Solution State Conformational Preferences of Dipeptides Derived from <i>N</i>-Aminoazetidinecarboxylic Acid: An Assessment of the Hydrazino Turn
作者:Amandine Altmayer-Henzien、Valérie Declerck、Denis Merlet、Jean-Pierre Baltaze、Jonathan Farjon、Régis Guillot、David J. Aitken
DOI:10.1021/jo400736t
日期:2013.6.21
Four model compounds and four dipeptides containing N-aminoazetidinecarboxylic acid (AAzC) and a particular stereoisomer of 2-aminocyclobutanecarboxylic acid (ACBC) were studied to establish their solution state conformational preferences, particularly regarding the ability of AAzC to induce a three-center hydrogen-bonded folding feature known as a “hydrazino turn”. On the basis of IR and NMR experiments
研究了包含N-氨基氮杂环丁烷羧酸(AAzC)和2-氨基环丁烷羧酸的特定立体异构体(ACBC)的四种模型化合物和四种二肽,以建立它们的溶液状态构象偏好,尤其是关于AazC诱导三中心氢原子的能力。粘合折叠功能,称为“水润弯头”。在红外和核磁共振实验的基础上,在分子模拟的支持下,在所有情况下,AAzC残基均采用在溶液中形成环状八元氢键构象的反式构型。通过精制的1 H– 15证明了AazC的杂环氮原子在反式结构中的含义。N HMBC实验给出了自然15 N同位素丰度下的可利用数据,为溶液状态肼基转弯构象提供了空前的证据。该二级结构特征的优势取决于二肽中相邻ACBC残基的构型:虽然反式-ACBC衍生物偏向肼基肼,但顺式-ACBC衍生物也可能构成低能10元氢键结合的环结构。三种化合物的X射线衍射分析证实,在两种情况下均存在固态肼基肼的拐角,其几何形状与从溶液状态研究得出的几何形状相似,但在第三种化合物中,没有分子内氢键的迹象。