Control Of Diastereoselectivity Research Articles

(S)- or (R)-3-(E-enoyl)-4-phenyl-1,3-oxazolidin-2-ones: ideal Michael acceptors to afford a virtually complete control of simple and face diastereoselectivity in addition reactions with glycine derivatives.

[formula: see text] Enantiomerically pure (S)- or (R)-3-(E-enoyl)-4-phenyl-1,3-oxazolidin-2-ones were found to serve as ideal Michael acceptors in addition reactions with achiral Ni(II) complexes of glycine Schiff bases. Virtually complete control of simple and face diastereoselectivity, observed in these reactions, combined with quantitative chemical yields renders this methodology synthetically superior to the previous methods.

Toward design of a practical methodology for stereocontrolled synthesis of χ-constrained pyroglutamic acids and related compounds. Virtually complete control of simple diastereoselectivity in the Michael addition reactions of glycine Ni(II) complexes with N-(enoyl)oxazolidinones

A Ni(II) complex of the Schiff base of glycine with o-[ N-α-picolylamino]benzophenone or -acetophenone as a nucleophilic glycine equivalent, and N- trans-enoyloxazolidinones, as a derivative of an α,β-unsaturated carboxylic acid, were found to be the substrates of choice in the corresponding Michael addition reactions. The reactions proceed at room temperature in the presence of catalytic amounts of DBU to afford quantitatively a virtually diastereocomplete formation of the corresponding addition products with (2 R*,3 R*) or (2 R*,3 S*) relative configuration, depending on the nature of the starting N-enoyloxazolidinones. Acidic decomposition of the products followed by treatment of the reaction mixture with NH 4OH gives rise to the corresponding diastereomerically pure 3-substituted pyroglutamic acids.

ChemInform Abstract: Hydroxy Group Directivity in the Epoxidation of Chiral Allylic Alcohols: Control of Diastereoselectivity Through Allylic Strain and Hydrogen Bonding

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.

Control of diastereoselectivity in metal-catalyzed 1,3-dipolar cycloaddition between diphenylnitrone and chiral auxiliary-substituted crotonyl amide

The 1,3-dipolar cycloaddition (1,3-DC) between diphenyl nitrone (1) and 4-(S)-benzyl-((E)-2′-butenoyl)-1,3-oxazolidin-2-one (2) was studied in the presence of several inorganic salts whose cations behave as Lewis acid. Depending on the salt and the experimental conditions, three products (3–5) can be obtained diastereoselectively. The type of conformation assumed by 2 when coordinated to the cation, allows the attack of 1 on either the Re- or the Si-face of the dipolarophile and rationalizes the resulting diastereoselectivity. The coordination of the reagents around the cation was studied by NMR spectroscopy with 2-acetyl-4-(S)-benzyl-1,3-oxazolidin-2-one (7) as model compound.

Hydroxy Group Directivity in the Epoxidation of Chiral Allylic Alcohols: Control of Diastereoselectivity through Allylic Strain and Hydrogen Bonding

Hydroxy Group Directivity in the Epoxidation of Chiral Allylic Alcohols: Control of Diastereoselectivity through Allylic Strain and Hydrogen Bonding

ChemInform Abstract: Diastereoselectivity Control in the TiCl4‐Mediated Addition Reaction of Allyltrimethylsilane to N,O‐Protected (L)‐Serinals.

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.

Diastereoselectivity control in the TiCl 4-mediated addition reaction of allyltrimethylsilane to N,O-protected ( l)-serinals

The TiCl 4- and SnCl 4-mediated addition reactions of allyltrimethylsilane ( 1) to protected ( l )-serinals ( 2–5) were studied, and in the case of TiCl 4 a large influence of the N- and O-protecting groups on the stereochemical course was observed.

Asymmetric Synthesis of Cyclopentenes by [3 + 2] Annulations between Vinylcarbenoids and Vinyl Ethers

Rhodium N-(dodecylbenzenesulfonyl)prolinate [(Rh2(S-DOSP)4 (1)]-catalyzed decomposition of diazobutenoates in the presence of vinyl ethers results in highly diastereoselective and enantioselective synthesis of donor/acceptor-substituted vinylcyclopropanes. Diethylaluminum chloride-induced rearrangement of these vinylcyclopropanes results in the formation of cyclopentenes with excellent control of diastereoselectivity and for the fused cyclopentenes good control of absolute stereochemistry. This study illustrates the synthetic utility of Rh2(S-DOSP)4 as a chiral catalyst for vinylcarbenoid cyclopropanations and the remarkable diastereocontrol that is possible in the diethylaluminum chloride-induced ring expansion of donor/acceptor-substituted vinylcyclopropanes.

Rigid Dipeptide Mimics: Synthesis of Enantiopure 5- and 7-Benzyl and 5,7-Dibenzyl Indolizidinone Amino Acids via Enolization and Alkylation of delta-Oxo alpha,omega-Di-[N-(9-(9-phenylfluorenyl))amino]azelate Esters.

Azabicyclo[X.Y.0]alkane amino acids are tools for constructing mimics of peptide structure and templates for generating combinatorial libraries for drug discovery. Our methodology for synthesizing these conformationally rigid dipeptides has been elaborated such that alkyl groups can be appended onto the heterocycle to generate mimics of peptide backbone and side-chain structure. Inexpensive glutamic acid was employed as chiral educt in a Claisen condensation/ketone alkylation/reductive amination/lactam cyclization sequence that furnished alkyl-branched azabicyclo[4.3.0]alkane amino acid. Enantiopure 5-benzyl-, 7-benzyl-, and 5,7-dibenzylindolizidinone amino acids 2-4 were stereoselectively synthesized via efficient reaction sequences featuring the alkylation of di-tert-butyl alpha,omega-di-[N-(PhF)amino]azelate delta-ketone 5. A variety of alkyl halides were readily added to the enolate of ketone 5 to provide mono- and dialkylated ketones 6 and 7. Hydride additions to 6 and 7, methanesulfonations, and intramolecular S(N)2 displacements by the PhF amine gave 5-alkylprolines that were converted by lactam cyclizations into 7- and 5-benzyl-, as well as 5,7-dibenzyl-2-oxo-3-N-(BOC)amino-1-azabicyclo[4.3.0]nonane-9-carboxylate methyl esters 10, 11, and 14. Epimerization of the alkyl-branched stereocenter via an iminium-enaminium equilibrium proved effective for controlling diastereoselectivity in reductive aminations with 6 and 7 in order to furnish 5-alkylprolines that were similarly converted to 7- benzyl- and 5,7-dibenzylindolizidinone N-(BOC)amino esters 10 and 14. Ester hydrolysis with hydroxide ion and potassium trimethylsilanolate then gave enantiopure indolizidinone amino acids 2-4. Epimerization at C-9 of benzylindolizidinone amino esters was also used to provide alternative diastereomers of 10, 11, and 14. This practical methodology for introducing side-chain groups onto the heterocycle with regioselective and diastereoselective control is designed to enhance the use of alkyl-branched azabicycloalkane amino acids for the exploration of conformation-activity relationships of various biologically active peptides.

ChemInform Abstract: Fusicoccin Ring System by [4 + 4] Cycloaddition. Control of Diastereoselectivity Through Hydrogen Bonding.

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.

Hydrophobic Control of Diastereoselectivity in the Synthesis of Double-Chain Surfactant Co(III) Complexes

A series of double-chain surfactant octahedral Co(III) complexes 1−4 has been prepared in both water and 20:1 (v/v) ethanol−water by the reaction of an N-alkylethylenediamine ligand (5) with sodium hexanitrocobaltate(III), followed by the addition of sodium perchlorate or sodium nitrate: trans-dinitro-cisoid-bis(N-alkylethylenediamine)cobalt(III) perchlorate (1) and nitrate (3), and trans-dinitro-transoid-bis(N-alkylethylenediamine)cobalt(III) perchlorate (2) and nitrate (4) (alkyl = hexyl, octyl, decyl, dodecyl, and hexadecyl). The cisoid 1(3)/transoid 2(4) diastereomer ratio increased on going from 20:1 ethanol−water to water, in particular by a factor of approximately 5 for the octyl and dodecyl perchlorate systems and approximately 8 for the hexadecyl perchlorate system. The increase in the relative amount of cisoid 1(3) is attributed to the hydrophobic effect associated with the aggregation of ligand 5 in water.

Fusicoccin Ring System by [4 + 4] Cycloaddition. Control of Diastereoselectivity through Hydrogen Bonding

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTFusicoccin Ring System by [4 + 4] Cycloaddition. Control of Diastereoselectivity through Hydrogen BondingScott McN. Sieburth, Kevin F. McGee, and Taleb H. Al-TelView Author Information Department of Chemistry State University of New York Stony Brook, New York 11794-3400 Cite this: J. Am. Chem. Soc. 1998, 120, 3, 587–588Publication Date (Web):January 8, 1998Publication History Received1 October 1997Published online8 January 1998Published inissue 1 January 1998https://doi.org/10.1021/ja973422qCopyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views517Altmetric-Citations34LEARN 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 Read OnlinePDF (67 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Conformation,Cyclization,Ethers,Noncovalent interactions,Solvents Get e-Alerts

A stereoselective and novel approach to the synthesis of 1,3-diols: simple control of diastereoselectivity

Complete control of simple diastereoselectivity in the synthesis of 1,3-diols was realized through the use of a one-pot aldol addition and reduction process.

The Tri- n-butyltin Group as a Novel Stereocontrol Element and Synthetic Handle in the Aza-[2,3]-Wittig Sigmatropic Rearrangement

The stereoselective trans hydrostannation of a non terminal alkynyl benzyl amine is described which furnished a tri- nbutyltin substituted aza-[2,3]-Wittig sigmatropic rearrangement precursor. Anionic rearrangement afforded a vinyl stannane product, in 71% yield, with near complete control of diastereoselectivity. Subsequent transition metal catalysed carbon-carbon bond forming reactions gave potential precursors to novel unnatural amino acids in good to moderate yields. © 1997 Elsevier Science Ltd. All rights reserved.

ChemInform Abstract: Reduction of 2‐Alkyl‐2‐carbomethoxycyclopentanone Derivatives with Sodium Borohydride. Part 2. The Elucidation of the Diastereoselective Control.

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.

Reversal of Anti to Syn Diastereoselectivity in Crotyltitanation Reaction

η3-2-Methylcrotyl(tiglyl)titanocene reacts with aldehydes to afford anti homoallylic alcohols when the reaction is carried out in THF, and preferentially syn products when the solvent is HMPA/THF=3:1. This simple control of anti versus syn diastereoselectivity expands considerably the synthetic uses of the crotyltitanation reaction.

Diastereoselectivity in the Reaction of RCH2C[CH2P (Ar)(Lr)]3 with Electrophiles: Enhancement of Diastereoselective Control by η3‐Coordination in {RCH2C[CH2P(Ar)(Li)3}Mo(Co)3

AbstractFollowing a procedure developed for H3CC[CH2P(Ph)2]3 (1a) as the starting compound, various tripod ligands RCH2C[CH2P(Ar)2]3 (1) have been transformed into the trilithiotriphosphides RCH2C[CH2P(Ar)(Li)]3 with various electrophiles R′ — Hal leads to the two diastereomers of RCH2C[CH2P‐(Ar)(R)]3 (6) with an (RRR/SSS : RRS/SSR) ratio close to the statistical value of 1:3, except when ArPh and R′Bzl, where the RRS/SSR diastereomer is obtained almost exclusively. In contrast, the reaction of [RCH2C[CH2P(Ar)(Li)[3]‐Mo(CO)3 (4) with electrophiles R′ — Hal tends to favour the formation of the homochiral RRR/SSS diastereomers. The triphosphide coordination compounds 4 are available by two different routes: either the complexes (RCH2C[CH2P‐(Ar)(H)]3Mo(CO)3, obtained from 2 and (CH3CN)3Mo(CO)3, are deprotonated by MeLi, or the trilithiotriphosphides RCH2C[CH2P(Ar)(Li)]3 are reacted with (CH3CN)3Mo(CO)3 to produce 4 in high yields. The ration in which the two diastereomeric forms of 5 are obtained depends on the nature of the electrophile: the greatest diastereomeric discrimination is obtained for ArPh, RPh, R′Bzl, where the homochiral relative to the RRS/SSR pair. Two‐dimensional NMR spectra and simulations of one‐dimensional spectra are used to ascertain the diastereomeric excess in each case. X‐ray analyses of three compounds of type 5 (5d, ArPh, RH, R′Ph, R′Bzl) indicate the remarkable conformational stability of the tripod metal scaffolding, with the conformations observed for these three compounds in three different solid‐state environments being closely similar, even with respect to the torsional arrangement of the phosphorus‐bound benzyl groups.

Reduction of 2-Alkyl-2-carbomethoxy-cyclopentanone Derivatives with Sodium Borohydride. II. The Elucidation of the Diastereoselective Controla

The synthesis and reduction of four new 2-substituted β-keto-ester derivatives (6–9), employing inexpensive sodium borohydride, were achieved to evaluate the diastereoselectivity of the reduction process of 2-allyl-2-carbomethoxy cyclopentanone derivative (1a) in the same conditions. These results indicating that the diastereoselective control in this process depend on blockage of the re-face of (1a) by a proposed carbonyl-π-stacking type interaction. aThis work represents the contribution # 19 from LASSBio, UFRJ.

Diels-Alder reaction of anthraceno[3.3]ortho-benzophane and -naphthophane. Control of π-facial diastereoselectivity by underlying π-systems

Dimethyl acetylenedicarboxylate, 1-phenyl-1,2-4-triazoline-3,5-dione and dimethyl azodicarboxylate cycloadded to benzo[3.3]orthoanthracenophane 1a and naphtho derivative 1b preferably from the outside-face of 1. On the other hand, the inside-face is the more favorite site in Diels-Alder reactions of 1 with maleic anhydride, maleimide, N-tert-butylmaleimide and N-phenylmaleimide. Naphthophane 1b is more π-face selective than benzophane 1a. Electrostatic and steric interactions between the facing aromatic ring of 1 and a dienophile are considered to control the π-facial selectivity in the reactions mentioned above.

ChemInform Abstract: Control of Regioselectivity, Diastereoselectivity and Enantioselectivity in the Antibody‐Catalyzed Diels‐Alder Reaction

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.