Reactions of Vinylcyclopropane and Bicyclopropyl Compounds With Maleic Anhydride

Vinylcyclopropane and bicyclopropyl C6 compounds are studied as diene precursors in the Diels-Alder reaction. Their rearrangement under different thermal and microwave conditions leads to specific isomeric hexa-, penta- or butadienes, condensed with maleic anhydride as a dienophile. Adduct stereochemistries were compared to those of previously-synthesized model compounds, and are fully characterized with 2D NMR and GC-MS spectroscopies. Some unsaturated terpenes bearing vinylcyclopropane moieties were also condensed, and their adduct structures assigned.

Comparing Different Methods of Volatile Compounds Determination in Wine by GC/MS

Volatile compounds are produced in wines during fermentation, distillation and ageing in oak barrels. Even if the wine volatile profile is extremely complex, containing more than 800 compounds, only 50 have an impact on wine quality (Colibaba 2009). Belonging to different groups of substances (terpens, aldehydes, esters, acids, alcohols etc.), the volatile compounds concentration ranges from a few ng to mg per liter, with different olfactory thresholds (Gerogiannaki-Christopoulou 2008). They are classified in volatiles of the primary aroma (terpens, pyrazines, C6 compounds, and aroma precursors), secondary aroma (ethanol, carbon dioxide, superior alcohols, fatty acids, esters, carbonylic compounds) and of the tertiary aroma of wines (esters, superior alcohols, terpens, nor-isoprenoids, rancid aroma etc.). Wine from different grape varieties (flavoured and some non-flavoured) contain specific aroma compounds, in different ratios (Lambropoulos 2007).

Aroma potential of three autochthonous grapevine varieties from Tunisia

<p style="text-align: justify;"><strong>Aims</strong>: The aim of the present work is to characterize the aromatic profiles of three Tunisian autochthonous grapevine (Vitis vinifera L.) varieties (Asli, Beldi and Ferrani).</p><p style="text-align: justify;"><strong>Methods and results</strong>: The GC-MS analysis of the autochthonous grapevine varieties studied allowed identifying 38 volatile compounds in the free fraction and 36 glycosidically bound aroma compounds. Volatile C6 compounds were typical for the studied varieties especially for Asli variety. The analysis of the liberated aglycones through enzymatic hydrolysis show that a-terpineol and cis linalool oxide pyran that did not appear as free aroma compounds were found with significantly highest concentration in Asli grape juice. Also, 3-oxo-a-ionol and 3-hydroxy-7,8-dihydro-b-ionol were found only under their glycosidically bound forms with significantly higher concentrations in Asli and Ferrani than in Beldi grape juices.</p><p style="text-align: justify;"><strong>Conclusion</strong>: The results obtained in the present work show qualitative and quantitative differences in the aroma profiles among the studied varieties. However, non-terpenyl compounds were the most abundant aroma substances in the three studied varieties.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The present work characterize, for the first time, the aromatic profiles of three Tunisian autochthonous grapevine varieties (Asli, Beldi and Ferrani) and constitutes a major contribution to the aroma chemistry of these three grape varieties.</p>