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Structural Characterization of Peptide Oligomers Containing (1 R ,2 S )‐2‐Aminocyclohexanecarboxylic Acid ( cis ‐ACHC)
Author(s) -
Choi Soo Hyuk,
Ivancic Monika,
Guzei Ilia A.,
Gellman Samuel H.
Publication year - 2013
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201300118
Subject(s) - chemistry , oligomer , dimer , tetramer , stereochemistry , diastereomer , hydrogen bond , foldamer , peptide , amino acid , cis–trans isomerism , crystallography , molecule , organic chemistry , enzyme , biochemistry
(1 R ,2 S )‐2‐Aminocyclohexanecarboxylic acid ( cis ‐ACHC) is a preorganized β‐amino acid. cis ‐ACHC favors two conformations that feature gauche conformations about the C α –C β bond with torsion angles of opposite signs. The diastereomeric β‐amino acid trans ‐ACHC has been widely studied as a foldamer building block, but cis ‐ACHC has received less attention in this regard. We examined the conformational behaviour of three types of oligomer: (1) homooligomers of cis ‐ACHC, (2) β‐peptides in which cis ‐ACHC and β 3 h‐Ala alternate, and (3) 1:1 α/β‐peptides in which cis ‐ACHC and Ala alternate. Two‐dimensional NMR experiments suggest that all three types of oligomer adopt extended conformations rather than folded conformations in solution. Two crystal structures of oligomers that contain cis ‐ACHC residues, a cis ‐ACHC dimer and an α/β‐peptide tetramer, show extended conformations in which the cis ‐ACHC residues contain six‐membered‐ring C=O ··· H–N hydrogen bonds.