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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
Author(s) -
Berger Gilles,
VilchisReyes Miguel,
Hanessian Stephen
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201506208
Subject(s) - polyproline helix , proline , chemistry , circular dichroism , tetramer , stereochemistry , oligomer , folding (dsp implementation) , crystallography , imino acid , molecule , amide , amino acid , peptide , biochemistry , organic chemistry , electrical engineering , enzyme , engineering
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.