Mass Spectrometry in Structural and Stereochemical Problems. XXXII.¹ Pentacyclic Triterpenes

Steroidal and triterpenoidal glucosides from Passiflora alata

“…In addition, there were two characteristic peaks at m/z 203 and 248 denoting the retro-Diels-Alder fragmentation commonly found in the spectra of oleanane or ursane derivatives 15 . Careful comparison of the 13 C NMR data of peracetylated compound 2a (Table 1) with those of peracetylated dumosasaponin 6 9 , allowed the unambiguous assignment of the signals of the oleanolic acid aglycone.…”

Further triterpenes, steroids and furocoumarins from brazilian medicinal plants of dorstenia genus (moraceae)

“…For the analysis of crude extracts, due to the presence of more polar compounds, only the hexane-soluble compounds were analyzed, since this solvent can selectively extract compounds appropriate to GC analysis, including low-functionalized steroids and triterpenoids. Despite a relatively longer analysis time, preliminary work with standards showed that derivatization of the triterpene and steroid alcohols is not essential, with the advantage of allowing direct comparison with literature data of underivatized compounds 9 . The HRGC-MS -TIC profile of the Dorstenia crude extracts showed some similarity between the chemical pattern of leaves and rhizomes, even from different species: the furocoumarins are eluted first, followed by the steroids, while the triterpenes are eluted later.…”

“…In both cases, chromatographic data were considered together with the comparison of MS data with those from authentic standards, obtained at similar ionization conditions (EI, 70 eV) in our laboratory. Tentative identi-fications were made by analysis of the fragmentation data, comparison with literature MS data 8,9,10 and computer search in the NBS library.…”

“…Most of the triterpenes found belong to the oleanane/ursane series, characterized by a base peak at m/z = 218 9 . Unequivocal differentiation between α and β-amyrin required co-injection with authentic samples, since these triterpenes have very similar MS spectra (in the chromatographic conditions utilized, β-amyrin elutes first).…”

“…Exchange of an hydroxy group for a keto group leads to a decrease of molecular weight and polarity, which leads to a lower tR in the column utilized for the HRGC analysis of these compounds. Besides, MS spectra of these compounds shows a peak at m/z 205, due to the fragmentation of a 3-keto-system involving rings A to C, and at m/z= 203, corresponding to the fragment originating from methyl loss of the diene portion originated from retro Diels-Alder fragmentation of a ∆ 12 -unsaturated oleanane or ursane 9 . With these data, they were tentatively identified as being α-or β-amyrone (3e-f).…”