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Application of amines for the preparation of chiral cyclic compounds
Formánek, Bedřich ; Veselý, Jan (advisor) ; Kočovský, Pavel (referee) ; Soural, Miroslav (referee)
Organocatalysis, along with catalysis by metal complexes or enzymes, has become one of the very useful tools of asymmetric synthesis. Different activation modes or their combinations into sequences (domino reactions) enable effective access to enantiomerically enriched complex substances. The objective of this work was the preparation of chiral molecules from simple precursors activated by amine-based organocatalysts. In particular, we were focused on a study of asymmetric allyl substitution of Morita-Baylis-Hillman carbonates and two-component domino reactions on sulfur-containing heterocycles. The thesis deals with the organocatalytic allyl amination of Morita-Baylis-Hillman carbonates with aromatic amines catalyzed by β-isocupreidine. The corresponding allylic amines were obtained in high yields (90-96%) with moderate enantiomeric excess. It was possible to get substances of high optical purity (ee 82-99%) by recrystallization of selected products. Furthermore, the developed method was applied in the preparation of enantiomerically enriched β-lactams, which represent valuable precursors, for example, in the synthesis of the drug Ezetimibe. The second part of the work is focused on stereoselective cyclization reactions comprising selected sulfur heterocycles. Although the cyclization reaction of...
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Synthesis of N-(per)fluoroalkyl azoles by rhodium(II)-catalyzed transannulation of N-(per)fluoroalkyl-1,2,3-triazoles
Bakhanovich, Olga ; Beier, Petr (advisor) ; Kočovský, Pavel (referee) ; Kvíčala, Jaroslav (referee)
This Thesis deals with the synthesis of N-fluoroalkyl azoles via rhodium(II)-catalyzed transannulation of N-fluoroalkyl-1,2,3-triazoles obtained through copper(I)-catalyzed azide- alkyne cycloaddition (CuAAC) of N-fluoroalkyl azides and alkynes. The introductory chapter describes general approaches towards N-fluoroalkyl azoles, focusing on the synthesis of N-fluoroalkyl pyrroles and azoles. In the first part of the Thesis, rhodium(II)-catalyzed transannulation of N-fluoroalkyl-1,2,3- triazoles with terminal alkynes is described. The reaction provides access to N-fluoroalkyl pyrroles. The regioselectivity of the reaction is investigated and modifications of the primary product are suggested. In the second part of the Thesis, the reactivity of 4-cyclohexyl-N-fluoroalkyl-1,2,3-triazoles is investigated. A one-pot two-step reaction is presented, providing access to novel N- fluoroalkyl indoles. Several modification routes are suggested.
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Vitamin D and its functions
De Brito, Christina ; Kočovský, Pavel (advisor) ; Máčová, Ludmila (referee)
Vitamin D is known for its role in the regulation of the metabolism of minerals in the body. Its deficiency is mainly associated with rickets and osteomalacia, characterized by defects in bone growth and development. However, the limits of this hormone's action extend much further. It can influence the differentiation of immune cells, thereby regulating the immune response and cell proliferation. After the discovery of its immunoregulatory functions, vitamin D became a hot candidate for the treatment of autoimmune diseases, such as multiple sclerosis, systemic lupus erythematosus, or diabetes mellitus. Furthermore, vitamin D was found to exhibit a suppressive effect on cancer cells. Vitamin D deficiency is a risk factor associated with the development of encephalomyelitis, schizophrenia, autism, and cardiovascular diseases. Currently, vitamin D analogs are being developed that are just as effective but do not affect calcium metabolism, thus eliminating the toxic effect of high doses of vitamin D. Key words: vitamin D3, 25-hydroxyvitamin D3, 25(OH)D3, cholecalciferol, 1α,25-dihydroxyvitamin D3, 1,25(OH)2D3, calcitriol, immunity, immunoregulatory function, vitamin D deficiency, autoimmune disease
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Asymmetric Tandem Lithium Amide Conjugate Addition/Radical Reactions and Their Application in the Total Synthesis of Natural Products
Hidasová, Denisa ; Jahn, Ullrich (advisor) ; Kočovský, Pavel (referee) ; Míšek, Jiří (referee)
This thesis deals with single-electron transfer (SET) radical processes mediated by ferrocenium hexafluorophosphate and TEMPO and their application in the total synthesis of natural products. Asymmetric aminooxygenation methodology for the synthesis of anti-β-amino-α-hydroxy acid derivatives has been developed by utilizing a highly diastereoselective aza-Michael addition of chiral lithium amides to various α,β-unsaturated esters or amides/SET oxidation/radical α-oxygenation. The potential of this methodology was demonstrated in short total syntheses of the anti-β-amino-α-hydroxy acid fragments of the macrocyclic (depsi)peptides perthamide C and largamide H, and (-)-cytoxazone, which is a selective modulator of TH2 cytokine secretion. The SET-catalyzed asymmetric tandem lithium amide conjugate addition/5-exo radical cyclization/oxygenation reactions were applied in the synthesis of highly substituted pyrrolidines, azabicyclo[n.3.0]alkanes and spiropyrrolidines. An enantioselective total synthesis of the pyrrolidine alkaloid (-)-α-kainic acid was accomplished by employing the SET-catalyzed 5-exo radical cyclization/oxygenation.
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Development of new glycosylation methods for the synthesis of nucleosides
Downey, Alan Michael ; Hocek, Michal (advisor) ; Křen, Vladimír (referee) ; Kočovský, Pavel (referee)
As they make up DNA and RNA, nucleosides are considered the key to life. Synthetic nucleosides also constitute many drugs that treat viral infections and cancer. As a result, more efficient methods to access these crucial molecules would have implications that extend beyond a synthetic chemist's benchtop and into medicinal chemistry and medical research. One of the most challenging steps in the synthesis of nucleosides is the glycosylation step between the acceptor heterocycle (nucleobase) and the saccharide-based donor. Often to obtain satisfactory yield of this step with good regio- and stereochemical control the extensive use of protecting groups must be employed to squelch reactivity at unwanted reactive groups. Consequently, this process of protection−glycosylation−deprotection is laborious, inefficient, and often requires the use of toxic reagents. It would be, therefore, highly welcomed if new methodology to effect this glycosylation step was designed that reduces or removes the need to use protecting groups, but would still provide nucleosides in good yield, regio- and stereoselectively. Herein, this thesis presents my efforts into achieving this end. By employing modified Mitsunobu conditions, I determined that it is possible to directly glycosylate a nucleobase with D-ribose to afford...
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Preparation of biologically active compounds using organocatalysis
Šimek, Michal ; Veselý, Jan (advisor) ; Kočovský, Pavel (referee)
This diploma thesis deals with the use of organocatalysis in an asymmetric allylic substitution reaction of Morita-Baylis-Hillman carbonates by aniline derivatives leading to enantiomerically enriched allylic amines. The first part of the thesis is focused on optimizing the reaction conditions in the organocatalytic reaction with respect to the yields and enantiomeric excesses of the products. In the second part of the thesis prepared enantiomerically enriched allylic amines are used in the cyclization step to give β-lactame cycles that serve as the key intermediates in the total synthesis of Ezetimib as is demonstrated in the final part of the diploma thesis.
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