The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Darren J. Dixon - One of the best experts on this subject based on the ideXlab platform.
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Enantioselective Construction of the ABCDE Pentacyclic Core of the Strychnos Alkaloids
Organic letters, 2017Co-Authors: Adam D. Gammack Yamagata, Darren J. DixonAbstract:An efficient enantioselective 12-step synthesis of the ABCDE pentacyclic core of the Strychnos alkaloids is described. A key feature of this approach is an organocatalyzed enantioselective desymmetrization to generate the morphan core in high ee and dr. After palladium-catalyzed installation of the indole moiety, a subsequent 5-exo-trig dearomatizing atom transfer radical cyclization was developed to construct the C-ring. Following a series of Functional Group Interconversions, the pentacyclic amine core was obtained with all the relevant architecture including five stereocenters pertaining to the Strychnos alkaloids.
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Enantioselective Construction of the ABCDE Pentacyclic Core of the Strychnos Alkaloids
2017Co-Authors: Adam Gammack D. Yamagata, Darren J. DixonAbstract:An efficient enantioselective 12-step synthesis of the ABCDE pentacyclic core of the Strychnos alkaloids is described. A key feature of this approach is an organocatalyzed enantioselective desymmetrization to generate the morphan core in high ee and dr. After palladium-catalyzed installation of the indole moiety, a subsequent 5-exo-trig dearomatizing atom transfer radical cyclization was developed to construct the C-ring. Following a series of Functional Group Interconversions, the pentacyclic amine core was obtained with all the relevant architecture including five stereocenters pertaining to the Strychnos alkaloids
Michael J. Krische - One of the best experts on this subject based on the ideXlab platform.
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Total Synthesis of (+)-SCH 351448: Efficiency via Chemoselectivity and Redox-Economy Powered by Metal Catalysis
Journal of the American Chemical Society, 2016Co-Authors: Gang Wang, Michael J. KrischeAbstract:The polyketide natural product (+)-SCH 351448, a macrodiolide ionophore bearing 14 stereogenic centers, is prepared in 14 steps (LLS). In eight prior syntheses, 22-32 steps were required. Multiple chemoselective and redox-economic Functional Group Interconversions collectively contribute to a step-change in efficiency.
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Total Synthesis of (+)-SCH 351448: Efficiency via Chemoselectivity and Redox-Economy Powered by Metal Catalysis
2016Co-Authors: Gang Wang, Michael J. KrischeAbstract:The polyketide natural product (+)-SCH 351448, a macrodiolide ionophore bearing 14 stereogenic centers, is prepared in 14 steps (LLS). In eight prior syntheses, 22–32 steps were required. Multiple chemoselective and redox-economic Functional Group Interconversions collectively contribute to a step-change in efficiency
David O'hagan - One of the best experts on this subject based on the ideXlab platform.
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Selectively fluorinated cyclohexane building blocks: Derivatives of carbonylated all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane.
Beilstein journal of organic chemistry, 2015Co-Authors: Mohammed Salah Ayoup, David B. Cordes, Alexandra M. Z. Slawin, David O'haganAbstract:Palladium catalysed carbonylation reactions using the meta- and para-iodo derivatives of all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane (4) are illustrated as the start point for a variety of Functional Group Interconversions. The resultant benzaldehyde and benzoic acids offer novel building blocks for further derivatisation and facilitate the incorporation of the facially polarised all-cis-1,2,4,5-tetrafluorocyclohexane motif into more advanced molecular scaffolds.
Eric E. Simanek - One of the best experts on this subject based on the ideXlab platform.
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Chemoselective building blocks for dendrimers from relative reactivity data.
Organic letters, 2003Co-Authors: Mackay B. Steffensen, Eric E. SimanekAbstract:Competition reactions for the substitution of monochlorotriazines with different amines provide relative reactivity data that can be used to identify new Groups for the chemoselective syntheses of dendrimers based on melamine. Target 1 is prepared using a one-pot per generation strategy without protecting Group manipulations or Functional Group Interconversions.
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Orthogonal, convergent syntheses of dendrimers based on melamine with one or two unique surface sites for manipulation.
Journal of the American Chemical Society, 2001Co-Authors: Wen Zhang, Daniel T. Nowlan, Lisa M. Thomson, And William M. Lackowski, Eric E. SimanekAbstract:An orthogonal, convergent route for the introduction of substoichiometric numbers of latent surface sites into dendrimers based on melamine is used to prepare targets that display one or two Boc-protected amines on the periphery. Asymmetry is the result of the stepwise incorporation of Functionalized and unFunctionalized dendrons onto the triazine cores, a highly selective process due to the different reactivities of the substituted triazines. The routes to the dendrons rely on iterative reactions of the growing dendrons with triazine cores and diamine linkers. p-Aminobenzylamine is used as a linking Group to avoid Functional Group Interconversions or protecting Group manipulations. Addition of the benzylamine Group to the monochlorotriazine of the dendron proceeds cleanly leaving a less reactive aniline for subsequent reaction with trichlorotriazine. The routes to these targets proceed in 5 or 6 linear steps (11 or 12 total steps) in 40% overall yield. The unique surface sites can be deprotected and subj...
Juraj Kuchár - One of the best experts on this subject based on the ideXlab platform.
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An efficient synthesis of the polar part of sulfamisterin and its analogs
Carbohydrate research, 2012Co-Authors: Miroslava Martinková, Jozef Gonda, Jana Raschmanová, Alena Uhríková, Juraj KuchárAbstract:An efficient synthesis of the polar part of sulfamisterin and its analogs starting from d-xylose is described. The corresponding allylic thiocyanates and trichloroacetimidates were subjected to aza-Claisen rearrangement that effectively generated a quaternary carbon having an amino Group as one of the substituents. Subsequent Functional Group Interconversions afforded the highly Functionalized branched aminopolyol 29 that is expected to have the crucial application in the construction of sulfamisterin. On the other hand, the second diastereoisomer 34 would be transformed to 2-epi-congener. With respect to the appropriate stereochemical arrangement, the prepared polar segments 29 and 34 can also be utilized for the synthesis of mycestericins (E, G) and their analogs.
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A facile synthesis of D-ribo-C(20)-phytosphingosine and its C2 epimer from D-ribose.
Carbohydrate research, 2011Co-Authors: Miroslava Martinková, Jozef Gonda, Kvetoslava Pomikalová, Jozef Kožíšek, Juraj KuchárAbstract:A facile synthetic route to d-ribo-C(20)-phytosphingosine 31 and its C2 epimer 32 is described. The Overman rearrangement of allylic trichloroacetimidates derived from the known ribose derivative 7 has been used as the key step. The subsequent Functional Group Interconversions in rearranged products 14 and 15 followed by Wittig olefination, Pd/C-mediated reduction and the removal of protecting Groups successfully constructed the final molecules.
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Total synthesis of a protected form of sphingofungin E using the [3,3]-sigmatropic rearrangement of an allylic thiocyanate as the key reaction
Carbohydrate research, 2010Co-Authors: Miroslava Martinková, Jozef Gonda, Jana Raschmanová, Michaela Slaninková, Juraj KuchárAbstract:Abstract An approach to the stereocontrolled synthesis of the protected form of sphingofungin E ( 32 ) starting from the known protected d -glucose derivative 3 is described herein. For the construction of a tetrasubstituted carbon atom that is substituted with nitrogen, the [3,3]-sigmatropic rearrangement of thiocyanate 8 was employed. Subsequent Functional Group Interconversions afforded the highly Functionalized fragment, allylic bromide 26 . Its coupling reaction with the known C 12 hydrophobic segment 2 , followed by further manipulation, completed the total synthesis.
