Thesis (Ph. D.)--Duquesne University, 2003. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, August 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, August 2003. / Includes bibliographical references. Also available on the Internet.

I. Completion of a Total Synthesis of Peloruside A: The completion of a 22 step synthesis of the marine natural product peloruside A is presented. The second generation strategy cuts 10 steps from longest linear sequence of the Evans group’s first generation synthesis of peloruside A by changing the order of fragment coupling operations and maintaining \(C_1\) and \(C_9\) at their final oxidation states over the course of most of the synthesis. Key steps include two highly diastereoselective aldol fragment couplings, a tin tetrachloride mediated hydrosilylation and a macrolactonization on a seco acid containing no cyclic templating elements. II. Studies toward the Total Synthesis of Spiro-Prorocentrimine: The development of an intermolecular Diels–Alder approach toward the marine natural product spiro–prorocentrimine is described. This work began with the adaptation of the Evans group’s previous intramolecular Diels–Alder approach. It was found that protonated imines bearing non-coordinating counterions were of sufficient reactivity to allow cycloaddition to occur even on dienes that were unreactive under the previous best conditions. In the course of these studies, isomerization of a macrocyclic diene during the course of a Diels–Alder reaction complicated the stereochemical outcome of the reaction. Reaction conditions to suppress the isomerization and obtain Diels–Alder adducts bearing the correct configuration at both \(C_9\) and \(C_{33}\) were developed based on a qualitative consideration of the pKas of species present in the reaction. The of several macrocyclic dienes was examined to help explain the course of the Diels–Alder reaction. Other key steps include an iron catalyzed olefin formation, the highly diastereoselective hydrogenation of a trisubstituted olefin in the presence of an enol ether, protecting group studies to suppress the contraction of a 15 membered lactone to a 6 membered lactone and studies of a protecting group strategy to allow installation of a sulfate. Lessons learned from this work and previous efforts are combined in a proposal for a bioinspired synthesis of spiro-prorocentrimine with a longest linear sequence of less than 30 steps. / Chemistry and Chemical Biology

published_or_final_version / Chemistry / Master / Master of Philosophy

Darbo tikslas – Ištirti žėlimo intensyvumą juodalksnynuose ir kokybę lemiančius veiksnius. Darbo uždaviniai – Ištirti žėlimo intensyvumą juodalksnynuose nuo motinio medyno amžiaus, nuo augavietės ir buvusio medyno rūšinės sudėties. Nustatyti žėlimo intensyvumą nuo kirtimui naudotos technologijos. Darbo objektas – Kazlų rūdos mokomosios miškų urėdijos Bagotosios girininkijos juodalksnynai. Darbo metodai – Tyrimui buvo atrinkta 18 juodalksnio biržių, nukirstų 1996-2006 metais. Parenkant kirtavietes, buvo atsižvelgta į tai, kad būtų skirtingos kirtimų technologijos, kad būtų įvairesnėse augavietėse, kad būtų įvairesnė rūšinė sudėtis, bet jose vyrautu juodalksnis. Atrinktuose plotuose buvo uždėtos apskaitos aikštelės, kuriuose siekiant nustatyti juodalksnio žėlimo intensyvumą, buvo atlikti tyrimai: aprašyta ploto charakteristika, nustatytas atauginių ir sėklinių juodalksnio savaiminukų, tame skaičiuje gyvybingų skaičius, kitų medžių rūšių savaiminukų skaičius, išmatuotas aukštesnių medelių aukštis ir storis. Apdorojant tyrimų duomenis, kiekvienam plotui nustatyta atauginio ir sėklinio juodalksnio žėlimo kokybė ir intensyvumas. Pagal miško atkūrimo ir įveisimo nuostatus įvertinta juodalksnio jaunuolynų būklė ir žėlinių kokybė. Darbo rezultatai – Kas met šalyje plynai iškertama šimtai hektarų juodalksnynų. 87% visų nukirstų juodalksnio kirtaviečių paliekamos žėlimui. Biržės sėkmingai želdosi tada, kai medynai kertami žiemą, kertama sėkliniais metais, kirtavietėse paliekami geri iš... [toliau žr. visą tekstą] / Goal of study – to find the reason of natural regeneration of black alders forests. Task of study – To find the intensity of the regeneration of black alders and to indentify how much does it depends on the main sort, age and the area. To find the intensity of the regeneration which depends on cutting technology Object of study – Black alders forests in Kazlu Rudas ferestry enterprice. Methods of study – There was 18 different areas of blac alders forests cutted in 1996-2006. For the researc of the areas there were been looking for the different technologies of the cutting, with a different forests, but most of all of black alders. In that areas were made special places of the counting, there were done these types of analysis: describtion of the area, counting of the natural regeneration of black alders, regeneration of another type of trees, intensity and the quality of the regeneration of black alders. Made a report of the condition and the quality of a young black alders forests. Results of study– There were cutted hundreds of hectares of black alders forests each year. About 87% of all cutted black alders areas were left to generate. The cutted areas are sucsesfully regenerating if they were cutted in winter time, and the year of the seeding. It is very important to leave the goog quality trees which had grown from the seeds. In the areas there were cutted using the footstalk technology the regeneration of black alders forests was good. In the most of all areas there... [to full text]

Darbo objektas – alksnio genties medžiai (juodalksnis (Alnus glutinosa L.), baltalksnis (Alnus incana L.) ir hibridinis (gauruotasis) alksnis (Alnus x hybrida A. Braun ex Rcchb). Darbo tikslas – ištirti hibridinio alksnio (Alnus x hybrida A. Braun ex Rcchb) mikrodauginimo audinių kultūroje sąlygas ir išauginti augalus – regenerantus. Darbo metodai – šiame darbe pasirinktas informacijos rinkimo metodas – eksperimentinis tyrimas. Eksperimentinio tyrimo etapai: 1. eksplantų paruošimas sterilinimui ir sterilinimas; 2. maitinamosios terpės ruošimas; 3. augalų regenerantų kultivavimas; 4. duomenų rinkimas, apdorojimas ir rezultatų analizė. Darbo rezultatai: Dauginamosios medžiagos sterilinimui tinkamiausias yra aseptikas „ACE“ ir sidabro nitratas AgNO3, nes priklausomai nuo genotipo, 89–93 procentai eksplantų išliko be užkrato. Nepaisant genotipo kalius 100 procentų susidarė ant visų mikroūglių, skyrėsi tik jo susidarymo laikas. Nustatyta, kad tinkamiausias mikroūglių regeneracijai yra BAP (citokininas) augimo reguliatorius. Hibridinis alksnis mikroūglių skaičiumi aplenkė juodalksnį ir baltalksnį. Didžiausias dauginimo galimybes turi alksnio hibridas, nes iš vieno kaliaus išaugusių mikroūglių skaičius buvo didžiausias. / Final work of University Postgraduate Studies studied the hybrid alder tissue culture and micropropagation of plants–regenerants grown. Research subject – genus alder trees (alder (Alnus glutinosa L.), gray alder (Alnus incana L.) and hybrid (Woolly) alder (Alnus x hybrida A. Braun ex Rcchb). Research aim – to investigate the hybrid alder (Alnus x hybrida A. Braun ex Rcchb) micropropagation conditions in the culture of tissue and to grow crops–regenerants. The experimental phases of the study: 1. the preparation to sterilized explants and sterilization; 2. the preparation of nutrient medium; 3. the cultivation of regenerants–plants; 4. collection, processing of data and analysis of the results. The results – The aseptic „ACE“ and silver nitrate AgNO3 is the most suitable for the sterilization, because depending on the genotype, 89-93 percent of the explants remained free of infection. Despite of genotype callus formed 100 percent on the every microshoots, only in the different time of life. It was found out the best growth regulator of microshoots regeneration is BAP (cytokinin). Hybrid alder by the number of microshoots outsriped alder and gray alder. The biggest opportunities of propagation has hybrid alder because the biggest number of microshoots grown from a single callus.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

This thesis describes synthetic studies directed towards the total synthesis of the natural products TEO3.1, hamigerone and embellistatin. Chapter One provides an overview, which details the role of antifungal natural products in the pharmaceutical and agrochemical industries, and describes the association between total synthesis and natural products. Three structurally related natural products TEO3.1, hamigerone and embellistatin are introduced as synthetic targets and a strategy for their synthesis is proposed involving an intramolecular Diels-Alder (IMDA) reaction, followed by addition-elimination chemistry. Investigations into the application of the IMDA reaction to the synthesis of the bicyclic core are described in Chapter Two. A Julia olefination reaction was used to install the diene moiety and allowed for the successful synthesis of a model triene precursor. The IMDA cyclisation of the triene was shown to proceed with high endo-selectivity. However, efforts to generate the diene-containing bicyclic core failed and, as a result, this approach to the natural products was abandoned. Chapter Three introduces the diene-regenerative Diels-Alder reaction as an alternative strategy for the direct installation of the diene moiety. The preparation of a model system is described, which established methodology for the efficient preparation of the pyrone-containing Diels-Alder substrate. Cyclisation of this material via a [4 + 2] cycloaddition reaction, followed by extrusion of carbon dioxide, proved a viable method for generating the desired cyclohexadiene system. In Chapter Four, the previously established methodology is applied to the synthesis of the fully functionalised bicyclic core of TEO3.1, hamigerone and embellistatin. The preparation of the racemic Diels-Alder substrate and its successful cyclisation to the bicyclic core is described. An investigation into the preparation of chiral material is also discussed, as well as the description of a model study for the installation of the various side-chains of the natural products. The chapter concludes with a brief discussion of the future studies required to complete the total synthesis of the TEO3.1, hamigerone and embellistatin.

Vinigrol was isolated in 1987 from the fungal strain Virgaria nigra F-5408 by Hashimoto and co-workers. This compound was identified as having antihypertensive and platelet aggregation properties as well as being recognized as a tumor necrosis factor inhibitor. Aside from its interesting biological activities, vinigrol also possesses a unique structural motif consisting in a decahydro-1,5-butanonaphthalene core decorated with 8 contiguous stereocenters. Despite synthetic efforts by many research groups since its isolation, it wasn’t until 2009 that the first total synthesis of vinigrol was reported by Baran and co-workers. Herein is presented a formal synthesis of this highly compact molecule which relies upon a highly diastereoselective ketal Claisen rearrangement as the stereodefining step and an intramolecular Diels-Alder reaction to access the tricyclic structure of the molecule. (+)-Digitoxigenin is a cardiac glycoside used in the treatment of many ailments such as congestive heart failure. It is a member of the cardenolides, a sub-type of steroid containing certain structural differences such as cis A/B and C/D ring junctions, a tertiary hydroxyl group at C14 and a butenolide substituent at C17. Although a few syntheses of this class of compounds have been reported, general strategies to access their framework is scarce. Herein we report our studies towards the total synthesis of digitoxigenin which rely upon a cascading gold-catalyzed cycloisomerization (or enyne metathesis)/Diels-Alder reaction.