Helical Structures of Bicyclic α‐Amino Acid Homochiral Oligomers with the Stereogenic Centers at the Side‐Chain Fused‐Ring Junctions |
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| Authors: | Kosuke Anan Yosuke Demizu Makoto Oba Masaaki Kurihara Mitsunobu Doi Hiroshi Suemune Masakazu Tanaka |
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| Institution: | 1. Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812‐8582, Japan;2. Division of Organic Chemistry, National Institute of Health Sciences, 1‐18‐1, Kamiyoga, Setagaya, Tokyo 158‐8501, Japan;3. Graduate School of Biomedical Sciences, Nagasaki University, 1‐14 Bunkyo‐machi, Nagasaki 852‐8521, Japan (phone/fax: +81‐95‐819‐2423);4. Osaka University of Pharmaceutical Sciences, Osaka 569‐1094, Japan |
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| Abstract: | Chiral bicyclic α‐amino acid (R,R)‐Ab5,6=c with stereogenic centers at the γ‐position of fused‐ring junctions, and its enantiomer (S,S)‐Ab5,6=c, were synthesized. The CD spectra of (R,R)‐Ab5,6=c oligomers indicated that the (R,R)‐Ab5,6=c hexapeptide formed a mixture of right‐handed (P)‐ and left‐handed (M)‐310‐helices, while, in the (R,R)‐Ab5,6=c nonapeptide, a right‐handed (P)‐310‐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)‐310‐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. |
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| Keywords: | Amino acids Oligomers homochiral Helical structures Foldamers |
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