Understanding the NMR properties and conformational behavior of indole vs. azaindole group in protoberberines: NICS and NCS analysis

► Conformational behavior characterized by NMR spectroscopy and DFT calculations. ► Role of nitrogen atom on the NMR chemical shifts. ► Differences in the NMR chemical shifts rationalized by using DFT calculations. ► Nucleus-independent chemical shifts and natural chemical shifts calculated and analyzed. ► Differences in NMR properties between indole and azaindole.