Download or read book Synthetic Studies Toward the Total Synthesis ajmaline and the Development Of Investigation Into and Application of a Phosphine catalyzed 4 1 Annulation written by Brian Richard Blank and published by . This book was released on 2014 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several synthetic routes toward the synthesis of the indole alkaloid (±)-ajmaline have been explored. The retrosynthetic plan was devised around two key transformations, one being a tandem aza-Michael-Michael reaction, and the other a phosphine-catalyzed [4+2] annulation. While these approaches have not allowed for the completion of ajmaline, they have provided a great deal of insight into the chemistry of many intermediates. For example, it was discovered that following installation of the D-ring, functionalization of the tricyclic scaffold to deliver a precursor for the aza-Michael-Michael sequence was a futile undertaking. As such, the necessary functionality had to be installed prior to the [4+2] annulation. For this purpose, ethyl 3-allyl-1H-indole-2-carboxylate was prepared by way of a stepwise Japp-Klingemann reaction, and a subsequent Fischer indolization. Successful conversion of this compound into the N-sulfonyl imine required the employment of 2,6-lutidine to impede isomerization of the allyl moiety. This imine was converted into the tetrahydropyridine through a phosphine-catalyzed [4+2] annulation with ethyl 2-methyl-2,3-butadienoate. Cross-metathesis with methyl acrylate provided the first precursor to the desired aza-Michael-Michael reaction sequence. Unfortunately, only mono-Michael addition was observed when this substrate was employed in the reaction, providing a tetracyclic structure instead of the desired pentacyclic scaffold. As a result, we are currently pursuing tricyclic derivatives that feature either alternative Michael donors or an increased strength of the second Michael acceptor. A phosphine-catalyzed [4+1] annulative rearrangement has been developed to prepare 3-pyrrolines from allenylic carbamates through phosphonium diene intermediates. This methodology was employed to synthesize an array of 1,3-disubstituted- and 1,2,3-trisubstituted-3-pyrrolines, including the often difficult to prepare 2-alkyl variants. A mechanistic investigation employing allenylic acetates and mononucleophiles unexpectedly unveiled that a phosphine-catalyzed [4+1] reaction previously reported by Tong might not occur through a phosphonium diene as was proposed, but rather involves multiple mechanisms working in concert to construct cyclopentene products. Consequentially, our phosphine-catalyzed rearrangement is most likely the first reaction that unequivocally forms a phosphonium diene intermediate along the reaction pathway. Concise formal syntheses of pyrrolizidine alkaloids (±)-trachelanthamidine and (±)-supinidine were completed, demonstrating the synthetic utility of this newly developed reaction.

Download or read book Studies Toward the Synthesis of Agelastatin a and Mechanistic Investigations of the Uncatalyzed Chlorocyclization of 4 phenyl 4 pentenoic Acid written by Emily R. Dzurka and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an investigation into efforts towards the total synthesis of agelastatin A, as well as a mechanistic study of the uncatalyzed chlorocyclization reaction of 4-phenyl-4-pentenoic acid.Chapter 1 introduces all the prior total syntheses completed to date of agelastatin A. This chapter details the benefits, and similarities between each synthesis, as well as serves as an introduction into why a different, and novel route to the molecule is beneficial. Chapter 2 presents the current studies towards synthesizing the molecule utilizing chemistry that was developed in the Borhan lab. Within this chapter, different synthetic routes to access the molecule are described.Chapter 3 focuses on the mechanistic studies to determine the molecularities that lead to the syn- and anti-chlorolactonization. Chemical kinetics were a central part of this investigation, as well as concentration studies. This information provided key insights into the postulated transition states that lead either the syn-addition or anti-addition product.

Download or read book Isocoumarin Thiaisocoumarin and Phosphaisocoumarin written by Sarbani Pal and published by Elsevier. This book was released on 2018-10-16 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Isocoumarin, Thiaisocoumarin and Phosphaisocoumarin: Natural Occurrences, Synthetic Approaches and Pharmaceutical Applications gives an overview of the various aspects of this class of heterocycle, with a major focus on synthesis and biological activity. Aromatic δ lactones or isocoumarins with thiaisocoumarins, phosphaisocoumarins and a-pyranone fused with a heteroaryl ring constitute an important class of heterocyclic compounds. This book provides the methods applied for the synthesis of thiaisocoumarins, phosphaisocoumarins, and a-pyranone fused with a heteroaryl ring. It is useful to medicinal and natural product chemists who want to synthesize target molecules and develop cutting-edge technologies to provide better solutions to researchers. Features an overview of isocoumarins and their role in pharmaceutical research Presents a template for the design, discovery and development of new and potential drugs in various therapeutic areas Includes comprehensive coverage of the synthesis of isocoumarins, from traditional methods, to transition metal catalyzed methods Looks at future applications for these important compounds in the areas of drug discovery and pharmaceutical research

Download or read book Development of Metal catalyzed Asymmetric Allylic Alkylations for the Total Synthesis of Alkaloids and Other Nitrogen Containing Biologically Active Targets written by Maksim Osipov and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation deals with the development of metal-catalyzed asymmetric allylic alklyations, and their use for the synthesis of alkaloids and other nitrogen-containing biologically active compounds. The synthesis of the drug ( -- )-ranirestat is disclosed, which relies on a Pd-catalyzed asymmetric allylic alkylation (Pd-AAA) as a key step. The development and application of pyrroles and indoles as nucleophiles in the Pd-AAA is described. A Pd-catalyzed decarboxylative asymmetric alkylation approach to constructing vicinal all-carbon quaternary stereocenters is disclosed, and this methodology is used to complete the formal synthesis of several cyclotryptamine alkaloids. Finally, a catalytic asymmetric total synthesis of the alkaloid ( -- )-perophoramidine and efforts towards the alkaloid communesin B are described. Both syntheses employ a molybdenum-catalyzed asymmetric allylic alkylation as a key asymmetric step. ( -- )-Ranirestat is a potent aldose reductase inhibitor currently in phase III clinical testing for its ability to treat diabetic neuropathy. We have developed a concise, catalytic asymmetric total synthesis of ( -- )-ranirestat, which was completed in 8 steps and 14% overall yield starting from inexpensive, commercially available 2-(trichloroacetyl)pyrrole. A palladium-catalyzed asymmetric allylic alkylation (Pd-AAA) of an imidomalonate and an allylic carbonate serve as a key transformation to construct the tetrasubstituted stereocenter in the target with high yield and enantioselectivity. Protiodesilylation followed by oxidative cleavage of the allyl moiety and cyclization are used to access ( -- )-ranirestat. Nitrogen heterocycles are found in a variety of natural products and other biologically active compounds. We have demonstrated that pyrroles and indoles bearing electron-withdrawing groups are competent nucleophiles in the Pd-AAA with vinyl aziridines. The resulting alkylated products were obtained with high levels of regio-, chemo-, and enantioselectivity. Both substituted 1H-pyrroles and 1H-indoles were successfully employed to give exclusively the branched N-alkylated products. The synthetic utility of this asymmetric process was demonstrated through the elaboration of pyrrole products into bromopyrrole alkaloids longamide B, longamide B methyl ester, hanishin, agesamides A and B, and cyclooroidin. Likewise, the synthetic utility of the indole products was demonstrated by elaboration into several patented piperazinones and piperazine medicinal chemistry lead compounds. 1H-Pyrroles have also shown to serve as nucleophiles with meso electrophiles in the Pd-AAA. The products from this transformation were obtained as a single regio- and diastereomer in high yield and % ee. To demonstrate synthetic utility, a pyrrole-substituted nucleoside analogue was synthesized employing this methodology as the asymmetric step. Quaternary all-carbon stereocenters are present in many natural products and biologically active compounds. The presence of this structural element greatly complicates the asymmetric assembly of molecules due to steric congestion. The asymmetric assembly is complicated further when a second vicinal, quaternary center is present in a molecular target. We have discovered that a two-fold Pd-DAAA of an oxindole-derived dienol carbonate can be used to construct two vicinal all carbon quaternary stereocenters in a diastereo- and enantioselective fashion. To demonstrate the synthetic utility of this process, the product of this transformation was used to complete the formal syntheses of the cyclotryptamine alkaloids ( -- )-chimonanthine, (+)-calycanthine ( -- )-folicanthine, and ditryptophenaline. Mechanistic investigations have suggested that the two-fold Pd-catalyzed transformation proceeds through an unusual matched and mismatched allylation to deliver the desired product. Perophoramidine was isolated from the ascidian organism Perophora namei and displays cytotoxicity toward the HCT116 colon carcinoma cell line with an IC50 of 60 æM. The complex polycyclic cage-like core of this alkaloid makes it a challenging and interesting target for total synthesis. A catalytic asymmetric total synthesis of ( -- )-perophoramidine was developed employing a molybdenum-catalyzed asymmetric allylic alkylation between an allylic phosphate and an alkyl oxindole as an asymmetric step. This key transformation provides a chiral oxindole product in high yield and with high levels of regio-, diastereo-, and enantioselectivity. The chiral oxindole product, which contains the key quaternary stereocenter present in perophoramidine, was further elaborated to a pentacyclic imino ether using a reductive cyclization, oxidative cleavage and lactamization as key transformations. The imino ether was alkylated with allyl iodide to construct the second vicinal quaternary stereocenter providing an allyl imino ether as a single regio- and diastereomer. The allyl imino ether was converted to an aldehyde via ozonolysis, which was subjected to a reductive amination and cyclization sequence to complete ( -- )-perophoramidine.

Download or read book New Gold Catalyzed Reactions and Applications for the Synthesis of Alkaloids written by Ana Escribano Cuesta and published by Springer Science & Business Media. This book was released on 2013-08-13 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ana Escribano Cuesta's thesis presents a detailed study of the inter- and intramolecular reactions of carbonyl compounds with 1,6-enynes using gold (I) complexes. An important part of the work involved streamlining the variables that allow the selective synthesis of different products such as tricyclic compounds, dihydropyrans, 1,3-dienes or cyclobutenes. The second chapter highlights the importance and difficulties in synthesising a cyclobutene subunit and the author includes a detailed description of how the products were prepared. The final chapter outlines the synthesis of lundurines using methodology developed by the author's research group for intramolecular gold-catalyzed cyclization of indoles with alkynes. The lundurine products developed in this work show significant in vitro cytoxicity toward B16 melanoma cells. The work in this thesis has led to a number of publications in high-profile chemistry journals.

Download or read book Emerging Synthetic Methods for Routes Towards Molecules of Biological Relevance written by Calum D. Forsyth and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigations into the application of catalysts, of the type [Ir(COD)(PR3)(NHC)]PF6, within the realm of alkyne dimerization have been undertaken. These novel catalysts, previously synthesised within our research group, feature both a bulky phosphine ligand and a sterically-encumbered N-heterocyclic carbene ligand. The use of these iridium complexes in alkyne dimerization has been examined, with particular emphasis being placed upon tuning the selectivity of the dimerization whilst maintaining high yields. The relative paucity of iridium-mediated (Z)-selective dimerization procedures detailed in the literature rendered this transformation an appealing process to investigate. Subsequent studies led to a broadly employable system being developed which was applied to a range of aryl alkynes, resulting in the formation of the analogous (Z)-enynes in good yield. Following this, a programme of research in collaboration with the Beatson Institute for Cancer Research, Glasgow, describes contributions towards the construction of specific '3D libraries' for potential application in fragment-based drug discovery. The chemistry investigated during this time forms the basis of the Beatson's contribution to the recently formed '3D libraries consortium' concerned with the fragment-based drug discovery. The ultimate goal was the preparation of an array of compounds featuring a non-planar conformation. It is hypothesised that the fragments will play key roles in inhibiting protein-protein interactions in key oncological processes. Further, it is envisaged that the conformational complexity imparted to the compounds will provide an advantage in overcoming difficulties associated with protein specificity. The aim of the project was to design a synthetic route to a novel pyridyl cyclopropane scaffold. The goal was that the preparative approach would allow for rapid access to a key late-stage intermediate, which in turn would then be able to undergo a series of transformations to allow for a range of fragments, based around a common scaffold, to be synthesised. The isolated compounds will form the basis of biophysical and biochemical based screening assays examining the compound's anti-cancer profile, with particular focus on identifying inhibitors of proteinprotein interactions. The final section of research centred on efforts towards the total synthesis of Agariblazeispirol C. As a result, significant steps towards the synthesis of the natural product have been achieved and a functionalised advanced intermediate has been reached. In this regard, a robust and efficient preparative pathway to the advanced intermediate has been designed. In addition, the key oxygenated sidechain has been installed in a late-stage species and represents an auspicious step towards the synthesis of the target molecule. The introduction of this key moiety was achieved following sustained synthetic efforts focusing on olefination and organometallic addition chemistry. The stereochemistry of the resulting intermediate has been deduced based on NMR studies. Subsequent synthetic investigations facilitated the formation of a suitable precursor for the ultimate synthetic transformation, a Pauson-Khand reaction. Preliminary attempts to promote the annulation protocol are discussed and it is likely that this work will significantly enhance the likelihood of accessing the natural product for the first time.

Download or read book A Preparative Route Investigation of N Heterocyclic Phosphine Catalysts and Their Application Towards the Synthesis of Colchinoid Analogues written by Adam Beckett and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A growing field in chemistry is the reduction of small molecules employing main group element catalysts. A recent advance has been the use of N-heterocyclic phosphines (NHPs) in the reduction of imines to produce secondary amines. NHPs can also perform conjugate reductions of electron poor alkenes.1 (-)-Colchicine is a natural product of biological interest due to its antimitotic properties. Current synthetic methods require expensive and toxic transition metal catalysts to generate colchinoids.2 The second chapter explores an alternative route towards the total synthesis of (-)-colchicine analogues by utilizing NHPs instead of traditional metal catalysis. A chemoselective conjugate reduction mediated by NHPs allows the expedient assembly of a precursor to a cyclization reaction. The next chapter provides a unique synthetic route towards the synthesis of previously inaccessible NHP moieties and preliminary exploration of their reactivity that aims to simplify current synthetic techniques by proposing an efficient one-pot synthesis.

Download or read book The logic of chemical synthesis written by E.J. Corey and published by Рипол Классик. This book was released on 1991 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Utility of New Ynamide and Organo allyltrifluoroborate Reagents written by Ramsay Eaton Beveridge and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthetic Studies Towards the Total Synthesis of Lancifodilactone G written by Sanil Sreekumar and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents our studies towards the first total synthesis of the novel anti- HIV agent lancifodilactone G, which has a highly unusual aliphatic enol. The first chapter provides a survey of architecturally diverse nortriterpenoids that were isolated from the Schisandraceae family. A proposed biosynthetic pathway for lancifodilactone G and closely related natural products provides a rationale for the formation of the consecutive 7/8/5 fused carbo cycles that are unique to Schisandra nortriterpenoids. Chapter 1 goes on to outline the reported strategies to access the core of lancifodilactone G and concludes with a retrosynthetic analysis proposed by the Evans group, which includes a biosynthetically inspired single-pot polycyclisation reaction. Chapter 2 describes the highly stereocontrolled synthesis of the eastern fragment (F-G rings) using transition metal-mediated Pauson-Khand reaction. This chapter also reviews the metal-mediated diastereoselective Pauson-Khand reaction directed by the stereogenic centre at C2, with the ample illustration to total synthesis. Attempted strategies for the assembly of the bicyclic cyclopentanone motif via a dienyl Pauson-Khand reaction of silicon- and oxygen- tethered diene-enes are presented. The failure of these strategies at different stages of the synthesis resulted in the exploration of a classical Pauson-Khand approach, which successfully furnished the eastern fragment. Finally, a second-generation synthesis is described which provided the fully functionalised eastern fragment with improved efficiency and overall yield. Chapter 3 discusses the successful synthesis of the western fragment (B-C rings) using a diastereoselective [4+3] cycloaddition strategy. Attempted strategies for the synthesis of the key 2,3-disubstituted furan derivative are presented, which was achieved via a hetero Pauson- Khand reaction. This chapter includes a brief account of the classical [4+3] cycloaddition reactions of furans using an in situ generated oxyallyl cation and also employing vinyl carbenoids in the metal-catalysed version. The review also highlights the application of the [4+ 3] cycloaddition reaction in the expeditious assembly of functionalised 7-membered rings that occur in a number of important biologically active natural products. The third chapter goes on to describe the application of these cycloaddition reactions in the synthesis of the fully functionalised western fragment of Lancifodilactone G. Chapter 4 describes a model study aimed at expediting the synthesis of the western fragment using a rhodium-catalysed allylic substitution reaction. A brief mechanistic discussion on unique aspects of the allylic alkylation reaction is illustrated. Chapter 4 concludes by outlining the coupling strategy for eastern and western fragments and the end game studies for the completion of the synthesis of lancifodilactone G.

Download or read book I Second Generation Total Synthesis of Nakadomarin A written by Kyle William Rugg and published by . This book was released on 2018 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Part I. The Second-Generation Total Synthesis of (-)-Nakadomarin A The second-generation total synthesis of (-)-nakadomarin A (1) has been described. A robust sequence toward the bicyclic lactam has been developed, allowing its production on > 5 g scale. This has been enabled by a number of significant improvements, including increased diastereoselectivity for the key SN2' cyclobutane formation, a scalable cyclobutanecarboximine formation/retro-aza-Claisen sequence, and the removal of a step from the longest-linear sequence by use of isocyanate addition to the bicyclic lactam in lieu of a two-step protocol. The Michael addition/spirocyclization's catalytic potential has been investigated, and a robust and scalable method for the synthesis of the spirocycle has been deployed. After pentacycle formation, macrocyclization, and reduction, (-)-nakadomarin A (1) is afforded with production of the target on over 0.5 g scale. This has resulted in a total synthesis of 1 in 16 steps (longest linear) and 6.5% overall yield. Part II. Studies Toward the Total Synthesis of (-)-Apoptolidin A A route toward the potent and selective apoptosis inducer (-)-apoptolidin A has been outlined. Production of the lactone comprising the southwestern quadrant of the natural product on scale by a previously described route has been investigated. Small-scale success in generating the lactone was ineffective on larger scales using the existing protocol due to the sensitive nature of an intermediate Diels-Alder adduct. Important advancement in material throughput was achieved by implementation of a robust two-step protocol for generating a critical intermediate alcohol on larger scales. Combined with the improvement of a deallylation protocol, a scalable route to the lactone of the southwestern quadrant of (-)-apoptolidin A has been established. With this, the completion of the southern hemisphere and aglycone of (-)-apoptolidin A will be accessible"--Pages x-xi.

Download or read book Synthetic Studies Towards a Total Synthesis of Roseophilin written by Eddy Michel Elie Viseux and published by . This book was released on 2006 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Total Synthesis of the Acetyl CoA Carboxylase Allosteric Inhibitor Soraphen A and the Development of New Catalytic Methods Using Palladium Iridium and Rhodium written by Tabitha Taylor Schempp and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal catalysis with palladium, iridium, and rhodium has provided a lexicon of synthetic transformations extensively utilized in the construction of complex molecules. The total synthesis of soraphen A, a type 1 polyketide allosteric inhibitor of Acetyl-CoA carboxylase, was completed in 11 steps (LLS), less than half the previously required steps. The synthesis maximizes convergency by exploiting the catalytic reactivity of transition metals to facilitate five asymmetric processes and four carbon-carbon bond formations. A key strategic element involves the development of a new synthetic method: a palladium-AntPhos catalyst directed diastereoselective hydrogenolysis of allylic carbonates to reveal a terminal olefin for successive olefin cross-metathesis. The development of palladium-catalyzed hydrogenolysis of allylic compounds, current asymmetric methods, and their application in the total synthesis of complex natural products will be described. In addition, an iridium-catalyzed enantioselective allylation of indoles and various azoles to access products with complete N- and branched-regioselectivity and a rhodium-catalyzed reductive coupling-internal redox isomerization of vinyl triflates and aldehydes to furnish ketones were developed

Download or read book Part I Mechanistic Studies Optimization and Further Applications of the Organocatalytic alpha hydroxymethylation of Aldehydes Part II Studies Toward the Total Synthesis of FK 506 written by Kyle Francis Biegasiewicz and published by . This book was released on 2016 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Part I. Mechanistic Studies, Optimization, and Further Applications of the Organocatalytic [alpha]-Hydroxymethylation of Aldehydes: Further developments in studies of the direct [alpha]-hydroymethylation of aldehydes employing the [alpha],[alpha]-diarylprolinol trialkylsilyl ether class of organocatalysts are described. This synthetic transformation has proven effective in expedient access to [beta]-hydroxycarboxylic acids and [delta]-hydroxy-[alpha],[beta]-unsaturated esters from aldehydes in moderate to excellent yields, excellent enantioselectivity, and compatibility across a wide range of funtional groups in the starting aldehyde. These studies have also been successful in identifying the critical reaction variables that influence the yield and enantioselectivity in the [alpha]-hydroxymethylation process including catalyst structure, pH of the reaction medium, purity of the reagents employed, nature of the buffer, along with standard reaction variables including the solvent, time, temperature, and mixing efficiency. In addition, the previously identified lactol intermediate has been further characterized and examined. The culmination of these studies has translated directly into an improved substrate scope, reproducibility, enantioselectivity, and yields of the described method. Finally, the described [alpha]-hydroxymethylation protocol has been applied to a multi-gram scale synthesis of the southern hemisphere of the apoptosis inducer, (-)-rasfon. Part II. Studies Toward the Total Synthesis of FK-506: An approach to the total synthesis of the immunosuppressant FK-506 is described. The synthetic strategy features the division of the macrocycle into four subunits allowing for a maximum degree of convergence in the forward synthesis. Improvements to the synthesis of a key intermediate vinyl bromide are described that have allowed for the multi-gram throughput of the southern portion of the macrocycle. Improvements have been made to the synthesis of the northern hemisphere of the macrocyle synthesis, again allowing for better material throughput. Finally, several coupling strategies have been explored and the culmination of these efforts have led to promising preliminary results on the unification of the northern and southern hemispheres, bringing the molecules synthesis to near completion"--Pages vii-viii.

Download or read book Studies Towards the Total Synthesis of Palau amine written by Daniel Rivalti and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The pyrrole-imidazole alkaloids (PIAs) are a family of structurally related natural products isolated from several species of marine sponges. Palau'amine, a dimeric PIA, has been a target for total synthesis ever since its isolation in 1993 due to its significant biological activity and, more importantly, its complex molecular architecture. In 2007, the structure ofpalau'amine was revised to incorporate a highly strained trans-fused azabicyclo[3.3.0]octane bicyclic system.This thesis follows the progression of efforts that culminated in the development of a cyclization strategy for the formation of the strained trans-fused 5,5-bicyclic ring system. In our initial exploration, attempts to secure the trans-fused 5,5-ring system via previously established metal-mediated diamination protocols and amidyl radical cyclization were thwarted. Finally, the synthesis of the trans-fused core within a simple cyclic model systemwas enabled by the conjugate addition of a carbamate nitrogen to an ynoate which furnishes a trans-fused azabicyclo[3.3.0]octane bicyclic system containing an exocyclic [alpha],[beta]-unsaturated ester. The latter would act as a synthetic handle to construct the remaining right-hand side core of palau'amine.Two particular monomeric PIAs, phakellin and phakellstatin, greatly resemble palau'amine in that they share the same ABCD tetracyclic core. The application of our conjugate addition strategy afforded the pyrrolidine A-ring, containing an exocyclic [alpha],[beta]-unsaturated ester. To access the phakellstatin core, the elaboration of that synthetic handle to the vinyl urea was achieved via a Curtius rearrangement. A cyclofunctionalization reaction secured the pyrazinone B-ring affording the desired tricyclic carbinolamine precursor suitable for the synthesis of phakellstatin. To access the phakellin core, the exocyclic [alpha],[beta]-unsaturated ester was elaborated, via a Curtius rearrangement/aza-Wittig one-pot process, to an advancedintermediate containing the complete nitrogen and carbon framework of phakellin. The cyclofunctionalization reaction with the guanidine-containing intermediate secured the pyrazinone B-ring affording the desired tricyclic carbinolamine. Unfortunately, final attempts to close the guanidine C-ring and to complete the synthesis of the natural product werehowever unsuccessful." --

Download or read book Studies Toward The Total Synthesis of Manzamine A written by Brian B. Filippini and published by . This book was released on 1995 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reactivity of P H Group of Phosphorus Based Compounds written by Kolio D. Troev and published by Academic Press. This book was released on 2017-09-06 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reactivity of P-H Group of Phosphorus Based Compounds bridges the gap between inorganic and organic phosphorus compounds, providing a basis to explore the myriad possibilities for synthesis of novel low and high molecular phosphorus-containing compounds. It covers well-documented reactions in detail, including: tautomerization, oxidation, reduction, alkylation, oxidation coupling, addition reaction to: carbon-carbon multiple bonds, Schiff base, isocyanates, nitriles, epoxides; addition to carbonyl group, Kabachnik- Fields reaction, cross-coupling reaction and more. In an accessible style complete with synthetic routes and figures, the resource then covers the reactivity of multiple P-H group members: phosphines, phosphine oxides, hypophosphorus acid, H-phosphinic acids and polys(alkylene H-phosphonate). This valuable coverage supports the advancement of research and applications in this area for scientists solving a scientific problem or starting a variety of new projects, such as a new reaction for the synthesis of biologically active compounds, new methods of polymer synthesis or a new methodology for polymer modification. Describes the diverse reactivity of the phosphorus-hydrogen group, perhaps the most powerful in organic chemistry Includes practical information for the synthesis of catalysts, biologically active substances, flame retardants, advance materials and polymer materials Offers a visually-accessible guide to important reactions by an internationally recognized chemist