Volume 54, Issue 45 pp. 13268-13272
Communication

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

Dr. Gilles Berger

Dr. Gilles Berger

Department of Chemistry, Université de Montréal, Station Centre-Ville, C.P. 6128, Montreal, QC, H3C 3J7 (Canada)

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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Dr. Miguel Vilchis-Reyes

Dr. Miguel Vilchis-Reyes

Department of Chemistry, Université de Montréal, Station Centre-Ville, C.P. 6128, Montreal, QC, H3C 3J7 (Canada)

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Prof. Dr. Stephen Hanessian

Corresponding Author

Prof. Dr. Stephen Hanessian

Department of Chemistry, Université de Montréal, Station Centre-Ville, C.P. 6128, Montreal, QC, H3C 3J7 (Canada)

Department of Chemistry, Université de Montréal, Station Centre-Ville, C.P. 6128, Montreal, QC, H3C 3J7 (Canada)Search for more papers by this author
First published: 08 September 2015
Citations: 25

Graphical Abstract

A crystalline PPII-type helical tetramer formed of cis-4,5-methano-L-proline is presented. X-ray diffraction and circular dichroism together with theoretical results highlight the differential behavior of cis- and trans-4,5-methano-L-proline oligomers. These proline methanologues could be incorporated in drugs and peptides as proline mimics with structurally tweaked properties.

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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