Related Experiment Video
Updated: Oct 20, 2025

Identification of Fatty Acids in Bacillus cereus
Published on: December 5, 2016
Detailed 1 H and 13 C NMR structural assignment of ent-polyalthic acid, a biologically active labdane diterpene
Pedro Y Kovatch1, Alexsandro E Ferreira1, Guilherme M L Ghizonni1
1Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, Universidade de Franca, Franca, São Paulo, Brazil.
Abstract:
In this paper, a complete 1 H and 13 C NMR data assignment of ent-polyalthic acid, a biologically active labdane-type diterpene, is presented. The assignments were carried on the basis of spectroscopic data from 1 H NMR, 13 C{1 H} NMR, gCOSY, gHMQC, and gHMBC experiments. Furthermore, a software-assisted methodology, using FOMSC3_rm_NB and NMR_MultSim programs, supported the detailed and unequivocal assignment of 1 H and 13 C signals, allowing all hydrogen coupling constants to be determined and thus clarifying all hydrogen signal multiplicities.
Related Concept Videos
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
NMR and Mass Spectroscopy of Carboxylic Acids
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the...
¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons
In chiral compounds such as 2-butanol, replacing the methylene hydrogens at C3 produces a pair of...
NMR Spectroscopy and Mass Spectrometry of Aldehydes and Ketones
UV–Vis Spectroscopy: Woodward–Fieser Rules
¹H NMR: Complex Splitting
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...

