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Development of new pathways for syntheses of sesquiterpenoids
Topolovčan, Nikola ; Kotora, Martin (advisor) ; Dvořák, Dalimil (referee) ; Pour, Milan (referee)
This work consists of four consecutive parts, each dealing with syntheses of structurally diverse compounds. The syntheses were based on the methods within the domain of transition-metal catalyzed and/or mediated reactions with particular emaphasis on the application of organozirconium chemistry. 1. A method for synthesis of tricyclic condensed hydrocarbons possessing 5(6)-7-6(aryl) framework was developed. It is based on reaction of bicyclic zirconacyclopentenes, prepared by oxidative dimerization of enynes on a low-valent zirconocene species (Negishi's reagent), with ortho-halobenzaldehydes in the presence of various additives. The presence of two different centers of reactivity - the sp2 C-Zr and sp3 C-Zr bond - allowed sequential functionalization of each bond. Thanks to its higher nucleophilicity, the sp3 C-Zr bond reacted preferentially with the carbonyl carbon of the aldehyde yielding an oxazirconacycloheptene. The subsequent transmetallation of the remaining sp2 C-Zr bond with CuCl in the presence of other additives (catalysts) enabled an intramolecular cross-coupling reaction with the aryl halide moiety furnishing the desired tricyclic products in reasonable yields. The scope of the reaction with respect to differently functionalized reactants was assessed, as well as its mechanistic...
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Synthesis of selaginpulvilins
Beytlerová, Nela ; Kotora, Martin (advisor) ; Hájíček, Josef (referee)
This bachelor thesis is focused on the application of [2+2+2] cyclotrimerization in the total synthesis of natural fluorene derivate, selaginpulvilin D, which was isolated from the plant Selaginella pulvinata. The plant is used in the traditional Chinese medicine for treatment of asthma and traumatic injuries. The study is focused on development of the catalytic cyclotrimerization reaction that is used to prepare the key intermediate. The integral part of the project is a study how various catalysts and catalytic systems, solvents and reaction temperatures affect the course of the reaction. Synthesis of the suitable cyclotrimerization precursor was achieved from benzaldehyde and the formal synthesis of selaginpulvilin D was completed by conversion of cyclotrimerization product to the known intermediate of the selaginpulvilin D synthesis. Key words: [2+2+2] cyclotrimerization, selaginpulvilin D, natural compound, fluorene core
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Application of enantioselective allylation for synthesis of compounds isolated from Streptomyces gramineus
Morávková, Terézia ; Kotora, Martin (advisor) ; Matoušová, Eliška (referee)
E-492, actinofuranone A, and JBIR-108 are natural compounds isolated from actinobacteria Streptomyces genus and can lead to the development of new pharmaceuticals as they have some biological interesting activities. Although the synthesis of these actinofuranones has been already published, this work brings new methods for the preparation of their fragments. The key step of the synthesis is enantioselective crotylboration of an aldehyde catalyzed by a chiral Brønsted acid and by which two centres of chirality are introduced in one step. The other crucial steps of the synthesis are composed of Ru-catalyzed alkene-alkene cross-metathesis and Pd- catalyzed Suzuki cross-coupling. Keywords: natural compound, enantioselective syntheses, crotylation, catalysis, actinofuranone fragment
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Development of new pathways for syntheses of sesquiterpenoids
Topolovčan, Nikola ; Kotora, Martin (advisor) ; Dvořák, Dalimil (referee) ; Pour, Milan (referee)
This work consists of four consecutive parts, each dealing with syntheses of structurally diverse compounds. The syntheses were based on the methods within the domain of transition-metal catalyzed and/or mediated reactions with particular emaphasis on the application of organozirconium chemistry. 1. A method for synthesis of tricyclic condensed hydrocarbons possessing 5(6)-7-6(aryl) framework was developed. It is based on reaction of bicyclic zirconacyclopentenes, prepared by oxidative dimerization of enynes on a low-valent zirconocene species (Negishi's reagent), with ortho-halobenzaldehydes in the presence of various additives. The presence of two different centers of reactivity - the sp2 C-Zr and sp3 C-Zr bond - allowed sequential functionalization of each bond. Thanks to its higher nucleophilicity, the sp3 C-Zr bond reacted preferentially with the carbonyl carbon of the aldehyde yielding an oxazirconacycloheptene. The subsequent transmetallation of the remaining sp2 C-Zr bond with CuCl in the presence of other additives (catalysts) enabled an intramolecular cross-coupling reaction with the aryl halide moiety furnishing the desired tricyclic products in reasonable yields. The scope of the reaction with respect to differently functionalized reactants was assessed, as well as its mechanistic...
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