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.
- 1Department of Chemistry, Université de Montréal, Station Centre-Ville, C.P. 6128, Montreal, QC, H3C 3J7 (Canada) 2Faculty of Pharmacy, Laboratory of Pharmaceutical Chemistry, Université Libre de Bruxelles, Campus Plaine CP205/5, Université Libre de Bruxelles, Bd du Triomphe, 1050 Brussels (Belgium) 3Department of Chemistry, Université de Montréal, Station Centre-Ville, C.P. 6128, Montreal, QC, H3C 3J7 (Canada)
http://onlinelibrary.wiley.com/doi/10.1002/anie.201506208/abstract
http://onlinelibrary.wiley.com/doi/10.1002/anie.201506208/epdf
http://onlinelibrary.wiley.com/doi/10.1002/anie.201506208/epdf
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 nπ* stabilization of the trans-amide conformation.
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