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.
Full Article
Instrument
J-820
Keywords
Circular dichroism, Secondary structure, Cotton effect, Thermal stability, Chemical stability, Organic chemistry