Global ETD Search
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Showing 1 to 20 of 29 for “"dihydroxylation"”.
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Total synthesis of lycoricidine via photochemical dearomative dihydroxylation
… utilizing a photochemical dearomative dihydroxylation of bromobenzene. Modified Narasaka-Sharpless dihydroxylation generates a product bearing both the electrophile and nucleophile for an unprecedented transpositive Suzuki coupling. Hetero-Diels-Alder cycloaddition is used to form the …
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Metal-free syn-dihydroxylation of alkenes using malonoyl peroxides
… malonoyl peroxide II in the metal-free syn-dihydroxylation of alkenes I. Chapter 1 outlines the available metal-free methods for achieving syn-1,2- dioxygenation of alkenes. The use of hypervalent iodine, selenium, sulfur and peroxide reagents are discussed in terms of the advantages and …
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Asymmetric Dihydroxylation and Aziridination of Allenes and Related Chemistry
… by the systematic investigation of asymmetric dihydroxylation of allenes. The efficiency of kinetic resolution of racemic allenes was also investigated by using the AD reaction on both 1,3-disubstituted and trisubstituted allenes. Steric effects, electronic effects and allene substitution are …
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Synthetic and mechanistic studies of the osmium-catalyzed asymmetric dihydroxylation of olefins
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1993
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Synthesis of cinchona alkaloid analogues as mechanistic probes of the osmium-catalyzed asymmetric dihydroxylation of olefins
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1991.
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Dearomative transformations in synthesis: I. Dearomative dihydroxylation with arenophiles II. Total synthesis of lycoricidine and narciclasine III. Towards the total synthesis of collybolide
… dearomatized intermediates with osmium-catalyzed dihydroxylation. Through this approach, we have accessed a number of dihydrodiol and diaminodiol compounds with functionality not tolerated in tradition dearomatization methodologies, and we have applied this strategy to the synthesis of high value …
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Réactivité du tétroxyde d'osmium et des osmates vis-à-vis des séléniures et des sélénoxydes: application à la synthèse d'alcools allyliques et à la dihydroxylation énantiosélective d'oléfines
… osmiques (VI) a conduit à un nouveau système de dihydroxylation catalytique énantiosélective d’oléfines générant dans tous les cas les diols correspondants avec de bons rendements chimiques et d’excellents excès énantiomériques. Une étude de l’influence exercée par la nature du sélénoxyde sur la …
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The development of organic peroxide mediated oxidations
… a novel metal-free method for the one-pot anti-dihydroxylation of alkenes to form diols using malonoyl peroxide 13. The reaction conditions were optimised and the scope of the optimal conditions were examined with a variety of stilbene, styrene and indene derivatives to give the corresponding …
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Generating structural diversity in \(\alpha\)[alpha],\(\alpha\)[alpha]-difluoromethyl ketones
… tested for reactivity in Sharpless Asymmetric Dihydroxylation. A 1,4-diene has been converted through to a fluorinated analogue of a dideoxyxylulose. A 1,3-diene has been successfully converted through to a difluorodeoxyxylulose of current interest. Key points involve regioselective and highly …
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Osmium Catalyzed Dihydroxylation And Oxidative Cleavage Of Vinyl Sulfone And Elucidation Of The Vinylsulfone Polypropionate Methodology For The Synthesis Of The C32 Des-Methyl C28-C34 Actin Binding Tail Of Aplyronine A
<p>A general methodology for the generation of dipropionate functionalities using cyclic 7-membered vinylsulfones has been devised for the purpose of synthesizing polyketide natural products such as aplyronine A. Final oxidative cleavage via ozonolysis has been shown to be difficult providing …
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Synthesis of unnatural analogues of narciclasine: Chemoenzymatic synthesis of 2-epi-1-hydroxymethylnarciclasine
… The synthesis relies on chemoenzymatic dihydroxylation of an arene, Stille coupling, and an intramolecular Heck reaction to affect key transformations. The synthesis of the targeted C-1 analogues addresses a gap in literature where few narciclasine analogues have been prepared, with no …
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The production and synthetic utility of the dioxygenase-derived metabolites of substituted aromatics
… approach toward tetrodotoxin. Enzymatic dihydroxylation of benzoic acid with R. eutropha B9 provided the corresponding ipso-diol that was used in the first total synthesis of pleiogenone A, a bioactive natural product. Experimental and spectral data are provided for all new compounds.
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Two enantiodivergent syntheses of balanol and the chemoenzymatic synthesis of oseltamivir
… each commencmg with the chemoenzymatic dihydroxylation of bromobenzene. This study also describes the steric and functional limitations of the toluene dioxygenase-mediated oxidation of benzoate esters. The metabolite derived from ethyl benzoate was employed in a formal synthesis of …
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Chemoenzymatic Formal Total Syntheses of Tetrodotoxin and an Approach to Daphenylline
… Key steps included toluene dioxygenase-mediated dihydroxylation of either iodobenzene or benzyl acetate and a [4+2] hetero-Diels-Alder cycloaddition/Kornblum–DeLaMare rearrangement sequence to construct a common enone intermediate. The resulting key enone was transformed into Fukuyama's …
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Developing test strips for naked-eye detection of alpha-hydroxy acids using indicator-displacement assays: an application of molecular recognition
… that produce tartrate. Two examples are the dihydroxylation of maleic acid and fumaric acid catalyzed by osmium tetroxide in water, and the hydrolysis of D-dimethyl tartrate. The assay employed a receptor that has 1,3,5-trisubstituted-2,4,6- triethylbenzene scaffold incorporating boronic acid …
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Total synthesis of a virotoxin and analogs for conformational studies
… residue, including a diastereoselective dihydroxylation. Nα-Carbobenzyloxy-(2S)-4,5-dehydroleucine was coupled with valine ethyl ester to give a dipeptide that was subjected to a Sharpless asymmetric dihydroxylation to introduce the diol. The relative configuration at C4 was assigned as S …
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The Synthetic Utility of Enol Derivatives and the Directed Aryltitanation of Homoallylic and Allylic Alcohols
… are subjected to the Sharpless Asymmetric Dihydroxylation to form enantiomerically enriched alpha-hydroxy aldehydes. Due to their instability, these alpha-hydroxy aldehydes are further transformed in situ to demonstrate their utility in organic synthesis. The second and third parts address …
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Development of oxygenase biocatalysts for the production of synthetically useful cis-diol compounds
… for chiral, asymmetric synthesis. The cis-dihydroxylation of ortho- and meta-substituted phenols by TDO produce cyclohexenone cis-diols. The keto group of cyclohexenone cis¬-diol tautomers increases the functionalisation and stability compared to other arene cis-dihydrodiols. …
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Synthesis and selective reactivity of 14β-formyl 19-norsteroids
… 14(3-formyl 19-norsteroids was undertaken. cis-Dihydroxylation of the dihydrocycloadduct gave an isomeric mixture of the 15a,16a- and 15β3,16β3-diols, which were protected via acetonide formation. Sequential reduction of the ester functionality, chemoselective mesylation of the 161-hydroxy group …
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Asymmetric synthesis of novel anthracyclinones
… an ene cyclisation and subjected to asymmetric dihydroxylation (AD). The products from the AD reactions are of considerable biological interest and have been characterized. Their stereochemistry has been assigned by 1H nmr comparisons with the parent diphenols, which have resulted in revisions …
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