已经研究了在其骨架中由脲类单元组成的中性螺旋折叠剂的阴离子结合性能。1周在各种有机溶剂包括DMSO 1 H NMR滴定的研究表明,脂族oligoureas和阴离子之间的相互作用(CH 3 COO -,H 2 PO 4 - ,氯- )是位点特异性的,因为它在很大程度上涉及位于尿素NHS螺旋的末端(螺旋的正极),不参与螺旋分子内氢键网络。这种结合方式与蛋白质类似,这种结合方式通常在α螺旋的N端发现阴离子结合位点。1个1 H NMR研究表明,即使在阴离子过量的情况下,寡聚体的螺旋在阴离子结合后仍保持大部分折叠。这项研究指出了寡聚螺旋体对小客体分子的选择性识别的潜在有用应用。
Effective Preparation of O-Succinimidyl-2- (tert-butoxycarbonylamino)ethylcarbamate Derivatives from β-Amino Acids. Application to the Synthesis of Urea-Containing Pseudopeptides and Oligoureas
progress has been made toward the development of metal-free catalysts of enantioselective transformations, yet the discovery of organic catalysts effective at low catalyst loadings remains a major challenge. Here we report a novel synergistic catalyst combination system consisting of a peptide-inspired chiral helical (thio)urea oligomer and a simple tertiary amine that is able to promote the Michael reaction
an isoatomic and isostructural γ-aminoacid. The approach was extended to solid-phase techniques to accelerate the synthesis of longer and more functionalized sequences. Under optimized conditions, an octamer hybrid oligomer incorporating a central guanidinium linkage was obtained in good overall yield and purity. This work also reports data related to the structural consequences of urea by guanidinium
One fold to rule them all: New heterogeneous aliphatic backbonefoldamers belonging to the γ‐peptide superfamily and containing various combinations of urea/amide (U/A) and urea/carbamate (U/C) units are reported. Structural studies at atomic resolution reveal hydrogen‐bonded helical structures akin to that formed by cognate Un homooligomers.
Caught in a fold: A simple and efficient coupling strategy to make aliphaticoligoureafoldamers is reported. Crystal structures show that the pyrrolidine units (red; see picture) do not impair the 2.5‐helical folding of the oligoureas. This modular strategy enables assembly of long helical segments containing non‐adjacent pyrrolidine units as exemplified by the synthesis of a helix that is approximately
Inducing achiral aliphatic oligoureas to fold into helical conformations
作者:Romina Wechsel、Julien Maury、Juliette Fremaux、Scott P. France、Gilles Guichard、Jonathan Clayden
DOI:10.1039/c4cc06754a
日期:——
The ability of urea-linked oligomers of achiral diamines (achiral analogues of the well-established chiral oligourea foldamers) to adopt helical conformations was explored spectroscopically. Up to four achiral units were ligated either to a well-formed helical trimer or to a single chiral diamine, and the extent to which they adopted a screw-sense preference was determined by NMR and CD. In the best performing cases, a trimeric chiral oligourea and even a single cis-cyclohexanediamine monomer induced folding into a helical conformation.