The 3,4-dihydro-1H-naphtho[2,3-c]pyran ring system is found in many natural products as the 5,10- or 6,9-quinones. These compounds have been synthesized by various research groups as a result of their wide range of biological activities. This thesis describes several investigations directed towards syntheses of compounds in this general area. Quinone A (16) and quinone A’(17), derived from the naturally occurring aphid insect pigments protoaphin-fb and protoaphin-sl respectively, were of particular interest. The first chapter describes the previous syntheses of some naphtho[c]pyrans including those relating to the aphid pigment derivatives, followed by the isolation and identification of the aphid pigments. Also described was the ability of these naphthopyranquinones to act as potential bioreductive alkylating or dealkylating agents. The latter part of the chapter deals with the syntheses of the racemates of the aphid pigment derivatives quinones A and A’ Œ and deoxyquinone as well as model studies toward the non-quinonoid cleavage product, glucoside B. The chapter concludes with the progress made towards the first asymmetric synthesis of these compounds. Chapter 2 reports the establishment of conditions which led to ortho or para regioselectivity in the intramolecular cyclisation of tethered lactaldehydes to form benzo[c]pyrans. This regioselectivity depended on whether either benzyl or tbutyldimethylsilyl was used as protecting group. This chapter also described a model for the control of stereochemistry leading to quinone A’. Chapter 3 describes the syntheses of naphthalenes as potential precursors to the naphthopyranquinones derived from the aphid insect pigments. This followed after problems were encountered in previous work with inappropriate protection in the oxidation of halogenated benzopyrans. Chapter 4 develops the first successful syntheses of enantiopure quinone A and quinine A’ with the correct absolute stereochemistry. This involved the regioselective addition of 1,3-bis(trimethylsilyloxy)-1-methoxybuta-1,3-diene toselectively halogenated benzopyranquinones. The latter were obtained through complementary series of highly diastereoselective transformations based on 2,5- dihydroxyacetophenone as starting material and (R)-lactate from the chiral pool as the source of asymmetry.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg In fulfillment of the requirements for the Degree of Doctor of Philosophy 10th May 2013 / The syntheses of the naturally occurring naphthoquinone fungal metabolites dehydroherbarin and anhydrofusarubin as well as the acetal core of marticin are described in this thesis. Starting from 2,4-dimethoxybenzaldehyde, dehydroherbarin was prepared in 11 steps in an overall yield of 4.5 %. The naphthalene segment of dehydroherbarin was constructed and functionalized utilizing reactions including a Stobbe condensation, O-allylation, and a Claisen rearrangement with the key step being a regioselective phenyliodine bis(trifluoroacetate) mediated methanol addition to the naphthalene. The pyran ring was assembled by a lithium aluminium reduction followed by Wackertype oxidation reaction. Two unnatural synthetic naphthoquinones, (3R,4R) 3-hydroxy-7,9-dimethoxy-3- methly-5,10-dioxo-3,4,5,10-tetrahydro-1H-benzo[g]isochromen-4-yl nitrate and 3,4- dihydroxy-7,9-dimethoxy-3-methyl-3,4-dihydro-1H-benzo[g]isochromene-5,10-dione, were also produced on route to accessing dehydroherbarin. Anhydrofusarubin was synthesized from 2,4,5-trimethoxybenzaldehyde in 12 steps in an overall yield of 5.3 % by employing the same synthetic methodology developed towards the assembly of dehydroherbarin. To our knowledge, this represents the first formal synthesis of anhydrofusarubin. The assembly of model system of the 6,6-bicyclic pyran ring arrangement found in the naturally occurring naphthoquinone marticin is also described. 11- (hydroxymethyl)-9-methyl-10,13-dioxatricyclo[7.3.1.02,7]trideca-2(7),4-diene-3,6- dione was produced racemically in 9 steps, starting from 2,5-dihydroxyacetophenone in a 3.3 % overall yield, with the key reaction again being a Wacker-type oxidation reaction The related 6,7-bicyclic acetal compound, 3,6-dimethoxy-9-methyl-10,13- dioxatricyclo[7.3.1.02,7]trideca-2,4,6-triene, was also made inadvertently in 7 steps, from 2,5-dihydroxyacetophenone in a 6.5 % overall yield.

Proefschrift--Faculteit der Wiskunde en Natuurwetenschappen en die der Geneeskunde--Universiteit Leiden, 2003. / Notes bibliogr.

The work reported is divided into two parts: fIrstly a section dealing with the preparation of some novel diazanaphthoquinones and their reactions, especially the Diels-Alder reaction, and secondly an account of some quinoxaline derivatives and their fluorescence properties. Quinoxaline quinones containing electron-donating groups at both the 2- and 3- position have shown a difference in their stability and their behaviour in the Diels-Alder reaction compared to the stability and the reactions of quinoxaline quinone. Symmetrical dienes in the Diels-Alder reaction yielded the initial addition products, which were resistant to oxidation, whereas unsymmetrical dienes produced fully aromatized products. Crown ether derivatives of 5,8-dimethoxyquinoxaline and the corresponding quinoxaline quinones were prepared. An improved method for the preparation of a fluorescent derivatising reagent is described. This compound was then used to prepare ion-responsive fluoroionophores containing monoazacrown ethers of different cavity sizes. The complexation of these fluoroionophores, in dichloromethane, was achieved by using perchlorates of alkali and alkaline earth metals. A strong correlation between the size of the metal ion and the cavity size of the crown ether was seen in the fluorescence quantum yields of the complex, and a fluoroionophore containing a diazacrown ether gave particularly noteworthy results. A bathochromic shift with a strong hyperchromic effect was the most important feature caused by complexation with metal ions for these fluoroionophores. Fluorescent open chain ethers (podands) were also prepared and their complexation with metal ions was studied. A strong bathochromic shift and a hypochromic effect was observed especially in their excitation spectra. A further novel fluorescent derivatising reagent was prepared by extending the conjugated system. This gave the expected improved results upon the preparation of the derivatives including fluoroionophores having crown ethers of different cavity sizes. However, the changes in fluorescence did not correlate with the relationship between the sizes of the metals ion and the cavity of the crown ether. Nevertheless, a large bathochromic shift was observed on complexation with metal ions.

Th. 3e cycle--Chim. organique--Paris 5, 1984. N°: 77.

From the culture medium of Shanorella spirotricha Benjamin, four p-benzoquinones have been isolated and identified. The major pigment is shanorellin (2,6-dimethyl-3-hydroxymethyl-5-hydroxy-1,4-benzoquinone). The other three pigments are the acetate, the ethyl ether and the dimer of shanorellin. Shanorellin was found to be synthesized via the acetate-polymalonate pathway by tracer experiments with ¹⁴C-labelled compounds and by chemical degradation of the labelled shanorellin produced. A study was made of the optimal conditions required for the production of these benzoqulnones. Significant factors were pH, temperature and sources of nitrogen and vitamins of the nutrient medium. / Science, Faculty of / Botany, Department of / Graduate

No description available.

The effect of substituents on the value of the oxidation potential of quinones is reviewed and attempts to prepare substituted diphenoquinones with high oxidation potentials are reported. Attempts to characterise the mechanism of addition and substitution in diphenoquinones by identifying the products of the Thiele acetylation of diphenoquinone are reported. The reaction proved most efficient when the incoming acetylinium ion is directed by substituents in the diphenoquinone. A 1,8-addition to diphenoquinone is reported and characterised by isolating the products of the reaction between acetyl chloride and diphenoquinone, with perchloric acid as catalyst. The alternating linewidth effects observed in e.s.r.spectra are discussed and applied to account for such effects observed in the e.s.r.spectra of diphenosemiquinone anion and cation radicals. The spectra are analysed and the intramolecular processes producing these effects are discussed. A dianion diradical where intramolecular rotation about the 1 - 1' bond is restricted is produced by the oxidation of 2,2' ,4,4' -tetra hydroxybiphenyl. Previous studies of diphenosemiquinone anions are reviewed and alkylated diphenosemiquinone anion are produced by the reduction of the parent quinone with potassium hydroxide solution, the resulting radical being stabilised by the presence of pyridine. A qualitative interpretation of the solvent-ion effect in alkylated diphenosemiquinone anions is given. Diphanosemiquinone cation radicals are reviewed and previous studies are re-examined.

Plant compounds play an important role in human medicine. They are a source of new drugs or serve as an inspiration for drugs' development. This thesis presents a study about syntheses of derivatives and biological activities of two groups of natural products, quinones and terpenoids. Terpenoids are plant secondary metabolites which are known for their antimicrobial, anti-inflammatory and anti-tumoral activities. We have focused on two representatives, paclitaxel and carvacrol. GnRH-paclitaxel anti-tumor conjugates potentially suitable for targeted delivery to cancer cells were prepared. Their antiproliferative activities in vitro were evaluated on MCF-7 cancer cell line and cytotoxicity in rat hepatocytes. Carvacrol and its derivative were tested for its possible anti- inflammatory effect, which was assessed in vitro as their potential to inhibit prostaglandin E2 biosynthesis via cyclooxygenase pathway. Quinones, other targets of the thesis, are well-known for biological activities similar to terpenoids. Thymoquinone, juglone and their derivatives were tested in vitro as inhibitors of cyclooxygenases and 5-lipoxygenase. Derivatives of juglone were prepared to help us to suggest structure-activity relationship of this compound. Thymoquinone and its derivatives were evaluated for their antioxidant capacity...

Thesis (Ph. D.)--University of Wisconsin--Madison, 1951. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.