(−)-epi-Presilphiperfolan-1-ol, a new triquinane sesquiterpene from the essential oil of Anemia tomentosa var. anthriscifolia (Pteridophyta)

Secondary Metabolites

“…anthriscifolia by CC on silicagel with a hexane-ethyl acetate gradient. A new structural formula, namely (−)-epi-presilphiperfolan-1-ol, was initially proposed, after extensive 1D-and 2D-NMR analyses, as well as by GC-MS, chiral bidimensional GC, dehydration reactions, and a comparative (GIAO/DFT) theoretical study of the 13 C NMR chemical shifts (Pinto et al, 2009a). Further examination by X-ray diffraction and vibrational circular dichroism studies, however, led to its reassignment to (−)-9-epipresilphiperfolan-1-ol (Figure 3), also a new compound.…”

GIAO‐HDFT scaling factor for 13C NMR chemical shifts calculation

“…NMR chemical shifts were computed at the B3LYP and B3PW91 with cc‐pVnZ ( n = 2–3) and augment aug‐cc‐pVnZ ( n = 2–3) levels using the GIAO method and are given relative to that of TMS calculated at the same level of theory. In the case of the (−)‐9‐ epi ‐presilphiperfolan‐1‐ol 20, 21 and its known three isomers, presilphiperfolan‐1‐ol 22, presilphiperfolan‐8‐ol 23, and presilphiperfolan‐9‐ol 24, their geometry optimizations were performed using the levels specified in the text. Vibrational frequency calculations were performed for all of the previous optimized geometries in order to ascertain the nature of their stationary points on the potential energy surfaces.…”

“…Here, we use such an approach combing the GIAO‐B3PW91/cc‐pVDZ//B3PW91/cc‐pVDZ protocol successfully applied by Siegel and Baldridge 18 in reproducing 1 H chemical shifts experimental data with an approach somewhat similar to that used in Aliev et al . s 19 study. We will also present a comparative study with Aliev's et al protocol in determining the chemical shifts of (−)‐9‐ epi ‐presilphiperfolan‐1‐ol, a recently reported new triquinane sesquiterpene 20, 21, and of its known three isomers, presilphiperfolan‐1‐ol 22, presilphiperfolan‐8‐ol 23, and presilphiperfolan‐9‐ol 24.…”

“…s 19 study. We will also present a comparative study with Aliev's et al protocol in determining the chemical shifts of (−)‐9‐ epi ‐presilphiperfolan‐1‐ol, a recently reported new triquinane sesquiterpene 20, 21, and of its known three isomers, presilphiperfolan‐1‐ol 22, presilphiperfolan‐8‐ol 23, and presilphiperfolan‐9‐ol 24.…”

“…In a recent study on 13 C chemical shifts, Aliev et al . 19, using a “chemical shift – chemical shift” approach, indicated that a linear scaling of the computed NMR chemical shifts was able to improve the result of the GIAO‐B3LYP/6‐311 + G(2d,p)//B3LYP/6‐31G(d) of 27 experimentally determined 13 C chemical shifts for 22 simple molecules with a sorting of different functionals groups. Their results show that while the GIAO B3LYP/6‐311 + G(2d,p)//B3LYP/6‐31G(d) gives a relatively large mean absolute deviation (MAD) of 4.80 ppm and a root mean square RMS of 6.18 ppm for the set of 27 chemical shifts, the subsequent linear scaling led to a three‐fold improvement, with the MAD value of 1.57 ppm and RMS of 1.89 ppm.…”