The stereochemical dependence of 13C chemical shifts in olean-12-enes and urs-12-enes as an aid to structural assignment

Epikatonic acid from Austroplenckia populnea: structure elucidation by 2D NMR spectroscopy and X‐ray crystallography

“…The MS showed the molecular ion at m/z 456 and fragments at m/z 208 and 248, associated with a retro-Diels-Alder fragmentation of the C ring of this pentacyclic triterpene, indicating that 1 is a member of an olean-12-ene system. 8 Absorption bands at 3400 and 1700 cm 1 in the IR spectrum showed the presence of hydroxyl and carboxyl groups in compound 1. Methyl groups are strategically located in this triterpene, providing a network of two-and three-bond connectivities; these tie the molecule together and allow the assignment with C-16, C-17 and C-22; and H-23 and H-24 with C-3, C-4 and C-5.…”

New Oleanene Glycosides from the Leaves of Acanthopanax japonicus

“…The hydroxyl group at C-3 appeared to have a bconfiguration based on its coupling constants in the 1 H-NMR spectrum. 13) The proton signals at d 3.71 and 4.16 were found to originate from the H-23 of oxymethylene group at C-4 based on the HMBC correlation between H-24 (d 1.05) and C-23 (d 68.1), and the functional group was concluded to be in the a-configuration according to 13 C-NMR spectral data (d C-23 68.1, d C-24 13.1). 1) Two carboxylic carbon signals at 180.6 and 181.0 were assigned to C-28 and C-29, respectively, by their HMBC and HMQC.…”

“…Since this compound was suspected to be a triterpenoidal saponin due to the positive Lieberman-Burchard reaction and by the 13 C-NMR spectral analysis, 4 was also subjected to alkali hydrolysis and yielded the aglycone 4a, which showed a quasimolecular ion peak at 509 due to [MϩNa] ϩ by positive FAB-MS, and a molecular ion (C 30 H 46 O 6 ) at m/z 486 along with fragments at m/z 248 and 203 in EI-MS. Consequently, 4a was identified as gypsogenic acid based on 1 H-and 13 C-NMR spectral data (Table 1). 16) It was ascertained by sugar analysis and its NMR spectral data that the sugar moiety of 4 was the same as that of 1. Thus, compound 4 was identified as gypsogenic Compound 6 (acanjaposide I) exhibited a quasimolecular ion at m/z 993.4661 due to [MϩNa] ϩ corresponding to the molecular formula C 48 H 74 O 20 in the HR-FAB-MS.…”

Évaluation de l'activité biologique du Ledum groenlandicum Retzius /

“…Les autres signaux ont ensuite été assignés avec l'aide des spectres deux dimensions COSY, TOCSY, HSQC et HMBC. L'identification de l'acide ursolique est de plus appuyée par l'analyse GC-MS d'un standard (acide ursolique, Sigma Aldrich) et en comparant les données RMN avec celle de la littérature (Doddrell et al 1974;Kriwacki et al 1989;Seo et al 1975 Activité anti-inflammatoire des extraits de L. sroenlandicum II est connu dans la littérature que les ROS et les RNS sont impliqués dans plusieurs maladies impliquant un processus inflammatoire (Beaurova and KBezek, 1999;Rahman, 2002;Horton, 2003). L'activité anti-inflammatoire a été évaluée en mesurant l'inhibition du relâchement d'oxyde nitrique dans les macrophages murins 264,7 stimulés au LPS (Green et al 1990).…”