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首页> 外文期刊>Chemistry: A European journal >Preferred 3D-structure of peptides rich in a severely conformationally restricted cyclopropane analogue of phenylalanine
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Preferred 3D-structure of peptides rich in a severely conformationally restricted cyclopropane analogue of phenylalanine

机译：富含严格构象受限的苯丙氨酸环丙烷类似物的肽的优选3D结构

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摘要

Terminally blocked, homopeptide amides of (R,R)-1-amino-2,3-diphenylcyclopropane-1-carboxylic acid (c(3)diPhe), a chiral member of the family of C-alpha-tetrasubstituted alpha-amino acids, from the dimer to the tetramer, and diastereomeric co-oligopeptides of (R,R)- or (S,S)-C(3)diPhe with (S)-alanine residues to the trimer level were prepared in solution and fully characterized. The synthetic effort was extended to terminally protected co-oligopeptide esters to the hexamer, where C(3)diPhe residues are combined with achiral alpha-aminoisobutyric acid residues. The preferred conformations of the peptides were assessed in solution by FT-IR absorption, NMR, and CD techniques, and for seven oligomers in the crystal state (by X-ray diffraction) as well. This study clearly indicates that CAPhe, a sterically demanding cyclopropane analogue of phenylalanine, tends to fold peptides into beta-turn and 3(10)- helix conformations. However, when C(3)diPhe is in combination with other chiral residues, the conformation preferred by the resulting peptides is also dictated by the chiral sequence of the amino acid building blocks. The (S,S)-enantiomer of this alpha-amino acid, unusually lacking asymmetry in the main chain, strongly favors the left-handedness of the turn/helical peptides formed.
机译：（R，R）-1-氨基-2,3-二苯基环丙烷-1-羧酸（c（3）diPhe），C-alpha-四取代的α-氨基酸家族的手性成员的末端封闭的同肽酰胺，从二聚体到四聚体，在溶液中制备了（R，R）-或（S，S）-C（3）diPhe与（S）-丙氨酸残基达到三聚体水平的非对映体共寡肽，并进行了充分表征。合成的努力扩展到末端保护的六聚体的共寡肽酯，其中C（3）diPhe残基与非手性α-氨基异丁酸残基结合。通过FT-IR吸收，NMR和CD技术在溶液中评估了肽的优选构象，并且还对了七种处于晶体状态的低聚物（通过X射线衍射）进行了评估。这项研究清楚地表明，CAPhe是苯丙氨酸的空间需求环丙烷类似物，它倾向于将肽折叠成β-turn和3（10）-螺旋构象。但是，当C（3）diPhe与其他手性残基结合时，所得肽优选的构象也由氨基酸构件的手性序列决定。这种α-氨基酸的（S，S）-对映异构体在主链中异常地缺乏对称性，强烈支持所形成的转/螺旋肽的左手性。

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