School of Chemistry - Theses
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ItemTowards the synthesis of the emestrin family of natural products( 2018)A Cope rearrangement of a vinyl pyrrole epoxide (397) was utilised to form the dihydrooxepino[4,3-b]pyrrole core (398) of the emestrin family of natural products which involved the first examples of the dearomatisation of pyrrole in this type of rearrangement. It was found that an electron withdrawing ester substituent on the C2 position of the epoxide was essential for the [3,3]-rearrangement to occur. The vinyl pyrrole epoxides were synthesised in an efficient manner by a vinylogous Darzens reaction. Density functional calculations showed lower transition state energies for Cope rearrangements of epoxides with C2 esters when compared to the unsubstituted substrates which agreed with the observed experimental results. Silyl substituted vinyl bromide esters also participated in the Darzens reactions to give the desired vinyl pyrrole epoxides in good to excellent yields. Only the triethoxysilyl vinyl epoxide 313c underwent Cope rearrangement to provide the fully substituted emestrin core dihydrooxepine. The anion derived from an aryl bromosulfone did not give the Darzens product but underwent a previously unobserved stereoselective trimerization to afford the cyclohexene 343 as a single diastereoisomer. A mechanistic rationale involving SN2’ additions, [3,3]-Cope rearrangements and a stereoselective intramolecular conjugate addition was proposed and this was supported by density functional theory (DFT) calculations. A four-step total synthesis of biaryl ether natural product violaceic acid (11) is described. The steps include an SNAr reaction to afford the biaryl ether 136, tin chloride-mediated chemoselective reduction of the nitro group to amine 135. A Cu-mediated Sandmeyer reaction of 135 gave violaceic acid methyl ester 374 which is hydrolysed to give pure violaceic acid 11. An improved synthesis of the known biaryl iodide 119 is also described via a Sandmeyer reaction of amine 135.
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ItemPorous titania-based composite materials and their high-throughput photocatalytic evaluation for environmental remediation( 2016)Semiconductor-mediated photocatalysis is a promising technology for environmental remediation. Among various materials, titania is a well-known photocatalyst, yet much improvement is still required to further improve its activity. This thesis presents some approaches used to optimize the photocatalytic activity of porous titania-based materials that are physically viable for practical operations. Specifically, the effect of the addition of nitrogen during synthesis and silver nanoparticles combined with various templating methods were examined. A high-throughput testing system based on parallelization and miniaturization of methylene blue photodegradation reactions was also developed to facilitate the photocatalytic evaluation in an efficient manner. Hierarchically porous, anatase titania thin films of varied thickness were fabricated by a one-pot, soft-templating technique combined with a phase separation route. The pore structure was readily tuned by adjusting the concentration of the polymeric components added during the sol-gel synthesis. Poly(vinylpyrrolidone) (PVP) altered the three dimensional pore structure, generating macroporous networks within the films. The highest photocatalytic activity under UV irradiation normalized by the accessible surface area was obtained by porous titania thin films prepared using 1:1:0 poly(ethylene glycol):PVP:F127. The addition of F127 did increase the overall photocatalytic activity, but lowered the activity per unit area because of obstructed light penetration. In order to effectively utilize the visible light, mesoporous anatase titania with nitrogen doping was prepared by a template-free, sol-gel synthesis route. The effect of calcination conditions and the type of titania precursor were investigated, highlighting their profound influence upon the adsorption and visible light activity. The titania crystallization in the presence of nitrogen was also studied using in situ synchrotron powder diffraction. The nitrogen modified titania prepared from titanium (IV) butoxide and diethanolamine calcined at 350 °C for 10 h exhibited a high methylene blue adsorption capacity (85 mg g-1) and high photocatalytic activity under visible light. The prominent photocatalytic performance was attributed to the synergetic effect from the abundant nitrogen content (10.91 at. %), relatively high specific surface area (154.8 m2 g-1), and enhanced surface acidity (isoelectric point ≈ 2.7). To further enhance the practicality of the titania composites with nitrogen modification, the synthesis method was then extended to obtain porous monolithic structures. The goal of this study was to investigate the relationship between the photocatalytic activity and the diverse porous morphologies produced using the phase separation route and agarose gel templating. The amount of polymer used in the phase separation induced monoliths and the infiltration method in the preparation of agarose templated monoliths were shown to affect both the physicochemical and optical properties. This comparative study showed that the highest UV and visible light activity for methylene blue removal was achieved by the agarose-templated monoliths that were infiltrated at 60 °C. This was accredited to their higher surface area and higher nitrogen content compared to those of the monoliths obtained from phase separation. The addition of nitrogen and silver nanoparticles was carried out simultaneously with a hard templating technique using silica spheres packed into a three dimensional “opal” structure to further optimize the performance of titania under visible light. All of the opal templated samples in this work performed better than the commercial titania, P25. The highest photocatalytic enhancement, showing more than eight times higher activity than the non-modified titania, was achieved by the opal templated sample prepared with 1.0 mol % of silver. Although both the nitrogen and silver addition and templating enhanced the visible light activity, the most significant improvement was afforded by the utilization of the silica opal template that gave rise to high surface area (>100 m2 g-1) and promoted the surface charge interaction.
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ItemFunctional conjugated polymers: from design to devices( 2015)Conjugated polymers are among the most promising materials for future technologies. These organic materials combine many of the properties of conventional polymers with the behaviour of inorganic semiconductors. The low-cost and solubility of many conjugated polymers make them attractive materials for use in future electronic and optoelectronic devices, such as field-effect transistors (FETs), polymer light-emitting diodes (PLEDs) and organic solar cells (OSCs). However, both design and synthesis of conjugated polymers with well-defined structures involve many intellectual and technological challenges. Although conjugated polymers of simple aromatic monomers have been studied in great detail, to date there is no sound methodology in rationalised design and synthesis of functional conjugated polymers. Therefore, controlling and fine-tuning the properties of conjugated polymers remains rather difficult to achieve, and thus limits their applications in devices. The purpose of this research is to develop a coherent strategy for the design and synthesis of functional conjugated polymers with well-controlled structures and properties, from simple aromatic molecules. The history, background and applications of conjugated polymers are reviewed before introducing the central concept in this work - modular design and synthesis of new materials. The approach adopted seeks to develop “greener” pathways to target materials, by avoiding many highly toxic solvents, highly corrosive reagents, and expensive organometallic catalysts. Some simple reactions in water or ethanol were utilised to synthesise early building blocks in large quantities, while Horner-Wadsworth-Emmons (HWE) olefination and Kumada coupling reactions were employed to construct carbon-carbon double and single bonds, respectively. A group of three conjugated polymers were first synthesised to investigate the practicality of the modular approach. These polymers were based on the alternating copolymer of phenylenevinylene (PV) with (2-ethylhexyloxy-4-methoxy)phenylenevinylene (MEHPV), or alt-co-MEH-PPV. Each polymer consists of three types of aromatic monomers in an alternating pattern. The properties of the novel polymers were compared to their parent polymers to reveal effects of inserting an additional type of monomer. Subsequent work investigated the synthesis and properties of conjugation confined MEHPPV polymers. The target polymers differ from polymers of similar type studied by other groups in both synthesis and properties. Regioregular, bifunctional oligomers of MEHPV were first synthesised, then polymerised with 4,4’-bis(methylenediethylphosphonate)-1,1’-biphenyl (bis(MDEP)-biphenyl) to yield poly(MEHPV-oligomer-alt-co-bp) polymers. These polymers have a higher density of chromophores, and demonstrated a clear structure-property correlation in their photophysical properties. Furthermore, a simple, empirical quantitative model was developed to describe the basic absorption and emission characteristics of the polymers. Successes in developing an efficient synthesis of bifunctional MEHPV oligomers paved the paths towards conjugated polymers with increased structural complexity. Similar schemes were developed to synthesis bifunctional oligomers of 3,4-dihexylthienylenvinylene (DHTV). Using a combinatorial matrix approach, varying the combination of the MEHVP and DHTV oligomers modules produced 16 conjugated polymers with well-defined structures. Basic photophysical properties of these polymers were studied in some detail and a number of simple quantitative, empirical models were discovered from data analysis, which described their absorption and emission characteristics to a high degree of accuracy. Photovoltaic devices were fabricated with selected polymers as the active layer in blends with PC60BM and an efficiency of 2.0% was obtained. The device performance was superior compared to devices utilising MEH-PPV or PTV. The combined combinatorial-modular approach was then used to synthesise another type of copolymers of interest, those of MEHPV and regioregular 3-hexylthiophene (3HT) oligomers. MEH-PPV and P3HT were chosen as they are among the most intensely investigated conjugated polymers. An efficient, palladium free synthesise of 3HT oligomers was developed, and the bifunctional modules were then combined with MEHPV modules to produce 12 alternating copolymers of MEHPV and 3HT oligomers with well-defined structures. The absorption and emission characteristics showed the limitations of the empirical model developed in the other synthesised polymers, demonstrating the complex role of polymer chain morphology in solutions and the solid state polymer photophysics. At Finally, 4 polymers consisting of DHTV and 3HT oligomers were synthesised and their basic photophysical properties were determined.
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ItemExploring the Petasis reaction through amino acid synthesis( 2015)The Petasis reaction was reviewed and shown to be a versatile and efficient reaction for the synthesis of nitrogen containing compounds and α-amino acids. Many different amines and amine equivalents can be used in the Petasis reaction, in conjunction with a wide variety of aryl and vinyl boronic acids and esters, and a small selection of aldehydes. Chiral reagents can enforce stereochemical control in the reaction. Certain chiral amines and chiral amine equivalents give the highest selectivity. Several limitations remained for the Petasis reaction: yields were low with sterically small amines and the organoborons were largely limited to aryl, heteroaryl and vinyl derivatives. These limitations were addressed to make the Petasis reaction a more well-rounded and useful synthetic method. tert-Butyl sulfinamide was explored as an amine equivalent and the kinetics of the Petasis reaction with this reagent were investigated through the use of in situ FT-IR and 1H NMR spectroscopy analysis. tert-Butyl sulfinamide and glyoxylic acid both had rate orders of one, whereas styrenyl boronic acid had a rate order of two. This accounted for an observed dramatic increase in reaction rate. A mechanism for this reaction system was proposed, in which the boronic acid acts as both a reagent and as a Lewis acid catalyst. Allyl boronic acid pinacol esters were synthesised by palladium catalysed borylation of allyl alcohols, and then reacted with tert-butyl sulfinamide and glyoxylic acid to yield allyl glycine derivatives. Isolated yields of the final amino acids were excellent, but the diastereoselective ratios achieved were low to moderate. The addition of scandium(III) triflate to the allyl-Petasis reaction gave excellent control over the syn/anti configuration of the product, resulting in diastereomeric ratios in the order of >20:1. However, stereochemical control at the α-carbon was still moderate. A mechanism was devised to explain this observation and several supporting reactions were conducted. N-Methyl tert-butyl sulfinamide was synthesised racemically in a single step from the commercially available tert-butyl sulfinyl chloride and methylamine solution. The product was isolated in a pure yield of 98%. Racemic N-methyl tert-butyl sulfinamide was applied to a modified allyl-Petasis reaction, which employed molecular sieves to promote the formation of the initial iminium ion, to yield N-methyl amino acids in a quick and efficient manner. The use of scandium(III) triflate gave excellent control of the syn/anti configurations. Enantiopure N-methyl tert-butyl sulfinamide was also synthesised and applied to the Petasis reaction, resulting in excellent yields and stereochemical control. This work demonstrated the robust and widely applicable nature of the Petasis reaction as a method to synthesise α-amino acids in an efficient manner. The Petasis reaction can therefore be utilised in the chemical total synthesis of more complex natural products containing unusual amino acids residues.
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ItemStudies towards the synthesis of rhizopodin( 2014)The asymmetric synthesis of the C1 – C18 fragment of rhizopodin is described. Initial work focused on the construction of the C9 – C18 fragment utilising the addition of the anion derived from 2-methyloxazole 195 to an aldehyde (235) to construct the C15 – C16 bond. The synthesis of iodide fragment 259 began with known aldehyde 244 and utilised a stereoselective novel acetylide addition to install the C3 stereocentre as well as a regioselective hydrostannylation of the terminal alkyne followed by tin-iodide exchange to install the vinyl iodide. Attempted construction of the C7 – C8 bond by intramolecular Heck coupling lead to the preferential formation of 6E, 8Z macrocycle 262 over the desired 6E, 8E 261 whilst an intermolecular Heck coupling between alkene 240 and iodide 259 resulted in the formation of a mixture of 6E, 8E (263) and 6E, 8Z (264) dienes with a slight preference towards the desired 6E, 8E (263). Due to the low selectivity, an alternative method for the construction of the C6 – C9 diene was then utilised. Suzuki coupling between boronate 311 and iodide 259 installed the diene (310), which was then esterified with acid 316. Installation of the azide by a Mitsunobu reaction (318) allowed for the application of an O, N-acyl shift to provide hydroxy amide 319 that was subjected to oxidation and cyclodehydration to give oxazole (320). This completed the synthesis of the C1 – C18 fragment of rhizopodin with NMR spectral analysis showing good correlations with literature values for the relevant fragments in rhizopodin (4) itself.
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ItemSynthesis of alkyl citrate natural products( 2014)An asymmetric total synthesis of squalene synthase (SSase) inhibitor ent-CJ-13,982 (ent-4) is presented along with work torwards SSase inhibitors L-731,120 (6), CJ-13,982 (5) the natural isomer of CJ-13,981 (5) and the viridiofungins. The common citrate moieties 286 and 289 were prepared from commercially available 2-deoxyribose. The key step utilised an Ireland-Claisen rearrangement of allyl ester 170 to install a new asymmetric centre. Another key step was a 1,4-addition to the α, β-unsaturated lactone 274 to introduce the C4 asymmetric centre with both diene isomers 279 and 280 being produced. Both isomers were elaborated to the triesters ent-175 and 283, before reduction and Wittig olefination to the citrate cross metathesis partners 286 and 289. Cross metathesis of 286 and 1-undecene followed by hydrogenation and deprotection afforded ent-CJ-13,982 (ent-4). The 3R, 3S diastereomer 295 was produced from 289 in the same manner. Both enantiomers of the L-731,120 side chain cross metathesis partner 227 were synthesised from a single chiral auxiliary 234. The key steps were a Grignard addition to give secondary alcohol 230 followed by a Johnson-Claisen rearrangement to give ester 229. Ester 229 was carried through to 227 using a Wittig olefination. Cross metathesis with both citrate isomers 286 and 289 and both enantiomers of the diene 227 produced the four cross metathesis products 306, 307, 308 and 309. The 3R, 4S, 12R isomer 308 underwent selective reductive hydrogenation to 311 using a NaBH4/RuCl3 procedure. Work towards the natural isomers was investigated with an Ireland-Claisen rearrangement of the extended esters 325 and 329. Ireland-Claisen rearrangement of 325 or 329 produced two new asymmetric centres with two diastereomers 327 and 328 being produced.
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ItemSynthesis and X-ray crystallographic studies of novel radioprotectors derived from Hoechst 33258( 2013)Hoechst 33258 is a fluorescent bibenzimidazole that has been shown to bind in AT-rich regions of the minor groove of B-DNA by X-ray, footprinting, NMR and other biophysical studies. An analogue of Hoechst 33258, methylproamine, was a radioprotector developed by the Peter MacCallum Cancer Institute and the White Group (initially David Kelly’s Group) at the School of Chemistry, University of Melbourne. Methylproamine was shown to be 100-fold more potent than the classical aminothiol radioprotector WR1065 in protecting cells against radiation damage. However, studies also revealed that it was toxic to cells at high concentrations, hence limiting its potential as a radioprotector. Nine novel radioprotectors based on Hoechst 33258 and methylproamine had been designed in an attempt to improve radioprotective activity. These compounds included low molecular weight analogues (41, 42, 60 and 73), selenium-containing (93–95) and tetrathiafulvalene-containing bibenzimidazoles (110 and 117). They were synthesised via a linear synthetic approach and their structures were determined by 1H, 13C, DEPT-135, gHSQC and gHMBC NMR, and mass spectrometry. Cyclic voltammetry experiments were conducted for the tetrathiafulvalene compounds and showed that they could undergo reversible oxidation and reduction reactions, which suggested that they might be recycled under biological conditions. The pharmacological properties of the bibenzimidazoles were investigated using in vitro biological and biochemical assays. DNA binding affinity was assessed by spectrophotometric titration, while cytotoxicity and radioprotective activity were evaluated using clonogenic survival assays. Preliminary results showed that the novel compounds were weaker binders than methylproamine. The low molecular weight bibenzimidazoles (except compound 73), selenium- (except compound 95) and tetrathiafulvalene-containing compounds had lower toxicity than methylproamine. Although the cytotoxicity property for most of the novel compounds had improved, they did not show a better radioprotection as hypothesised. Among the new analogues, only the low molecular weight compound, 60, demonstrated a significant radioprotective activity with low toxicity. Crystallographic studies of novel Hoechst 33258 analogues (42, 60, 110; and 59, 125, 126 and 127) complexed with dodecamers d(CGCAAATTTGCG)2 and d(CGCGAATTCGCG)2 showed that they also bind in the AT-rich region of the minor groove. The compounds adapted to the irregular curve of the minor groove by adjusting the torsion angles between the aromatic systems. Numerous intermolecular interactions, such as van der Waals, electrostatic and hydrogen bonding played vital roles in stabilising the ligand/DNA structures. For all of the DNA complexes, the nitrogen atoms (N3′ and N3′′) of the ligand benzimidazole groups formed bifurcated hydrogen bonds with the hydrogen bond acceptors of the DNA molecule.
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ItemConfined conjugation MEH-PPV derivatives: synthesis, photophysics and energy transfer( 2012)Conjugated polymers based on poly(2-methoxy-5-(2’-ethylhexyloxy)-1,4- phenylenevinylene) (MEH-PPV) have received considerable attention owing to their interesting luminescent and semi-conducting properties. The performance of optoelectronic devices based on conjugated polymers, such as organic light-emitting diodes (OLEDs) and organic photovoltaic devices (OPVs), is predicated by an understanding of energy transfer processes occurring within and between polymer chains. Despite the large body of knowledge accumulated over the last twenty years, there remains a need to develop an energy transfer model capable of describing the observed fluorescence properties of MEH-PPV. The purpose of this thesis is to explore the photophysics and energy transfer dynamics of well-defined MEH-PPV oligomers and pendant polymers. These materials allow for the establishment of structure-property relationships, and serve as models for understanding the fluorescence properties of MEH-PPV. A series of MEH-PPV oligomers, ranging from 3 to 5 repeat units, was prepared using Horner-Wadsworth-Emmons chemistry from readily synthesised precursors. The oligomers displayed the expected red-shift in absorption and emission maxima as conjugation length increased. Fluorescence quantum yields and fluorescence lifetimes decreased in the order trimer > tetramer > pentamer, owing to increases in the rates of both radiative and non-radiative processes. The non-mirror image relationship between absorption and emission spectra, also observed in MEH-PPV, was investigated using a number of techniques. X-ray crystallography on n-hexyl derivatives, synthesised via a similar route to the MEH-PPV oligomers, showed that the oligomers adopted twisted helical conformations in the ground state, with dihedral angles of ~7° measured for the MEH-PPV trimer. MM2 calculations on a methoxy substituted trimer indicated that a family of conformers was likely to exist in room temperature solution. Temperature dependent absorption and fluorescence measurements provided additional evidence for the presence of non-isoenergetic torsional isomers in the ground state. The rate of conformational relaxation in the excited state was measured using ultrafast transient absorption spectroscopy on the MEH-PPV tetramer and pentamer, with relaxation times of 4 and 5 ps obtained, respectively. Luminescence measurements in neat films and in PMMA matrices demonstrated aggregation occurred in the solid state. Pendant polymers consisting of short MEH-PPV segments (from 3 to 5 units) attached to a non-conjugated poly(styrene) backbone were prepared using a post-polymerisation functionalisation approach. This method involved RAFT polymerisation of vinylbenzyl chloride, followed by a series of post-polymerisation modifications. The final polymers possessed narrow polydispersities (1.08 for each), and molecular weights ranging from 10100 to 17500 g/mol. The absorption and fluorescence profiles of the polymers redshifted as side-chain conjugation length increased. The non-mirror image relationship between absorption and emission spectra was attributed to absorption by a population of side-chain torsional isomers, followed by geometry relaxation to more planar structures prior to emission. Fluorescence decays were modelled using a double-exponential function, although this most likely approximated more complex decay behaviour. Thin film measurements provided evidence for aggregation in the series, with red-shifting of the [0,0] band observed in the neat film emission spectra. Energy transfer in the series was investigated using fluorescence polarisation measurements, and was found to be highly efficient. A Förster resonance energy transfer model was applied for describing energy transfer dynamics between adjacent chromophores, giving rates in the order of 1012 s-1. Pendant polymers labelled with low band-gap acceptors were also investigated. A statistical donor-acceptor polymer consisting of 15 trimer donor chromophores for every pentamer acceptor was prepared by a post-polymerisation functionalisation approach. Photophysical measurements indicated that energy transfer occurred with an average efficiency of 85%. A pendant polymer bearing a terminal perylene diimide (PDI) end-group was also prepared. This synthesis required the use of a PDIfunctionalised RAFT agent, followed by post-polymerisation functionalisation to attach the tetramer donor chromophores. This system was found to undergo electron transfer following selective excitation of the tetramer donors. The relative HOMO/LUMO levels were determined for the model poly(tetramer), and found to be conducive for electron transfer to PDI. The synthesis and solution photophysics of a water-soluble polymer were also explored. Water solubility was conferred by functionalisation of each pendant trimer chromophore with a PEG-3 group. This polymer adopts an aggregate structure in aqueous solution and intermolecular energy transfer between this polymer and an encapsulated MEH-PPV pentamer acceptor was demonstrated
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ItemSynthesis of histrionicotoxin analogues using coventional and continuous flow approaches( 2011)The histrionicotoxins are a family of alkaloids, originally isolated from the skin extracts of the amphibian Dendrobatidae histrionicus, that display non-competitive inhibition of the nicotinic acetylcholine receptor. The biological activity of these compounds, combined with a protected natural source, has given rise to considerable interest from a synthetic chemistry standpoint. This manuscript describes the synthesis of 6,6,5-isoxazolidine scaffolds of the histrionicotoxin spirocycles, from bis-α,β-unsaturated nitrile intermediates of well defined stereochemistry, using both conventional batch-type and continuous flow techniques. A library of both racemic and enantiomeric examples of perhydrohistrionicotoxin and its conformationally restricted precursors has been synthesised. Additionally, analogues of perhydrohistrionicotoxin, one example bearing an epimeric centre and other species furnished with pendant side chains of increased length have been synthesised.
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ItemStudies towards the synthesis of mulberry Diels-Alder adducts( 2011)The synthetic studies of mulberry Diels-Alder adducts are described. Two dehydroprenylarylbenzofuran adducts, mulberrofuran C hexamethyl ether (325) and mulberrofuran J hexamethyl ether (326) were obtained from the cycloaddition Diels-Alder reaction between diene dehydroprenylarylbenzofuran (118) and chalcone dienophile 264. Chalcomoracin hexamethyl ether (330) and mongolicin F hexamethyl ether (331) were also obtained from cycloaddition Diels-Alder reaction between the arylbenzofuran diene 118 and prenyl chalcone 267. Prenyl chalcone 267 was synthesised from commercially available 2,4-dihydroxyacetophenone 175 and 2,4-dihydroxybenzaldehyde 176 in four steps. An aldol condensation between methyl ethers acetophenone 262 and benzaldehyde 263 using Claisen-Schmidt condition afforded chalcone 264. Ortho-prenylation and [1,3]- rearrangement successfully furnished the desired chalcone 267. The dehydroprenylarylbenzofuran 118 was synthesised from a Suzuki coupling reaction between arylbenzofuran iodide 315 and dienylboronate 322. The key step in the synthesis of arylbenzofuran iodide 315 is the Sonogashira coupling reaction between alkyne 306 and iodide 310. Methanolysis of 313, followed by TBAF-induced cyclisation afforded the arylbenzofuran iodide 315 in good yield. Alkyne 306 was synthesised from commercially available 3,5-dihydroxybenzoic acid (262) in five steps. The iodide partner 310 was prepared from commercially available 3-methoxyphenol 311 in three steps. The stereochemistry of the endo adduct was confirmed by direct 1H NMR signals comparison of the product which was obtained from permethylation of chalcomoracin hexamethyl ether (330), with an authentic sample of chalcomoracin (47). The cis, trans-configuration of the endo adducts, mulberrofuran C hexamethyl ether (325) and chalcomoracin hexamethyl ether (330) was confirmed by 2D NMR spectroscopic analysis. From the analysis of variable temperature 1H NMR spectra, the exo adducts, mulberrofuran J hexamethyl ether (326) and mongolicin F hexamethyl ether (331) showed a significant restricted rotation. The deydroprenylchalcone adducts, kuwanon J heptamethyl ether (339) and kuwanon I heptamethyl ether (340) were also synthesised from a cycloaddition Diels-Alder reaction between a dehydroprenylchalcone 338 and a chalcone dienophile 267. The key Suzuki coupling reaction chalcone-iodide 337 and dienylboronate 322 afforded dehydroprenylchalcone 338. The chalcone iodide 337 was prepared from an aldol condensation between methyl ether derivatives of acetophenone 335 and benzaldehyde 263. The exo adduct, kuwanon I heptamethyl ether (340) appeared as a mixture of atropisomers as a result of significant restricted C3”-C4” rotation. This phenomenon was confirmed by 1H NMR variable temperature experiments. Since the global deprotection of mulberrofuran C hexamethyl ether (325) only led to incomplete demethylation and decomposition, orthogonal protecting groups were also investigated for the synthesis of mulberry Diels-Alder adducts. Debenzylation of adduct 368 using a Lewis acid, BCl3 and C6HMe5 at -78 °C gave the monobenzylated product 370. However, when the reaction was allowed to warm from -40 °C to 0 °C, an undesired product whose structure could not be determined was isolated. MOM deprotection of kuwanon V (77) was achieved using HCl to afford the cyclised product 407 which was found to be unstable. Attempts at deprotection of benzyl, methyl and MOM ether derivative of kuwanon V 415 were not successful.