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Showing 1 to 20 of 72 for “"stereogenic"”.
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Synthesis of P-Stereogenic Bisphosphine Ligands: Application as Hemi-labile Ligands in the Asymmetric Pauson-Khand Reaction
The synthesis of new P-stereogenic ligands and investigation of their use in a Co-catalysed asymmetric Pauson-Khand reaction has been carried out. The ligands were synthesised by asymmetric lithiation of a phosphine sulfide or a phosphine borane using alkyllithium/()-sparteine complexes, trapping …
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New Methods for the Formation of Methyl Bearing Stereogenic Centers via Methylketene Dimerization and Free Radical Additions to Allyl Bromides
Two organic synthetic methods for the generation of methyl bearing chiral centers have been developed using: 1) dimerization of methylketene and 2) a free radical-based addition/elimination reaction involving allyl bromides. The first method, the asymmetric dimerization of methyl ketene, followed …
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Design and Modification of Half-Sandwich Ir(III), Rh(III), and Ru(II) Amino Acid Complexes for Application in Asymmetric Transfer Hydrogenation Reactions
… these complexes is pseudotetrahedral, leading to stereogenic metal ions (SM, RM). The addition of another stereogenic center from the amino acid ligand (the carbon, RC or SC;glycine) gives rise to two pairs of diastereomeric complexes.
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Synthesis, study and application of silyl ketene imines in Lewis base catalyzed carbonyl addition
… products containing secondary and tertiary stereogenic centers are obtained in high yield and with excellent stereoselectivities. Despite the breadth of reactivity that has been observed for additions to aldehydes under this mode of catalysis certain structural motifs, such as quaternary …
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Tandem Double Intramolecular [4+2]/[3+2] Cycloaddition of Nitro Olefins: Part I: Construction of Piperidine Rings. Part II: Construction of Vicinal Quaternary Stereogenic Centers. Part III: Progress Toward a Total Synthesis of Daphnilactone B
The fully functionalized nitroalkene intermediate for the total synthesis of daphnilactone has also been prepared and participated in the high yielding tandem double-intramolecular [4+2]/[3+2] cycloaddition to provide a mixture of two epimeric nitroso acetals. Ozonolysis of the cycloadducts, …
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Memory of Chirality in 1,4-Benzodiazepin-2-ones
… benzodiazepines containing a "quaternary" stereogenic center. This research will discuss the stereochemical properties of 1,4-benzodiazepin-2-ones, and provide a novel approach to synthesize enantiomerically enriched "quaternary" benzodiazepines with stereogenic centers through MOC, without …
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Delta-Hydroxy-beta,beta-disubstituierte-beta-Aminosäuren: asymmetrische Synthese und Überführung in Dipeptide
… acids having three contiguous stereogenic centers and the conversion of these molecules to dipeptides. The advantages of the herein described synthetic strategy relies on the extended variability concerning the substituents to be incorporated with excellent stereoselectivity in …
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Asymmetrische Synthese von Thiadecalinen : Organokatalytische Dominoreaktionen kombiniert mit intramolekularen Michael-Reaktionen
… of four new bonds and allows the control of six stereogenic centers. Thiadecalins are known for their antimicrobial properties.
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Design, synthesis, and evaluation of bioactive molecules; Chiral polyvinylpyrrolidones supported Cu/Au nanoclusters catalyzed cyclization of 5-substituted nona-1,8-dien-5-ols
… A five-member cyclized lactone possessing a stereogenic tetrasubstituted carbon center was formed in a one-step Cu/Au nanoclusters-hydrogen peroxide oxidation reaction. This developed a novel and simple method to synthesize tetrasubstituted carbon stereogenic center. Drawbacks of the method …
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Mechanistic Studies on Memory of Chirality Alkylations of 1,4-Benzodiazepin-2-ones & Structure-based Design of Insecticidal AChE Inhibitors for Malaria Mosquito, Anopheles gambiae
… In these reactions the configuration of the sole stereogenic center of the enantiopure starting material is "memorized" by a chiral non-racemic conformation in the intermediate; trapping then captures the stereochemical information, and generates a new stereogenic center with high fidelity. We …
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APPROACHES TO THE TOTAL SYNTHESIS OF DICTYOSTATIN AND SYNTHESIS OF EPI-DICTYOSTATINS
… and global deprotection. Eleven stereogenic centers and four stereogenic double bonds were obtained with a high level of stereocontrol. Surprisingly, the addition of vinylzincate C10-C26 to aldehyde C1-C9 led to a complete stereoselectivity in favor of the 9R-epimer, which is …
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Totalsynthese von (+)-2-epi-Deoxoprosopinin und neue Hydrazin-Harze für die organische Festphasensynthese
… were employed to generate two of the three stereogenic centers. Creation of the third stereogenic center was achieved in a domino deprotection/cyclisation/reduction sequence. In the second part, a novel N-butyl-N-methylpolystyrene-hydrazine linker resin was developed. Polymer supported …
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Asymmetric Syntheses With (-)-Sparteine-Complexed Benzylic and Allylic Organolithium Reagents
… 1,4-addition products with three contiguous stereogenic centers with high stereoselectivities. In all cases of a 1,4-addition selectivity factors >20 were obtained, as calculated using the enantiomeric excess of the conjugate addition product.
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I. Chemoselective Dehydrative Glycosylation With Application Toward Oligosaccharide Synthesis. II. Sulfide-Mediated Direct Glycosylation of C(1)-Hydroxyl Glycosyl Donors. III. Studies Toward the Total Synthesis of Auriside A
… olefination for the installation of the C(5)-stereogenic center, the 14-membered macrolactone, and the conjugated bromodiene moiety, respectively.
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Synthesis of 3'-deoxy- and 2',3'-dideoxy-4'-C-alkyl-D-nucleosides: potential antiviral agents
… exceptional stereocontrol over the C4' stereogenic center; and a semi-convergent synthesis, allowing the late stage N-glycosylation of heterocyclic bases. Both 4'-C-alkyl substituent variety and control of the C4' stereocenter are addressed by introducing the alkyl substituents and …
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Efficient Synthetic Strategies for Discrete Macromolecules: Enabling Exploration of Structure-Property Relationships in Biological and Materials Applications
… stereochemistry and varied distance between stereogenic centers. After polymerizing these macromolecules using ring-opening metathesis polymerization (ROMP) to generate bottlebrush polymers with uniform arms, we evaluated their interactions with biological systems both in vitro and in vivo, …
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Modular asymmetric synthesis of functionalized azaspirocycles based on the sulfoximine auxiliary
… tertiary C-atom and three contiguous stereogenic centers was achieved in three steps from cyclic allylic sulfoximines. The first key step was a titanium-mediated gamma-hydroxyalkylation of named sulfoximines. In the course of this reaction two new stereogenic centers and a double bond …
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Synthetic studies on the spiroacetal moiety of stenocarpin, a metabolite of Diplodia maydis
… absolute configuration of the C(3) spiroacetal stereogenic center remained unknown. The aim of the synthetic studies described in this dissertation was to develop a synthetic methodology for the spiroacetal moiety present in stenocarpin in order to establish unambiguously the C(3) absolute …
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Pin1 Catalytic and WW Domain Ligands
… of 2.0% and 1.4%, respectively. The newly formed stereogenic center in the piperidyl ring was introduced by a Luche reduction, followed by a stereoselective [2,3]-Still-Wittig rearrangement. The configuration of the stereocenter was determined by NOESY of a bicyclic derivative. The (Z)- to …
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