Organocatalytic approach for a formal 1,6-conjugate addition

Dans cette thèse, une nouvelle méthodologie d’addition-1,6 énantiosélective formelle sur des accepteurs de Michael vinylogues a été développée. La stratégie repose sur une étape clé d’addition-1,4 de sulfa-Michael organocatalysée, hautement énantiosélective (jusqu’au 95% ee), sur des acrylates vinylogues d’hexafluoro iso-propanol en utilisant le catalyseur de Takemoto. Ceci constitue un des rares cas d’addition conjuguée-1,4 régio- et énantiosélective organocatalysée sur des dérivés d’acrylates vinylogues. Ces composés ont été ensuite convertis en adduits de sulfa-Michael possédant une fonction amide. Après mono-oxydation du centre soufré, un réarrangement sigmatropique [2,3] de Mislow-Braverman-Evans a été mis en oeuvre. Il a permis l’introduction d’un groupement hydroxyle en position δ avec un excellent transfert de chiralité-1,3. En bilan, notre approche résulte en une addition-1,6 énantiosélective formelle de type oxa-Michael.In this PhD work, a new methodology for the formal enantioselective organocatalytic 1,6-addition to vinylogous Michael acceptors has been developed. Our strategy is based on a highly enantioselective 1,4-sulfa-Michael addition (up to 95% ee) to vinylogous hexafluoro iso-propanol acrylates as a key step, using the Takemoto catalyst. This constitutes a rare example of an organocatalyzed regio- and enantioselective 1,4-conjugate addition on vinylogous acrylate derivatives. These compounds were subsequently converted into sulfa-Michael adducts possessing an amide function. After mono-oxidation of the sulfur center, a Mislow-Braverman-Evans sigmatropic [2,3] rearrangement is involved to introduce a hydroxyl group in the δ-position with an excellent 1,3-chirality transfer. To resume, our approach would result in an oxa-Michael type formal enantioselective 1,6-addition

FecX(Bar) a Novel BMP15 mutation responsible for prolificacy and female sterility in Tunisian Barbarine Sheep

Naturally occurring mutations in growth and differentiation factor 9 (GDF9) or bone morphogenetic protein 15 (BMP15) genes are associated with increased ovulation rate (OR) and litter size (LS) but also sterility. Observing the Tunisian Barbarine ewes of the "W" flock selected for improved prolificacy, we found prolific and infertile ewes with streaky ovaries. Blood genomic DNA was extracted from a subset of low-ovulating, prolific and infertile ewes of the "W" flock, and the entire coding sequences of GDF9 and BMP15 were sequenced. We evidenced a novel polymorphism in the exon 1 of the BMP15 gene associated with increased prolificacy and sterility. This novel mutation called FecX(Bar) is a composite polymorphism associating a single nucleotide substitution (c.301G > T), a 3 bp deletion (c. 302_304delCTA) and a C insertion (c. 310insC) in the ovine BMP15 cDNA leading to a frame shift at protein position 101. Calculated in the "W" flock, the FecX(Bar) allele increased OR by 0.7 ova and LS by 0.3 lambs (p = 0.08). As for already identified mutations, homozygous females carrying FecX(Bar) exhibited streaky ovaries with a blockade at the primary stage of folliculogenesis as shown by histochemistry. Our investigation demonstrates a new mutation in the BMP15 gene providing a valuable genetic tool to control fecundity in Tunisian Barbarine, usable for diffusion program into conventional flocks looking for prolificacy improvement

Biochemical characterization of olive oil samples obtained from fruit mixtures and from oil blends of four cultivars grown in Central Tunisia

Blends of olive oils obtained from four cultivars (Olea europaea L. cv. Chemlali, Chetoui, Oueslati and Koroneiki) were produced by two different methods of blending: processing fruit mixtures or mixing monovarietal oils, using the same proportions of selected cultivars. The obtained blends were biochemically characterized to evaluate quality, and the two methods were compared. The results indicated that the most successful formulations are mainly F8 (60% Chemlali × 20% Oueslati × 20% Koroneiki) characterized by the highest contents of phenols and an elevated oxidative stability, and F5 (50% Chemlali × 50% Koroneiki) containing the highest MUFA level and the highest oxidative stability. The effect of the blending process on pigments and volatiles cannot be easily regulated, unlike phenols, fatty acid composition and OS, all of which positively correlated to the fruit mass ratio in the blend. Results suggest that processing fruit mixtures of different cultivars resulted in a better oil quality than that of oils obtained by the common oil blending method. This blending procedure offers a possibility to modulate the contents of antioxidants, fatty acids and volatile compounds in virgin olive oil, and therefore, its quality and sensorial characteristics