Identification of Absolute Helical Structures of Aromatic Multilayered Oligo(m-phenylurea)s in Solution

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• 作者：Mayumi Kudo ; Takayuki Hanashima ; Atsuya Muranaka ; Hisako Sato ; Masanobu Uchiyama ; Isao Azumaya ; Tomoya Hirano ; Hiroyuki Kagechika ; Aya Tanatani
• 刊名：Journal of Organic Chemistry
• 出版年：2009
• 出版时间：November 6, 2009
• 年：2009
• 卷：74
• 期：21
• 页码：8154-8163
• 全文大小：1027K
• 年卷期：v.74,no.21(November 6, 2009)
• ISSN：1520-6904

文摘

The oligomeric aromatic ureas bearing N,N′-dimethylated urea bonds such as 3 have aromatic multilayered structure, based on the (cis,cis)-urea structure, and also have dynamic helical structure (all-R or all-S axis chirality) when the benzene rings are connected at the meta positions. The absolute helical structure of oligo(m-phenylurea)s were identified by the empirical and theoretical studies on the CD and vibrational CD (VCD) spectra. Thus, each enantiomer of the oligo(m-phenylurea)s 4 bearing a chiral N-2-(methoxyethoxyethoxy)propyl group were synthesized. Intense dispersion-type CD spectra of 4 were observed, which indicated the induction of handedness in the helical structure. In the VCD spectra of 4 in the film state, the signals due to the carbonyl and aromatic ring vibrations were seen with negative and positive values for compounds 4a and 4b, respectively. The calculations of both CD and VCD spectra of oligo(m-phenylurea)s 3 without any chiral N-substituent gave the same assignment about the axis chirality of 4. Thus, the absolute configurations of 4a and 4b are all-R and all-S structures, respectively.