Sterically Hindered <i>C</i><sup>α</sup><sup>,</sup><sup>α</sup>-Disubstituted α-Amino Acids: Synthesis from α-Nitroacetate and Incorporation into Peptides
作者:Yanwen Fu、Lars G. J. Hammarström、Tod J. Miller、Frank R. Fronczek、Mark L. McLaughlin、Robert P. Hammer
DOI:10.1021/jo015809o
日期:2001.10.1
demanding C(alpha,alpha)-dibenzylglycine (Dbg) has been incorporated into a peptide using solid-phase synthesis. It was found that once sterically congested Dbg is at the peptide N-terminus, further chain extension becomes very difficult using uronium or phosphonium salts (PyAOP, PyAOP/HOAt, HATU). However, preformed amino acid symmetrical anhydride couples to N-terminal Dbg in almost quantitative yield
描述了通过硝基乙酸乙酯的烷基化制备位阻和多官能的Cα-α-二取代的α-氨基酸(ααAA),并转化成可掺入肽的衍生物的方法。在催化量的四烷基铵盐存在下,用N,N-二异丙基乙基胺(DIEA)处理硝基乙酸乙酯,然后加入活化的烷基卤化物或Michael受体,以良好的产率获得了双C烷基化产物。在阮内镍上用锌在乙酸或氢中进行选择性的硝基还原,得到相应的氨基酯,在皂化后,可用芴基甲氧羰基(Fmoc)保护。正交保护的天冬氨酸四官能C(α,α)-二取代类似物的第一次合成,描述了2-双(叔丁基羧甲基)甘氨酸(Bcmg)。而且,已经使用固相合成将空间上需要的Cα-α-二苄基甘氨酸(Dbg)掺入肽中。已经发现,一旦Dbg在空间上处于肽N-末端,使用铀盐或phospho盐(PyAOP,PyAOP / HOAt,HATU)进一步的链延伸变得非常困难。然而,在非极性溶剂(二氯乙烷-DMF,9:1)中,预先形成的氨基酸对