No description available.

No description available.

No / A novel and efficient procedure for the synthesis of furo[3,2-c] coumarins from readily available 4-oxohydrocoumarins and alkenes in the presence of a catalytic amount of Pd(CF3COO)2 has been developed. Atom-economical characteristics and mild conditions of this method are in accord with the concept of modern green chemistry.

Leung Pui-Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 226-266). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.i / ABBREVIATIONS --- p.iii / ABSTRACT --- p.viii / 撮要 --- p.xii / TABLE OF CONTENTS --- p.xvi / Chapter CHAPTER 1: --- GENERAL INTRODUCTION / Chapter 1.1 --- Hematopoiesis & Leukemia --- p.1 / Chapter 1.1.1 --- Introduction to Hematopoiesis and its Regulation --- p.1 / Chapter 1.1.2 --- Leukemia --- p.7 / Chapter 1.1.2.1 --- Classification and Epidemiology of Leukemia --- p.7 / Chapter 1.1.2.2 --- Conventional Approaches to Leukemia Therapy --- p.13 / Chapter 1.1.2.3 --- New Approaches to Leukemia Therapy --- p.16 / Chapter 1.2 --- Coumarins --- p.18 / Chapter 1.2.1 --- Introduction to Coumarins --- p.18 / Chapter 1.2.1.1 --- "Historical Development, Occurrence of Coumarins and their Functions in Plants" --- p.18 / Chapter 1.2.1.2 --- Beneficial Effects of Coumarins for Human Use --- p.20 / Chapter 1.2.2 --- Phytochemistry and Metabolism of Coumarins --- p.22 / Chapter 1.2.2.1 --- Chemical Structures of Coumarins --- p.22 / Chapter 1.2.2.2 --- Biosynthesis of Coumarins --- p.24 / Chapter 1.2.2.3 --- Toxicology of Coumarins --- p.24 / Chapter 1.2.2.4 --- Mode of Entry of Coumarins --- p.25 / Chapter 1.2.2.5 --- Metabolic Pathways of Coumarins --- p.27 / Chapter 1.2.3 --- Pharmacological Activities of Coumarins --- p.30 / Chapter 1.2.3.1 --- Anti-edema and Anti-inflammatory Activities --- p.30 / Chapter 1.2.3.2 --- Cardiovascular Protective Function --- p.32 / Chapter 1.2.3.3 --- Anti-tumor Activity --- p.33 / Chapter 1.2.3.3.1 --- Anti-tumor Activity In Vitro --- p.33 / Chapter 1.2.3.3.2 --- Anti-tumor Activity In Vivo and Clinical Applications --- p.34 / Chapter 1.2.3.4 --- Immunomodulatory Activity --- p.36 / Chapter 1.2.3.4.1 --- Immunological Considerations --- p.36 / Chapter 1.2.3.4.2 --- Immunomodulation In Vitro --- p.37 / Chapter 1.2.3.4.3 --- Immunomodulation In Vivo --- p.38 / Chapter 1.3 --- Aims and Scopes of This Investigation --- p.41 / Chapter CHAPTER 2: --- MATERIALS AND METHODS / Chapter 2.1 --- Materials --- p.43 / Chapter 2.1.1 --- Animals --- p.43 / Chapter 2.1.2 --- Cell Lines --- p.43 / Chapter 2.1.3 --- "Cell Culture Medium, Buffers and Other Reagents" --- p.44 / Chapter 2.1.4 --- Reagents for 3H-Thymidine Incorporation Assay --- p.49 / Chapter 2.1.5 --- Reagents and Buffers for Flow Cytometry --- p.49 / Chapter 2.1.6 --- Reagents for DNA Extraction --- p.52 / Chapter 2.1.7 --- Cell Death Detection ELISAplus Kit --- p.54 / Chapter 2.1.8 --- Reagents for Total RNA Isolation --- p.55 / Chapter 2.1.9 --- Reagents and Buffers for RT-PCR --- p.56 / Chapter 2.1.10 --- Reagents and Buffers for Gel Electrophoresis of Nucleic Aicds --- p.60 / Chapter 2.1.11 --- "Reagents, Buffers and Materials for Western Blot Analysis" --- p.61 / Chapter 2.1.12 --- Reagents for Measuring Caspase Activity --- p.67 / Chapter 2.1.13 --- Reagents for Neutral Red Assay --- p.70 / Chapter 2.2 --- Methods --- p.71 / Chapter 2.2.1 --- Culture of the Tumor Cell Lines --- p.11 / Chapter 2.2.2 --- Determination of Cell Proliferation by [3H]-TdR Incorporation Assay --- p.71 / Chapter 2.2.3 --- Determination of Cell Viability --- p.72 / Chapter 2.2.4 --- In Vivo Anti-tumor Study --- p.73 / Chapter 2.2.5 --- Analysis of Cell Cycle Profile/DNA Content by Flow Cytometry --- p.74 / Chapter 2.2.6 --- Measurement of Apoptosis --- p.74 / Chapter 2.2.7 --- "Islation ,Preparation and Culture of Mouse Peritoneal Macrophages" --- p.76 / Chapter 2.2.8 --- Gene Expression Study --- p.77 / Chapter 2.2.9 --- Protein Expression Study --- p.80 / Chapter 2.2.10 --- Determination of the Mitochondrial Membrane Potential --- p.84 / Chapter 2.2.11 --- Measurement of Caspase Activity --- p.84 / Chapter 2.2.12 --- In Vivo Macrophage Migration Assay --- p.85 / Chapter 2.2.13 --- Study of Endocytic Activity of Macrophages --- p.85 / Chapter 2.2.14 --- Determination of Nitric Oxide Production by Macrophages --- p.86 / Chapter 2.2.15 --- Study of Mitogenesis of Murine Splenocytes --- p.87 / Chapter 2.2.16 --- Analysis of T Cell Population and its Sub-populations --- p.88 / Chapter 2.2.17 --- Measurement of Lymphokine Activated Killer (LAK) Cell Activity by Neutral Red Assay --- p.90 / Chapter 2.2.18 --- Statistical Analysis --- p.91 / Chapter CHAPTER 3: --- STUDIES ON THE ANTI PROLIFERATIVE EFFECT OF COUMARINS ON MACROPHAGE-LIKE LEUKEMIA CELLS / Chapter 3.1 --- Introduction --- p.92 / Chapter 3.2 --- Results --- p.94 / Chapter 3.2.1 --- Anti-proliferative Effect of Coumarins on Various Macrophage-like Leukemia Cell Lines In Vitro --- p.94 / Chapter 3.2.2 --- Kinetic and Reversibility Studies of the Anti-proliferative Effect of Coumarins on Macrophage-like Leukemia PU5-1.8 Cells --- p.105 / Chapter 3.2.3 --- Cytotoxic Effect of Coumarins on Macrophage-like Leukemia PU5-1.8 Cells In Vitro --- p.110 / Chapter 3.2.4 --- Effect of Coumarins on the Cell Cycle Kinetics of the Macrophage-like Leukemia PU5-1.8 Cells In Vitro --- p.113 / Chapter 3.2.5 --- Effect of Coumarins on the Expression of Cell Cycle- and Growth-regulatory Genes in the Macrophage-like Leukemia PU5-1.8 Cells --- p.119 / Chapter 3.2.6 --- Effect of Coumarins on the Expression of Cell Cycle-regulatory Proteins in the Macrophage-like Leukemia PU5-1.8 Cells --- p.123 / Chapter 3.2.7 --- Effect of Coumarins on the In Vivo Tumorigenicity of the Macrophage-like Leukemia PU5-1.8 Cells --- p.127 / Chapter 3.2.8 --- Effect of Coumarins on the In Vivo Growth of the Macrophage- like Leukemia PU5-1.8 Cells in Syngeneic BALB/c Mice --- p.131 / Chapter 3.3 --- Discussion --- p.133 / Chapter CHAPTER 4: --- STUDIES ON THE APOPTOSIS-INDUCING EFFECT OF COUMARINS ON MACROPHAGE-LIKE LEUKEMIA PU5- CELLS --- p.1.8 / Chapter 4.1 --- Introduction --- p.143 / Chapter 4.2 --- Results --- p.152 / Chapter 4.2.1 --- Induction of Apoptosis in the Murine Macrophage-like Leukemia PU5-1.8 Cells by Coumarins --- p.152 / Chapter 4.2.2 --- Modulatory Effect of Coumarins on the Expression of Apoptosis-regulatory Genes in the Macrophage-like Leukemia PU5-1.8 Cells --- p.159 / Chapter 4.2.3 --- Modulatory Effect of Coumarins on the Expression of Apoptosis-regulatory Proteins in the Macrophage-like Leukemia PU5-1.8 Cells --- p.166 / Chapter 4.2.4 --- Effect of Coumarins on the Mitochondrial Membrane Depolarization of the Macrophage-like Leukemia PU5-1.8 Cells --- p.169 / Chapter 4.2.5 --- Effect of Coumarins on the Induction of Caspase Activity in the Macrophage-like Leukemia PU5-1.8 Cells --- p.172 / Chapter 4.2 --- Discussion --- p.177 / Chapter CHAPTER 5: --- STUDIES ON THE IMMUNOMODULATORY EFFECT OF COUMARINS ON MURINE MACROPHAGES AND OTHER IMMUNE CELLS / Chapter 5.1 --- Introduction --- p.184 / Chapter 5.2 --- Results --- p.187 / Chapter 5.2.1 --- Effect of Coumarins on the Viability of Macrophages In Vitro --- p.187 / Chapter 5.2.2 --- Effect of Coumarins on the In Vivo Migration of Macrophages --- p.190 / Chapter 5.2.3 --- Effect of Coumarins on the Endocytic Ability of Murine Macrophages --- p.192 / Chapter 5.2.4 --- Effect of Coumarins on the Nitric Oxide Production by Murine Macrophages --- p.194 / Chapter 5.2.5 --- Effect of Coumarins on the Viability of Murine Splenocytes --- p.199 / Chapter 5.2.6 --- Effect of Coumarins on the Mitogenesis of Murine Splenocytes --- p.201 / Chapter 5.2.7 --- Effect of Coumarins on T-cell Population and its Sub-populations --- p.205 / Chapter 5.2.8 --- Effect of Coumarins on the Induction of Murine LAK Activity --- p.208 / Chapter 5.3 --- Discussion --- p.210 / Chapter CHAPTER 6: --- CONCLUSIONS AND FUTURE PERSPECTIVES --- p.218 / REFERENCES --- p.226

Leung Po-Ki. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 204-235). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.i / ABBREVIATIONS --- p.ii / ABSTRACT --- p.vi / 撮要 --- p.x / TABLE OF CONTENTS --- p.xiii / Chapter CHAPTER 1: --- GENERAL INTRODUCTION / Chapter 1.1 --- Hematopoiesis & Leukemia --- p.1 / Chapter 1.1.1 --- An Overview on Hematopoiesis --- p.1 / Chapter 1.1.2 --- Leukemia - Aberrant Hematopoiesis --- p.4 / Chapter 1.1.2.1 --- Classification and Epidemiology of Leukemia --- p.4 / Chapter 1.1.2.2 --- Pathophysiology and Etiology of Leukemia --- p.7 / Chapter 1.1.2.3 --- Conventional Treatments for Leukemia --- p.9 / Chapter 1.1.2.4 --- New Avenues for Leukemia Therapy --- p.11 / Chapter 1.2 --- Coumarins: General Properties and Pharmacological Activities --- p.13 / Chapter 1.2.1 --- Introduction to Coumarins --- p.13 / Chapter 1.2.1.1 --- Historical Development of Coumarins --- p.13 / Chapter 1.2.1.2 --- Occurrence and Functions of Coumarins in Plants --- p.13 / Chapter 1.2.2 --- Phytochemistry and Metabolism of Coumarins --- p.14 / Chapter 1.2.2.1 --- Chemical Structures of Coumarins --- p.14 / Chapter 1.2.2.2 --- Biosynthesis of Coumarins --- p.18 / Chapter 1.2.2.3 --- Toxicology of Coumarins --- p.18 / Chapter 1.2.2.4 --- Metabolic Pathways and Pharmacokinetics of Coumarins --- p.19 / Chapter 1.2.3 --- Pharmacological Activities of Coumarins --- p.22 / Chapter 1.2.3.1 --- Anti-edema and Anti-inflammatory Activities --- p.22 / Chapter 1.2.3.2 --- Immunomodulatory Activity --- p.23 / Chapter 1.2.3.3 --- Anti-tumor Activity --- p.23 / Chapter 1.2.3.3.1 --- Mode of Entry of Coumarins into Tumor Cells --- p.23 / Chapter 1.2.3.3.2 --- Anti-carcinogenic Effect --- p.24 / Chapter 1.2.3.3.3 --- Anti-proliferative Activity --- p.25 / Chapter 1.2.3.3.4 --- Induction of Cell Differentiation --- p.26 / Chapter 1.2.3.3.5 --- Other Biological Activities --- p.26 / Chapter 1.2.4 --- Clinical Applications of Coumarins --- p.27 / Chapter 1.2.4.1 --- Treatment of Lymphoedema and Other High-protein Edemas --- p.27 / Chapter 1.2.4.2 --- Treatment of Thermal Injuries --- p.27 / Chapter 1.2.4.3 --- Therapeutic Agent for Renal Cell Carcinoma --- p.28 / Chapter 1.2.4.4 --- Therapy of Prostate Cancer --- p.29 / Chapter 1.3 --- Tumor Models Used in This Study --- p.30 / Chapter 1.3.1 --- Myeloid Leukemias --- p.30 / Chapter 1.3.1.1 --- HL-60 --- p.30 / Chapter 1.3.1.2 --- K562 --- p.30 / Chapter 1.3.1.3 --- EoL-1 --- p.30 / Chapter 1.3.1.4 --- WEHI-3B JCS --- p.31 / Chapter 1.3.2 --- Neuroblastoma - Neuro-2a BU-1 --- p.31 / Chapter 1.4 --- Aims and Scopes of This Investigation --- p.33 / Chapter CHAPTER 2: --- MATERIALS AND METHODS / Chapter 2.1 --- Materials --- p.36 / Chapter 2.1.1 --- Animals --- p.36 / Chapter 2.1.2 --- Cell Lines --- p.36 / Chapter 2.1.3 --- "Cell Culture Medium, Buffers and Other Reagents" --- p.37 / Chapter 2.1.4 --- [methyl-3H] Thymidine (3H-TdR) --- p.40 / Chapter 2.1.5 --- Methylthiazoletetrazolium (MTT) --- p.41 / Chapter 2.1.6 --- Nitro Blue Tetrazolium (NBT) --- p.41 / Chapter 2.1.7 --- Liquid Scintillation Cocktail --- p.42 / Chapter 2.1.8 --- Reagents and Buffers for Flow Cytometry --- p.42 / Chapter 2.1.9 --- Mouse Anti-MAP-2 Monoclonal Antibody --- p.44 / Chapter 2.1.10 --- Reagents for DNA Extraction --- p.44 / Chapter 2.1.11 --- Reagents for Total RNA Isolation --- p.45 / Chapter 2.1.12 --- Reagents and Buffers for RT-PCR --- p.46 / Chapter 2.1.13 --- Reagents and Buffers for Gel Electrophoresis --- p.49 / Chapter 2.1.14 --- Reagents and Buffers for Western Blot Analysis --- p.50 / Chapter 2.1.15 --- Reagents for Measuring Caspase Activity --- p.58 / Chapter 2.2 --- Methods / Chapter 2.2.1 --- Culture of the Tumor Cell Lines --- p.61 / Chapter 2.2.2 --- "Isolation, Preparation and Culture of Mouse Peritoneal Macrophages" --- p.61 / Chapter 2.2.3 --- Determination of Cell Proliferation by [3H]-TdR Incorporation Assay --- p.62 / Chapter 2.2.4 --- Determination of Cell Viability --- p.62 / Chapter 2.2.5 --- Cell Morphology Study --- p.63 / Chapter 2.2.6 --- Immunocytochemistry --- p.64 / Chapter 2.2.7 --- Confocal Microscopy --- p.64 / Chapter 2.2.8 --- NBT Reduction Assay --- p.65 / Chapter 2.2.9 --- In vivo Tumorigenicity Assay --- p.65 / Chapter 2.2.10 --- In vivo Anti-tumor Study --- p.65 / Chapter 2.2.11 --- Measurement of In vivo Macrophage Migration --- p.66 / Chapter 2.2.12 --- Measurement of Cytokine Production by ELISA --- p.66 / Chapter 2.2.13 --- Measurement of Apoptosis by DNA Fragmentation Analysis --- p.67 / Chapter 2.2.14 --- Determination of the Mitochondrial Membrane Potential --- p.67 / Chapter 2.2.15 --- Cell Cycle/DNA Content Evaluation --- p.68 / Chapter 2.2.16 --- Nitric oxide/Annexin V-PE Dual Sensor Assay --- p.68 / Chapter 2.2.17 --- Gene Expression Study --- p.68 / Chapter 2.2.18 --- Protein Expression Study --- p.71 / Chapter 2.2.19 --- Measurement of Caspase Activity --- p.74 / Chapter 2.2.20 --- Statistical Analysis --- p.75 / Chapter CHAPTER 3: --- STUDIES ON THE ANTI-TUMOR ACTIVITIES OF COUMARINS ON MYELOID LEUKEMIA CELLS / Chapter 3.1 --- Introduction --- p.76 / Chapter 3.2 --- Results --- p.18 / Chapter 3.2.1 --- Differential Anti-proliferative Effect of Coumarins on Various Leukemic Cell Lines In Vitro --- p.78 / Chapter 3.2.2 --- Cytotoxic Effect of Coumarins on Various Leukemic Cell Lines In Vitro --- p.91 / Chapter 3.2.3 --- "Kinetic, Reversibility and Stability Studies of the Anti- proliferative Effect of Coumarins on the Leukemia JCS cells" --- p.94 / Chapter 3.2.4 --- Induction of DNA Fragmentation in Myeloid Leukemia Cells by Coumarins --- p.100 / Chapter 3.2.5 --- Effect of Coumarins on the Cell Cycle Kinetics of the Leukemia JCS Cells In Vitro --- p.107 / Chapter 3.2.6 --- Effect of Coumarins on the In Vivo Tumorigenicity of the Leukemia JCS Cells --- p.112 / Chapter 3.2.7 --- Effect of Esculetin on the In Vivo Growth of the Leukemia JCS cells in Syngeneic Mice --- p.115 / Chapter 3.3 --- Discussion --- p.117 / Chapter CHAPTER 4: --- AN INVESTIGATION ON THE DIFFERENTIATION- INDUCING EFFECT OF COUMARINS / Chapter 4.1 --- Introduction --- p.122 / Chapter 4.2 --- Results --- p.124 / Chapter 4.2.1 --- The Differentiation-inducing Effect of Coumarins on Myeloid Leukemia Cells --- p.124 / Chapter 4.2.1.1 --- Morphological Changes in Coumarin-treated HL-60 Cells --- p.124 / Chapter 4.2.1.2 --- NBT Reduction of HL-60 Cells --- p.127 / Chapter 4.2.1.3 --- Effects of Coumarins on the Cell Size and Granularity of HL-60 Cells --- p.129 / Chapter 4.2.2 --- The Anti-proliferative and Differentiation-inducing Effects of Coumarins on Neuroblastoma Cells --- p.131 / Chapter 4.2.2.1 --- Anti-proliferative Effect of Coumarins on the BU-1 Cell Line In Vitro --- p.131 / Chapter 4.2.2.2 --- Morphological Changes in Coumarin-treated BU-1 Cells --- p.134 / Chapter 4.2.2.3 --- Immunocytochemistry of Coumarin-treated BU-1 Cells --- p.137 / Chapter 4.3 --- Discussion --- p.139 / Chapter CHAPTER 5: --- MECHANISTIC STUDIES ON THE ANTI-LEUKEMIC ACTIVITIES OF COUMARINS / Chapter 5.1 --- Introduction --- p.142 / Chapter 5.2 --- Results --- p.147 / Chapter 5.2.1 --- Modulatory Effects of Coumarins on the Expression of Apoptosis-regulatory Genes in the Leukemia JCS Cells --- p.147 / Chapter 5.2.2 --- Modulatory Effects of Coumarins on the Expression of Growth-related Genes in the Leukemia JCS Cells --- p.151 / Chapter 5.2.3 --- Modulatory Effects of Coumarins on the Expression of Apoptosis-regulatory Proteins in Leukemia JCS Cells --- p.157 / Chapter 5.2.4 --- Modulatory Effects of Coumarins on the Expression of Growth-related Proteins in Leukemia JCS Cells --- p.162 / Chapter 5.2.5 --- Effect of Coumarins on the Mitochondrial Membrane Depolarization of the Leukemia JCS cells --- p.165 / Chapter 5.2.6 --- Induction of Apoptosis and Nitric Oxide Production in Leukemia JCS Cells by Coumarins --- p.168 / Chapter 5.2.7 --- Effects of Coumarins on the Caspase Activity in the Leukemia JCS cells --- p.172 / Chapter 5.3 --- Discussion --- p.177 / Chapter CHAPTER 6: --- STUDIES ON THE IMMUNOMODULATORY EFFECT OF COUMARINS ON MURINE MACROPHAGES / Chapter 6.1 --- Introduction --- p.185 / Chapter 6.2 --- Results --- p.188 / Chapter 6.2.1 --- Effect of Coumarins on the Viability of Macrophages In vitro --- p.188 / Chapter 6.2.2 --- Effect of Coumarins on the In vivo Migration of Macrophages --- p.190 / Chapter 6.2.3 --- Effect of Coumarins on Cytokine Production by Macrophages --- p.192 / Chapter 6.3 --- Discussion --- p.194 / Chapter CHAPTER 7: --- CONCLUSIONS AND FUTURE PERSPECTIVES --- p.197 / REFERENCES --- p.204

No description available.

The Baylis-Hillman reaction between substituted salicylaldehydes and various acrylate species has been shown to afford complex reaction mixtures, careful chromatography of which has led to the isolation of an extensive range of novel compounds. One- and two-dimensional NMR spectroscopic, mass spectrometric and X-ray crystallographic analysis of these compounds have permitted identification of no less than eight general classes of chromene and coumarin derivatives. The formation of the various product types is attributed to cascades of successive reactions stemming, in each case, from a Baylis-Hillman product as the common intermediate. The mechanistic sequence involved in the formation of the various chromene and coumarin derivatives have been elucidated by examining isolated or specifically prepared compounds as putative reaction intermediates. Conjugate addition and acyl or allylic substitution by various nucleophiles appear to be common processes in the formation of the chromene and coumarin derivatives, and studies focussing on these processes have been undertaken. Reactions of Baylis-Hillman adducts have been carried out, using oxygen, sulfur and nitrogen nucleophiles, in order to explore stereoselectivity and regioselectivity trends. The results show that the reactions proceed with a very high degree of regioselectivity, affording conjugate addition rather than acyl substitution products. The diastereoselectivity observed for the addition products, however was typically low. A kinetic study to explore the regioselectivity of the reaction between various Baylis-Hillman derived halogeno esters and the nucleophile, methyl 3-oxobutanolate enloate, in two different base-solvent systems at high dilution was also undertaken. The reactions were monitored by ¹H NMR spectroscopy, and the results revealed that the reaction kinetics are more complex than originally anticipated. A mechanistic rationalisation is offered which is consistent with both the kinetic data and the observed regioselectivity trends.

This study has focussed on several aspects of chromone chemistry, viz., (i) the influence of remote substituents on the basicity of 2-(N,N-dimethylamino)chromones, (ii) MoritaBaylis-Hillman reactions of substituted chromone-3-carbaldehydes and (iii) an investigation into the application of chromone chemistry in the total synthesis of the marine natural product, Rietone A. Selected 2-(N,N-dimethylamino )chromones were prepared using two different methods; firstly, via cyclisation of salicylate-derived N,N-dimethyl-3;.(2-hydroxyphenyl)-3- oxopropanamide precursors and, secondly, via 2-hydroxyacetophenone boron difluoride complexes. ¹³C NMR analysis of the 6- and 7-methoxy-2-(N,N-dimethylamino)chromones confirmed that protonation occurs at the chromone carbonyl oxygen rather than the amino nitrogen - a conclusion supported by mol~cular orbital calculations. Potentiometric analysis of 2-(N,N-dimethylamino )chromones in ethanol-water afforded pKa (pK [subscript a]) values in the range 2.22 - 2.52. The observed trend has been rationalised in terms of substituent effects with the aid of molecular orbital calculations at the semi-empirical and ab initio levels, while hydrogen-bonding effects have been used to account for the apparently anomalous result obtained for the 6-nitro derivative. A series of seven substituted chromone-3-carbaldehydes, prepared by the application of Vilsmeier-Haack methodology to the corresponding 2-hydroxyacetophenones, have been examined as substrates for Morita-Baylis-Hillman reactions, using DABCO as the catalyst and three different activated alkenes, viz., methyl acrylate, methyl vinyl ketone and acrylonitrile. In all cases, with the exception of 6-nitrochromone-3-carbaldehyde, the reactions have been shown to afford the expected Morita-Baylis-Hillman products. Use of methyl acrylate and methyl vinyl ketone as the activated alkene has been observed to afford additional, unprecedented dimeric products, which have been unambiguously characterised using a combination of single crystal X-ray analysis and spectroscopic (high resolution MS and NMR) techniques. Different dimer-like adducts have been isolated from reactions in which acrylonitrile was used as the activated alkene, and the structures of these novel products have-been determined <spectroscopically. Tentative mechanistic rationalisations for the formation of the "dimeric" products have been presented. Optimisation studies, aimed at improving the yields of the Morita-Baylis-Hillman products, have resulted in significant increases in conversion efficiency (up to 95%). It has also been shown that the Morita-Baylis-Hillman products may be readily converted to the corresponding "dimers". An exploratory study into the synthesis of Rietone A has been initiated. Ring-opening of a chromone derivative was expected to provide access to the aromatic moiety, while retrosynthetic analysis of the aliphatic side chain suggested possible strategies for its construction. These approaches have proved largely unsuccessful, but preliminary studies involving Fries rearrangement of 4-(carbomethoxymethyl)phenyl 3,7-dimethyl-2,6-octadienoate appear to hold some promise for future development.

A range of chromone-2-carboxylic acids has been prepared by condensing suitably substituted 2-hydroxyacetophenones with diethyl oxalate. pK₂ Studies of these acids revealed that 6- or 7-methoxy substituents decreased acidity while the 6-nitro group enhanced acidity; the strongest acid was the 3-chloro derivative, the increase in acidity being attributed to steric inhibition of acid-weakening delocalisation between the carboxyl group and the chromone system. Various chromone-2-carboxamides, derived from acid chloride precursors, were converted to polysubstituted acrylamides by nucleophilic ring-opening with selected amine nucleophiles. The main fragmentation patterns exhibited by these acrylamides were elucidated using a combination of low resolution, high resolution and meta-stable peak analysis, while the effect of substituents on the simultaneous internal rotation involving the carboxamide and enamine moieties were studied using dynamic NMR spectroscopy. Rotational barriers of ca. 67.1 kJmol ̄¹ and ca. 102 kJmol ̄¹ were found for the enamine and amide rotors, respectively. Several synthetic pathways were followed to prepare a series of 2-(N,N-dialkylamino)chromones which were subjected to detailed mass spectral analysis. In addition to substituent-specific fragmentations , the 2-aminochromones appear to fragment via 3 major pathways. The effect of substituents on the internal rotation of the amino moeity was investigated by variable temperature ¹H NMR spectroscopy and the resulting DNMR data was used to calculate the rotational barriers. Examination of the data reveals that the electron-releasing 6- and 7- substituents reduce the C-NMe₂ rotational barrier to ca. 43.5 kJmol ̄¹ , while the nitro analogue has the largest rotational barrier (ca. 46.1 kJmol ̄¹) because of the electron-withdrawing effect of this substituent.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1976 / Vita. / Includes bibliographical references. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Chemistry