Synthesis and Conformational Analysis of Alternately N-Alkylated Aromatic Amide Oligomers

April 9, 2019

Title

Synthesis and Conformational Analysis of Alternately N-Alkylated Aromatic Amide Oligomers

Author

Ko Urushibara, Hyuma Masu, Hirotoshi Mori, Isao Azumaya, Tomoya Hirano, Hiroyuki Kagechika, Aya Tanatani

Year

2018

Journal

The Journal of Organic Chemistry

Abstract

Alternately N-alkylated aromatic amides such as 1 to 3 bearing various side chains were designed and synthesized as novel helical foldamers. The CD spectra of oligomers with chiral side chains showed a positive Cotton effect, which indicates that these oligomers take helical conformations in solution. The CD intensity gradually increased with increasing chain-length, and pentamer 3d showed remarkably strong CD signals in chloroform. The absorption maxima of the UV spectra were increasingly red-shifted with increasing chain length, in contrast to the case of poly(p-N-alkylbenzamide)s. Structure optimization of the oligomers based on the crystal structure of 1a as the monomer unit supported the formation of helical structure with a large cavity, and also suggested intramolecular hydrogen bond formation between secondary amides. The results of calculation were consistent with the observed spectroscopic features.

Instrument

V-650

Keywords

Organic chemistry, Chemical stability, Biochemistry