Abstract

9-Hydroxynerolidol, 9-oxonerolidol, and chiliadenol B are three farnesane-type sesquiterpenoids isolated from Chiliadenus lopadusanus that have shown an interesting activity against human pathogens as Gram+ and Gram− bacteria resistant to antibiotics. However, the absolute configuration (AC) of these interesting sesquiterpenes has not been assigned so far. Vibrational and electronic circular dichroism spectra have been recorded and correlations are pointed out for the three compounds. Density functional theory (DFT) calculations are used in conjunction with Mosher’s method of investigation to assign AC. Statistical analysis is considered to quantitatively define the choice of AC from VCD spectra.

Highlights

  • Following the recommendation of Polavarapu et al [28], we will consider electronic circular dichroism (ECD) data in conjunction with vibrational circular dichroism (VCD): we think that the synergistic use of the two types of data is opportune in the present case since the expected number of possible conformers makes this study difficult, already noticed by Merten et al, for some diterpenes, namely elegandiol and other linear diterpenes from Bifurcaria family [26,27]

  • Stereogenic carbon 3 is shared by all three compounds examined here and it is reassuring to state that, problem, related to the huge number of conformers and to interactions with the solvent, which have not been treated in the present work

  • VCD and ECD allied to Density functional theory (DFT) calculations and ancillary theoretical-statistical analysis, the three related linear farnesane-type sesquiterpenes 9-hydroxynerolidol (1), 9-oxonerolidol

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Summary

Introduction

Biomolecules 2021, 11, 1902 while sphaeropsidin A inhibited biofilm formation These results are very promising and suggested to some of us how to develop a suitable drug formulation, in particular, for wound protection against serious infection advancement [10]. These results prompted further research on fungi and plants to identify the bioactive natural substances with antibiotic activity against human pathogens as antibiotic-resistant bacteria.,aascreening screeningof ofendemic endemicplants plantscollected collectedin indifferent differentregions regionsof ofthe theMediterMediterbacteria. Following the recommendation of Polavarapu et al [28], we will consider electronic circular dichroism (ECD) data in conjunction with VCD: we think that the synergistic use of the two types of data is opportune in the present case since the expected number of possible conformers makes this study difficult, already noticed by Merten et al, for some diterpenes, namely elegandiol and other linear diterpenes from Bifurcaria family [26,27]

General Experimental Procedures
Plant Material
Isolation of Fungal Metabolites and Synthesis of Ancillary Products
Hemisynthesis of 4
Hemisynthesis of 5
VCD and ECD Spectroscopies
Calculations
Results and Discussion
Comparison
Conclusions

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