room temperature for 2 h. Et3N (0.12 ml) was added and the mixture was stirred at room temperature for 15 min. The solvents were removed in vacuo, and the residue was extracted with ethyl acetate. The combined organics were washed wi

57、th sodium bicarbonate and brine, dried over sodium sulfate and filtered. Solvents were removed and the residue was used directly in the next step.US200502030782.1 g (4.45 mmol) of compound 1 in 30 ml of CH2Cl2 were combined with 1.9 ml (13.4 mmol) Me3SiI and stirred for 16 h at room temperature. Then 20 ml of MeOH were a