Lupeol Derivatives Research Articles

Assignment of1H and13C spectra and investigation of hindered side-chain rotation in lupeol derivatives

Complete 1H and 13C spectral assignments are reported for lupeol (1a) and two derivatives where the C-30 methyl group is replaced by CH2OH (1b) and HC O (1c). Compound 1c shows conformationally dependent substituent effects on 1H chemical shifts. It also shows line broadening of some 13C signals at 25 °C, suggesting hindered rotation of the side-chain group. This is confirmed by low-temperature spectra which show splitting of broadened peaks into pairs in a ca 2 : 1 area ratio. The free energy of activation of hindered rotation is estimated as 13.5 kcal mol−1. By contrast, 1a shows no evidence of hindered rotation down to −40 °C although NOE data suggest the presence of two conformers. Spartan molecular mechanics calculations confirm the presence of two stable conformers for 1a and 1c but overestimate the rotational barrier in 1a. The additional barrier in 1c probably reflects loss of conjugative stabilization during rotation. Copyright © 2000 John Wiley & Sons, Ltd.

Chemical Constituents from the Root and Aerial Parts of Rosa taiwanensis

AbstractThe root and aerial parts of Rosa taiwanensis Nakai contain the chemical constituents phenols, unsaturated acids, loliolide, abscisic acid, flavones, sterols, lupeol, betulin, betulinic acid, oleanolic acid and ursolic acid derivatives. Among them, 2α,3α‐dihydroxyurs‐12,19‐dien‐28‐oic acid and its C‐3 epimer are new compounds.

Characteristics of aromatic hydrocarbons in crude oils

Crude oils from different basins in China, Australia and New Zealand were analyzed to character ize aromatic hydrocarbons produced in different environments by means of GC/MS. The distributions of some common compounds such as naphthalene, phenanthrene, ehrysene, pyrene, fluoranthene, fluorene, dibenzothiophene and dibenzofuran were found to be related to sedimentary environments. Especially the relative contents of fluorenes, dibenzofurans and dibenzothiophenes can be used to divide the oils into three types: (1) saline or marine carbonate environment; (2 ) fresh-brackish water lake; (3) swamp and coal-bearing sequence. Aromatic biomarkers (e.g. retene, nor-abietene, derivatives of lupeol and β-amyrin) represent higher plant inputs with respect to the precursors of crude oils. High contents of sulphur-containing compounds like benzothiophene and dibenzothiophene series indicate a reducing sulphur-abundant diagenetic condition. The benzohopane series (C32–C35) was identified both in hypersaline and coal-bearing basins, and it is postulated to be the result of strong bacteria activity. In all the samples, a complete series of alkyl benzenes was analyzed. The similarity of its carbon-number distribution with that of n-alkanes probably suggests their genetic relationship. The distribution of the methylphenanthrene series reflects the evolution degree of crude oils, MPI holding a positive correlation with C29-sterane 20S/(20S+20R).

Sesquiterpenic Lactones of Some Species of Genus Vernonia SCHREB.

Four species of the genus Vernonia, endemic in Cuba, have been investigated on the presence of sesquiterpenic lactones. In addition to two derivatives of lupeol, scopoletin, genkwanin and velutin, total 15 sesquiterpenic lactones have been isolated, four of which are described for the first time.

Sesquiterpene lactones and monoterpene glucopyrano-sides of Tetraneuris linearifolia var. Arenicola

Aerial parts of a new variety of Tetraneuris linearifolia, var. arenicola afforded, in addition to known helenanolides and germacranolides, a new guaianolide, 10 new esterified glucopyranosides of 9-hydroxy-γ-geraniol, two palmitates of lupeol derivatives, a mixture of glucopyranoside p-coumarates and eight flavonoids including the new 5,8,3′-trimethoxy-5,7,4′,5′-tetrahydroxyflavone.

Dehydrogenation with mercuric acetate in the lupane series. Part IV. Acidic products of the reaction

The hexacyclic aromatic acid (VId) is formed by dehydrogenation of lupeol derivatives with mercuric acetate. When the reaction is conducted in chloroform–acetic acid solution, there are formed, in addition to the aromatic acid, two hexacyclic homo-acids, which derive the additional carbon atom from chloroform present in the solvent system.

The degradation of lupeol derivatives to C27‐ketones

AbstractThe degradation of α‐lupene to trisnorlupanone has been re‐examined and analogous reactions with lupenyl acetate have yielded the corresponding C27 keto‐acetate. Conclusive evidence of the presence of a carbonyl group in these compounds has been obtained by spectrographic methods and by lithium aluminium hydride reduction.