The first abiotic foldamer tertiary structures have been recently reported in the form of aromatic helix-turn-helix motifs based on oligo-quinolinecarboxamides held together by intramolecular hydrogen bonds. Tertiary folds were predicted...
A palladium-catalyzed α-arylation of cyclic vinylogous esters to form products that are converted in one step to γ-alkyl-γ-aryl-substituted cyclohexenones is reported. This Pd-catalyzed reaction proceeds at room temperature, is generally high-yielding, and uses an amount of a commercially available catalyst as low as 0.25 mol %. The scope of aryl bromides is particularly broad, and alkenyl bromides can also be used. This two-step protocol, comprising α-arylation and reductive transposition, can be performed in one pot and is applicable to gram-scale synthesis.
Aromatic oligoamide sequences programmed to fold into stable helical conformations were designed to display a linear array of hydrogen‐bond donors and acceptors at their surface. Sequences were prepared by solid‐phase synthesis. Solution 1H NMR spectroscopic studies and solid‐state crystallographic structures demonstrated the formation of stable hydrogen‐bond‐mediated dimeric helix bundles that could be either heterochiral (with a P and an M helix) or homochiral (with two P or two M helices). Formation of the hetero‐ or homochiral dimers could be driven quantitatively using different chlorinated solvents—exemplifying a remarkable case of either social or narcissistic chiral self‐sorting or upon imposing absolute handedness to the helices to forbid PM species.
Helically folded oligoamides of 8-amino-2-quinolinecarboxylic acid composed of up to 41 units were prepared using optimized manual solid-phase synthesis (SPS). The high yield and purity of the final products places these SPS protocols among the most efficient known to date. Furthermore, analytical methods allowing for the clear identification and purity assessment of the products were validated, including 1 H NMR, a seldom used method for such large molecules. Adaption of the SPS protocols, in particular using in situ acid chloride activation under Appel's conditions, made it possible to efficiently implement SPS on a commercial peptide synthesizer, leading to a dramatic reduction of the laboratory work required to produce long sequences. Automation constitutes a breakthrough for the development of helical aromatic oligoamide foldamers.
Four helically folded aromatic oligoamide sequences containing either a chiral monomer based on 2-(2-aminophenoxy)-propionic acid, an N-terminal (1H)-camphanyl group, or both, were synthesized. Spectroscopic solution investigations using 1H NMR and...
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