The determination of the stereochemistry of five-membered α,β-unsaturated lactones with an exomethylene double bond based on the allylic long-range couplings of exomethylene protons

Allergenic sesquiterpene lactones fromEupatorium cannabinum L. andKaunia rufescens (Lund ex de Candolle)?

“…The immediate positive reaction with the peroxide reagent [Rücker et al, 1995], as well as the fragments at m/z 515 [M-OOHϩmNBAϩH ϩ ] and at m/z 362 [M-OOHϩH ϩ ] in the FAB mass spectrum, suggest the presence of a hydroperoxy group. A comparison of the 1 H-and 13 C-NMR spectra with the data of eucannabinolide [Samek, 1979;Drozdz et al, 1972;Herz and Govindan, 1980;Heiden, 1996], which is also present in E. cannabinum, show a close resemblance. Merely, the signals for the acetyloxy group at C-3 are missing in 3␤-peroxyeucannabinolide.…”

Structure elucidation and complete NMR spectral assignments of a novel sesquiterpene glycoside from Ixeris sonchifolia

“…The coupling constants between H-6 and H-7 (J D 10.0 Hz) indicated the relative configurations of H-6 (ˇ) and H-7 (˛). 18 Further relative stereochemistry of 1 was confirmed by NOESY experiment, which proved 3-OH as˛-configuration, according to the correlations of H-6-H-5, H-5-H-3; the aglycone was deduced as -cis, cis-according to the correlations between H-1 with H-5 and H-15, H-5 with H-15, and between H-14 with H-15. The sugar moiety was confirmed as glucose by acid hydrolysis and subsequent TLC sugar analysis.…”

Cytotoxic Germacranolide Sesquiterpene from Inula cappa

“…This paper reports the isolation of a new germacranolide (1) along with 16 known compounds from the whole plant of I. cappa DC. The structures of the known compounds were determined to be friedelin (2), 6) epifriedelanol (3), 7) a-amyrin (4), 8) b-amyrin (5), 9) oleanolic acid (6), ursolic acid (7), stigmast-4-en-3-one (8), 10) stigmasta-4,22-dien-3-one (9), 11) b-sitosterol (10), stigmasterol (11), 12) 7-oxo-b-sitosterol (12), 13) stigmast-5-ene-3b,7b-diol (13), 14) stigmasta-5,22-diene-3b,7b-diol (14), stigmast-5-ene-3b,7a-diol (15), stigmasta-5,22-diene-3b,7a-diol (16), and daucosterol (17) by analysis of physical and spectroscopic evidence, and confirmed by comparison of their spectral data with values reported in the literature or those of authentic samples. In addition, the cytotoxic activities of 1 were determined in vitro against human cervical cancer HeLa, human leukemia K562, and human nasopharyngeal carcinoma KB cell lines.…”

“…H-5a, H-6b, and H-7a oriented. 15,16) These assignments were based on the fact that H-7 has been assumed to be a-oriented as in all other naturally occurring germacranolides. 17 (Fig.…”