芐基（Bn）是也最穩(wěn)定的氨基保護(hù)基之一，同PMB一樣，對大多數(shù)反應(yīng)都是穩(wěn)定的，但比PMB更加穩(wěn)定，因而也更難脫除。酰胺的芐基，常規(guī)加氫方法不易脫除，可以通過Na/NH3脫除。
芐基（Bn）的引入
一般和PMB 一樣也采用C6H4CH2Br或C6H4CH2Cl和K2CO3、DIPEA、NaH、Et3N和n-BuLi在有機(jī)溶劑(如DMF、二氯甲烷和乙腈等)中反應(yīng)來引入，或C6H4CHO/NaBH4、NaBH3CN或NaBH(OAc)3還原胺化引入。
烷基化引入芐基(Bn)示例
J. Cossy; I.Pevet et al., Eur. J. Org. Chem., 2001, 15, 2841
AnhydrousK2CO3(500 mg, 3.62 mmol, 2.0 equiv.), n-Bu4NI (66 mg, 0.18mmol, 0.1 equiv.), and benzyl bromide (0.24 mL, 1.98 mmol, 1.1 equiv.) wereadded successively to a solution of compound 1 (500 mg, 1.81mmol) in CH3CN (5 mL). After 2 h at 35 - 40 °Cand overnight at room temperature, the reaction mixture was diluted with ether,filtered, and concentrated under reduced pressure. The crude material waspurified by flash chromatography (cyclohexane - AcOEt, 95:5 to 90:10) to give compound2 (0.54 g, 81%) as a colorless oil. [α]D20= +12.9 (c =1.99, CHCl3).
還原胺化引入芐基（Bn）示例
Rompaey, Karolien Van;Eynde, Isabelle Van den et al., Tetrahedron,2003, 59(24), 4421-4432
Compound 1 (0.5 g, 1.70 mmol) was dissolved in 1,2-dichloroethane(50 mL) and the aldehyde (0.122 g,1.70 mmol), Et3N (0.172 g,1.70 mmol), NaBH(OAc)3 (0.505 g,2.38 mmol) and MgSO4(30wt%) were added. The reaction was stirred at room temperature. RP-HPLCindicated reaction times between 2 and 4 h. The mixture was quenched with saturatedNaHCO3(50mL) and extracted with EtOAc (3 x 70 mL). The organiclayer was dried (MgSO4), filtered and evaporated to give compound 2, which were used without furtherpurification.
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