Short peptides containing C
α,α
-dipropylglycine (Dpg) at alternating sequence positions were synthesized and examined for conformational behavior. Peptide assembly was performed using Fmoc-solid-phase chemistry where the coupling with PyAOP could be significantly enhanced at elevated temperature. Circular dichroism (CD) and NMR conformational studies revealed that incorporation of Dpg residues induced folded structures into peptides. It was observed that Dpg residues adopted helical conformation in a helix-promoting sequence. The resulting helical structure was comprised of consecutive β-turns whose structure was stabilized by salt bridge in aqueous solution.
In this study, the preparation of sterically and polyfunctional C
α,α
-disubstituted amino acids (ααAAs) via alkylation of ethyl nitroacetate and transformation into derivatives ready for incorporation into peptides are described. Treatment of ethyl nitroacetate with N,N-diisopropylethylamine in the presence of a catalytic amount of tetraalkylammonium salt, followed by the addition of an activated alkyl halide or Michael acceptor, gave the doubly C-alkylated product in good to excellent yields. Selective nitro reduction with Zn in acetic or hydrogen over Raney Ni gave the corresponding amino ester that, upon saponification, can be protected with the fluorenylmethyloxycarbonyl (Fmoc) group. The synthesis of a sterically demanding C
α,α
-dibenzylglycine (Dbzg), and an orthogonally protected, tetrafunctional C
α,α
-disubstituted analogue of aspartic acid Bcmg is described.
The preparation of amyloid fibril blocker peptides based on amyloid peptide hydrophobic core Aβ
16-20
is described. These blocker peptides containing sterically
含有Cα,α-二丙基甘
氨酸(Dpg)的短肽序列被合成并检测其构象行为。肽组装使用Fmoc固相
化学方法进行,其中与
PyAOP的偶联可以在升高的温度下显著增强。圆二色性(CD)和NMR构象研究表明,Dpg残基的引入使肽中产生了折叠结构。观察到Dpg残基在螺旋促进序列中采用螺旋构象。所得到的螺旋结构由连续的β-转角组成,在
水溶液中由盐桥稳定其结构。本研究介绍了通过乙基
硝酸酯的烷基化和转化成准备好用于肽中的衍
生物来制备立体和多功能的Cα,α-二取代
氨基酸(αα
AAs)的方法。在四烷基
铵盐的催化下,将乙基
硝酸酯与N,N-
二异丙基乙基胺反应,然后加入活化的烷基卤或迈克尔受体,以良好至优良的收率得到双重C-烷基化产物。在
乙酸或Raney Ni的氢中,用Zn选择性还原硝基,得到相应的
氨基酸酯,经皂化后可以用
芴甲氧羰基(Fmoc)基团保护。介绍了一种立体要求高的Cα,α-二苄基甘
氨酸(Dbzg)和一个正交保护的、四功能的Cα,α-二取代
天冬氨酸类似物Bcmg的合成方法。介绍了基于淀粉样蛋白肽疏
水核心Aβ16-20的淀粉样纤维阻滞肽的制备方法。这些阻滞肽含有立体的残基,可以阻止淀粉样纤维的形成。