C−H⋅⋅⋅O Hydrogen Bond Mediated Chain Reversal in a Peptide Containing a γ-Amino Acid Residue, Determined Directly from Powder X-ray Diffraction Data


  • We are grateful to the EPSRC, the University of Birmingham, Purdue Pharma, Wyeth Ayerst, and the Department of Biotechnology of the Government of India (under the Drug and Molecular Design Programme) for financial support.


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Similar to the classical β turn: An intramolecular cyclic 10-atom motif is defined in the molecular conformation of Piv-lPro-γ-Abu-NHMe (see powder X-ray diffraction structure; Piv: pivaloyl, Lpro: L-proline, γ-Abu: γ-aminobutyric acid) by a C−H⋅⋅⋅O interaction. This study emphasizes the considerable potential of powder X-ray diffraction as an alternative to single-crystal X-ray diffraction.