- ELABORATION OF THE CARBON SKELETON OF QUASSINOIDS SYNTHESIS OF (1β,9β)-1-HYDROXYPICRAS-12-EN 176-ONE
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The synthesis of (1β,9β)-1-hydroxypicras-12-en-16-one (2) which possesses the tetracyclic carbon framework of quassinoids (e.g., quassin) has been achieved via a remarkable Diels-Alder reaction.
- Grieco, Paul A.,Vidari, Giovanni,Ferrino, Sergio
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- A new directing mode for singlet oxygen ene reactions: The vinylogous gem effect enables a 1O2 domino ene/[4 + 2] process
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The singlet oxygen reactions of 4-methyl-2,4-hexadienoates E,E- and E,Z-4 proceed in a highly mode selective and regioselective domino process. The initial product is the allylic hydroperoxide 5 directed by a vinylogous gem effect. The subsequent 1O2 [4 + 2] cycloaddition delivers a 3:2 diastereoisomeric mixture of 1,2-dioxanes 8 in a one-pot process. The identical protocol delivers from the more reactive α-methylated substrates E,E-10 and E,Z-10 with excellent primary regioselectivity the 1,2-dioxane 13.
- Griesbeck, Axel G.,Kiff, Alan De
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- Confirmation of the pentadienyl/alkyne [5 + 2] cycloaddition reactivity of the Cp*Co(η5-1,2,5-trimethylpentadienyl)+complex
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The [5 + 2] cycloaddition reactivity of the Cp*Co(η5-1,2,5-trimethylpentadienyl)+complex and ethyne has been demonstrated. This reactivity was predicted computationally and runs against previous synthetic observations of decreasing reactivity with increasing substitution. The pentadienyl complex and the resulting Cp*Co(η2,η3-1,2,5-trimethylcycloheptadienyl)+species have been characterized spectroscopically and crystallographically. The X-ray structure of the pentadienyl complex has a dihedral angle between the two η5-bound planes that falls within the range expected for reactivity (3.1(8)°), providing strong support for our computationally proposed structure/reactivity relationship.
- Ramful, Chandika D.,Konway, Zachary E.,Boudreau, Stephanie,Areephong, Jetsuda,Robertson, Katherine N.,Ylijoki, Kai E.O.
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- Step-Economic Synthesis of Biomimetic β-Ketopolyene Thioesters and Demonstration of Their Usefulness in Enzymatic Biosynthesis Studies
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Studies on the biosynthetic processing of polyene thioester intermediates are complicated by limited access to appropriate substrate surrogates. We present a step-economic synthetic access to biomimetic β-ketopolyene thioesters that is based on an Ir-catalyzed reductive Horner-Wadsworth-Emmons olefination. New β-ketotriene and pentaenethioates of pantetheine and N-acetylcysteamine were exemplarily synthesized via short and concise routes. The usefulness of these compounds was demonstrated in an in vitro assay with the ketoreductase domain MycKRB from mycolactone biosynthesis.
- Hahn, Frank,Ro?, Theresa,Schr?der, Marius,Wunderlich, Johannes
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supporting information
(2020/07/04)
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- Palladium-catalysed regio- And stereoselective arylative substitution of γ,δ-epoxy-α,β-unsaturated esters and amides by sodium tetraaryl borates
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Palladium-catalysed reactions of γ,δ-epoxy-α,β-unsaturated esters and amides with NaBAr4 reagents proceeded regio- and stereoselectively, producing allylic homoallyl alcohols with aryl-substituents in the allylic position for a wide range of substrates. A
- Artok, Levent,Bilgi, Yasemin,Ku?, Melih
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supporting information
p. 6378 - 6383
(2020/09/07)
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- TRIENETHER COMPOUND, PERFUME COMPOSITION, FOOD AND DRINK PRODUCT AND PERFUMERY AND COSMETIC EACH CONTAINING THEM
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PROBLEM TO BE SOLVED: To provide a means capable of imparting unique sweetness and fruit juice feeling suggestive of fruit flesh feeling of mango and a core part of pineapple. SOLUTION: A trienether compound having an isopropenyloxy group as represented by formula (1) is provided. EFFECT: Excellent fruit-like fragrance and flavor with unique sweetness and fruit juice feeling can be imparted by adding the compound represented by formula (1) to food and drink product, and perfumery and cosmetic. SELECTED DRAWING: None COPYRIGHT: (C)2019,JPOandINPIT
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Paragraph 0082-0084
(2019/04/11)
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- Total synthesis of the antibiotic Elansolid B1
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The antibiotic elansolid B1 was prepared by a convergent strategy that relied on a highly diastereoselective, biomimetic intramolecular Diels-Alder cycloaddition (IMDA) that furnished the tetrahydroindane unit. Other key features are a double Sonogashira cross-coupling and a substratecontrolled Yamamoto aldol reaction.
- Weber, Arne,Dehn, Richard,Schl?ger, Nadin,Dieter, Bastian,Kirschning, Andreas
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supporting information
p. 568 - 571
(2014/04/03)
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- Ene-diene transmissive cycloaddition reactions with singlet oxygen: The vinylogous gem effect and its use for polyoxyfunctionalization of dienes
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The singlet oxygen reactivities and regioselectivities of the model compounds 1b-d were compared with those of the geminal (gem) selectivity model ethyl tiglate (1a). The kinetic cis effect is kE/kZ = 5.2 for the tiglate/angelate system 1a/1a′ without a change in the high gem regioselectivity. Further conjugation to vinyl groups enabled mode-selective processes, namely, [4 + 2] cycloadditions versus ene reactions. The site-specific effects of methylation on the mode selectivity and the regioselectivity of the ene reaction were studied for dienes 1e-g. A vinylogous gem effect was observed for the γ,δ-dimethylated and α,γ,δ-trimethylated substrates 1h and 1i, respectively. The corresponding phenylated substrates 1j-l showed similar mode selectivity, as monomethylated 1j exhibited exclusively [4 + 2] reactivity while the tandem products 12 and 14 were isolated from the di- and trimethylated substrates 1k and 1l, respectively. The vinylogous gem effect favors the formation of 1,3-dienes from the substrates, and thus, secondary singlet oxygen addition was observed to give hydroperoxy-1,2-dioxenes 19 and 20 in an ene-diene transmissive cycloaddition sequence. These products were reduced to give alcohols (16, 17, and 18) or furans (24 and 25), respectively, or treated with titanium(IV) alkoxides to give the epoxy alcohols 26 and 27. The vinylogous gem effect is rationalized by DFT calculations showing that biradicals are the low-energy intermediates and that no reaction path bifurcations compete.
- Eske, Angelika,Goldfuss, Bernd,Griesbeck, Axel G.,De Kiff, Alan,Kleczka, Margarethe,Leven, Matthias,Neudoerfl, Joerg-M.,Vollmer, Moritz
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p. 1818 - 1829
(2014/03/21)
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- Substrate-controlled stereoselectivity in the Yamamoto aldol reaction
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The Yamamoto aldol reaction is a vinylogous aldol reaction that relies on bulky aluminium-based Lewis acids. These activate both the aldehyde as well as become part of the enolate moiety. The report discloses the first detailed study on the substrate-controlled Yamamoto aldol reaction in which 2,3-syn and 2,3-anti disubstituted aldehydes serve as the stereodirecting elements. The "size" of the substituent in the β-position strongly determines the facial selectivity of enolate addition to the aldehyde. Large substituents favour formation of 1,3-syn diols while slim alkynyl groups preferentially lead to 1,3-anti products. The Royal Society of Chemistry 2012.
- Schl?ger, Nadin,Kirschning, Andreas
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supporting information
p. 7721 - 7729
(2013/04/23)
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- Key structural features of cis-cinnamic acid as an allelochemical
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1-O-cis-cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals isolated from Spiraea thunbergii Sieb. It is suggested that it derives its strong inhibitory activity from cis-cinnamic acid, which is crucial for phytotoxicity. It was synthesized to confirm its structure and bioactivity, and also a series of cis-cinnamic acid analogues were prepared to elucidate the key features of cis-cinnamic acid for lettuce root growth inhibition. The cis-cyclopropyl analogue showed potent inhibitory activity while the saturated and alkyne analogues proved to be inactive, demonstrating the importance of the cis-double bond. Moreover, the aromatic ring could not be replaced with a saturated ring. However, the 1,3-dienylcyclohexene analogue showed strong activity. These results suggest that the geometry of the C-C double bond between the carboxyl group and the aromatic ring is essential for potent inhibitory activity. In addition, using several light sources, the photostability of the cinnamic acid derivatives and the role of the C-C double bond were also investigated.
- Abe, Masato,Nishikawa, Keisuke,Okuda, Katsuhiro,Shindo, Mitsuru,Fukuda, Hiroshi,Nakanishi, Kazunari,Tazawa, Yuta,Taniguchi, Tomoya,Park, So-Young,Hiradate, Syuntaro,Fujii, Yoshiharu
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p. 56 - 67,12
(2012/12/12)
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- De novo synthesis of 2-substituted syn-1,3-diols via an iterative asymmetric hydration strategy
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(Chemical Equation Presented) The enantioselective syntheses of several protected 4-substituted syn-3,5-dihydroxy carboxylic esters have been achieved from the corresponding achiral (E,E)- or (E,Z)-1,3-dienoates. The route relies upon an enantio- and regi
- Ahmed, Md. Moinuddin,Mortensen, Matthew S.,O'Doherty, George A.
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p. 7741 - 7746
(2007/10/03)
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- Reaction principles and crystal structure design for the topochemical polymerization of 1,3-dienes
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Stacking made to order: Weak intermolecular interactions such as 2D hydrogen-bonding networks, aromatic-ring stacking, and CH/π or halogen-halogen interactions account for the columnar organization of muconic and sorbic acid derivatives in the crystalline state (see picture). When the stacking distance is close to 5 A these 1,3-dienes undergo topochemical polymerization upon irradiation.
- Matsumoto, Akikazu,Sada, Kazuki,Tashiro, Kohji,Miyata, Mikiji,Tsubouchi, Takashi,Tanaka, Toshihiro,Odani, Toru,Nagahama, Sadamu,Tanaka, Tomoyuki,Inoue, Katsunari,Saragai, Seishi,Nakamoto, Shinsuke
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p. 2502 - 2505
(2007/10/03)
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- Diastereo- and enantioselective total synthesis of stigmatellin A
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Stigmatellin A (1) isolated from the myxobacterium Stigmatella aurantiaca is a powerful inhibitor of electron transport in mitochondria and chloroplasts. The first highly diastereo- and enantioselective total synthesis of this important natural product is
- Enders, Dieter,Geibel, Gunter,Osborne, Simon
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p. 1302 - 1309
(2007/10/03)
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- SYNTHETIC STUDY TOWARDS THE TETRACYCLIC QUASSINOID SKELETON
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The optically active tetracycle (6) with two trans-fused angular methyl groups is constructed from tiglic aldehyde and (S)-carvone in 9 steps involving a stereocontrolled aldol reaction and an endo-selective intramolecular Diels-Alder (IMDA) reaction.
- Shing, Tony K. M.,Tang, Ying
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p. 2187 - 2194
(2007/10/02)
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- An Expeditious and Enantioselective Entry to the ABC Ring of the Quassinoid Skeleton
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The tricycle (5) with two trans-fused angular methyl groups is constructed from tiglic aldehyde and (S)-carvone involving a stereocontrolled aldol reaction and an endo-selective intramolecular Diels-Alder (IMDA) reaction; the stereochemistry was established by an X-ray study.
- Shing, Tony K. M.,Tang, Ying,Malone, John F.
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p. 1294 - 1295
(2007/10/02)
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- QUASSINOIDS: TOTAL SYNTHESIS OF DL-QUASSIN
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The total synthesis of quassin (1), the major constituent of quassia wood, is described in racemic form.The synthesis features the Lewis acid catalyzed intermolecular Diels-Alder reaction between dienophile 8 and ethyl (E)-4-methyl-3,5-hexadienoate (9).Di
- Vidari, Giovanni,Ferrino, Sergio,Grieco, Paul A.
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p. 3539 - 3548
(2007/10/02)
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