Complete ¹H and 13C NMR structural assignments for a group of four goyazensolide-type furanoheliangolides

Abstract

Recebido em 23/5/12; aceito em 21/8/12; publicado na web em 15/10/12Four goyazensolide-type sesquiterpene lactones -lychnofolide, centratherin, goyazensolide and goyazensolide acetate -were thoroughly studied by NMR experimental techniques.

A systematic investigation of the fragmentation pattern of two furanoheliangolide C‐8 stereoisomers using electrospray ionization mass spectrometry

“…This explains the loss of 100 u for both compounds (Scheme ), because budlein A and centratherin do not differ in terms of the position of these hydrogens. Hydrogen nuclear magnetic resonance ( 1 H‐NMR) analysis reinforced this hypothesis: budlein A (H 9α = 2.3 ppm and H 9β = 2.5 ppm) (see Supporting Information); centratherin (H 9α = 2.5 ppm and H 9β = 2.3 ppm) . Considering these similar chemical shifts, it is possible to confirm that these hydrogens are under equivalent magnetic effects in the compounds (although it has inverse values for the α‐ and β‐orientations) and, consequently, similar acidity.…”

Crystal Structures and Human Leukemia Cell Apoptosis Inducible Activities of Parthenolide Analogues Isolated from Piptocoma rufescens

“…The isolation and identification of (−)-goyazensolide ( 1 ), (−)-15-deoxygoyazensolide ( 2 ), (−)-ereglomerulide ( 3 ), and (+)-rufesolide A ( 4 ) have been reported previously, ,− with the 1 H and 13 C NMR data of 1 – 4 assigned completely by analysis of their 1 H, 13 C, and 2D NMR spectra (Tables S1 and S2 and Figures S1–S3, Supporting Information). ,, The molecular structure of 1 was established by X-ray crystallographic analysis in 1982, but H-8 was omitted from this previous report . The crystal structure, conformation of the central ring system, and absolute configuration of (+)-rufesolide A ( 4 ) have been reported in our previous study, but the crystal structures and crystallographic data of 2 and 3 have not been published.…”

“…■ RESULTS AND DISCUSSION Crystal Structures of 1−3. The isolation and identification of (−)-goyazensolide (1), (−)-15-deoxygoyazensolide (2), (−)-ereglomerulide (3), and (+)-rufesolide A (4) have been reported previously, 5,9−11 with the 1 H and 13 C NMR data of 1− 4 assigned completely by analysis of their 1 H, 13 C, and 2D NMR spectra (Tables S1 and S2 and Figures S1−S3, Supporting Information). 5,12,13 The molecular structure of 1 was established by X-ray crystallographic analysis in 1982, but H-8 was omitted from this previous report.…”

Absolute Configuration of (−)-Centratherin, a Sesquiterpenoid Lactone, Defined by Means of Chiroptical Spectroscopy

“…The isolated compound was determined as centratherin based on, among other facts, 1D and 2D NMR studies and by comparison of its 1 H and 13 C NMR spectra with published data. , As incorrect assignments for the structure of centratherin have been published, , we also made comparisons of the calculated 13 C NMR chemical shifts for centratherin with those obtained experimentally for the isolated compound (Table S1, Supporting Information). The 13 C NMR shielding constants (σ) were calculated by a gauge including atomic orbitals-hybrid density functional theory (GIAO-HDFT) calculation procedure at the GIAO-mPW1PW91/6-31G­(d)//mPW1PW91/6-31G­(d) level of theory in the gas phase, using the Gaussian 09 software package.…”