作者:Liam Byrne、Jordi Solà、Thomas Boddaert、Tommaso Marcelli、Ralph W. Adams、Gareth A. Morris、Jonathan Clayden
DOI:10.1002/anie.201308264
日期:2014.1.3
An N‐terminal L‐α‐methylvaline dimer induces complete conformational control over the screwsense of an otherwise achiral helical peptide foldamer formed from the achiral quaternary amino acids Aib and Ac6c. The persistent right‐handed screw‐sense preference of the helix enables remote reactive sites to fall under the influence of the terminal chiral residues, and permits diastereoselective reactions
Engineering the Structure of an N-Terminal β-Turn To Maximize Screw-Sense Preference in Achiral Helical Peptide Chains
作者:Matteo De Poli、Liam Byrne、Robert A. Brown、Jordi Solà、Alejandro Castellanos、Thomas Boddaert、Romina Wechsel、Jonathan D. Beadle、Jonathan Clayden
DOI:10.1021/jo500714b
日期:2014.5.16
preference are induced by bulky chiral tertiary amino acids carrying amide protecting groups or by chiral quaternary amino acids carrying carbamate protecting groups. Tertiary l-amino acids at the N-terminus of the oligomer induce a left-handed screwsense, while quaternary l-amino acids induce a right-handed screwsense. A screw-sense preference may also be induced from the second position of the chain
Measuring Screw-Sense Preference in a Helical Oligomer by Comparison of <sup>13</sup>C NMR Signal Separation at Slow and Fast Exchange
作者:Jordi Solà、Gareth A. Morris、Jonathan Clayden
DOI:10.1021/ja1097034
日期:2011.3.23
While an unequal population of rapidly inter-converting left- and right-handed conformers of a helical oligomer can be detected by circular dichroism, precise quantification of a conformer ratio has not previously been achieved. We demonstrate, using a set of labeled peptide analogues, that simple analysis of peak separation in their C-13 NMR spectra at slow and fast exchange allows an accurate value for the ratio of helical conformers to be obtained. The method reports the ratio of conformers at the site of the label and can therefore be used to investigate local variations in helical conformational control.
Duality of Mechanism in the Tetramethylfluoroformamidinium Hexafluorophosphate-Mediated Synthesis of <i>N</i>-Benzyloxycarbonylamino Acid Fluorides
作者:Roberto Fiammengo、Giulia Licini、Alessia Nicotra、Giorgio Modena、Lucia Pasquato、Paolo Scrimin、Quirinus B. Broxterman、Bernard Kaptein
DOI:10.1021/jo0009393
日期:2001.8.1
Nitroxyl Peptides as Catalysts of Enantioselective Oxidations
作者:Fernando Formaggio、Marcella Bonchio、Marco Crisma、Cristina Peggion、Stefano Mezzato、Alessandra Polese、Alessandra Barazza、Sabrina Antonello、Flavio Maran、Quirinus B. Broxterman、Bernard Kaptein、Johan Kamphuis、Rosa Maria Vitale、Michele Saviano、Ettore Benedetti、Claudio Toniolo
The achiral, nitroxyl-containing a-amino acid TOAC (TOAC 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), in combination with the chiral alpha-amino acid C-alpha-methyl valine [(alphaMe)Val]. was used to prepare short peptides (from di- to hexa-) that induced the enantioselective oxidation of racemic I-phenylethanol to acetophenone. The best catalyst was an N-alpha-acylated dipeptide alkylamide with the -TOAC-(alphaMe)Val- sequence folded in a stable, intramolecularly hydrogen-bonded beta-turn conformation with large. lipophilic (hydrophobic) N- and C-terminal blocking groups. We rationalized our findings by proposing models for the diastereomeric intermediates between (R)-[and (S)]-1-phenylethanol and the catalyst Fmoc-TOAC-L(alphaMe)Val-NHiPr, based on the X-ray diffraction structure of the latter.