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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

THE THERMODYNAMICS OF THE LANTHANIDE WITH ORGANIC ACIDS

Unknown Date (has links)
The thermodynamic parameters ((DELTA)G, (DELTA)H & (DELTA)S) of the formation of the europuim monooxalate complex has been determined at 25(DEGREES)C and 0.1M ionic strength (NaClO(,4)) by means of solvent extraction. (DELTA)G values show that the 5-membered oxalate ring is more stable than those of longer chain aliphatic dicarboxylates (malonate, succinate, glutarate or adipate). This effect is reflected in the complexation entropy values, (DELTA)S(,101). / The stability constants for trivalent Eu complexes with benzene polycarboxylates (trimellitate, hemimellitate and pyromellitate) were measured using a solvent extraction system at 25(DEGREES)C and 0.1M ionic strength (NaClO(,4)). The values measured at varying hydrogen ion concentrations show that either protonated species do not form or their formation constants are not significant enought to influence the overall observed conditional constants. The enthalpies for lanthanide hemimellitate and pyromellitate were determined by calorimetric titration. / Solvent extraction studies were conducted for Eu and Am complexes with mellitate at 0.1M and 2.0M (NaClO(,4)). In this case the stability constants for protonated species, MHL and MH(,2)L, were determined. The effective charges calculated from the experimental free energy values of these polycarboxylates indicate a significant charge polarization in the ligand which could be induced through inductive and/or resonance effects. / Source: Dissertation Abstracts International, Volume: 46-06, Section: B, page: 1918. / Thesis (Ph.D.)--The Florida State University, 1985.
112

STEREOSELECTIVE TRANSFORMATIONS OF CHIRAL IRON COMPLEXES

Unknown Date (has links)
A study of the reactivity of transition metal acyl enolates, in particular enolates of a chiral iron acyl complex, CpFe(CO)(PPh(,3))(COCH(,3)), has been undertaken. Concurrent with the above study has been the study of methods for the recovery of functionalized transition metal acyl ligands after enolate reaction. These recovered acyl ligands were found to have a defined relative stereochemistry at new chiral centers formed under the chiral iron atom's influence. A survey of reactivity with a variety of electrophiles was undertaken for a variety of transition metal acyl enolates. The types of reactions encompassed included enolate alkylations, stereoselective aldol and imine condensations, and condensations wtih nitrones and epoxides. The positively charged counterion associated with a transition metal acyl enolate was found to influence both the reactivity and stereoselectivity of the enolate in its reactions with prochiral substrates. The acyl ligands in transition metal acyl enolate alkylation products could be cleaved to esters, the aldol products cleaved to beta-hydroxy esters, and the imine condensation products converted into beta-lactams. A conjugate addition/alkylation sequence involving chiral alpha, beta unsaturated iron acyl complexes was also discovered. In this reaction, two new chiral centers were formed stereoselectively under the influence of the chiral iron in one reaction. The elaborated acyl ligands in these complexes could then be easily convered into single diastereomers of cis-disubstituted beta-lactams when primary amine anions were used for the conjugate addition, or erythro carboxylic acids when alkyl lithiums were used for the conjugate addition. / Source: Dissertation Abstracts International, Volume: 46-08, Section: B, page: 2674. / Thesis (Ph.D.)--The Florida State University, 1985.
113

A STUDY OF THE PHENOLIC OXIDATIVE COUPLING REACTION IN THE SYNTHESIS OF MORPHINE ALKALOIDS. AN APPROACH TO THE ASYMMETRIC SYNTHESIS OF CODEINE

Unknown Date (has links)
Oxidation of ((+OR-))-N-ethoxycarbonyl-N-norreticuline (16)* with VOCl(,3) in the presence of trifluoroacetic acid or its anion gave 69% and 78% of ((+OR-))-N-ethoxy-N-norisoboldine (18)*, respectively. / Oxidation of ((+OR-))-cis-3-methoxycarbonyl-N-methoxycarbonyl- N-norreticuline (40)* with phenyliodosodiacetate in the presence of trifluoroacetic acid gave ((+OR-))-16-methoxycarbonyl-N-methoxy- carbonyl-N-norsalutaridine (65)*, ((+OR-))-5-methoxycarbonyl-N-meth- oxycarbonyl-N-norisoboldine (77)* and ((+OR-))-N-methoxycarbonyl-7-hydroxy-6-methoxy-1-(4-methoxy-2,5-dioxocyclohex-3,6-dienyl) methyl 3-methoxycarbonyl-1,2,3,4-tetrahydroisoquinoline (80)* in yields of 25%, 20% and 9%, respectively. Oxidation of 40 with VOCl(,3) gave an 80% yield of 77*. Oxidation of 40* with thallium (III) tri- fluoroacetate gave 3% and 27% yields of 77* and 80*, respectively. / Reduction of 65* with NaBH(,4), followed by treatment with dimethylformamide dineopentyl acetal, gave a 77% yield of thebaine derivative 90*. Hydrolysis of 90* in aqueous sodium hydroxide, followed by reductive decarboxylation of the acid by photochemically induced decomposition of the derived N-hydroxy-pyridine-2-thione ester in the presence of tert-butyl thiol gave ((+OR-))-thebaine derivative 92*. The latter compound was converted to ((+OR-))-codeine upon sequential treatment with anhydrous HBr in n-butylether, aqueous sodium bicarbonate and then LiAlH(,4). / Using the same synthetic approach, (-)-(1R,3R)-40 was synthesized in 54% ee (based on HPLC analysis of its Mosher ester derivative) from optically active amino acid (R)-94*, which had been generated by asymmetric hydrogenation. Oxidation of (-)-40* with PhI(OAc)(,2) gave a 25% yield of (+)-(9R)-65* (58% ee based on HPLC analysis using a Pirkle HPLC column). Since ((+OR-))-65* had been / converted to ((+OR-))-codeine*, this work constituted a novel formal approach to the asymmetric synthesis of codeine. / *See the following pages in dissertation for illustration: 8, 23, 38, 52, 55, 62, 64 and 4. / Source: Dissertation Abstracts International, Volume: 46-11, Section: B, page: 3851. / Thesis (Ph.D.)--The Florida State University, 1985.
114

Stereochemistry of the Michael addition of ester enolates to alpha,beta-unsaturated esters: An approach to the synthesis of lonomycin A

Unknown Date (has links)
Part one describes a systematic study of the diastereoselectivity of the Kinetic Michael addition of ester enolates to $\alpha$,$\beta$-unsaturated esters. Numerous examples of high selectivity have been discovered, and the factors that influence this selectivity were examined. The results are consistent with a chelated transition state. In most cases, there is a strong correlation between enolate geometry and the stereostructure of the adducts. By suitable modification of the substrate, excellent control over the stereoselectivity of the addition can often be achieved. Furthermore, the utility of the Michael intermediate has been developed and construction of several stereocenters by one synthetic operation has been achieved. / Part two describes a synthesis of the C$\sb3$-C$\sb{13}$ synthon of lonomycin A. A new tool for construction of the complex polypropionate-derived natural product was introduced. One of the prominent structural features in lonomycin is the repeating pattern of methyl and methoxyl substituents in the tetrahydrofuran and pyran rings of the molecule. The prospect of employing the Michael addition in an iterative fashion without being submerged in a myriad of diastereomers stood as one of the goals for the application of this methodology to the synthesis of complex structures. Stereoselective debromination of acyclic compounds has also been achieved. The union of the tetrahydropyran rings was accomplished through an aldol bond construction, and the factors controlling the stereoselective outcome were discussed. / Source: Dissertation Abstracts International, Volume: 52-10, Section: B, page: 5269. / Major Professor: Robert A. Holton. / Thesis (Ph.D.)--The Florida State University, 1991.
115

Asymmetric synthesis of amines and its application to synthesis of simple tetrahydroisoquinoline alkaloids. Synthesis of phosphinate-based peptide analogue inhibitors of matrix metalloproteinases

Unknown Date (has links)
The diastereoselective addition of organometallic reagents to nitrones bearing carbohydrates as chiral auxiliaries was investigated. The Grignard addition to N-(2,3:5,6-di-O-isopropylidene- scD-gulofuranosyl)benzylidenamine N-oxide (1) at $-$78$\sp\circ$C has shown good to excellent diastereoselectivity. Addition products N-hydroxy-N-(2,3:5,6-di-O-isopropylidene- scD-gulofuranosyl)-(R)-alkylbenzylamine (alkyl = methyl, ethyl and benzyl; 2-4) were hydrolyzed to give corresponding (R)-alkylbenzyl hydroxylamines 5-7 in 85%, 79% and 72% yields for two steps, respectively, and in 93%, 86% and 84% enantiomeric excess, respectively. The chiral auxiliary 2,3:5,6-di-O-isopropylidene- scD-gulofuranose (8) was recovered in 75% yield from the selective hydrolysis procedure. Optically active amines 9-11 could be obtained by hydrogenolysis of 5-7 in quantitative yields. The Grignard addition to mannofuranosyl and glucopyranosyl nitrones was also studied, and low chemical yields (18% and 22%) and moderate stereoselectivities (66% and 77%, respectively) were obtained. / A new method for synthesis of hindered N-sec-alkyl-N-tert-butylamines 12 (alkyl = PhCHCH$\sb3$, 3,4-(MeO)$\sb2$PhCHCH$\sb3$ and cyclohexyl) and N-di-t-butylamine (13) was developed via organometallic addition to ketonitrones. It was found that the addition of ethereal solutions of various Grignard reagents to ketonitrones 14 in benzene solution proceeded smoothly at 0-25$\sp\circ$C, and the addition products were subsequently reduced with CS$\sb2$ to give the hindered secondary amines 12 in good overall yields. This method was also applied to synthesis of optically active hindered (R)-(+)-methyl-3,4-dimethoxybenzylamine (15). / Amine 15 derived from asymmetric synthesis and hindered amine synthesis was employed in enantioselective synthesis of simple tetrahydroisoquinolines (R)-(+)- salsolidine (16), (R)-(+)-carnegine (17) and (R)-(+)-isosalsoline (18) in 63%, 62% and 48% overall yields, respectively, via a short sequence. In the key step of acid-promoted cyclization-rearrangement of 2-diazo-N- ((R)-($-$)-methyl-3,4-dimethoxybenzyl) -N-(1,1-dimethylethyl)acetamide (19), the stereochemistry at the chiral carbon involved in the migration process was proven to be retained. / Syntheses of phosphinate-based peptide analogue inhibitors of matrix metalloproteinases (MMP) were carried out. Eighteen tri- and tetrapeptide analogue phospohinates containing either the (Gly-PO$\sb2$H)-(CH$\sb2$- scDL-Leu) or (Ala-PO$\sb2$H)-(CH$\sb2$- scDL-Leu) dipeptide surrogate functionality were synthesized. It was found from IC$\sb{50}$ measurements that the more-polar diastereomer of 3-BrNpt-(Gly-PO$\sb2$H)-(CH$\sb2$- scDL-Leu)-Trp-NHBn (3-BrNpt = 3-bromo-1,8-naphthoyl) was the most potent inhibitor against the five MMP studied: 1.3 nM for human neutrophil collagenase, 1.6 nM for human fibroblast collagenase, 1.6 nM for human neutrophil gelatinase, 7.6 nM for human fibroblast gelatinase and 100 nM for human fibroblast stromelysin. / Source: Dissertation Abstracts International, Volume: 53-04, Section: B, page: 1850. / Major Professor: Martin A. Schwartz. / Thesis (Ph.D.)--The Florida State University, 1992.
116

THE MECHANISM OF PRODUCT FORMATION IN ANTHRACENE/TRANS,TRANS-2,4-HEXADIENE SYSTEM

Unknown Date (has links)
The photochemical reaction of anthracene (A) with trans,trans-2,4-hexadiene (D) produces anthracene dimer (A(,2)), a major 4(pi)+4(pi) cross-adduct (Ad), and three minor cross-adducts: Ad' (4(pi)+4(pi)), Ad'' (4(pi)+2(pi)), and Ad''' (yet unknown). Quantum yields were studied as a function of anthracene and diene concentration and in the presence of a triplet sensitizer, a triplet quencher, and a heavy atom solvent in order to establish the role of excited anthracene singlets and triplets in product formation. Fluorescence quenching studies were conducted, when necessary, to obtain the appropriate rate constants for our mechanism. Using anthracene - ('14)C and isotopic dilution analysis, it was established that diene does not enhance, but instead diminishes dimer yields. The high A losses previously attributed to A(,2) formation were shown to be accounted for entirely by the thermal addition of Ad to A to give A(,2)d, a 2:1 anthracene to diene adduct. The structure of A(,2)d was established by X-ray crystallography, and thus the structure of Ad was confirmed by inference. These observations confirmed Kaupp's qualitative results concerning the role of diene in quenching A(,2) yields and thermal A(,2)d formation. The results presented demonstrate that Ad and Ad' are derived from the interaction of diene with anthracene singlets. Formation of Ad'' and Ad''', on the other hand, was shown to result from the interaction of diene with anthracene triplets. An excited triple complex, involving the interaction of A/D singlet exciplex with ground state A, is not a precursor leading to A(,2) or A(,2)d. Though the quantum yield expressions derived from the proposed mechanism are complex and contain many kinetic parameters, a large number of these parameters are known from previous spectroscopic and photochemical kinetic measurements. Thus the interpretation of the data / required a minimum number of derived parameters. These parameters describe the fate of singlet and triplet (A/D) exciplexes in cross-adduct formation ('1)(AD)*(--->) (beta) Ad + (beta)' Ad' + (1-(beta)-(beta)') (A+D); ('3)(AD)*(--->) (gamma) Ad'' = (gamma)' Ad''' + (1-(gamma)-(gamma)') (A+D) where (beta) = 0.46, (beta)' + 0.11, (gamma) = 0.16(,2), and (gamma)' = 0.052. / Source: Dissertation Abstracts International, Volume: 46-04, Section: B, page: 1168. / Thesis (Ph.D.)--The Florida State University, 1985.
117

PHTHALOYLMETAL COMPLEXES IN SYNTHESIS. REGIOSPECIFIC TOTAL SYNTHESIS OF PYRANOQUINONE ANTIBIOTICS (DIELS-ALDER)

Unknown Date (has links)
A synthesis of benzocyclobutenedione and substituted analogs was developed based on a Diels-Alder route. The benzocyclobutenediones were reacted with low valent transition metals which gave high yields of phthaloylmetal complexes (metalla-2-indane-1,3-diones). Upon reaction with alkynes the phthaloylmetal complexes gave high yields of substituted 1,4-naphthoquinones. The reaction was compatible with a variety of functionality on the alkyne. Regiochemical control of the quinone forming reaction was realized by attaching an appropriately substituted alkyne to the phthaloylmetal complex and performing the reaction in an intramolecular fashion. The resulting 11 and 13-membered macrocyclic 1,4-naphthoquinones were transformed to the pyranoquinone antibiotics isoeleutherin and nanaomycin A. / Source: Dissertation Abstracts International, Volume: 44-02, Section: B, page: 0501. / Thesis (Ph.D.)--The Florida State University, 1983.
118

SYNTHESIS AND STRUCTURAL STUDIES OF CYSTEINE CONTAINING POLYPEPTIDES RELATED TO COLLAGEN

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 31-09, Section: B, page: 5253. / Thesis (Ph.D.)--The Florida State University, 1970.
119

THE PHOTOCHEMISTRY OF AROMATIC KETONES IN SOLUTION

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 31-09, Section: B, page: 5255. / Thesis (Ph.D.)--The Florida State University, 1970.
120

THE SYNTHESIS RESOLUTION AND REACTIONS OF (10-ETHYL-10-PHENYL-9, 10-DIHYDRO-9-ANTHRYLIDENE) ACETIC ACID AND ITS DERIVATIVES

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 31-03, Section: B, page: 1146. / Thesis (Ph.D.)--The Florida State University, 1969.

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