Structural Properties and Stereochemically Distinct Folding Preferences of 4,5‐cis and trans‐Methano‐L‐Proline Oligomers: The Shortest Crystalline PPII‐Type Helical Proline‐Derived Tetramer |
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| Authors: | Dr Gilles Berger Dr Miguel Vilchis‐Reyes Prof?Dr Stephen Hanessian |
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| Affiliation: | 1. Department of Chemistry, Université de Montréal, Station Centre‐Ville, C.P. 6128, Montreal, QC, H3C 3J7 (Canada);2. Faculty of Pharmacy, Laboratory of Pharmaceutical Chemistry, Université Libre de Bruxelles, Campus Plaine CP205/5, Université Libre de Bruxelles, Bd du Triomphe, 1050 Brussels (Belgium) |
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| Abstract: | The synthesis, structural properties, and folding patterns of a series of L ‐proline methanologues represented by cis‐ and trans‐4,5‐methano‐L ‐proline amides and their oligomers are reported as revealed by X‐ray crystallography, circular dichroism measurements, and DFT calculations. We disclose the first example of a crystalline tetrameric proline congener to exhibit a polyproline II helical conformation. Experimental evidence of PPII‐type helical arrangement (both in solution and in the solid state) of cis‐4,5‐methano‐L ‐proline oligomers is supported by theoretical calculations reflecting the extent of n→π* stabilization of the trans‐amide conformation. |
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| Keywords: | circular dichroism methanoproline natural bond orbitals polyproline |
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