The Experts below are selected from a list of 672 Experts worldwide ranked by ideXlab platform
Emmanuel A. Theodorakis - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson Annulation.
Beilstein Journal of Organic Chemistry, 2013Co-Authors: Lynnie Trzoss, Michelle H. Lacoske, Emmanuel A. TheodorakisAbstract:An enantioselective synthesis of the core framework of neurotrophic Illicium majucin-type sesquiterpenes is described here. This strategy is based on an organocatalyzed asymmetric Robinson Annulation and provides an efficient approach for a diversity-oriented synthesis of Illicium natural products that holds remarkable therapeutic potential for neurodegenerative diseases.
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Enantioselective Total Synthesis of (−)‐Jiadifenolide
Angewandte Chemie International Edition, 2011Co-Authors: Lynnie Trzoss, Weng K. Chang, Emmanuel A. TheodorakisAbstract:The first total synthesis of jiadifenolide (1), a potent neurotrophic modulator, has been reported. Highlights of the synthesis include: construction of the B ring via an asymmetric Robinson Annulation; assembly of the E ring lactone via a novel acid-induced cascade reaction; and Pd(0)-mediated carbomethoxylation and methylation reactions for the construction of the C and A rings respectively.
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Enantioselective synthesis of the ABC ring motif of norzoanthamine based on asymmetric Robinson Annulation reactions.
Organic Letters, 2011Co-Authors: Thong X. Nguyen, Lynnie Trzoss, Marianna Dakanali, Emmanuel A. TheodorakisAbstract:An enantioselective strategy for the synthesis of tetracyclic motif 5, representing the northern fragment of norzoanthamine, is presented. Key to the strategy is the use of two asymmetric Robinson Annulation reactions that produce the tricyclic ABC ring system with excellent stereoselectivity. Further functionalization at the periphery of the C ring produces compound 5 containing six contiguous stereocenters of the natural product.
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Stereoselective synthesis of the ABC ring system of norzoanthamine.
Organic Letters, 2004Co-Authors: Subhash Ghosh, Fatima Rivas, Derek Fischer, Miguel González, Emmanuel A. TheodorakisAbstract:An efficient synthesis of enone 4, representing the ABC ring motif of norzoanthamine, is presented. The crucial C22 quaternary center was introduced via a stereoselective methylation of enone 8. The trans-anti-trans relative configuration of the ABC framework of 4 was installed via a sequence of reactions that included a hydroboration and a modified Robinson Annulation.
Xianfu Lin - One of the best experts on this subject based on the ideXlab platform.
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d-Aminoacylase-initiated cascade Aldol condensation/Robinson Annulation for synthesis of substituted cyclohex-2-enones from simple aldehydes and acetone
Amino Acids, 2014Co-Authors: Ziwei Xiang, Yiru Liang, Xiang Chen, Xianfu LinAbstract:As an important building block, developing efficient and green synthesis strategy of cyclohex-2-enones is of great importance. In this present work, a general approach to the mild synthesis of substituted cyclohex-2-enones derivatives starting fro m simple aldehydes and acetone have been achieved via d-aminoacylase-initiated Aldol condensation/Robinson Annulation cascade reaction using imidazole as an additive in organic media. The influences of reaction conditions including solvents, enzyme concentration, additives type, molar ratio of enzyme to additive, and substrate scopes were systematically investigated. Furthermore, some experiments were designed to explore the catalytic roles of d-aminoacylase and imidazole in the multistep cascade process, and one possible mechanism was proposed.
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d aminoacylase initiated cascade aldol condensation Robinson Annulation for synthesis of substituted cyclohex 2 enones from simple aldehydes and acetone
Amino Acids, 2014Co-Authors: Ziwei Xiang, Yiru Liang, Xiang Chen, Xianfu LinAbstract:As an important building block, developing efficient and green synthesis strategy of cyclohex-2-enones is of great importance. In this present work, a general approach to the mild synthesis of substituted cyclohex-2-enones derivatives starting fro m simple aldehydes and acetone have been achieved via d-aminoacylase-initiated Aldol condensation/Robinson Annulation cascade reaction using imidazole as an additive in organic media. The influences of reaction conditions including solvents, enzyme concentration, additives type, molar ratio of enzyme to additive, and substrate scopes were systematically investigated. Furthermore, some experiments were designed to explore the catalytic roles of d-aminoacylase and imidazole in the multistep cascade process, and one possible mechanism was proposed.
Hisashi Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Formal Synthesis of Platencin.
ChemInform, 2010Co-Authors: Hisashi YamamotoAbstract:A facile formal synthesis of platencin is developed involving the Lewis acid catalyzed tropone Diels—Alder reaction [(III)] and the amino acid salt catalyzed intramolecular Robinson Annulation of aldehyde (VIII) as the key steps.
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Formal synthesis of platencin.
Chemical Communications, 2010Co-Authors: Hisashi YamamotoAbstract:Formal synthesis of platencin was achieved by assembling its tricyclic core structure through a Robinson Annulation reaction, whose precursor was made from a bicyclo[3.2.2] ring structure, product of a tropone Diels–Alder reaction.
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Amino acid salt catalyzed intramolecular Robinson Annulation
Chemical Communications, 2009Co-Authors: Pingfan Li, Hisashi YamamotoAbstract:The silica gel absorbed amino acid salt catalyzed asymmetric intramolecular Robinson Annulation reaction has been developed; up to 97% ee was obtained with this readily recoverable organocatalyst.
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Enantioselective Route to Platensimycin: An Intramolecular Robinson Annulation Approach
Journal of the American Chemical Society, 2007Co-Authors: Joshua N. Payette, Hisashi YamamotoAbstract:An enantioselective route to the tetracyclic core structure of the novel antibiotic lead compound platensimycin is accomplished in 10 steps from simple commercially available starting materials. Highlights of this synthesis include (1) a regio- and enantioselective Diels−Alder reaction between methyl acrylate and methyl cyclopentadiene to give adduct 2 with essentially complete regio-, diastereo-, and enantiocontrol; (2) oxidative decarboxylation of ester 2 using nitrosobenzene; (3) a one-pot reductive cyanation of lactone 4; (4) a stereoselective intramolecular Michael addition between an α-branched aldehyde moiety and a β-substituted enone part of 8, followed by aldol dehydration in one pot to give the Robinson Annulation product 9.
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regioselective Robinson Annulation realized by the combined use of lithium enolates and aluminum tris 2 6 diphenylphenoxide atph
Bulletin of the Chemical Society of Japan, 1997Co-Authors: Susumu Saito, Itsuro Shimada, Yusuke Takamori, Masashi Tanaka, Keiji Maruoka, Hisashi YamamotoAbstract:Michael addition of lithium enolates derived from ketones to a variety of α,β-unsaturated ketones was realized in the presence of aluminum tris(2,6-diphenylphenoxide) (ATPH). In this reaction, ATPH can be used as a carbonyl protector of α,β-unsaturated carbonyl substrates upon complexation, which facilitates the regioselective 1,4-addition of lithium enolates to Michael acceptors. Similarly, dianions of β-dicarbonyl compounds undergo Michael addition smoothly using ATPH as an effective promoter of the reaction. Subsequent regioselective, intramolecular aldol condensation was also demonstrated, leading to bicyclic carbon ring systems. Such systems are difficult to obtain by the Robinson Annulation usually performed in protic media.
Carlos F. Barbas - One of the best experts on this subject based on the ideXlab platform.
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A proline-catalyzed asymmetric Robinson Annulation reaction
Tetrahedron Letters, 2000Co-Authors: Tommy Bui, Carlos F. BarbasAbstract:Abstract A single-step enantioselective synthesis of the Wieland–Miescher ketone ( 5 ) is presented. We show that l -proline as well as a number of other chiral amines can act as catalysts of both steps of the Robinson Annulation reaction. Other chiral amines are identified as catalysts of Michael and aldol addition reactions.
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Antibody-Catalyzed Enantioselective Robinson Annulation
Journal of the American Chemical Society, 1997Co-Authors: Guofu Zhong, Samuel J. Danishefsky, Torsten Hoffmann, Richard A. Lerner, Carlos F. BarbasAbstract:The Skaggs Institute for Chemical Biologyand the Department of Molecular BiologyThe Scripps Research Institute10550 North Torrey Pines Road, La Jolla, California 92037Laboratory for Bioorganic ChemistryThe Sloan-Kettering Institute for Cancer Research1275 York AVenue, New York, New York 10021ReceiVed March 25, 1997We report an antibody that is remarkable in that it catalyzesboth steps of an important synthetic transformation, the Rob-inson Annulation. The Robinson Annulation which accomplishes,in net terms, the conversion of a f c occupies a key role inorganic synthesis.
Ziwei Xiang - One of the best experts on this subject based on the ideXlab platform.
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d-Aminoacylase-initiated cascade Aldol condensation/Robinson Annulation for synthesis of substituted cyclohex-2-enones from simple aldehydes and acetone
Amino Acids, 2014Co-Authors: Ziwei Xiang, Yiru Liang, Xiang Chen, Xianfu LinAbstract:As an important building block, developing efficient and green synthesis strategy of cyclohex-2-enones is of great importance. In this present work, a general approach to the mild synthesis of substituted cyclohex-2-enones derivatives starting fro m simple aldehydes and acetone have been achieved via d-aminoacylase-initiated Aldol condensation/Robinson Annulation cascade reaction using imidazole as an additive in organic media. The influences of reaction conditions including solvents, enzyme concentration, additives type, molar ratio of enzyme to additive, and substrate scopes were systematically investigated. Furthermore, some experiments were designed to explore the catalytic roles of d-aminoacylase and imidazole in the multistep cascade process, and one possible mechanism was proposed.
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d aminoacylase initiated cascade aldol condensation Robinson Annulation for synthesis of substituted cyclohex 2 enones from simple aldehydes and acetone
Amino Acids, 2014Co-Authors: Ziwei Xiang, Yiru Liang, Xiang Chen, Xianfu LinAbstract:As an important building block, developing efficient and green synthesis strategy of cyclohex-2-enones is of great importance. In this present work, a general approach to the mild synthesis of substituted cyclohex-2-enones derivatives starting fro m simple aldehydes and acetone have been achieved via d-aminoacylase-initiated Aldol condensation/Robinson Annulation cascade reaction using imidazole as an additive in organic media. The influences of reaction conditions including solvents, enzyme concentration, additives type, molar ratio of enzyme to additive, and substrate scopes were systematically investigated. Furthermore, some experiments were designed to explore the catalytic roles of d-aminoacylase and imidazole in the multistep cascade process, and one possible mechanism was proposed.
