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Asymmetric chirality

Chiral Center. The chiral center, which is the chiral element most commonly met, is exemplified by an asymmetric carbon with a tetrahedral arrangement of ligands about the carbon. The ligands comprise four different atoms or groups. One ligand may be a lone pair of electrons another, a phantom atom of atomic number zero. This situation is encountered in sulfoxides or with a nitrogen atom. Lactic acid is an example of a molecule with an asymmetric (chiral) carbon. (See Fig. 1.13b.)... [Pg.46]

FIGURE 1.13 Asymmetric (chiral) carbon in the lactic acid molecule. [Pg.46]

Figure 8. Equatorial el,e2, e3 and axial al,a2, a3 conformations of the carvone molecule. The asymmetric (chiral) carbon is shaded light gray, the =CH2 carbon in the isopropenyl tail is shaded mid-gray and the carbonyl oxygen atom is shaded dark gray. Taken from Ref. [38]. Figure 8. Equatorial el,e2, e3 and axial al,a2, a3 conformations of the carvone molecule. The asymmetric (chiral) carbon is shaded light gray, the =CH2 carbon in the isopropenyl tail is shaded mid-gray and the carbonyl oxygen atom is shaded dark gray. Taken from Ref. [38].
Direct condensation of 4, 5-dimethoxy-[2- F]fluorobenzaldehyde with an asymmetric chiral inductor [170] followed by L-selectride reduction of the olefinic double bond and hydrolysis leads to [6- F]fluoro-L-DOPA in 3 % radiochemical yield and an ee higher than 90% (total synthesis time 125 min) (Scheme 34). This method avoids the preparation of F-fluorobenzylhalides. [Pg.232]

Asides from the application of imines on conjugate addition reactions, Deng [87, 88] reported the first asymmetric chiral thiourea catalyzed Friedel-Crafts reaction of indoles with iV-tosyl imines (Scheme 35). The reaction was receptive to various aromatic, heteroaromatic, and aliphatic imines in good yield and high enantioselec-tivity (Scheme 36). [Pg.171]

Multi-step syntheses of a radiopharmaceutical involving an aromatic nucleophilic radiofluorination An example of a multi-step radiosynthetic pathway is the no-carrier-added synthesis of 6-[ F]fluoro-L-DOPA (Scheme 45). The first step involves the preparation of 4,5-dimethoxy-2-[ F]fluorobenzaldehyde from the corresponding nitro-substituted benzaldehyde. The following steps involve its condensation with an asymmetric chiral inductor [206] followed by L-selectride reduction of the... [Pg.38]

All the monosaccharides except dihydroxyacetone contain one or more asymmetric (chiral) carbon atoms and thus occur in optically active isomeric forms (pp. 17-19). The simplest aldose, glyceraldehyde, contains one chiral center (the middle carbon atom) and therefore has two different optical isomers, or enantiomers (Fig. 7-2). [Pg.239]

Stereoisomers Structural isomers having an identical chemical constitution but exhibiting differences in the spatial arrangement of their atoms are called stereoisomers [7], One case of stereoisomerism, denoted asymmetric chirality, comprises molecules that are mirror images of each other. Such pairs of molecules are called enantiomers. Figure 1.2.3 illustrates the two chiral molecules of 1-bromo-1-chloroethane. The line in the middle represents a symmetry plane. Note that it is... [Pg.7]

The cyclic ketenes were generated from /V-acy 1-1,3-thiazolidine-2-carboxylic acids by means of Mukaiyama s reagent. The same reaction generated enantio-merically pure 1,3-thiazolidine-derived spiro-p-lactams, using optically active /V-A rt-butoxycarbonyl-1,3-thiazolidine-2-carboxylic acid derivatives as precursors of the asymmetrical chiral cyclic ketenes (7< r/-butoxy carbonyl Boc) [101]. [Pg.123]

D. E. Drayer, The early history of stereochemistry from the discovery of molecular asymmetry and the first resolution of a racemate by Pasteur to the asymmetrical chiral carbon of van t Hoff and le Bel , in Clin. Pharmacol. vol.18, Drug Stereochemistry (2nd edn.), D. E. Drayer and I. W. Weiner, Dekker, New York, NY, 1993, pp. 1-24. [Pg.81]

The efficiency and low relative environmental impact of the asymmetric chiral synthetic route to armodafinil (Scheme 7) is a significant process chemistry achievement by the Cephalon/Novasep team.34 It offers several advantages over the isomeric resolution processes The process begins with low-cost achiral raw materials and overall is a true catalytic process. Throughout the four-step process, only two intermediates are isolated, which not only saves operating costs and time but also simplifies the unit operation. From a process viewpoint, intermediates 25 and 10 are both liquids, and are therefore not ideal for purification. Thus, the formation of 25 and 10 must be carried out with sufficient control over purity to avoid additional purification steps. In this case, it appears that the process is sufficiently robust to use the intermediates on an as is basis and still produce the key intermediate 11 as a pure solid compound. In addition, the armodafinil isolated from the asymmetric oxidation is typically > 99% chemical purity and > 99.5% chiral purity, meeting the specification in every way for the API. [Pg.302]

Note The protocol can also be applied to 1,2-diaminoethane to form the corresponding imidazolidine system [29]. If the carbon atoms of the ethane (propane) backbone are chosen to be asymmetric, chirality is introduced into the ring rather than the wingtip groups. [Pg.282]

The successful example of catalytic asymmetric chiral sulfonium epoxidation was reported with enantiomeric excess (43%) of trans-stilbene oxide (3.71) by the reaction of 4-chlorobenzaldehyde with benzyl bromide in acetonitrile at room temperature by using 0.5 equiv. of optically active sulfide 3.70 (with exo-OH group). Powdered KOH was used as a base. f... [Pg.143]

This rotation of polarized light is an important physical property that is used in chiral detection. If a molecule has two asymmetric (chiral) carbon atoms in its structure, then it is possible to have two pairs of optically active molecules and the pairs are said to be diastereoisomers as in the second diagram. If the two asymmetric carbons have identical substitution, again there will be two pairs of diastereoisomers formed, but one pair will possess a plane of symmetry and thus be optically inactive. The inactive pair are called me so diastereoisomers. [Pg.299]

From the Discovery of Molecular Asymmetry and the First Resolution of a Racemate by Pasteur to the Asymmetrical Chiral Carbon of van"t Hoff and Le Bel... [Pg.1]

Helmchen, G. Enantioselective palladium-catalyzed allylic substitutions with asymmetric chiral ligands. J. Organomet. Chem. 1999, 576, 203-214. [Pg.695]

Figure 8-13. Natural semisynthetic solonaceous alkaloids (Trade names are in parentheses). Asymmetric (chiral) center, tAlso used in ophthalmology. Figure 8-13. Natural semisynthetic solonaceous alkaloids (Trade names are in parentheses). Asymmetric (chiral) center, tAlso used in ophthalmology.
All of this group of compounds contain an asymmetric (chiral) centre and illicit materials generally contain racemic mixtures of each opfical isomer, in the case of ecstasy, R (-) and S (+) MDMA (Figure 2). [Pg.78]

It is imperative to recall that enantiomers, albeit different molecules with different lUPAC names, behave identically in a symmetric, nonchiral environment, but behave differently in an asymmetric, chiral environment. This nonequivalence is the key ingredient that makes chiral chromatography work and, as we shall see below, the... [Pg.331]

Diastereomers (or diastereoisomers) are stereoisomers that are not mirror images of each other. Diastereomers include molecules containing more than one asymmetric (chiral) center and geometric isomers. They have different physical and chemical... [Pg.794]

The receptor site is clearly asymmetric. Chirality is Important, both by simple inspection of cases and supported by discrete sub-structural contributions. The R-configuration for both cyclic and acyclic analogs is favored at uptake sites. If we assume the amino and carboxyl groups to bind specifically, then the cavity between these sites is most likely a flexible, narrow gap. Congeners are permitted to bind (flexibility), but all substituents from the 2- to... [Pg.288]

Whilst cholesteric liquid crystals, as the name implies, were originally based on cholesterol structures, it is useful to consider the structural features of other molecules that exhibit these phase characteristics. In general, cholestric mesogens are twisted nematic phases, but the feature that separates them from other similar molecules is that they possess an asymmetric chiral centre. The structural and geometric factors which influence the temperature of the N I transition are exactly those which influence the other nematic liquid crystals. It is usually found that the twisting power of the system diminishes as the chiral centre is moved away from the core structure, i.e. as n increases in the structure shown below ... [Pg.67]


See other pages where Asymmetric chirality is mentioned: [Pg.455]    [Pg.516]    [Pg.119]    [Pg.309]    [Pg.186]    [Pg.491]    [Pg.18]    [Pg.80]    [Pg.98]    [Pg.332]    [Pg.14]    [Pg.373]    [Pg.604]    [Pg.140]    [Pg.616]    [Pg.138]    [Pg.72]   
See also in sourсe #XX -- [ Pg.7 ]




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1.4- Asymmetric induction with chiral auxiliaries

ASYMMETRIC HYDROGENATION WITH CHIRAL RUTHENIUM CATALYSTS

ASYMMETRIC REDUCTION IN A CHIRAL REACTION FIELD

Alkene chiral ketone-catalyzed asymmetric

Alkenes chiral ylides, asymmetric reactions

Alkylations asymmetric, chiral phase-transfer

Applications of Chiral Phosphorous Ligands in Rhodium-Catalyzed Asymmetric Hydrogenation

Aryl asymmetric epoxidation with chiral

Asymmetric Activation of Chirally Flexible (Tropos) Catalysts

Asymmetric Autocatalysis Triggered by Chiral Organic Compounds

Asymmetric Autocatalysis Utilizing Enantiomorphous Inorganic Crystals as an Initial Source of Chirality

Asymmetric Aziridination of Olefins with Chiral Nitridomanganese Complexes

Asymmetric Catalysis by Chiral Indium Complexes

Asymmetric Diels-Alder reaction chiral auxiliaries

Asymmetric Enolate Alkylations Using Chiral Auxiliaries

Asymmetric Hydroborations with Chiral Boranes

Asymmetric Reactions using Chiral Auxiliaries

Asymmetric Simmons-Smith reactions chiral auxiliaries

Asymmetric Transformations Using Resin-Bound Chiral Catalysts and Auxiliaries

Asymmetric aldol reaction chiral oxazolidines

Asymmetric aldol reactions using chiral

Asymmetric aldol reactions using chiral boron enolates

Asymmetric alkylations via chiral

Asymmetric amplification chiral reagents

Asymmetric aryl alkene with chiral ketone

Asymmetric autocatalysis chiral initiators

Asymmetric aza Diels-Alder reactions synthesis of tetrahydroquinoline derivatives using a chiral lanthanide Lewis acid as catalyst

Asymmetric catalysis chiral lanthanoid complexes

Asymmetric catalysis, chiral sulfonated

Asymmetric catalysis, chiral sulfonated phosphines

Asymmetric chiral Lewis bases

Asymmetric chiral additives

Asymmetric chiral amines

Asymmetric chiral auxiliary-directed

Asymmetric chiral catalyst-driven

Asymmetric chiral cation

Asymmetric chiral crown ethers

Asymmetric chiral dendrimer

Asymmetric chiral drugs

Asymmetric chiral poisoning method

Asymmetric chiral sulfur-containing compounds

Asymmetric conjugate addition chiral nickel complex

Asymmetric cyclisation with chiral lithium amides

Asymmetric cyclization of chiral acetal

Asymmetric enolate with oxazolidinone chiral

Asymmetric epoxidation catalyzed by novel azacrown ether-type chiral quaternary ammonium salts under phase-transfer catalytic conditions

Asymmetric epoxidation chiral amines

Asymmetric epoxidation chiral hydroperoxides

Asymmetric epoxidation chiral metal complex catalysis

Asymmetric epoxidation chiral quaternary ammonium salts

Asymmetric hydrogenation chiral amine synthesis

Asymmetric hydrogenation chiral phosphines

Asymmetric hydrogenation chiral phosphinite

Asymmetric hydrogenations over chiral metal

Asymmetric hydrogenations over chiral metal complexes immobilized in SILCA

Asymmetric induction chiral ketones

Asymmetric induction chiral sulfoxides

Asymmetric induction using chiral transition

Asymmetric induction using chiral transition metal catalysts

Asymmetric induction with chiral templates

Asymmetric ligands allylic derivatives, substitution reactions, chiral

Asymmetric metal-catalyzed sulfoxidations chiral catalysts

Asymmetric nucleophilic aromatic substitution chiral catalyzed

Asymmetric nucleophilic aromatic substitution chiral nucleophiles

Asymmetric organocatalysts chiral guanidines

Asymmetric organocatalysts chiral imidazoles

Asymmetric oxidation with chiral titanium complexe

Asymmetric reactions chiral auxiliaries

Asymmetric reactions chiral auxiliary removal

Asymmetric reactions chiral dipolarophiles

Asymmetric reactions chiral dipoles

Asymmetric reactions chiral ylides

Asymmetric reactions with chiral amino acid

Asymmetric reduction chiral boranes

Asymmetric reductions with chiral aluminum reagents

Asymmetric reductive amination diastereoselective chiral auxiliaries

Asymmetric synthesis chiral lithium amide reactions

Asymmetric synthesis from chiral pool compounds

Asymmetric synthesis in chiral

Asymmetric synthesis of chiral alkaloids

Asymmetric synthesis of chiral isoquinolines

Asymmetric synthesis of chiral piperidines

Asymmetric synthesis via chiral organoborane

Asymmetric synthesis via chiral organoboranes

Asymmetric synthesis with chiral auxiliaries

Asymmetric synthesis with chiral catalysts

Asymmetric synthesis with chiral reagents

Asymmetric synthesis with chiral sulfur reagent

Asymmetric synthesis, chiral auxiliaries

Asymmetric transfer hydrogenation chiral alcohol production

Asymmetric transfer hydrogenation chiral amino alcohol ligand

Asymmetric using chiral auxiliaries

Asymmetric using chiral catalysts

Borohydrides, chiral, asymmetric

Borohydrides, chiral, asymmetric reducing agents

Carbenes asymmetric reactions, chiral auxiliaries

Catalytic Asymmetric Aza Diels-Alder Reactions Promoted by Chiral Ytterbium Catalysts

Catalytic Asymmetric Induction with Chiral Lewis Acids

Catalytic Asymmetric Induction with Chiral Lewis Bases

Catalytic Asymmetric Induction with Chiral Thiols

Catalytic Asymmetric Induction with Chiral Thioureas

Catalytic asymmetric allylation chiral amide

Chiral Allylsilanes by Asymmetric Grignard Crossoupling

Chiral Amines as Catalysts in Asymmetric Mannich Reactions

Chiral Auxiliaries and Ligands in Asymmetric Synthesis

Chiral Auxiliary Mediated Asymmetric Ireland-Claisen Rearrangements

Chiral Catalysts for Asymmetric Allylation

Chiral Compounds without Asymmetric Atoms

Chiral acetals asymmetric cyclization

Chiral acetals asymmetric synthesis from

Chiral acetals for asymmetric bromolactonizations

Chiral alcoholates, asymmetric synthesis

Chiral alcohols asymmetric synthesis

Chiral alkaloids asymmetric synthesis

Chiral amides, asymmetric Michael reactions

Chiral amides, asymmetric crotylation

Chiral amines asymmetric synthesis

Chiral asymmetric Darzens reaction

Chiral asymmetric aminocatalysis

Chiral asymmetric bioreduction

Chiral asymmetric catalysis

Chiral asymmetric hydrogenation

Chiral asymmetric induction

Chiral asymmetric ligands

Chiral asymmetric synthesis

Chiral auxiliaries Asymmetric aldol with

Chiral auxiliaries asymmetric aldol reactions

Chiral auxiliaries asymmetric alkylations

Chiral auxiliaries asymmetric metathesis

Chiral auxiliaries asymmetric oxidation

Chiral auxiliaries in asymmetric Diels-Alder

Chiral auxiliaries in asymmetric Diels-Alder reaction

Chiral auxiliaries, diastereoselectivity, asymmetric

Chiral auxiliaries, diastereoselectivity, asymmetric Michael additions

Chiral auxiliaries, diastereoselectivity, asymmetric alkenes

Chiral auxiliaries, diastereoselectivity, asymmetric cleavage

Chiral auxiliaries, diastereoselectivity, asymmetric cycloadditions

Chiral auxiliaries, diastereoselectivity, asymmetric facial selectivity

Chiral auxiliaries, diastereoselectivity, asymmetric intramolecular cycloadditions

Chiral auxiliaries, diastereoselectivity, asymmetric nitrile oxide cycloadditions

Chiral auxiliaries, diastereoselectivity, asymmetric reactions

Chiral auxiliaries, diastereoselectivity, asymmetric stereoselectivity

Chiral auxiliary, in asymmetric aldol reaction

Chiral biaryls asymmetric synthesis

Chiral boron reagent in asymmetric Diels-Alder

Chiral building blocks asymmetric synthesis

Chiral catalysts, asymmetric metal-catalyzed

Chiral catalyzed asymmetric nucleophilic aromatic

Chiral cavities asymmetric syntheses

Chiral compounds asymmetric hydroformylation

Chiral compounds asymmetric reaction products

Chiral compounds asymmetric variants

Chiral dipoles, diastereoselectivity. asymmetric

Chiral enamine asymmetric

Chiral enol ethers asymmetric

Chiral epoxides, enantioselective asymmetric

Chiral hydride reagents asymmetric reduction

Chiral hydroperoxides allylic alcohol asymmetric epoxidation

Chiral initiators, enantioselective asymmetric

Chiral initiators, enantioselective asymmetric autocatalysis

Chiral ketone-catalyzed asymmetric epoxidation

Chiral lanthanoid complexes, asymmetric

Chiral ligand asymmetrical synthesis

Chiral ligands asymmetric Heck reaction

Chiral ligands asymmetric amplification

Chiral ligands asymmetric hydrogenation

Chiral ligands for asymmetric hydrosilylation

Chiral ligands, Sharpless asymmetric

Chiral ligands, Sharpless asymmetric hydroxylation reactions

Chiral lithium amides in asymmetric synthesis

Chiral metal complexes asymmetric synthesis

Chiral monophosphine catalytic asymmetric hydrogenation

Chiral organoboranes, asymmetric

Chiral phase-transfer catalysis asymmetric alkylations

Chiral poisoning, asymmetric amplification

Chiral pool asymmetric synthesis with

Chiral pyridines asymmetric reactions catalysis

Chiral salen catalysts, olefins asymmetric

Chiral solvents asymmetric synthesis

Chiral substrates, asymmetric addition

Chiral substrates, asymmetric conjugate

Chiral synthesis asymmetric aminohydroxylation

Chiral tertiary alcohols asymmetric synthesis

Chiral titanium complexes asymmetric oxidation with

Chiral vinyl ethers, asymmetric tandem

Chiral, asymmetric polymerization

Chirality asymmetric amplification

Chirality asymmetric dihydroxylation

Chirality asymmetric metal catalysis

Chirality asymmetric synthesis

Chirality compounds without asymmetric

Chirality enzyme-mediated asymmetric

Cinchona Alkaloids as Chiral Ligands in Asymmetric Oxidations

Cinchona-Derived Chiral Phase-Transfer Catalysts for Other Asymmetric Synthesis

Cinchona-Derived Chiral Poly(Phase-Transfer Catalysts) for Asymmetric Synthesis

Crystals, chiral, absolute asymmetric transformation

Dipolarophiles asymmetric cycloaddition reactions, chiral

Direct Examination of Extraterrestrial Chirality in Meteorites Using Asymmetric Autocatalysis

Discrimination and Asymmetric Induction with Chiral Polyanilines

Enantioselective Synthesis Mediated by Chiral Crystals of an Achiral Organic Compound in Conjunction with Asymmetric Autocatalysis

Epoxidations, asymmetric chiral ketone-catalyzed

Ether compounds asymmetric reactions, chiral auxiliaries

Ethers, Taddol, Nobin and Metal(salen) Complexes as Chiral Phase-Transfer Catalysts for Asymmetric Synthesis

Evans asymmetric aldol reactions chiral auxiliaries

Heterogeneous asymmetric catalysis chirally modified catalysts

Hydrogenation chiral hgands, asymmetric

Ketones asymmetric reductive amination, chiral

Metallated chiral asymmetric alkylation

Nitroso compounds, chiral, asymmetric

Other Chiral Phase-Transfer Catalysts for Asymmetric Synthesis

Oxazoline, chiral remote asymmetric induction

Peracids, chiral, asymmetric oxidation

Phase-transfer catalysis chiral, asymmetric

Practically Perfect Asymmetric Autocatalysis with Amplification of Chirality

Pyridyl alcohol, chiral, Asymmetric

Reagent controlled asymmetric synthesis chirality

Reversible chiral auxiliaries, asymmetric

Rhodium , chiral “binap” complexes asymmetric hydrogenation with

Rhodium catalyzed asymmetric chiral 1,4 diphosphine ligands

Ring-closing metathesis asymmetric, using chiral catalyst

Selective asymmetric hydrogenations over chiral

Some Examples of Chiral Organometallic Complexes and Asymmetric Catalysis

Study 6.21 Asymmetric synthesis in crystals application of chiral auxiliaries

Sulfinimines, chiral asymmetric synthesis

Sulfoxide, chiral vinyl asymmetric induction

Sulfoxides, asymmetric reduction chiral

Synthesis, asymmetric chiral from achiral

Two-Center Chiral Phase-Transfer Catalysts for Asymmetric Synthesis

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