Software-assisted methodology for complete assignment of 1H and 13C NMR data of poorly functionalized molecules: The case of the chemical marker diterpene ent‑copalic acid.

Abstract

This work describes a methodology for the complete assignment of 1H and 13C NMR data of poorly functionalized molecules through spectral simulations conducted with computer programs available for free. We have been able to achieve the complete assignment, including the clarification of multiplicities and the determination of all the hydrogen homonuclear coupling constants, which is not common for poorly functionalized compounds. We have performed 1H NMR, 13C{1H} NMR, DEPT-135, gCOSY, gHSQC, gHMBC, NOESY, and J-resolved experiments and obtained the required dataset for the complete and unequivocal assignment of the spectra of ent‑copalic acid.