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chemistry of Briareum asbestinum
Title
The chemistry of Briareum asbestinum.
Creator
Rondeau, Melody D., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
Briareum asbestinum, a soft coral, is a rich source of diterpenoid natural products. The secondary metabolites of B. asbestinum fall into four classes : asbestinins, briarellins, briareolate esters, and briaranes. Briareolate esters have been shown to possess biological activity and were previously only reported from Tobago. Our group recently isolated briareolate esters from a specimen collected off the coast of Boca Raton, Florida. To determine whether location has an impact on the...
Show moreBriareum asbestinum, a soft coral, is a rich source of diterpenoid natural products. The secondary metabolites of B. asbestinum fall into four classes : asbestinins, briarellins, briareolate esters, and briaranes. Briareolate esters have been shown to possess biological activity and were previously only reported from Tobago. Our group recently isolated briareolate esters from a specimen collected off the coast of Boca Raton, Florida. To determine whether location has an impact on the chemistry produced by the organism, a method to discern between chemotypes was sought. Several techniques including thin layer chromatography (TLC), high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and sclerite analysis were employed, with NMR being the most successful method. By utilizing both 1H and COSY NMR experiments, it is possible to differentiate between the chemotypes of B. asbestinum. Application of this method allowed analysis of chemical variability with respect to location.
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Date Issued
2012
PURL
http://purl.flvc.org/FAU/3355882
Subject Headings
Heterocyclic compounds, Synthesis, Coral reef ecology, Marine organisms, Environmental aspects, Biochemical markers
Format
Document (PDF)
Development and applications of nucleophile assisting leaving groups (NALGs) with Titanium (IV) and Grignard reagents
Title
Development and applications of nucleophile assisting leaving groups (NALGs) with Titanium (IV) and Grignard reagents.
Creator
Li, Songye., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
We report here the development of very efficient aryl- and quinolinyl- sulfonate based leaving groups, termed Nucleophile Assisting Leaving Groups (NALGs), which substantially accelerate the rate of nucleophilic substitution reactions with metal halides. Detailed synthesis and kinetics study are described herein. Our synthesized NALGs have shown great reactivity towards poor nucleophiles and/or substrates traditionally considered too hindered to undergo nucleophilic attack. The abundant...
Show moreWe report here the development of very efficient aryl- and quinolinyl- sulfonate based leaving groups, termed Nucleophile Assisting Leaving Groups (NALGs), which substantially accelerate the rate of nucleophilic substitution reactions with metal halides. Detailed synthesis and kinetics study are described herein. Our synthesized NALGs have shown great reactivity towards poor nucleophiles and/or substrates traditionally considered too hindered to undergo nucleophilic attack. The abundant existence of halide, azide and amine in natural products demands new synthetic pathway. To fulfill this requirement, new mild stereoretentive halogenations (chlorination, bromination and iodination) reactions have also been developed for secondary cyclic alcohols using NALGs involving titanium (IV) reagents. The novel methodology can be extended to Azidation reactions as well with titanium (IV) azide, in which Ti (N3)4 is the first time being engaged in organic synthesis. Beased on the NALGs theory we discover the chlorosulfite can be a simplest NALG and applied as the intermediate in mild one-pot stereoretentive halogenations (chlorination and bromination) using titanium (IV) halides as catalysts or stoichiometric reagents. These reactions were found to be particularly efficient for cyclic alcohols. Finally, an efficient mild bromination and iodination reaction for primary and secondary alcohols with Grignard reagents is also reported. This reaction exhibits the generality with substrates with various leaving groups. The important features of this reaction are that, for the first time, bromide formation using Grignard reagents without the Cu (I) catalysts.
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Date Issued
2011
PURL
http://purl.flvc.org/FAU/3183130
Subject Headings
Chemical kinetics, Chemical reaction, Condition and laws of, Organic compounds, Synthesis, Organotransition metal compounds, Intermediates (Chemistry), Organic reaction mechanisms
Format
Document (PDF)
Development of Nucleophile Assisting Leaving Groups (NALGs) and new stereoselective reactions using titanium(IV) reagents
Title
Development of Nucleophile Assisting Leaving Groups (NALGs) and new stereoselective reactions using titanium(IV) reagents.
Creator
Mondal, Deboprosad., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
We report here the development of very efficient sulfonate based leaving groups, termed Nucleophile Assisting Leaving Groups (NALGs), to accelerate the rate of nucleophilic substitution reactions involving poor nucleophiles and/or substrates traditionally considered too hindered to undergo nucleophilic attack. Indeed NALGs have shown exceptional ability in improving rate of nucleophilic substitution reactions. New very mild stereoretentive halogenations and azidation reactions have also been...
Show moreWe report here the development of very efficient sulfonate based leaving groups, termed Nucleophile Assisting Leaving Groups (NALGs), to accelerate the rate of nucleophilic substitution reactions involving poor nucleophiles and/or substrates traditionally considered too hindered to undergo nucleophilic attack. Indeed NALGs have shown exceptional ability in improving rate of nucleophilic substitution reactions. New very mild stereoretentive halogenations and azidation reactions have also been developed for secondary cyclic alcohols using NALGs involving titanium(IV) reagents. This reaction is particularly significant since the carbon-halogen bond is found widely in natural products and is used extensively as a synthesis intermediate. Azide is also a synthetically important functional group from which a variety of biologically important functional groups are conveniently obtained. Though stereoretentive chlorination and bromination reactions are known, we have developed, for the first time, a stereoretentive azidation reaction using titanium(IV) azide, a reagent not previously used in organic synthesis. During our development of stereoretentive reactions, we eventually developed very efficient, mild, two-step one-pot stereoretentive halogenations (chlorination and bromination) using titanium(IV) halides as catalysts or stoichiometric reagents. These reactions were found to be particularly efficient for cyclic alcohols. An efficient one pot stereoretentive amidation reaction for secondary cyclic alcohols is also reported. The important features of this reaction are that, for the first time, chlorosulfite (prepared in situ from alcohol using thionylchloride) has been used as a leaving group and titanium(IV) fluoride as an activator., Utilization of those two reagents is unique as thionylchloride has never been used for nucleophilic substitution reactions except in chlorination procedures. In addition, this work has found new and creative applications for titanium (IV) fluoride, a reactant rarely used in organic synthesis. Further exploiting the unique reactivity of titanium(IV), reactions of alkenes with various nucleophiles have been developed with this reagent in both catalytic and stoichiometric quantities. It was observed that a-substituted aromatic conjugated alkenes dimerize to generate important indan class of compounds which are very important in the polymer industry. In addition, non conjugated unactivated alkenes react with various nucleophiles to yield the adduct.
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Date Issued
2010
PURL
http://purl.flvc.org/FAU/3159264
Subject Headings
Chemical reaction, Condition and laws of, Organic compounds, Synthesis, Chemical templates, Intermediates (Chemistry), Organotransition metal compounds, Organic reaction mechanisms
Format
Document (PDF)
Methodologies Towards One Pot Synthesis of α-Arylated Amino Esters And Applications in Total Synthesis
Title
Methodologies Towards One Pot Synthesis of α-Arylated Amino Esters And Applications in Total Synthesis.
Creator
Samanta, Shyam S., Roche, Stephane P., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
In this dissertation, we discuss the development of a synthetic method to functionalize various α-haloglycine esters, as key precursors to a large variety of non-proteinogenic α-amino acids (Xaas). At first, we discovered a very practical and high yielding acetyl chloride-mediated cascade reaction to synthesize α-arylated amino esters in one-pot. In this multicomponent reaction (MCR), a primary carbamate was condensed with a glyoxylate, followed by an in situ halogenation which proved...
Show moreIn this dissertation, we discuss the development of a synthetic method to functionalize various α-haloglycine esters, as key precursors to a large variety of non-proteinogenic α-amino acids (Xaas). At first, we discovered a very practical and high yielding acetyl chloride-mediated cascade reaction to synthesize α-arylated amino esters in one-pot. In this multicomponent reaction (MCR), a primary carbamate was condensed with a glyoxylate, followed by an in situ halogenation which proved essential to trigger the final Friedel−Crafts functionalization. After careful reaction optimization, a plethora of arene nucleophiles were reacted with high regioselectively in CHCl3 at low temperatures (Method A) while less activated arenes reacted more cleanly in CH3CN and at higher temperatures (Method B). To broaden the scope of this reaction to acid sensitive nucleophiles, a one-pot reaction was designed via evaporation of all acid by-products at the α-haloglycine stage. The anion-binding Schreiner’s thiourea catalyst proved to be extremely efficient to promote this complementary approach (Method C) which relies on the chloride leaving group activation by the catalyst to assist the functionalization stage and deliver the α-amino ester product. In the second chapter, some highly practical and efficient preparations of α-haloglycine esters in one-pot have been developed to generate useful precursors of non-proteinogenic α-amino esters. Also, a mild and unique AcOH(cat.)/AcCl system was found to promote an autocatalytic-like condensation/deoxy halogenation and facilitate the multicomponent assembly of non-proteinogenic α-amino esters. Friedel–Crafts reaction between α-chloroglycine and N-methylindole have been studied in details to understand the mechanistic intricacy of this reaction. Our findings through the initial kinetic profiling support that the arylation likely proceeds via a SN1-like (or SN2C+) mechanism. In third chapter, we discuss the development of the most challenging α,α-disubstituted amino esters in a multicomponent fashion. Our results highlight that the MCR proceeds via the formation of an enamide intermediate, which is further tautomerized to corresponding iminium to produce the desired product. In collaboration with Eli Lilly at the Automated Synthesis Laboratory (ASL), we have developed silver (I) salts mediated Friedel–Crafts reaction for synthesis of α-trifluoromethylated α-amino esters on a fully automatized robot.
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Date Issued
2018
PURL
http://purl.flvc.org/fau/fd/FA00013160
Subject Headings
Esters, Synthesis, Amino Acids
Format
Document (PDF)
Studies towards a catalytic asymmetric isomerization of manganese complexed alkynes to allenes using chiral bases
Title
Studies towards a catalytic asymmetric isomerization of manganese complexed alkynes to allenes using chiral bases.
Creator
He, Chang., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
The conversion of alkynyl carbonyls to allenyl carbonyls via manganese mediated coordination followed by a base-catalyzed isomerization was carried out using a range of chiral and achiral amine bases. Chiral amidine and chiral DBU derivatives were synthesized to carry out the isomerization enantioselectively. We employed HPLC equipped with a chiral column to determine the enantiomeric excess. We also proved that the mechanism of that the manganese-coordinated alkyne/allene rearrangement...
Show moreThe conversion of alkynyl carbonyls to allenyl carbonyls via manganese mediated coordination followed by a base-catalyzed isomerization was carried out using a range of chiral and achiral amine bases. Chiral amidine and chiral DBU derivatives were synthesized to carry out the isomerization enantioselectively. We employed HPLC equipped with a chiral column to determine the enantiomeric excess. We also proved that the mechanism of that the manganese-coordinated alkyne/allene rearrangement reaction involved an intermediate cumenolate. It was also confirmed that amine base with pKa lower than that of DBU (pKa = 13.6) would not carry out the isomerization. Alkoxy base were also used in isomerization and the mechanism was also investigated.
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Date Issued
2009
PURL
http://purl.flvc.org/FAU/192983
Subject Headings
Enzyme kinetics, Organometallic compounds, Synthesis, Asymmetric synthesis, Methathesis (Chemistry), Carbonyl compounds, Synthesis
Format
Document (PDF)
Synthesis and new reactions of allenyl carbonyls
Title
Synthesis and new reactions of allenyl carbonyls: studies towards the total synthesis of anti-thrombotic natural products Vitisinol D and C.
Creator
Maity, Pradip., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
We report here the development of new and more general synthetic pathways for the preparation of allenyl and alkynyl carbonyls. These highly dense functionalized compounds were utilized as key intermediates for the synthesis of [3.2.1] and [3.3.1] bicyclic framework, the motifs found in many natural products. A convenient method described for the dehydration of ketoesters to generate conjugated and deconjugated alkynyl esters and conjugated allenyl esters. This sequential one-pot method...
Show moreWe report here the development of new and more general synthetic pathways for the preparation of allenyl and alkynyl carbonyls. These highly dense functionalized compounds were utilized as key intermediates for the synthesis of [3.2.1] and [3.3.1] bicyclic framework, the motifs found in many natural products. A convenient method described for the dehydration of ketoesters to generate conjugated and deconjugated alkynyl esters and conjugated allenyl esters. This sequential one-pot method involves the formation of a vinyl triflate monoanion intermediate that leads to the selective formation of alkynes or allenes depending on additives and conditions used. Product outcomes appear to be a function of unique monoand dianion mechanisms which are described. Our design of a Morita-Baylis-Hilman (MBH) reaction to include a fast silyl 1,3- Brook rearrangement has enabled the first ever anion-catalysis. This new reaction makes possible the addition of both aliphatic and aromatic aldehydes to s ilylallenes leading to carbinol allenoates. These new MBH reactions products allow for a fasttracked synthesis of [3.2.1] bisoxa-bicycles which make up the framework of many biologically active natural products including Vitisinol D. The development of cyclic addition of hydrazine nitrogen to unactivated alkynes catalyzed by non-metals is reported. Starting from readily accessible silyl allenyl esters, alkynyl hydrazines are prepared in one step and subsequently undergo unprecedented cyclization reactions in the presence of ammonium and phosphonium catalysts leading to dehydro-azaproline products. These heterocycles were also produced in high enantiomeric excesses using chiral ammonium phase transfer catalysts via a kinetic resolution pathway., The racemic synthesis of fully functionalized bicyclic core of Vitisinol D was achieved using allenyl ester as a key intermediate. The required electron withdrawing group (EWG) at the position was screened for better addition followed by the compatibility towards successive transformation and, finally, the ease of removal. A reductive aldol method to transform lactone-enol to the desired [3.2.1] bicycle was extensively studied to understand the stereoelectronic requirements for the formation of such bicyclic structures. Due to the necessity of selective protection and deprotection of many phenolic and aliphatic hydroxyls as well as ester groups, orthogonal protecting groups were established accordingly.
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Date Issued
2011
PURL
http://purl.flvc.org/FAU/3332717
Subject Headings
Organic compounds, Synthesis, Carbonyl compounds, Synthesis, Cardiovascular system, Diseases, Treatment
Format
Document (PDF)
Synthesis and photophysical measurements of a series of lanthanide-benzenedicarboxylate coordination polymers
Title
Synthesis and photophysical measurements of a series of lanthanide-benzenedicarboxylate coordination polymers.
Creator
Clark, Jessica Montressa., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
Within solid-state chemistry, coordination polymers have gained interest for use in various applications such as sensing, catalysis, display technology, hydrogen storage, etc. The use of lanthanide ions in these materials provides a mean of exploring how structure may affect luminescence efficiency. In this study, the photophysics of several lanthanide benzenecarboxylates was studied. This data combined with data from other coordination polymers created in our lab indicate that the...
Show moreWithin solid-state chemistry, coordination polymers have gained interest for use in various applications such as sensing, catalysis, display technology, hydrogen storage, etc. The use of lanthanide ions in these materials provides a mean of exploring how structure may affect luminescence efficiency. In this study, the photophysics of several lanthanide benzenecarboxylates was studied. This data combined with data from other coordination polymers created in our lab indicate that the established guidelines for producing highly efficient materials may not correlate directly from solution to the solid state and that structure may also play a role.
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Date Issued
2013
PURL
http://purl.flvc.org/fcla/dt/3362332
Subject Headings
Rare earth metals catalysts, Metallic composites, Speciation, Lanthanide shift reagents, Organic compounds, Synthesis, Polymers, Biotechnology
Format
Document (PDF)
Toward the synthesis of organic moieties for use in luminescent lanthanide materials
Title
Toward the synthesis of organic moieties for use in luminescent lanthanide materials: from benzodithiophene based linkers to a series of 2,3 pyridinedicarboxylate coordination polymers.
Creator
Ramirez, Amanda Lyn Staggers., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
The main focus of this thesis is to present the structural and photophysical characteristics of the coordination polymers [Ln(C7H3NO4)(C7H4NO4)(H2O)]n (Ln is Pr, Nd, Sm, Eu, and Tb), as well as attempting to synthesize the novel organic linker 4,4'(4,8-Dihydrobenzo[1,2-b:4,5-b']dithiophene-4,8-diyl)dibenzoic acid (BDTDC). Various lanthanide salts were coordinated with 2,3-pyridinecarboxylate (2,3- pydc) via hydrothermal synthesis. ... Progress was made toward the synthesis of a novel metal...
Show moreThe main focus of this thesis is to present the structural and photophysical characteristics of the coordination polymers [Ln(C7H3NO4)(C7H4NO4)(H2O)]n (Ln is Pr, Nd, Sm, Eu, and Tb), as well as attempting to synthesize the novel organic linker 4,4'(4,8-Dihydrobenzo[1,2-b:4,5-b']dithiophene-4,8-diyl)dibenzoic acid (BDTDC). Various lanthanide salts were coordinated with 2,3-pyridinecarboxylate (2,3- pydc) via hydrothermal synthesis. ... Progress was made toward the synthesis of a novel metal-organic framework linker BDTDC. Synthesis of the intermediate benzo[1,2-b:4,5-b']dithiophene as well as the determination of the crystal structure, were performed successfully and are reported herein.
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Date Issued
2013
PURL
http://purl.flvc.org/fcla/dt/3362561
Subject Headings
Metathesis (Chemistry), Supramolecular chemistry, Organic compounds, Synthesis, Macromolecules, Synthesis
Format
Document (PDF)