published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

by Xiao-Ping Cao. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 119-126). / Acknowledgement --- p.i / Contents --- p.ii / List of Schemes --- p.iv / List of Tables and Figures --- p.v / List of Spectra --- p.vi / Abstract --- p.ix / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- "1,2,3-Butatrienes" / Chapter 2.1. --- "Preparation of 1,2,3-Butatrienes" --- p.4 / Chapter 2.2. --- Our Synthetic Approach --- p.9 / Chapter 2.3. --- Results and Discussion --- p.10 / Chapter Chapter 3. --- "1,3,5-Hexatrienes" / Chapter 3.1. --- "Preparation of 1,3,5-Hexatrienes" --- p.16 / Chapter 3.2. --- Results and Discussion / Chapter 3.2.1. --- Preparation of Hexatrienes Using the Ramberg-Backlund Reaction --- p.24 / Chapter 3.2.2. --- Preparation of Stereoisomerically Pure Diallylic Sulfides and Sulfones --- p.29 / Chapter 3.2.3. --- The Stereochemistry of the Ramberg-Backlund Rearrangement of Diallylic Sulfones --- p.34 / Chapter 3.2.4. --- Effect of Solvent and Temperature on the Stereochemistry of the Newly Formed Double Bond --- p.38 / Chapter 3.2.5. --- Total Synthesis of Galbanolenes --- p.39 / Chapter 3.3. --- Conclusions --- p.41 / Chapter Chapter 4. --- Enediynes / Chapter 4.1. --- "Preparation of 3-Ene-l,5-diynes" --- p.42 / Chapter 4.2. --- Results and Discussion --- p.48 / Chapter Chapter 5. --- "1,3,5,7-Octatetraenes" / Chapter 5.1. --- "Preparation of 1,3,5,7-Octatetraenes" --- p.53 / Chapter 5.2. --- "Preparation of 1,3,5,7-Octatetraenes Using the Ramberg-Backlund Reaction" --- p.57 / Experimental --- p.64 / References --- p.119 / List of Publications Based on Research Reported in This Thesis --- p.127 / Spectra --- p.128

by Qin Jiang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (p. 131-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

by Pei Yu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (p. 141-149). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

No description available.

The title compound was synthesized and its chemistry studied for the first time. It reacts with carbon electrophiles initially at its $ epsilon$-position. The condensation with aliphatic imidazolides or similar acylating agents furnished methyl 6-alkyl-2,4-dihydroxy benzoates in a 5C + 1C fashion. Reaction with aromatic imidazolides, also in a 5C + 1C manner, gave unsymmetrical biphenyls with the 2-carbomethoxy-3,5-dihydroxyphenyl moiety. A regiocontrolled synthesis of naphthalene derivatives was developed by reaction with the appropriate 1,3,5-tris-electrophiles in a 5C + 5C fashion.

No description available.

The enantioselective approach to bonandiol, also known as magydardiendiol, has utilized two novel synthetic methodologies. The first is the diastereoselective cyclopropanation of a homochiral eneketal prepared from (2R,3R)- or (2S,3S)-2,3-butanediol and possessing C₂ symmetry. Simmons-Smith cyclopropanation gave good diastereoselectivity (69-75%) in addition to excellent amounts of monocyclopropanated material obtained (90-96%). The second method utilized is the nickel acetylacetonate catalyzed coupling of dimethylzinc to a sterically hindered cyclic β-keto enolphosphate in 76-92% yield. This approach to the A ring of hyperforin starting from commercially available citral allows for the introduction of all but one isoprenyl appendage.

Biomimetic synthesis is the branch of synthetic organic chemistry which attempts to learn from nature into order to solve the challenges of chemical synthesis. This thesis describes application of biomimetic principles to the total synthesis of three phenylethanoid alkaloid natural products: incargranine B; millingtonine and incargranine A. Chapter 1 provides a general introduction to the area. Specific introductions can be found at the start of each chapter. Chapter 1 introduces the concept of biomimicry and provides a brief overview of the development of the underlying concepts and terminology. The major biosynthetic pathways involved in the production of incargranine B, millingtonine and incargranine A (shikimic acid, ornithine alkaloids) are also introduced. Chapter 2 discusses the synthesis of incargranine B. Biosynthetic analysis of this dimeric alkaloid led us to question its structural assignment and suggest a structural revision. This speculative reassignment was validated through a biomimetic total synthesis of our proposed structure. Incargranine B was successfully prepared in a longest linear sequence of six steps, forming three new rings, four bonds and three contiguous stereocentres in a single biomimetic domino condensation/Mannich/SEAr sequence. Chapter 3 describes the synthesis of millingtonine. We proposed that millingtonine is biosynthetically related to incargranine B through a divergent/re-convergent network of pathways. Synthetic exploration of this hypothesis culminated in the total synthesis of millingtonine and discovery of an unanticipated biosynthetic intermediate, dia-millingtonine, which we propose as a previously unidentified natural product. . Chapter 4 details the synthesis of incargranine A. Incorporating dia-millingtonine into our biosynthetic hypothesis allowed the development of a four step bioimimetic total syntheses of incargranine A which was scaled-up to provide over one gram of natural product. Chapter 5 summarises the work presented and provides a perspective on its contribution to the field.

Two new synthetic methods for the construction of the C-D moiety of streptonigrin have been developed. The first is the cyclization of beta, gamma unsaturated ketals to cyanopyridines. These ketals were prepared from akylidenemalononitriles. The second method utilized is the ortho-directed metalation of benzamide or oxazoline derivative to give keto compounds. However, attempts to transform these keto compounds to akylidenemalononitriles by Knoevenagel condensations were unsuccessful. With the ease of the reaction and ready availability of starting materials, the beta, gamma unsaturated ketals offer versatile synthons for pyridine C ring synthesis.