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Peptoid Atropisomers

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posted on 20.07.2011, 00:00 by Bishwajit Paul, Glenn L. Butterfoss, Mikki G. Boswell, P. Douglas Renfrew, Fanny G. Yeung, Neel H. Shah, Christian Wolf, Richard Bonneau, Kent Kirshenbaum
We report the isolation of N-aryl peptoid oligomers that adopt chiral folds, despite the absence of chiral centers. Peptoid monomers incorporating ortho-substituted N-aryl side chains are identified that exhibit axial chirality. We observe significant energy barriers to rotation about the stereogenic carbon–nitrogen bond, allowing chromatographic purification of stable atropisomeric forms. We study the atropisomerism of N-aryl peptoid oligomers by computational modeling, NMR, X-ray crystallography, dynamic HPLC, and circular dichroism. The results demonstrate a new approach to promote the conformational ordering of this important class of foldamer compounds.