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Research demonstrates the highly selective addition of the bis(allyl)titanium complexes to alpha-imino esters to form (syn, E)-configured amino acids of different types and the synthesis of two new N-sulfonyl alpha-imino esters.

Research has been conducted on the medium chain acyl-CoA dehydrogenase inhibited by the racemic 3,4-dienoyl-CoA derivatives. The synthesis of R- and S-3,4-decadienoyl-CoA demonstrates that R-enantiomer is a stoichiometric enzyme inhibitor.

Research has been conducted on the phosphinic esters. The preparation of these esters via the use of the phosphinic analogue of Cbz-Phe-Gly-OEt as a template and the derivatives' reactivity investigated under the conventional deprotection conditions are discussed.

Research has been conducted on the ester-armed cyclens accommodating a Na (super)+ ion. Results indicate that these ester-functionalized sidearms provide coordination with the Na (super)+ ion trapped in the cyclen ring.

Research has been conducted on the porphyrins with the fused aromatic rings. The synthesis of the fluoranthoporphyrins has been carried out in investigating the effect of the ring annealation on the porphyrin chromophore.

Results show that the nitrosation reaction of the ethyl cyclohexanone-2-carboxylate (ECHC)enol and ester hydrolysis are inhibited by the beta-cyclodextrin in acidic environment due to inclusion complex formation. However, the ester hydrolysis is not affected under alkaline conditions due to the prevention of the inclusion complex formation.

Research describes a method for the stereocontrol of ylide cyclopropanation that can be utilized in the preparation of vinylcyclopropane derivatives. A procedure on tuning the stereoselectivity in the cyclopropanation reaction of ylides is also presented.

The photolysis of ten substituted arylalkyl esters in methanol leads to the formation of phenol and tert-butyl-substituted phenols via photo-Fries reaction. The substituent effects and photochemical efficiency of the reactions are discussed.

A computational analysis of the hydrolysis of the racemic esters to their cognate chiral secondary benzyl alcohols, catalyzed by Pseudomonas cepacia lipase. Data discuss the tolerance and the enantioselectivity of the bacterial lipase mediated ester hydrolysis.

The authors describe the catalytic asymmetric synthesis of (-)-podophyllotoxin and its C (sub)2-epimer. The enzymatic desymmetrization of the meso diacetate is described.

The anomeric configuration of the donor pairs does not effect the outcome of a reaction that is related to the activation of sulfoxides with Tf2O, thioglycosides with PhSOTf and bromides with AgOTf. Synthesis of S-phenyl 2, 3, 4-tri-0-benzoyl-1-deoxy-1thia-beta-D-xylopyranoside enriched with C was observed for each of the three carbonyl carbons. Meanwhile, analysis of all methods reveals the importance of hindered base in ortho esters.

The transformation of heteroaromatic esters to methyl ketones through the use of trimethylaluminum has been undertaken. The lower reactivity of trimethylaluminum compared to Grignard reagents allows for the practical monoketonization of diesters and for the excellent regioselectivity. The transformation of the esters implies that an intramolecular alkylation pathway with initial complexation of the trialkylaluminum reagent with the neighboring nitrogen may be operating.

The alkaline hydrolysis of C-4 to C-8 ethyl esters indicates autocatalytic kinetics under two-phase conditions without any mixing solvent. A dynamic model that quantitatively represents the kinetic behavior was developed. The model considers the key processes happening in the biphasic medium and the corresponding thermodynamic computations of the average size and stoichiometry of the molecular aggregates.

The allylic alkylation of allylic esters and allylic alcohols was done using an iridium complex. The iridium complex proved to be an efficient catalyst and alkylation at the substituted allylic terminus was realized using (E)-2-alkenyl esters and 1-substituted-2-propenyl esters. However, the regioselectivity was reversed when (Z)-2-alkenyl esters were used. It was also observed that (Z)-selective allylic alkylation could also be done at the unsubstituted allylic terminus.

A poly(vinylcarboxylic acid) and its analogue alkyl ester exhibited significantly different thermal degradation mechanisms under pyrolysis conditions. The greatly enhanced monomer production of poly(alkylvinylcarboxylate) during pyrolysis makes possible qualitative analysis of poly(vinylcarboxylic acid) through its derivatized alkyl ester. In this study, copolymers containing poly(methacrylic acid) and methacrylic acid were used to demonstrate the pyrolysis gas chromatography qualitative analysis of derivatized polymer. The thermal decomposition mechanisms of poly(methacrylic acid), and poly(methyl methacrylate) were studied. The advantages and disadvantages of this derivatized process as related to Py-GC analysis are discussed.

A novel approach involving the introduction of ester moieties was applied in constructing calix{8}arene with regioselectively functionalized upper rim. Two other compounds which may potentially support the formation of supramolecules were then prepared. The compounds contained different substituents at the upper rim and exhibited similar spectral variations over the temperature range from -50 to 90 degrees C. One of the compounds cannot be analyzed further due to the superposition of the mythelene signals of benzylic bridges and ethyl groups.

Absolute rate coefficient measurements were performed for the Cl atom reaction with a series of esters at room temperature and in the pressure range 15-60 Torr by applying the laser photolysis-resonance fluorescence method. The reactivity of Cl with the investigated esters can be compared with the reactivity of OH radicals with the same esters. The Cl and OH reaction rate coefficients indicated similar trends with the number of carbon atoms and the branching in the esters as was shown for Cl and OH reactions with alkanes.

The aryl esters of 4-hydroxy-beta-styrenesulfonic acid are subjected to alkaline hydrolysis to determine the role of sulfoquinone intermediate in the reaction pathway. Data such as activation parameters, reactivity comparisons and the substituent effect in the leaving group are analyzed. Results show the strong tendency of sulfonyl derivatives to hydrolyze through dissociative mechanism.

A study was conducted on the three-dimensional structure of human lysosomal arylsulfatase A (ASA) and a mechanism for the hydrolysis of sulfate esters. The findings indicate the presence of a 2-fold disordered aldehyde group with the possible contribution of an aldehyde hydrate, -CH(OH)2, with gem-hydroxyl groups. The results also confirm the functional importance of the unusually modified amino acid.

Ab initio calculations and continuum dielectric methods have been employed to map out the lowest activation free-energy profiles for the alkaline hydrolysis of a five-membered cyclic phosphate, methyl ethylene phosphate (MEP), its acyclic analog, trimethyl phosphate (TMP), and its six-membered ring counterpart, methyl propylene phosphate (MPP). The rate-limiting step for the three reactions was found to be hydroxyl ion attack at the phosphorus atom of the triester. By performing constrained optimization along the reaction coordinate, defined as the phosphorus to incoming hydroxyl oxygen distance, and computing the solvation free energies of the resulting stationary points, the rate-limiting transition states have been relocated in solution. Dihedral ring constraints in the five-membered ring leading to a more solvent-exposed hydroxyl group and, thus, better solvation of the cyclic transition state compared to its acyclic counter-part was found to be the dominant factor governing the rate enhancement of cyclic MEP relative to acyclic TMP alkaline hydrolysis. However, both ground-state destabilization of MEP relative to MPP, due to ring strain, and transition-state stabilization of the five-membered cyclic phosphate transition state relative to its six-membered ring analog, due to the differential location of the transition states in solution, were found to contribute to the enhanced rates of alkaline hydrolysis of five-membered ring MEP compared to six-membered ring MPP.

Populations and free-energy differences for the E and Z conformations of S-methyl, cyclopropyl, isopropyl, and cyclopentyl thioformate were determined by low-temperature 1H NMR spectroscopy, and free-energy barriers of 10.63 and 11.84 kcal/mol were obtained for interconversion of E and Z conformations of S-methyl thioformate at -52.4 [degrees] C. Populations and free-energy differences were also determined at room temperature by using 13C NMR for a series of N-substituted formamides and N-cyclopropylacetamide in 1% solutions in C[D.sub.2][Cl.sub.2]/C[H.sub.2][Cl.sub.2]. In both sets of compounds, electron-withdrawing groups attached to sulfur or nitrogen appear to favor the E conformations. The electronegativities of the groups are taken to increase in the order methyl < vinyl [similar to] phenyl [similar to] cyclopropyl < hydrogen < ethynyl. Data from the literature are discussed in these terms, including the E-Z energy differences for formic acid and its ethynyl, vinyl, and methyl esters.

Research was conducted to examine Chaperon effect in the nitration of aromatics. Several reagents and solvents were used in the study while nitrations were performed according to a single procedure. Results showed that the ether function characterized a weak ortho orientation effect while the hydroxyl group was prone to oxidation. They also indicated that 1-methylethyl benzenacetate undergoes nitration to produce the same isomeric ratio as methyl and ethyl esters.

A novel method for the facile conversion of methyl esters into their corresponding isoproxy-substituted allylic silanes was developed based on the utilization of Tamao's hydroxymethyl anion. The synthetic strategy involves the generation of allylic alcohol by the oxidative cleavage of functionalized allylic silanes. The conditions for each step are both mild and general due to the prevention of allylic silyl cleavage on the silane intermediates. Furthermore, the alpha-epimerization and beta-elimination was not detected during the conversion of the carboxylic acids.

The kinetics of microwave-mediated model reactions under controlled conditions was analyzed during the hydrolysis of bis(p-nitrophenyl) phosphodiester by copper(II) 2,2'-bipyridyl. The microwave-mediated model reactions for carbohydrate hydrolysis and Cu(II) 2,2'-bipyridyl complex-mediated hydrolysis did not exhibit microwave enhancement. The activity of the cellulase enzyme in the carbohydrate hydrolysis model was not affected by microwave radiation.

A method for the synthesis of trimethyl alpha-keto esters and dimethyl alpha-keto dithioacetals was developed based on a [tris(methylthio)methyl]lithium-catalyzed process. The synthetic strategy utilizes aromatic derivatives of acyl chlorides as starting materials for the target compounds. The highest yield was obtained by the reaction of N,N-diethylamides with [tris(methylthio)methyl]lithium due to the smaller amount of reagent that was required for the reaction compared to aromatic esters.

A method for the synthesis of 2-benzoylbenzoate esters acid was developed based on the DCC coupling of alcohol with commercially available 2-benzoylbenzoic acid. The 2-benzoylbenzoate esters are effective photolabile protecting groups for alcohols and the presence of a good H atom donor or electron donor led to efficient photoreduction. The 2-benzoylbenzoate esters can also be converted to alcohol or thiol and 3-phenylphthalide under electron transfer conditions.

The diastereoselective cycloaddition of N-Boc-alpha-amino aldehydes with alpha-(silyloxy) aldehydes and dicholoroketene led to the synthesis of alpha, alpha-dichloro beta-lactones. The synthetic process involves the coupling of the intermediate product from highly diastereoselective cycloaddition with alpha-amino acid esters leading to the formation of peptide mimics after dehalogenation with H2. The alpha, alpha-dichloro beta-lactones from single synthetic step also undergo omicron-acyl fission with alpha-amino acid esters.

A method for the synthesis of dimethyl acetal tri-tert-butyl ester was developed based on the rearrangement of a suitably constructed hexose to a 1,6-anhydrofuranose. The synthetic strategy involves the formation of an essential 1,6-anhydrofuranose core of the zaragozic acids which was converted to the C1 side chain and three carboxy groups. Furthermore, the final product of the synthetic process was identical to the material prepared by the degradation of zaragozic acid.

Alkyl radical reactions involving homolytic breakage and formation of carbon-oxygen bonds are important in biological systems and synthetic chemistry. Fragmentation reactions may occur by purely radical mechanisms, or by radical-ionic processes. Ionizing radiation of water produces hydroxyl radicals responsible for cleavage of oligonucleotides. Stereochemical labeling with isotopes allows reaction pathways to be identified.

Laser desorption/ionization mass spectrometry (LDI-MS) at 337 nm laser wavelength was used to analyze retinol and several long-chain fatty acid esters of retinol. Employing this ionization technique helped to overcome the inherent problems resulting from thermal instability of retinyl esters which render this group of compounds rather difficult for standard ionization techniques. Mass spectra were recorded with a linear time-of-flight instrument in positive ion mode. Under these conditions, retinyl esters formed radical molecular ions ([M.sup.[center dot]+]) and in addition fragmented by elimination of the fatty acyl chain to uniformely form a peak at m/z = 269 u. The elimination of carbon dioxide was also observed in the spectra. The method is suitable to identify specific retinyl esters in complex mixtures of these compounds. A gradient reversed-phase high-performance liquid chromatography (HPLC) is described for the separation of retinol and 15 related fatty acid esters within 28 min. HPLC was applied to separate retinyl esters from rat liver extracts. The LDI mass spectrum of the collected HPLC fraction of rat liver extract showed the molecular parent ions of retinyl myristate, pentadecanoate, palmitoleate, palmitate, heptadecanoate, linoleate, oleate, stearate, and 3,4-didehydroretinyl palmitate. LDI-MS was found to be more appropriate than matrix-assisted laser desorption/ionization for the described analytical task.

A novel method of synthesizing seven-membered cyclic enol ether derivatives was developed through the utilization of Michael-intramolecular Wittig reaction. The design featured the reaction of cyclic phosphonium with enoates and a rigid phosphabicyclic substrate as the starting material for generating enol ether derivatives with high stereoselectivity. The reaction mechanism indicated that trans enol ether derivatives were produced predominantly.

A novel method of synthesizing (-)-trans-cembranolide, a 14-membered-diterpenoid lactone, was developed through Rh-mediated cyclization reaction. The design featured the cyclization of pure diazo ester into enantiomerically pure tetrahydrofuran. The terminal C-H site was then activated on the farnesyl skeleton through oxidation of the sulfone, thereby, constructing the 14-membered ring.

A novel synthesis of acyl radicals was designed through nonreducing, tin-free conditions. The design featured the condensation of unsaturated carboxylic acid. The Boc protecting group was removed and the amine was isolated from isoamyl nitrite yielding diazonium salts. Primary radicals were generated following exo cyclization capped by iodine trapping. Intramolecular SH2 substitution of aryl radical sulfur liberated the aryl radical.

A novel reaction of in situ formed pentacarbonyl(1-acycloxyalkylidene)chromium(O) complexes affording enol esters was developed resulting in the formation of z-enol esters. Acid halides were made to react with pentacarbonyl(1-acyloxyalkylidene)chromium(O) complexes resulting in high yield z-enols in the presence of pyridine.

The mechanism of aminolysis phenyl dithioacetates in acetonitrile was investigated through probing the effects of the substituents in the nucleophile and leaving group. It was shown that the mechanism was an uncomplicated one involving only one tetrahedral intermediate. The fast proton transfer step was rate-determining in the aminolysis of thiono and dithiono esters and carbonates.

The alpha-keto beta-amido acid and its methyl esters exist in the enol form both in solid and dissolved states. However, in aqueous solution they were largely ketonized and partly hydrated at equilibrium. Ketonization was noted to be slow at neutral pH but accelerated by acids. It was found that the behavior of the title compounds were very similar to that of 3-arylpyruvates.

A novel method of synthesizing optically active tertiary alcohol (-)-{{alpha}31 D-19.8(c 1.32, CHCl3)} as a chiral auxiliary was described. the design featured the introduction of a methyl group into (8R, 9R, 10R)-8-phenyl-1-decalone. The optically active spiroisoxazoline methyl ester was found to be useful as a synthon for the synthesis of other bromotyrosine-derived natural marine metabolites.

A Lewis acid catalyst prepared by the reaction of trimethylaluminum with 2,4,6-tri-tert-butylphenol was utilized to synthesize nitroolefins of varying configuration. An additional use of excessive '+CH2CH2NH2' synthon was developed following nitroethylene activation. It was found that the alkylation of the E- and Z-ketene silyl acetals with beta-nitrostyrene was stereoconvergent.

A convenient, quantitative, and ambiguous model system assay involving the solid-phase assembly of a model tripeptide Gly-Cys-Phe on a peptide amide linker support was developed. The model system was utilized to probe the cysteine racemization as a function of synthesis and reaction design. The racemization of cysteine can be minimized through the use of CH2Cl2-DMF as a solvent, in addition to the replacement of conventional N,N-diisopropylethylamine or N-methylmorpholine base with 2,4,6-trimethylpyridine.

A novel method for the alkyne synthesis of esters and benzotriazol derivatives was developed based on the formation and utilization of alpha-(benzotriazol-1-yl) ketones as starting materials. The reaction of the ketones with a (p-toluenesulfonyl)hydrazine led to the formation of p-tosylhydrazones. The tosyl group, dinitrogen and benzotriazolyl groups of the intermediate p-topsylhydrazones also undergo base-assisted eliminations to afford the desired alkynes.

A novel method of synthesizing lipids whichg emphasized the polymerization of the inverted phase was designed. Redux-initiated radical polymerizations were utilized to synthesize [1,2,bis[2,4,13-(E,E,Z)-docosatrienoyl]-sn-glycerol]-3-phosphoethanolamine containing dienoyl group which was used as the starting material. The design required for a poorly hydrated phosphoethanolamine compound to mediate the lipid reorganization during the lamellar to nonlamellar transition.

Optically active dicarbonyl cyclopentadienyliron(vinyl ether) BF4 salts were synthesized and utilized as chiral 3-hydroxypropionate 2,3-dication equivalents for the formation of beta, delta-dihydroxy esters. The synthetic strategy was characterized by the formation of of the diastereoisomers from the reaction of the starting material with (S)-propane-1,2-diols. The organometallic salts behaved as stabilized enantioselective carbocations toward carbon nucleophiles and mediated the formation of the desired esters via redox-promoted methoxycarbonylation.

The mechanisms that mediate the hydrolytic reaction of the monothioate analogs of 5'-omicron-methyluridine and 2'- and 3'-dimethylphosphates were analyzed under neutral and acidic conditions. Analysis of the hydrolytic reaction indicated the presence of two competing reactions. The reactions were characterized by the mutual introconversion of the 2'- and 3'-isomers and phosphoester hydrolysis to a mixture of phosphorothioate esters. Furthermore, the introconversion and phosphoester hydrolysis exhibited first-order dependence on the rate of acidity.

A series of 1,2-benzisoselenazol-3(2H)-ones was synthesized from the irradiation of pyridine-2-thioneoxycarbonyl (PTOC) imidate esters in a water-cooled benzene solution. The synthetic process for the formation of ebselen and its analogues involved the photochemical decomposition of PROC imidate esters and homolytic intramolecular substitutions which led to the formation of amidyl radical. Furthermore, the target compounds were also synthesized from the reaction of 2,2'-diselenobis(N-alkylbenzamides) with benzoyl or tert-butyl peroxides.

Ab initio quantum mechanical calculations at the HF/6-31G(d) level were utilized to evaluate the effects of the methylene units on the conformation of dimethyl succinate and ethylene glycol diacetate. Ab initio HF-6-31G(d) quantum mechanical calculations of the conformational of dimethyl succinate and ethylene glycol diacetate indicated the tendency of the methylene units to fold in the gauche conformation in the presence of diesters. Furthermore, the folding of the methylene units in the dicarbonylic compounds was not dependent on the chemical structure of the carbonyl group.

A novel method of the conversion of phosphinic acid esters to beta-carboxamido-substituted phosphinic acids was developed based on acid-catalyzed hydrolysis. The synthetic process was characterized by the formation of a phosphinate intermediate product from bis(trimethylsilyl)phosphonite via Michael addition reactions. However, the acid-catalyzed hydrolysis of the phosphinic acid ester in the presence of an amide did not affect the chiral centers that were located near the carboxyamido group of the beta-carboxiamido-substituted acid.

A novel method for the synthesis of 3-(nosyloxy)-2-keto esters from 2-keto esters was developed based on sequential reactions involving trimethylsilyl enol ether and p-nitrobenzenesulfonyl peroxide. The synthetic strategy involved the formation of alpha-amino ketones via a nosylate substitution-ketone reduction sequence mediated by amine nucleophiles. The interchange of the ketone and nosylate groups during the formation of the alpha-amino ketones altered the reactivity patterns due to the sensitivity of the synthetic process to a polyfunctional environment.

A novel method for the synthesis of 4-(N,N-dibenzylamino)-3-keto esters and statine derivatives was developed based on the utilization of scalemic alpha-hydroxy methyl esters. The synthetic process involved the conversion of alpha-hydroxy esters to alpha-trifloxy esters which reacted with amine nucleophiles to produce amino esters. The synthetic process of the generation of diverse statin analogs with natural and unnatural configurations exhibited high diastereoselectivity.

A one-pot synthesis procedure for the synthesis of 3'-omicron- and 5'-omicron-phosphorodithioate derivatives of four deoxyribonucleosides was developed based on the phosphitylation of corresponding alcohols. The synthetic process was characterized by the sulfurization of intermediary 2-alkoxy-1,3,2-dithiaphospholane with elemental sulfur to produce 2-alkoxy-2-thio-1,3,2-dithiaphospholane. An intermediate omicron, omicron-dialkyl-S-(beta-mercaptoethyl)phosphorodithiolate was also produced by the fast elimination of ethylene disulfide.

A method for the stereoselective synthesis of Z-unsaturated esters was developed by utilizing novel ethyl(diarylphosphono)acetates that were generated from triethyl phosphonoacetate, PCl5 and phenols. The novel Horner-Emmons reagents reacted with benzyltrimethylammonium hydroxide and benzaldehyde in tetrahydrofuran to produce a Z-isomer in 98% chemical yield. The reaction of the novel Horner-Emmons reagents with trans-2-hexenal also improved Z-selectivity.