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Helical Structures of Bicyclic α ‐Amino Acid Homochiral Oligomers with the Stereogenic Centers at the Side‐Chain Fused‐Ring Junctions
Author(s) -
Anan Kosuke,
Demizu Yosuke,
Oba Makoto,
Kurihara Masaaki,
Doi Mitsunobu,
Suemune Hiroshi,
Tanaka Masakazu
Publication year - 2012
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201200403
Subject(s) - stereocenter , chemistry , tripeptide , bicyclic molecule , stereochemistry , enantiomer , ring (chemistry) , helix (gastropod) , crystallography , side chain , amino acid , enantioselective synthesis , ecology , biochemistry , polymer , organic chemistry , snail , biology , catalysis
Chiral bicyclic α ‐amino acid ( R , R )‐Ab 5,6= c with stereogenic centers at the γ ‐position of fused‐ring junctions, and its enantiomer ( S , S )‐Ab 5,6= c, were synthesized. The CD spectra of ( R , R )‐Ab 5,6= c oligomers indicated that the ( R , R )‐Ab 5,6= c hexapeptide formed a mixture of right‐handed ( P )‐ and left‐handed ( M )‐ 3 10 ‐helices, while, in the ( R , R )‐Ab 5,6= c nonapeptide, a right‐handed ( P )‐ 3 10 ‐helix slightly dominated over the ( M )‐helix. X‐Ray crystallographic analyses of ( S , S )‐tripeptide and ( R , R )‐hexapeptide revealed that both the tripeptide and hexapeptide formed a mixture of ( P )‐ and ( M )‐ 3 10 ‐helices, respectively. These results indicated that the side‐chain environments around the stereogenic centers are particularly important to control the helical‐screw handedness of foldamers.