- Synthesis and Structural Revision of Glyphaeaside C
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The iminosugar core of natural glyphaeaside C, originally assigned as a derivative of the piperidine natural product 1-deoxynojirimycin (DNJ), has been revised as a derivative of 2,5-dideoxy-2,5-imino-l-mannitol (l-DMDP) by the total synthesis of its enantiomer. This revised l-DMDP-derived configuration is the first of its kind to be observed in nature. The prepared iminosugars displayed the nanomolar inhibition of bovine liver β-glucosidase and β-galactosidase.
- Byatt, Brendan J.,Kato, Atsushi,Pyne, Stephen G.
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p. 4029 - 4033
(2021/05/29)
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- Palladium-catalyzed tandem isomerization/hydrothiolation of allylarenes
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Herein we report a tandem olefin migration/hydrothiolation of allyl benzenes facilitated by an in situ generated palladium hydride. A catalyst system composed of palladium acetate and bidentate ligand dtbpx (1,2-bis(di-tert-butylphosphinomethyl)benzene in the presence of catalytic amounts of triflic acid led to the tandem transformation, which furnished benzylic thioethers. The reaction exhibits high regioselectivity and can be conducted under mild conditions. The robustness of the catalyst is displayed through reactions with coordinating thiols.
- Kathe, Prasad M.,Fleischer, Ivana
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supporting information
p. 2213 - 2217
(2019/03/26)
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- Combining spiro-fused cyclohexadienone – tetrahydrofuran ring system with glycine: Asymmetric synthesis of a new class of α-amino acid derivatives
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Herein, we present the asymmetric synthesis of spiro-fused cyclohexadienone – tetrahydrofuran-embedded glycine derivatives as a new class of nonproteinogenic α-amino acid derivatives. Starting from commercially available 2-allylphenols, key β-hydroxy-α-am
- Devi, Runjun,Das, Sajal Kumar
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supporting information
p. 2281 - 2283
(2018/05/23)
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- Copper(I)-Catalyzed Allylic Substitutions with a Hydride Nucleophile
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An easily accessible copper(I)/N-heterocyclic carbene (NHC) complex enables a regioselective hydride transfer to allylic bromides, an allylic reduction. The resulting aryl- and alkyl-substituted branched α-olefins, which are valuable building blocks for synthesis, are obtained in good yields and regioselectivity. A commercially available silane, (TMSO)2Si(Me)H, is employed as hydride source. This protocol offers a unified alternative to the established metal-catalyzed allylic substitutions with carbon nucleophiles, as no adaption of the catalyst to the nature of the nucleophile is required.
- Nguyen, T. N. Thanh,Thiel, Niklas O.,Pape, Felix,Teichert, Johannes F.
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p. 2455 - 2458
(2016/06/09)
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- The biomimetic synthesis and first characterization of the (+)- and (-)-isocentrolobines, 2,6-cis- and 2,6-trans-disubstituted tetrahydro-2H-pyrans
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The four stereoisomers of the novel title compounds were prepared by oxidative cyclization of their enantiomerically pure diarylheptanoid precursors by means of the straightforward biomimetic approach presented in the preceding article. The isocentrolobin
- Rogano, Frank,Froidevaux, Georges,Rueedi, Peter
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experimental part
p. 1299 - 1312
(2010/09/12)
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- Development of highly chemoselective bulky zincate complex, tBu 4ZnLi2: Design, structure, and practical applications in small-/macromolecular synthesis
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We present full details of the unique reactivities of the newly developed dianion-type bulky zincate, dilithium tetra-ferf-butylzincate (tBu 4ZnLi2). With this reagent, halogen-zinc exchange reaction of variously functionalized haloaromatics and anionic polymerization of N-isopropylacrylamide (NIPAm)/styrene with excellent chemoselectivity were realized. Halogen-zinc exchange reaction followed by electrophilic trapping with propargyl bromide provided a convenient route to functionalized phenylallenes, particularly those with electrophilic functional groups (such as cyano, amide and halogens). Spectral and computational studies of the structure in the gas and liquid phases indicated extraordinary stabilization of this dianion-type zincate by its bulky ligands.
- Furayama, Taniyuki,Yonehara, Mitsuhiro,Arimoto, Sho,Kobayashi, Minoru,Matsumoto, Yotaro,Uchiyama, Masanobu
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supporting information; experimental part
p. 10348 - 10356
(2009/10/10)
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- Toward a protecting-group-free halogen-metal exchange reaction: Practical, chemoselective metalation of functionalized aromatic halides using dianion-type zincate,tBu4ZnLi2
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A versatile preparation method for aromatic zincate compounds through a halogen-zinc exchange reaction using dilithium tetra-tert-butylzincate (tBu4ZnLi2) has been developed. This reagent permits efficient preparation of highly functionalized aromatic zincates, particularly, those with electrophilic functional groups, such as ester, amide, alcohol, and phenol. Halogen-zinc exchange reactions followed by electrophilic trapping (with allyl bromide or benzaldehyde) proved to be a powerful tool for C-C bond formation on functionalized aromatic rings. The functionalized aromatic zincate intermediate was also found to undergo copper- and palladium-catalyzed C-C bond-forming reactions with good yields and high chemoselectivity. Copyright
- Uchiyama, Masanobu,Furuyama, Taniyuki,Kobayashi, Minoru,Matsumoto, Yotaro,Tanaka, Kentaro
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p. 8404 - 8405
(2007/10/03)
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- Chavicol formation in sweet basil (Ocimum basilicum): Cleavage of an esterified C9 hydroxyl group with NAD(P)H-dependent reduction
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Propenyl- and allyl-phenols, such as methylchavicol, p-anol and eugenol, have gained importance as flavoring agents and also as putative precursors in the biosynthesis of 9,9′-deoxygenated lignans, many of which have potential medicinal applications. In spite of several decades of investigation, however, the complete biosynthetic pathway to a propenyl/allylphenol had not yet been reported. We have subjected a Thai basil variety accumulating relatively large amounts of the simplest volatile allylphenol, methylchavicol, to in vivo administration of radiolabeled precursors and assays of protein preparations in vitro. Through these experiments, the biosynthesis of chavicol was shown to occur via the phenylpropanoid pathway to p-coumaryl alcohol. Various possibilities leading to deoxygenation of the latter were examined, including reduction of the side-chain double bond to form p-dihydrocoumaryl alcohol, followed by dehydration to afford chavicol, as well as formation of p-methoxycinnamyl alcohol, with further side-chain modification to afford methylchavicol. A third possibility studied was activation of the side-chain alcohol of p-coumaryl alcohol, e.g. via esterification, to form a more facile leaving group via reductive elimination. The latter was shown to be the case using p-coumaryl esters as potential substrates for a NAD(P)H-dependent reductase to afford chavicol, which is then O-methylated to afford methylchavicol. The Royal Society of Chemistry 2006.
- Vassao, Daniel G.,Gang, David R.,Koeduka, Takao,Jackson, Brenda,Pichersky, Eran,Davin, Laurence B.,Lewis, Norman G.
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p. 2733 - 2744
(2008/10/09)
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- A general synthetic route towards bastadins. Part 1: Synthesis of the eastern part of bastadins 4-16
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A general synthetic route for the construction of the eastern part of the macrocyclic bastadins 4-16 is presented. The brominated biaryl ethers are synthesized using the iodonium salt method. The synthesis is accomplished within 18 steps in 15.5% overall
- Couladouros, Elias A.,Moutsos, Vassilios I.
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p. 7023 - 7026
(2007/10/03)
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