The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hitoshi Takeshita - One of the best experts on this subject based on the ideXlab platform.
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synthetic photochemistry lxvii a total synthesis of hinesol and agarospirol via retro Benzilic Acid Rearrangement
Bulletin of the Chemical Society of Japan, 1995Co-Authors: Toshihide Hatsui, Jinjun Wang, Hitoshi TakeshitaAbstract:A mild base-catalyzed retro-Benzilic Acid Rearrangement of a proto-photocycloadduct, formed in highly stereoselective photoaddition of methyl 2,4-dioxopentanoate to 1,5-dimethyl-6-methylene-1-cyclohexene, afforded a spiro[4.5]decenedione derivative. Reductive elimination of the α-dicarbonyl function and C1-homologation furnished (±)-hinesol and (±)-agarospirol.
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synthetic photochemistry lxiv mild base induced retro Benzilic Acid Rearrangement of isolated proto photocycloadducts of methyl 2 4 dioxopentanoate to terpinolene facile synthesis of α chamigrene and α chamigren 3 one
Bulletin of the Chemical Society of Japan, 1994Co-Authors: Toshihide Hatsui, Jinjun Wang, Hitoshi TakeshitaAbstract:In the photoaddition reaction of terpinolene with methyl 2,4-dioxopentanoate, the products derived from the tetrasubstituted C=C were four proto-[2+2] photocycloadducts, together with ene reaction products. When these proto-cycloadducts were treated with aqueous sodium carbonate, a facile retro-Benzilic Acid Rearrangement to form substituted cyclopentenone derivatives occurred. The product from the other trisubstituted C=C was an ordinary retro-aldol product of the [2+2] cycloadduct and an ene reaction product. One of the proto-photocycloadducts was transformed into α-chamigren-3-one and further to α-chamigrene.
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one pot formation of functionalized cyclopentenone derivatives via retro Benzilic Acid Rearrangement of the proto photocycloadducts of methyl 2 4 dioxopentanoate to methylenecycloalkanes
Chemistry Letters, 1992Co-Authors: Toshihide Hatsui, Shinya Ikeda, Hitoshi TakeshitaAbstract:The proto-Photocycloadducts of methyl 2,4-dioxopentanoate to several methylenecycloalkanes and -alkenes spontaneously caused retro-Benzilic Acid Rearrangement, exclusively. The reaction proceeded quite cleanly, and a simple work-up without chromatographic separation allowed to isolate the products directly in very good material balance.
Toshihide Hatsui - One of the best experts on this subject based on the ideXlab platform.
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synthetic photochemistry lxvii a total synthesis of hinesol and agarospirol via retro Benzilic Acid Rearrangement
Bulletin of the Chemical Society of Japan, 1995Co-Authors: Toshihide Hatsui, Jinjun Wang, Hitoshi TakeshitaAbstract:A mild base-catalyzed retro-Benzilic Acid Rearrangement of a proto-photocycloadduct, formed in highly stereoselective photoaddition of methyl 2,4-dioxopentanoate to 1,5-dimethyl-6-methylene-1-cyclohexene, afforded a spiro[4.5]decenedione derivative. Reductive elimination of the α-dicarbonyl function and C1-homologation furnished (±)-hinesol and (±)-agarospirol.
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synthetic photochemistry lxiv mild base induced retro Benzilic Acid Rearrangement of isolated proto photocycloadducts of methyl 2 4 dioxopentanoate to terpinolene facile synthesis of α chamigrene and α chamigren 3 one
Bulletin of the Chemical Society of Japan, 1994Co-Authors: Toshihide Hatsui, Jinjun Wang, Hitoshi TakeshitaAbstract:In the photoaddition reaction of terpinolene with methyl 2,4-dioxopentanoate, the products derived from the tetrasubstituted C=C were four proto-[2+2] photocycloadducts, together with ene reaction products. When these proto-cycloadducts were treated with aqueous sodium carbonate, a facile retro-Benzilic Acid Rearrangement to form substituted cyclopentenone derivatives occurred. The product from the other trisubstituted C=C was an ordinary retro-aldol product of the [2+2] cycloadduct and an ene reaction product. One of the proto-photocycloadducts was transformed into α-chamigren-3-one and further to α-chamigrene.
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one pot formation of functionalized cyclopentenone derivatives via retro Benzilic Acid Rearrangement of the proto photocycloadducts of methyl 2 4 dioxopentanoate to methylenecycloalkanes
Chemistry Letters, 1992Co-Authors: Toshihide Hatsui, Shinya Ikeda, Hitoshi TakeshitaAbstract:The proto-Photocycloadducts of methyl 2,4-dioxopentanoate to several methylenecycloalkanes and -alkenes spontaneously caused retro-Benzilic Acid Rearrangement, exclusively. The reaction proceeded quite cleanly, and a simple work-up without chromatographic separation allowed to isolate the products directly in very good material balance.
Jinjun Wang - One of the best experts on this subject based on the ideXlab platform.
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synthetic photochemistry lxvii a total synthesis of hinesol and agarospirol via retro Benzilic Acid Rearrangement
Bulletin of the Chemical Society of Japan, 1995Co-Authors: Toshihide Hatsui, Jinjun Wang, Hitoshi TakeshitaAbstract:A mild base-catalyzed retro-Benzilic Acid Rearrangement of a proto-photocycloadduct, formed in highly stereoselective photoaddition of methyl 2,4-dioxopentanoate to 1,5-dimethyl-6-methylene-1-cyclohexene, afforded a spiro[4.5]decenedione derivative. Reductive elimination of the α-dicarbonyl function and C1-homologation furnished (±)-hinesol and (±)-agarospirol.
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synthetic photochemistry lxiv mild base induced retro Benzilic Acid Rearrangement of isolated proto photocycloadducts of methyl 2 4 dioxopentanoate to terpinolene facile synthesis of α chamigrene and α chamigren 3 one
Bulletin of the Chemical Society of Japan, 1994Co-Authors: Toshihide Hatsui, Jinjun Wang, Hitoshi TakeshitaAbstract:In the photoaddition reaction of terpinolene with methyl 2,4-dioxopentanoate, the products derived from the tetrasubstituted C=C were four proto-[2+2] photocycloadducts, together with ene reaction products. When these proto-cycloadducts were treated with aqueous sodium carbonate, a facile retro-Benzilic Acid Rearrangement to form substituted cyclopentenone derivatives occurred. The product from the other trisubstituted C=C was an ordinary retro-aldol product of the [2+2] cycloadduct and an ene reaction product. One of the proto-photocycloadducts was transformed into α-chamigren-3-one and further to α-chamigrene.
Karl Gademann - One of the best experts on this subject based on the ideXlab platform.
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Mapping Out Biogenetic Hypotheses by Chemical Synthesis.
CHIMIA International Journal for Chemistry, 2017Co-Authors: Raphael Liffert, Karl GademannAbstract:Synthesis of natural products via their postulated or established biosynthetic intermediates ('biomimetic synthesis' or 'bio-inspired synthesis') has the power to identify both yet undiscovered intermediates and undiscovered mechanistic pathways for their formation. In this account, we report on our recent studies on unusual hypotheses for biosynthetic transformations, such as a late-stage aldol reaction (periconianone A), Benzilic Acid Rearrangement (taiwaniaquinone H), a redox-neutral light-driven C-H activation (taiwaniaquinol A and cyclocoulterone), a hetero Diels-Alder reaction (obtusinones), aziridinium chemistry (Securinega alkaloids), and a [3+2] nitrone olefin cycloaddition (virosaine A). All these studies provided evidence on the molecular level for the feasibility of these transformations, and suggest that further studies investigating the relevance of these hypotheses in biological systems are warranted.
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A Synthetic Entry into the Taiwaniaquinoids Based on a Biogenetic Hypothesis : Total Synthesis of (-)-Taiwaniaquinone H
Chemistry - A European Journal, 2010Co-Authors: Chandan K. Jana, Rosario Scopelliti, Karl GademannAbstract:(Chemical Equation Presented) Less carbon: Following a biogenetic proposal, the unusual 6-5-6 carbon skeleton of C19 taiwaniaquinoids was obtained by an intramolecular Benzilic Acid Rearrangement from a C20 precur-sor. A protecting-group-free total synthesis then allowed for the preparation of (-)-taiwaniaquinone H (see scheme). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Connecting C-19 Norditerpenoids to C-20 Diterpenes: Total Syntheses of 6-Hydroxy-5,6-dehydrosugiol, 6-Hydroxysugiol, and Taiwaniaquinone H, and Formal Synthesis of Dichroanone
Synthesis, 2010Co-Authors: Chandan K. Jana, Rosario Scopelliti, Karl GademannAbstract:Oxidation of the B-ring of abietane derivatives by Sharpless dihydroxylation gave the natural products 6-hydroxy-5,6-dehydrosugiol and 6-hydroxysugiol. Moreover, further oxidation gave a hydroxy dione derivative that provides a synthetic entry into the C-19 taiwaniaquinoid family of natural products. This route is based on biosynthetic considerations and involves a Benzilic Acid Rearrangement followed by decarboxylation. On the basis of this approach, a total synthesis of (-)-taiwaniaquinone H and a formal synthesis of (-)-dichroanone have been achieved.
Jung Woon Yang - One of the best experts on this subject based on the ideXlab platform.
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Transition-Metal-Free and Chemoselective NaOtBu–O2-Mediated Oxidative Cleavage Reactions of vic-1,2-Diols to Carboxylic Acids and Mechanistic Insight into the Reaction Pathways
Organic Letters, 2014Co-Authors: Sun Min Kim, Dong-wan Kim, Jung Woon YangAbstract:A method for efficient oxidative cleavage of vic-1,2-diols using a NaO(t)Bu-O2 system resulted in the formation of carboxylic Acids in high yields. The present protocol is an eco-friendly alternative to a conventional transition-metal-based method. This new strategy allows large-scale production with nonchromatographic purification while also suppressing competitive reaction pathway such as Benzilic Acid Rearrangement.
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Transition-Metal-Free and Chemoselective NaOtBu–O2‑Mediated Oxidative Cleavage Reactions of vic-1,2-Diols to Carboxylic Acids and Mechanistic Insight into the Reaction Pathways
2014Co-Authors: Sun Min Kim, Dong-wan Kim, Jung Woon YangAbstract:A method for efficient oxidative cleavage of vic-1,2-diols using a NaOtBu–O2 system resulted in the formation of carboxylic Acids in high yields. The present protocol is an eco-friendly alternative to a conventional transition-metal-based method. This new strategy allows large-scale production with nonchromatographic purification while also suppressing competitive reaction pathway such as Benzilic Acid Rearrangement