Gianfranco Fontana

Sesquiterpene compounds from Inula viscosa

Two new compounds, 2,5-dihydroxyisocostic acid and 2,3-dihydroxycostic acid together with three known sesquiterpene compounds, Isocostic acid, Carabrone and Tomentosin, have been isolated from the acetone extract of Inula viscosa (L.) Aiton. The structures of all new compounds were determined by spectroscopic methods, in particular 1D and 2D 1H- and 13C-NMR. The 13C-NMR spectra of Isocostic acid and of Tomentosin are reported here for the first time.

Effects of ajugarins and related neoclerodane diterpenoids on feeding behaviour of Leptinotarsa decemlineata and Spodoptera exigua larvae.

Three naturally occurring ajugarins and seven semisynthetic derivatives of them, possessing different functionalities in the decalin part, together with two natural furoneoclerodane diterpenes, have been assessed as feeding behavior modifying agents of larvae of the generalist Spodoptera exigua and a specialist like Leptinotarsa decemlineata. Ajugarin I and some of its derivatives exhibited a significant antifeedant activity against larvae of S. exigua in both choice and no-choice assays. Conversely, the furoneoclerodane diterpenes only presented antifeedant activity against larvae of L. decemlineata. These results indicate that the biological action of the tested substances is strongly modulated by minimal structural variations, which are also responsible for the specificity of action.

Unusual 6'-fatty acid esters of (24S)-24-ethylcholesta-5,25-dien-3β-yl β-D-glucopyranoside from Teucrium fruticans

Abstract An unusual (24S)-24-ethylcholesta-5,25-dien-3β-yl β- d -glucopyranoside possessing a mixture of fatty acid esters at the C-6′ position of the sugar moiety has been isolated from Teucrium fruticans. Spectroscopic studies and chemical transformations allowed the characterization of the sterol and sugar parts and palmitic, stearic, oleic, linoleic and linolenic acids as the main constituents of the 6′-O-acyl moiety.

Volatile constituents of aerial parts of two Mediterranean species of Inula: Inula crithmoides L. and I. verbascifolia (Willd.) Hausskn. (Asteraceae)

Inula crithmoides L. grows along the Mediterranean coasts and is used as an edible vegetable as the young leaves or shoots are eaten raw, cooked or pickled. Inula verbascifolia (Willd.) Hausskn. is a quite localised species growing mainly along the Adriatic Sea coasts. In this study the volatile components of the aerial part of both species are described. Gas chromatography and gas chromatography mass spectrometry analysis showed the presence of 41 components in I.crithmoides and 75 compounds in I.verbascifolia, respectively, and a very different profile in the composition of the two species. The chemotaxonomy of I. crithmoides, by comparison with other data reported in the literature, is discussed.

Kinetic study of base‐promoted elimination reactions of some 1,1,1‐trihalo‐2,2‐bis(dimethoxyphenyl)ethanes in alcoholic solutions

The base–promoted elimination reactions of 1,1,1-trichloro-2,2-bis(dimethoxyphenyl)ethanes were investigated. The bis(3,4-dimethoxyphenyl)ethane was found to be more reactive than the bis(2,5-dimethoxyphenyl)ethane and the latter more reactive than the bis(2,4-dimethoxyphenyl)ethane. Kinetic data relative to 1,1,1-trihalo(chloro or bromo)-2,2-bis(3,4-dimethoxyphenyl)ethanes show that the tribromo reacts faster than trichloro derivative and that the reactions are general-base promoted with Bronsted β values of about 0.6. A kinetic isotope effect, with kH/kD ratio ranging from 3.5 to 5.7, for the base-promoted elimination reaction of 1,1,1-trichloro-2,2-bis(3,4-dimethoxyphenyl)ethane was found. Tunneling occurs for methoxide and ethoxide ion-promoted eliminations. Activation parameters for alkoxy-promoted elimination show a similar trend for chloride and bromide derivatives. The data collected seem to confirm that there is contiguity between E1cBirr and E2 mechanisms.