Carbamate is an emerging class of a polymer backbone
for constructing
sequence-defined, abiotic polymers. It is expected that new functional
materials can be de novo designed by controlling
the primary polycarbamate sequence. While amino acids have been actively
studied as building blocks for protein folding and peptide self-assembly,
carbamates have not been widely investigated from this perspective.
Here, we combined infrared (IR), vibrational circular dichroism (VCD),
and nuclear magnetic resonance (NMR) spectroscopy with density functional
theory (DFT) calculations to understand the conformation of carbamate
monomer units in a nonpolar, aprotic environment (chloroform). Compared
with amino acid building blocks, carbamates are more rigid, presumably
due to the extended delocalization of π-electrons on the backbones. Cis configurations of the amide bond can be energetically
stable in carbamates, whereas peptides often assume trans configurations at low energies. This study lays an essential foundation
for future developments of carbamate-based sequence-defined polymer
material design.