Synthesis and Folding Propensity of Aliphatic Oligoureas Containing Repeats of Proline-Type Units

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• 作者：Juliette Fremaux ; Brice Kauffmann ; Gilles Guichard
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：June 20, 2014
• 年：2014
• 卷：79
• 期：12
• 页码：5494-5502
• 全文大小：436K
• 年卷期：v.79,no.12(June 20, 2014)
• ISSN：1520-6904

文摘

The synthesis and conformational analysis of aliphatic oligoureas containing multiple adjacent N-alkylated units derived from proline (i.e., Pro^u) are reported. The insertion of trisubstituted ureas in the main chain of N,N鈥?linked oligourea foldamers locally impairs the characteristic three centered-hydrogen bonding pattern associated with the formation of 2.5-helical structures. Three series of oligomers have been studied: one series in which the Pro^u repeat is flanked on both sides by canonical urea residues (e.g., oligomers 2鈥?b>6), one series with canonical residues on either side of the Pro^u repeat (oligomers 12 and 23), and one series consisting exclusively of Pro^u residues (oligomers 25 and 26). Spectroscopic (NMR and electronic circular dichroism) and X-ray diffraction studies reveal that the 2.5-helix formed by oligomers of N,N鈥?disubstituted ureas is robust enough to accommodate short oligopyrrolidine segments (Pro^u)_n (n < 7) that alone display no intrinsic folding propensity.