| Summary: | Texte intégral accessible uniquement aux membres de l'Université de Lorraine The general objective of this work is to study and to optimise the enzymatic synthesis of new esters of tlavonoide. Immobilized lipase of Candida antarctica was used as biocatalyst in an organic medium with low waler content (< 300 ppm). The obtained results showed that trans-esterification is less performant than direct esterification due to the fact that the hydrolytic reaction is predominant compared to the flavonoids ester synthesis. The water content of the medium along the time course of the reaction plays an essential role. Even if at a low level It provokes a drastic decrease of the conversion yield. Among, the various sol vents tested methyl- 2-butanol 2 gives the best results. The study of the effect of structure of the donors of alcohol and acyl on the performance of acylation shown that best initial rates and conversion yields were obtained with rutin (71 %, 3.1.[mu]ole.h-1 and the esculin (80%, 8.7 [mu]ole.h-1) in the presence of fatty acids with carbon chain higher than C12 (87%, 15 [mu]ole.h-1). The acylation of the flavonoides leads only to monoesters and the it takes place on the primary 6''-OH of the esculin and secondary 4''-OH of rotin. This study showed also that the aromatic ester synthesis of flavonoide is feasible and the conversion yield of this acylation can reach in some cases 75 %. The use of an experimental design showed that the initial rates of substrates conversion and the selectivity of the reaction depends on the nature ofsolvent and the initial concentrations of the substrates. L'objectif général de ce travail est l'étude et l'optimisation des réactions de synthèse enzymatique de nouveaux esters de flavonoïde. Ce travail a été réalisé en présence de la lipase immobilisée de Candida antarctica et dans un milieu organique à faible teneur en eau (<300 ppm). Dans une première étape, une étude préliminaire des paramètres clef de la réaction a montré que la transestérification est moins performante ...
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