Engineering the Structure of an N-Terminal 尾-Turn To Maximize Screw-Sense Preference in Achiral Helical Peptide Chains

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• 作者：Matteo De Poli ; Liam Byrne ; Robert A. Brown ; Jordi Sol脿 ; Alejandro Castellanos ; Thomas Boddaert ; Romina Wechsel ; Jonathan D. Beadle ; Jonathan Clayden
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：May 16, 2014
• 年：2014
• 卷：79
• 期：10
• 页码：4659-4675
• 全文大小：656K
• 年卷期：v.79,no.10(May 16, 2014)
• ISSN：1520-6904

文摘

Oligomers of 伪-aminoisobutyric acid (Aib) are achiral peptides that typically adopt 3<sub>10sub> helical conformations in which enantiomeric left- and right-handed conformers are, necessarily, equally populated. Incorporating a single protected chiral residue at the N-terminus of the peptide leads to induction of a screw-sense preference in the helical chain, which may be quantified (in the form of 鈥渉elical excess鈥? by NMR spectroscopy. Variation of this residue and its N-terminal protecting group leads to the conclusion that maximal levels of screw-sense preference are induced by bulky chiral tertiary amino acids carrying amide protecting groups or by chiral quaternary amino acids carrying carbamate protecting groups. Tertiary <span class="smallcaps">lspan>-amino acids at the N-terminus of the oligomer induce a left-handed screw sense, while quaternary <span class="smallcaps">lspan>-amino acids induce a right-handed screw sense. A screw-sense preference may also be induced from the second position of the chain, weakly by tertiary amino acids, and much more powerfully by quaternary amino acids. In this position, the <span class="smallcaps">lspan> enantiomers of both families induce a right-handed screw sense. Maximal, and essentially quantitative, control is induced by an <span class="smallcaps">lspan>-伪-methylvaline residue at both positions 1 and 2 of the chain, carrying an N-terminal carbamate protecting group.