A complete 1H and 13C NMR analysis for a group of four sesquiterpene lactones isolated from Eremanthus elaeagnus (Asteraceae) is described in this work. 1H NMR, 13C {1H} NMR, gCOSY, gHMQC, and gHMBC experiments were performed to provide sufficient structural information to allow an unequivocal assignment. All hydrogen coupling constants were measured, clarifying all hydrogen signal multiplicities.
In this paper, a complete 1H and 13C 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 1H NMR, 13C{1H} 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 1H and 13C signals, allowing all hydrogen coupling constants to be determined and thus clarifying all hydrogen signal multiplicities.
A set of seven diterpenes, three kauranes and four trachylobanes, isolated from the African plant Psiadia punctulata were assayed against Mycobacterium tuberculosis and reached activity comparable with cycloserine, a second line drug used to treat tuberculosis (TB). Several structural properties of those diterpenes, such as lipophilicity, HOMO and LUMO energies, charge density, and intramolecular hydrogen bond (IHB) formation, were obtained by theoretical calculations and compared with their activities. Peculiar correlations were observed, especially between activity, lipophilicity and IHB formation.
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