期刊
MACROMOLECULES
卷 43, 期 21, 页码 8813-8820出版社
AMER CHEMICAL SOC
DOI: 10.1021/ma1014726
关键词
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资金
- Shanghai Institute of Organic Chemistry
- National Science Council, Taipei
- National Taiwan University
- National Natural Science Foundation of China, Beijing
Upon complexation with protonated amino acids, one-handed helical polynorbornenes appended with monoaza-18-crown-6 (7a) are obtained. The cooperativity is observed as revealed by the sergeant soldier effect and the majority rule. When sterically hindered amino acids such as phenylalanine, isovaline or proline, esters of amino acids, and aminoalcohols are used, the Delta epsilon values in CD spectra are significantly reduced. The protonated ammonium ion may form complex with a crown ether moiety whereas the carboxylic acid may form hydrogen bonding with the adjacent crown ether pendant resulting in unidirectional orientation of the pendants leading to a helical scaffold. The corresponding dimer 10 with the same isotactic stereochemistry as that of polynorbornene 7a behaves similarly to exhibit bisignate CD curve upon treatment with protonated alanine. On the other hand, polynorbornene with monoaza-15-crown-5 (7b) does not exhibit any CD response under the same conditions.
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