Tyrosine-based poly(m-phenyleneethynylene-p-phenyleneethynylene)s. Helix folding and responsiveness to a base |
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Authors: | Ruiyuan Liu Masashi Shiotsuki Fumio Sanda |
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Affiliation: | a Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510, Japan b Faculty of Engineering, Department of Environmental and Biological Chemistry, Fukui University of Technology, 3-6-1 Gakuen, Fukui 910-8505, Japan |
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Abstract: | The Sonogashira-Hagihara polymerization of 3′,5′-diiodo-N-α-tert-butoxycarbonyl-l-tyrosine methyl ester (1) and 3′,5′-diiodo-N-α-tert-butoxycarbonyl-O-methyl-l-tyrosine methyl ester (2) with para-diethynylbenzene (3) was carried out to obtain optically active poly(m-phenyleneethynylene-p-phenyleneethynylene)s poly(1) and poly(2)] with Mn’s ranging from 9900 to 15,000 in 80-87% yields. Poly(1) exhibited intense CD signals in DMSO and THF, but did not in CH2Cl2, indicating that it took a predominantly one-handed helical conformation in the former two solvents. On the other hand, there was no evidence for poly(2) to take a helical structure in these solvents. Poly(1) turned the CD sign at 390 nm from plus to minus in DMSO/H2O = 9/1 (v/v) by the addition of NaOH. Alkaline hydrolysis of ester moieties of poly(1) and poly(2) gave the corresponding polymers having carboxy groups poly(1a) and poly(2a)]. Poly(1a) and poly(2a) increased the CD intensity by the addition of NaOH. |
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Keywords: | Amino acid Helix Poly(phenyleneethynylene) |
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