Asymmetric Organic Synthesis Research Articles

Recoverable catalysts for asymmetric organic synthesis.

Recoverable catalysts for asymmetric organic synthesis.

Divergent reaction pathways in amine additions to β-lactone electrophiles. An application to β-peptide synthesis

β-Lactone electrophiles are subject to regioselective addition–elimination (AE) or S N2 ring opening with various nitrogen-based nucleophiles. Primary and secondary amines promote AE ring opening to deliver products that are the functional equivalent of amide aldol adducts. Azide and sulfonamide anion nucleophiles engender S N2 lactone ring opening to deliver N-protected β-amino acid derivatives. These nucleophile-dependent ring opening pathways, coupled with the convenient access to highly enantoenriched β-lactones afforded by acyl halide–aldehyde cyclocondensations, constitute versatile methodologies for asymmetric organic synthesis. The application of this reaction technology to a new method for β-peptide synthesis based on the optically active β-azido acids emerging from the AAC-ring opening sequence is also described.

Epoxidation of Geraniol: An Advanced Organic Experiment that Illustrates Asymmetric Synthesis

The Sharpless epoxidation reaction is considered one of the most powerful advances in asymmetric organic synthesis (1). It is a classic example of the use of an asymmetric catalyst to provide an enantiomerically enriched mixture of epoxy alcohols. The procedure typically uses titanium(IV) tetraisopropoxide (Ti(OiPr)4) as a catalyst, a peroxide, and dialkyl tartrates to induce asymmetry in the epoxidation reaction of allylic alcohols. The experiment described in this paper illustrates the principle of asymmetric epoxidation and enables students to determine enantiomeric product ratios using chiral shift reagents and NMR spectroscopy.

Design of optically active selenium reagents having a chiral tertiary amino group and their application to asymmetric inter- and intramolecular oxyselenenylations

A new class of chiral selenium reagents 4–7 was synthesized on the basis of the concept that the strong intramolecular interaction between an electrophilic selenium and an optically modified tertiary amine (Se…N interaction) would induce asymmetric induction in the reaction between the selenium reagent and olefins. When 7, which showed the most powerful asymmetric induction, was applied to asymmetric methoxyselenenylation of ( E)-phenylpropene under optimum reaction conditions, the highest diastereomeric excess (d.e.) of the trans-addition product was obtained (97 % d.e.). The same reaction conditions were employed in asymmetric methoxyselenenylation of various olefins (up to 97 % d.e.) and also in asymmetric intramolecular oxyselenenylation of terminal olefins (up to 59 % d.e.) and internal olefins (up to 98 % d.e.). The results show that this class of selenium reagents with a strong Se…N interaction is useful for asymmetric organic synthesis.

ChemInform Abstract: Asymmetric Organic Synthesis with Catalytic Antibodies

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Variable influence of ferric and cupric ions on Saccharomyces cerevisiae strains used in asymmetric organic synthesis

Fe (III) and Cu (II) each at 50 μM in four commercial strains of Saccharomyces cerevisiae induced an increase of NAD(P)+ reduction in one strain (Turkish), but two others (Chilean and Brazilian), the presence of Fe(III) and/or Cu(II) diminished NAD(P)+ reduction presumably due to free radicais formation inside these living cells. Suprisingly, in the American strain, Fe(III) induced a decrease and Cu (II) an increase of NAD(P)+ reduction.

Asymmetric organic synthesis with catalytic antibodies.

The science of catalytic antibodies has undergone a rapid maturation process within its first nine years of existence. From initial 'proof of concept' and demonstration of fundamental, enzyme-like characteristics, antibodies have been shown to catalyze a remarkably broad scope of organic transformations, including difficult and unfavorable chemical reactions. Yet, the ultimate testing ground for new concepts in organic chemistry has always been the synthesis of natural products. Here we focus on several issues related to the applicability of antibody catalysis in organic synthesis. We show that (a) in the hydrophobic environment of the antibody active site, short-lived intermediates can be formed and reacted in a controlled way, thus allowing antibodies to catalyze reactions that are normally incompatible with aqueous media, (b) the intrinsic order of reactivity (chemoselectivity) in a series of structurally related enol ethers and ketals can be inverted from 1:10 in the uncatalyzed hydrolysis reaction to 1000:1 under antibody catalysis, and (c) an efficient total synthesis of alpha-multistriatin, an important, biologically active natural product can be achieved via antibody catalysis.

Asymmetric syntheses, opioid receptor affinities, and antinociceptive effects of 8-amino-5,9-methanobenzocyclooctenes, a new class of structural analogues of the morphine alkaloids.

Several 8-amino-5,9-methanobenzocyclooctenes have been prepared by asymmetric organic synthesis techniques. Opioid receptor affinity studies have revealed the virtual absence of enantioselectivity for receptor binding, particularly at the mu-receptor, for the (+)-3a-f and the (-)-3a-f series. It is noteworthy that inversion of configuration at the nitrogen-bearing carbon atom [5S,8S,9S)-8-amino-3-hydroxy-5, 9-methano-9-(methoxymethyl)-5-methylbenzocyclooctene, (+)-3a vs (5S,8S,9R)-8-amino-3-hydroxy-5, 9-methano-9-(methoxymethyl)-5-methylbenzocyclooctene, (dl)-22] resulted in a > 10-fold increase in kappa-receptor affinity. Antinociceptive studies demonstrated that (dl)-22 was a full kappa-agonist while (+)-3a and (-)-3a did not possess kappa-activity. Although both (dl)-22 and (+)-3a/(-)-3a had high affinity for the mu-receptor, these compounds did not act as high-affinity agonists or antagonists at this receptor.

Asymmetric Organic Synthesis. Radical Cyclizations of Chiral Enamides

Stereoselective radical cyclizations to the enamide double bond have excellent potential for utilization in alkaloid and related nitrogen heterocycle synthesis. Complete facial selectivity has been found for radical cyclizations of chiral substrates la 2,7 €411 12 + 13,15 16 + 17, and 19 20. The stereoselectivity for reduction of the intermediate tertiary radicals with BugSnH correlates with product stability. For example, 7 gives cis-dihydro 8 with no trace of the trans-dihydro isomer 9,3.6 kcal/mol less stable than 8. Radical cyclization of 11 gave a 1:l mixture of the six-membered ring lactam 12 and the spirocyclic lactam 13. Diastereomers 12 and 14 have near equivalent stabilities, but radical reduction from the b-face is blocked by the presence of the adjacent benzyloxycarbonyl substituent. The formation of 20 from 19, by way of a disfavored 5-endo-trig cyclization pathway may have value as a model for synthesis of kopsinine-type alkaloids. The conversion of 8 to the functionalized hexahydrojulolidine 23 also is described.

ChemInform Abstract: Asymmetric Organic Synthesis. Preparation and Birch Reduction‐ Alkylation of 2‐Methyl‐3,4‐dihydroisoquinolin‐1‐ones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric organic synthesis. Preparation and birch reduction-alkylation of 2-methyl-3,4-dihydroisoquinolin-1-ones

Birch reductions of 2-methyl-3,4-dihydroisoquinolin-1-ones 1 and 6 generate enolates 2a and 2b and alkylations provide 1,4-cyclohexadienes 3a–3e and 7a–7c. The synthesis of a racemic structural analogue, 9, of the potent analgetic levorphanol is described.

Progress in the Development of Methods for Asymmetric Organic Synthesis

AbstractMethods for the enantioselective synthesis of chiral cyclohexane derivatives from aromatic carboxylic acids are presented. Birch reduction‐alkylation of chiral benzamides of type 1 occur with high diastereose‐lectivities to give 1,4‐cyclohexadiene derivatives with quaternary centers located at C(6). Early applications of this chemistry provided target structures with a quaternary center derived from C(1) of the starting benzoic acid derivative. Herein are described 1) the development of a more versatile Birch reduction‐alkylation, 2) a practical “asymmetric linkage” between aromatic carboxylic acids and chiral acyclic structures, and 3) asymmetric syntheses of unnatural alkaloids; applications to opiate receptor pharmacology.

Introduction to stereochemistry and conformational analysis

Chirality. Absolute Configuration. Stereochemical and Conformational Descriptors. Chiroptic Properties in Chiral Molecules. Stereochemistry of Organic Reactions. Prochirality. Asymmetric Organic Synthesis: Principles. Enantiomeric Purity. Resolution of Racemates. Asymmetric Synthesis via a Chiral Catalyst. Asymmetric Syntheses with Chiral Substrates. Asymmetric Reactions Between Achiral Substrates and Chiral Reagents. Miscellaneous Methods for the Control of Stereochemistry. The Conformational Analysis of Acyclic and Cycloalkanes. Applications of Dynamic NMR Spectroscopy in Conformational Analysis. Conformational Analysis of Heterocycles. The Anomeric Effect. The Attractive and Repulsive Gauche Effects. Author Index. Subject Index.

Transition-metal-catalyzed asymmetric organic synthesis via polymer-attached optically active phosphine ligands. 13, Asymmetric hydrogenation with polymer catalysts containing primary and chiral secondary pendant alcohols

Activite de composes sous forme de polymeres insolubles a sites chiraux de Rh et sites alcool

ChemInform Abstract: Preparation of Optically Active Phosphonic Acid Derivatives Using Ethyl L‐Prolinate and Their Application to Asymmetric Organic Synthesis.

AbstractAus L‐Prolin wird der optisch aktive Phosphonsäureester (I) hergestellt, der in eine Reihe weiterer optisch aktiver Phosphonsäureester (II) übergeführt wird.

Preparation of Optically Active Phosphonic Acid Derivatives Using Ethyl L-Prolinate and Their Application to Asymmetric Organic Synthesis

Preparation of Optically Active Phosphonic Acid Derivatives Using Ethyl L-Prolinate and Their Application to Asymmetric Organic Synthesis

Molecular Handedness and the Origins of Chiral Discrimination

Abstract The development of the conception of handedness in the physical world is outlined, culminating with the views of Pasteur on the role of chiral structures and dissymmetric forces in nature. The evolution is traced of the general conclusion that steric congruence dominates chiral discrimination in biochemical enantioselection, asymmetric organic synthesis, the crystal structures of enantiomers and racemates, and the distinction between homochiral and heterochiral interactions in the fluid state. The significance of the unification of the electromagnetic with the weak interaction is discussed with reference to the proposed universality of optical activity, and of the particular terrestrial enantioselection observed in natural products.

Transition-metal-catalyzed asymmetric organic synthesis via polymer-attached optically active phosphine ligands. 5. Preparation of amino acids in high optical yield via catalytic hydrogenation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransition-metal-catalyzed asymmetric organic synthesis via polymer-attached optically active phosphine ligands. 5. Preparation of amino acids in high optical yield via catalytic hydrogenationGregory L. Baker, Scott J. Fritschel, John R. Stille, and John K. StilleCite this: J. Org. Chem. 1981, 46, 14, 2954–2960Publication Date (Print):July 1, 1981Publication History Published online1 May 2002Published inissue 1 July 1981https://doi.org/10.1021/jo00327a023RIGHTS & PERMISSIONSArticle Views1204Altmetric-Citations124LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (911 KB) Get e-Alerts Get e-Alerts

Transition-metal-catalyzed asymmetric organic synthesis via polymer-attached optically active phosphine ligands. 6. Asymmetric hydrogenation with polymer catalysts containing optically active pendent alcohols

Transition-metal-catalyzed asymmetric organic synthesis via polymer-attached optically active phosphine ligands. 6. Asymmetric hydrogenation with polymer catalysts containing optically active pendent alcohols

Transition-metal-catalyzed asymmetric organic synthesis via polymer-attached optically active phosphine ligands. 4. Asymmetric hydroformylation

Transition-metal-catalyzed asymmetric organic synthesis via polymer-attached optically active phosphine ligands. 4. Asymmetric hydroformylation