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.
Subject(s)
Diterpenes , Protons , Carbon Isotopes/chemistry , Diterpenes/chemistry , Magnetic Resonance Spectroscopy/methodsABSTRACT
A complete 1 H and 13 C NMR analysis for a group of four sesquiterpene lactones isolated from Eremanthus elaeagnus (Asteraceae) is described in this work. 1 H NMR, 13 C {1 H} 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.
Subject(s)
Asteraceae/chemistry , Lactones/isolation & purification , Sesquiterpenes/isolation & purification , Carbon-13 Magnetic Resonance Spectroscopy , Lactones/chemistry , Molecular Conformation , Proton Magnetic Resonance Spectroscopy , Sesquiterpenes/chemistry , StereoisomerismABSTRACT
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.
