<p>Abnormal aggregation of misfolded proteins is related to numerous neurodegenerative diseases, which include Alzheimer’s, Parkinson’s disease and prion diseases. Luminescent conjugated probes (LCPs) have been used as dyes for these supramolecular assemblies termed amyloid fibrils. To these probes, metalloporphyrin (MP) derivates have been attached to achieve new spectroscopic properties, which will allow for new ways to study protein aggregation diseases.</p><p>In this thesis the synthesis of two different LCPs anchored porphyrin derivates are described. The LCPs are synthesized from 3-thiopheneacetic acid and additional thiophene units are added with the use of Suzuki cross coupling reaction. The porphyrin is synthesized from pyrrol, benzaldehyde and methyl-4- formylbenzoate in a condensation reaction. In the first target molecule (TM) the porphyrin and thiophene are coupled with a spacer and the second one is a direct coupling between the two compounds.</p>

Abnormal aggregation of misfolded proteins is related to numerous neurodegenerative diseases, which include Alzheimer’s, Parkinson’s disease and prion diseases. Luminescent conjugated probes (LCPs) have been used as dyes for these supramolecular assemblies termed amyloid fibrils. To these probes, metalloporphyrin (MP) derivates have been attached to achieve new spectroscopic properties, which will allow for new ways to study protein aggregation diseases. In this thesis the synthesis of two different LCPs anchored porphyrin derivates are described. The LCPs are synthesized from 3-thiopheneacetic acid and additional thiophene units are added with the use of Suzuki cross coupling reaction. The porphyrin is synthesized from pyrrol, benzaldehyde and methyl-4- formylbenzoate in a condensation reaction. In the first target molecule (TM) the porphyrin and thiophene are coupled with a spacer and the second one is a direct coupling between the two compounds.

Sulfenic acids figure prominently in biological and natural products chemistry as important intermediates. For example, cysteine derived sulfenic acids are key intermediates in cell signaling and play both catalytic and structural roles in enzymes. Due to the ubiquitous nature of protein sulfenic acids in cells, methods have been developed to detect and quantitate them. Although they can be detected, the mechanisms by which they form and react remain unclear. In addition, sulfenic acids are important enzymatic intermediates in Allium chemistry. Garlic, a member of the Allium genus, is known to have powerful antioxidant activity and this has recently been attributed to allyl sulfenic acid. Allicin, the thisolufinate that gives garlic its characteristic odor and flavor, decomposes to yield allyl sulfenic acid, which is believed to trap chain-carrying peroxyl radicals by readily donating a hydrogen atom, thus inhibiting autoxidations of hydrocarbons. Despite their important biological roles, little is known of the physicochemical properties of sulfenic acids. This is primarily due to their instability in air and high reactivity as both electrophiles and nucleophiles, giving them the tendency to self-condense and form thiosulfinates. Few persistent sulfenic acids, stabilized by alkyl steric protecting groups surrounding the sulfenic acid functional group, have been reported in the literature. Herein we report our synthetic efforts toward two such sulfenic acids, 9-triptycene sulfenic acid, and trans-9-decalinsulfenic acid, which were expected to be appropriate models for cysteine-derived and allyl sulfenic acids. Using 9-triptycene sulfenic acid, we were able to provide insight into the thermodynamics (O-H BDE) and kinetics (kinh) of the reactions of sulfenic acids with peroxyl radicals, which provide a clear connection between the antioxidant activity in garlic and sulfenic acids. We also preliminarily characterized the electrochemical behaviour of this compound, as well as determined its pKa. / Thesis (Master, Chemistry) -- Queen's University, 2010-12-03 17:33:02.142

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Chapter 1 reviews the literature concerning transition metal n3-oxodimethylenemethane-(metallacyclobutan-3-one), metallathietane-3-oxide, metallathietane-3,3-dioxide and ureylene complexes. The review also briefly discusses the use of the oxodimethylenemethane metal fragment in organic synthesis. The preparation and characterisation of platinathiazetidine-3-imine complexes [Pt{NPhC(=NPh)S}L2] are described in Chapter 2. X-ray crystallographic studies on two of these derivatives (L = PPh3 or PMePh2) revealed the near-planarity of the four-membered ring. Both triphenylphosphine ligands in [Pt{NPhC(=NPh)S} (PPh3)2] are easily displaced by more basic phosphines or a chelating phosphine, and one is displaced by t-butyl isocyanide to give a monosubstituted derivative. The complex reacts with carbon monoxide to give a ring expansion product. Attempted ring expansions with small cumulenes were unsuccessful. Treatment of [Rh(C1)(CO)(dppm)]2 with the dianion of N,N'-diphenylthiourea led to formation of the "A"-frame complex [Rh2(micro-S)(CO)2(dppm)2]. Chapter 3 describes the synthesis and characterisation of platinathiadiazetidine-3,3-dioxide complexes of the type [Pt{NRS(O)2NR}L2] (R = H or Ph). X-ray crystallographic studies on two of the derivatives (R = H, L = PMePh2; R = Ph, L2 = COD) showed the four-membered rings to be entirely flat, the molecules possessing a two-fold rotation axis about the platinum-sulphur vector. Efforts to insert small cumulene molecules into the N-H bonds of [Pt{NHS(O)2NH}(PMePh2)2] are described. Treatment of this complex with phenylacetylene gave trans-[Pt(C=CPh)2(PMePh2)2], whereas with dimethyl acetylenedicarboxylate the complex [Pt{C(CO2Me)=C(CO2Me)NHS(O)2NH} (PMePh2)2] was obtained, formally derived from insertion of the acetylene into a platinum-nitrogen bond. An X-ray crystallographic study revealed that the six-membered ring in this complex adopted a "pseudo-boat" conformation. Reaction of [PtC12(COD)] with sulphamide and excess silver(I) oxide in refluxing dichloromethane, followed by treatment of the filtrate from this reaction with an excess of t-butyl isocyanide afforded a complex which was formulated as [Pt{C(=NBut)NHS(O)2NHC(=NBut)}(CNBut)2]. One phosphine ligand in [Pt{NPhS(O)2NPh)(PPh3)2] can be replaced by t-butyl isocyanide to give a monosubstituted complex. The final Chapter briefly describes attempts to synthesise further Pt(II) complexes from cis-[PtC12L2] and ligands possessing "activated" protons. The interaction of cis-[PtC12(PPh3)2] with some p-tosylhydrazones in the presence of silver(I) oxide is investigated, and liquid ammonia as a synthetic reagent was also used in some of these reactions instead of silver(I) oxide. The complexes cis-[Pt{NHS(O)2C6H4-P-R}2L2] (R = H or Me) are obtained on reaction of cis-[PtC12L2] with the appropriate sulphon-amide and an excess of silver(I) oxide in dichloromethane. The reaction of cis-[PtC12(PPh3)2] with urea and silver(I) oxide in dichloromethane, or with urea in liquid ammonia, was investigated.

The chemistry of heterocyclic analogues of orthoquinodimethane is reviewed. Benzothieno[2,3-c]pyran-3-ones and the isomeric [3,2-c]pyranones are stable analogues of benzothiophene-2,3-qyinodimethane. When heated with alkynes they undergo Diels-Alder reaction to give, after loss of carbon dioxide, dibenzothiophenes.

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