The Experts below are selected from a list of 423 Experts worldwide ranked by ideXlab platform
Paul R. Hanson - One of the best experts on this subject based on the ideXlab platform.
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The synthesis of sterically demanding amino acid-derived cyclic Phosphonamides.
The Journal of organic chemistry, 2000Co-Authors: Kevin T. Sprott, Paul R. HansonAbstract:The preparation and utilization of C2-symmetric 1,4-diamines in the synthesis of amino acid-derived cyclic Phosphonamides 1−3 are described. The 1,4-diamines are synthesized via three methods: (i) amino acid/fumaryl chloride coupling followed by amide reduction, (ii) amino acid/1,4-diamine coupling followed by amide reduction, and (iii) a template-supported ring-closing metathesis/hydrolysis sequence. The pseudo C2-symmetric cyclic Phosphonamides 1−3 are prepared by condensation of the C2-symmetric 1,4-diamines to P(III) centers, followed by oxidation.
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Diastereotopic differentiation on phosphorus templates via the ring-closing metathesis reaction.
Organic letters, 2000Co-Authors: Diana S. Stoianova, Paul R. HansonAbstract:A strategy is described in which the ring-closing metathesis reaction is utilized to desymmetrize a number of pseudo-C2-symmetric phosphorus templates 1−3. These reactions give excellent levels of selectivity (12−15:1) with vinyl Phosphonamides containing a (E)-Ph group on the diastereotopic olefins. This approach is being developed as an effective method of obtaining P-chiral Phosphonamides and phosphonates.
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Ring Closing Metathesis Reactions on Phosphonamide and Phosphonate Templates
Phosphorus Sulfur and Silicon and the Related Elements, 1999Co-Authors: Paul R. Hanson, Diana S. StoianovaAbstract:Abstract Phosphonrs containing organic compounds have shown enormous potential in the development of novel pharmaceutical and agricultural agents [1,2]. One attractive route into the formation of complex Phosphonamides and phosphonates is via the RCM reaction of acyclic substrates such as 1,4. and 6. Recently we published the first example of a RCM reaction on a phosphonate template [4]. Although the RCM reaction has emerged as a powerful tool in the synthesis of complex ring systems [3]. only one other example exists in the literature of a RCM reaction on phosphines using a tungsten carbene catalyst [5]. As part of our program aimed at developing organometallic approaches to diverse phosphorus containing compounds, we herein report the first examples of RCM reactions on Phosphonamide templates such as 1 and 4 using the ruthenium catalyst 2. In addition. we report new examples of RCM reactions on phosphonate templates such as 6.
Stephen Hanessian - One of the best experts on this subject based on the ideXlab platform.
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Application of cyclic Phosphonamide reagents in the total synthesis of natural products and biologically active molecules
Beilstein journal of organic chemistry, 2014Co-Authors: Thilo Focken, Stephen HanessianAbstract:A review of the synthesis of natural products and bioactive compounds adopting Phosphonamide anion technology is presented highlighting the utility of Phosphonamide reagents in stereocontrolled bond-forming reactions. Methodologies utilizing Phosphonamide anions in asymmetric alkylations, Michael additions, olefinations, and cyclopropanations will be summarized, as well as an overview of the synthesis of the employed Phosphonamide reagents.
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Total synthesis of (+)-ambruticin S: probing the pharmacophoric subunit.
The Journal of organic chemistry, 2010Co-Authors: Stephen Hanessian, Thilo Focken, Rupal Oza, Bin Chen, Dougal J. Ritson, Renaud BeaudegniesAbstract:An enantioselective synthesis of the antifungal natural product (+)-ambruticin S has been accomplished starting with the readily available methyl α-d-glucopyranoside, (R)-Roche ester, and (S)-glycidol as chirons, which encompassed seven of the 10 stereogenic centers of the target molecule. The remaining three centers were set by a highly diastereoselective, asymmetric cyclopropanation employing a chiral, nonracemic Phosphonamide reagent. Our strategy for the construction of the dihydropyran subunit involved a highly syn-selective Lewis acid catalyzed 6-endo-trig cyclization. Other key steps in the synthesis featured an epoxide opening with a dithiane anion, two efficient Phosphonamide-anion based olefinations, and a late-stage C-glycosylation.
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synthesis and stereochemical confirmation of the secoiridoid glucosides nudiflosides d and a
Organic Letters, 2006Co-Authors: Stephen Hanessian, And Emily Mainetti, Fabien LecomteAbstract:We describe herein an efficient access to the highly substituted cyclopentane unit present in the Nudifloside secoiridoid family via crotyl Phosphonamide anion mediated conjugate addition to cyclopentenone.
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The synthesis of enantiomerically pure disubstituted aziridines and N -alkoxy aziridines
Tetrahedron Letters, 2000Co-Authors: Stephen Hanessian, Louis-david CantinAbstract:The addition of a chloroallyl Phosphonamide anion to oximes has allowed the preparation of a variety of cis-disubstituted N-alkoxy aziridines in enantiomerically pure form. Oxidative cleavage of the chiral auxiliary followed by derivatization of the products has allowed the preparation of enantiopure N-alkoxy aziridines.
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Total Synthesis and Absolute Configuration of (-)-Anthoplalone.
The Journal of organic chemistry, 1999Co-Authors: Stephen Hanessian, Louis-david Cantin, Daniele AndreottiAbstract:We report the total synthesis of the cytotoxic agent (−)-anthoplalone and the determination of its absolute stereochemistry. The cyclopropane moiety was prepared using a nonracemic bicyclic chloroallyl Phosphonamide anion addition to tert-butyl 3,3-dimethyl acrylate. Several pathways were studied to secure the E-trisubstituted olefin of the left part of the molecule.
Cosimo Cardellicchio - One of the best experts on this subject based on the ideXlab platform.
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Stacked aryl groups in P-resolved cyclic Phosphonamides as a new conformational constraint
CrystEngComm, 2019Co-Authors: Maria Annunziata M. Capozzi, Claudia Pigliacelli, Giancarlo Terraneo, Cosimo CardellicchioAbstract:Along the lines of a systematic investigation of conformational constraints promoted by weak interactions, the aryl-stacked structures of some chiral cyclic Phosphonamides synthesised with the aid of Betti bases as chirality inducers were investigated by X-ray diffraction analysis and NMR spectroscopy. The synthesised systems showed the stacked conformation between two of their aryl groups, leading to pre-organized structures. The π–π stacking motif between the aromatic rings was observed in solid state and in solution, suggesting that this supramolecular synthon could be used as a conformational constraining tool in the development of drug molecule candidates based on chiral cyclic Phosphonamides. The disabling of the π–π stacking motif was pursued by adding an ortho-substituent on one aromatic ring.
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Stacked naphthyls and weak hydrogen-bond interactions govern the conformational behavior of P-resolved cyclic Phosphonamides: a combined experimental and computational study.
The Journal of organic chemistry, 2014Co-Authors: Maria Annunziata M. Capozzi, Francesco Capitelli, Andrea Bottoni, Matteo Calvaresi, Cosimo CardellicchioAbstract:P-Enantiomerically pure cyclic Phosphonamides have been synthesized via a cyclization reaction of (S,S)-aminobenzylnaphthols with chloromethylphosphonic dichloride. The reaction is highly stereoselective and gives almost exclusively (S,S,SP)-cyclic Phosphonamides in good yields. Analysis of the X-ray crystal structures shows clearly that the cyclization reaction forces the two naphthyl rings into a stable parallel displaced stacking assembly and indicates also the existence of intramolecular CH···π interactions and weak forms of intermolecular hydrogen bondings, involving the oxygen and the chlorine atoms. QM computations and NMR spectra in solution confirm the stacked molecular assembly as the preferred arrangement of the two naphthyl groups.
K. N. Houk - One of the best experts on this subject based on the ideXlab platform.
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A THEORETICAL INVESTIGATION OF PHOSPHONAMIDATES AND SULFONAMIDES AS PROTEASE TRANSITION STATE ISOSTERES
Journal of Organic Chemistry, 1998Co-Authors: Jennifer L. Radkiewicz, Michael A. Mcallister, Elisheva Goldstein, K. N. HoukAbstract:The conformations and electrostatic potentials of Phosphonamides, phosphonamidates and sulfonamides have been compared to the tetrahedral intermediate for base-catalyzed amide hydrolysis. The wide variation in inhibition by these similar compounds is explained through differences in electrostatic effects.
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Theoretical Study of Phosphonamidates, Phosphonamides and Sulfonamides as Transition State Isosteres of Hiv Protease
Phosphorus Sulfur and Silicon and the Related Elements, 1996Co-Authors: Elisheva Goldstein, Jennifer L. Radkiewicz, Michael A. Mcallister, K. N. HoukAbstract:Abstract Ab-initio calculations at the RHF/6-31+G* level are performed on the N-methyl(methyl) conformers of phosphonamidates, Phosphonamides, and sulfonamides. Sulfonamides and phosphonamidates are found to have very similar conformers and energies as potential transition state isosteres. Local minima in both are separated by a 2.0 kcal/mol barrier. The anti conformation and molecular dipole moments of Phosphonamides play a role in the transition state isostere as was previously evidenced in the hydroxyethylene based mimics.
Debabrata Maiti - One of the best experts on this subject based on the ideXlab platform.
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Incorporating Unbiased, Unactivated Aliphatic Alkenes in Pd(II)-Catalyzed Olefination of Benzyl Phosphonamide
ACS Catalysis, 2017Co-Authors: Kapileswar Seth, Milan Bera, Massimo Brochetta, Soumitra Agasti, Ashis Das, Andrea Gandini, Alessio Porta, Giuseppe Zanoni, Debabrata MaitiAbstract:The use of unbiased aliphatic alkene as the coupling partner for C–H olefination continues to be a challenging task. A suitable chelating directing group allowed ortho C–H olefination of benzyl Phosphonamide with unactivated aliphatic alkenes. The broad substrate scope with respect to variation of benzyl Phosphonamides and aliphatic alkenes as well as examples of sequential hetero-bis-olefinations offer diversity along with excellent linear/branch selectivity.
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Incorporating Unbiased, Unactivated Aliphatic Alkenes in Pd(II)-Catalyzed Olefination of Benzyl Phosphonamide
2017Co-Authors: Kapileswar Seth, Milan Bera, Massimo Brochetta, Soumitra Agasti, Ashis Das, Andrea Gandini, Alessio Porta, Giuseppe Zanoni, Debabrata MaitiAbstract:The use of unbiased aliphatic alkene as the coupling partner for C–H olefination continues to be a challenging task. A suitable chelating directing group allowed ortho C–H olefination of benzyl Phosphonamide with unactivated aliphatic alkenes. The broad substrate scope with respect to variation of benzyl Phosphonamides and aliphatic alkenes as well as examples of sequential hetero-bis-olefinations offer diversity along with excellent linear/branch selectivity
