Diastereomeric Right‐ and Left‐Handed Helical Structures with Fourteen (R)‐Chiral Centers. Issue 72 (4th December 2017)

• Record Type: Journal Article
• Authors: Eto, Ryo; Oba, Makoto; Ueda, Atsushi; Uku, Tsubasa; Doi, Mitsunobu; Matsuo, Yosuke; Tanaka, Takashi; Demizu, Yosuke; Kurihara, Masaaki; Tanaka, Masakazu
• Is Part Of: Chemistry. Volume 23:Issue 72(2017)
• Page Start: 18120
• Page End: 18124
• Publication Date: 2017-12-04
• Subjects: amino acids -- chirality -- conformation analysis -- foldamers -- helical structures; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201705306
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The relationship between chiral centers and the helical‐screw control of their peptides has already been reported, but it has yet to be elucidated in detail. A chiral four‐membered ring α, α‐disubstituted α‐amino acid with a ( R, R )‐butane‐2, 3‐diol acetal moiety at the γ‐position, but no α‐chiral carbon, was synthesized. X‐ray crystallographic analysis unambiguously revealed that its homo‐chiral heptapeptide formed right‐handed ( P ) and left‐handed ( M ) 310 ‐helical structures at a ratio of 1:1. They appeared to be enantiomeric at the peptide backbone, but diastereomeric with fourteen ( R )‐configuration chiral centers. Conformational analyses of homopeptides in solution also indicated that diastereomeric ( P ) and ( M ) helices existed at approximately equal amounts, with a slight preference toward right‐handedness, and they quickly interchanged at room temperature. The circumstances of chiral centers are important for the control of their helical‐screw direction. Abstract : Do the twist : The relationship between the right‐handed ( P ) and left‐handed ( M ) helices of the ( R, R )‐Ac4 c 3BD heptapeptide appears to be enantiomeric at the peptide backbone. However, these helices are diastereomeric because both helices have fourteen ( R )‐configuration chiral centers.