- Method for efficiently preparing enol through selective hydrogenation of alkynol
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The invention provides a method for efficiently preparing enol through selective hydrogenation of alkynol. A conventional tank reactor and a micro-channel reactor are combined for use, and the micro-channel reactor can be used for quickly preparing an enol product after immobilizing a rare earth metal doped catalyst, so that the reaction time is shortened, and the production efficiency is improved. And a phosphine compound is added as a side reaction inhibitor to improve the selectivity.
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Paragraph 0062-0071
(2021/03/24)
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- Sesquiterpene Cyclizations inside the Hexameric Resorcinarene Capsule: Total Synthesis of δ-Selinene and Mechanistic Studies
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The synthesis of terpene natural products remains a challenging task due to the enormous structural diversity in this class of compounds. Synthetic catalysts are unable to reproduce the tail-to-head terpene cyclization of cyclase enzymes, which create this diversity from just a few simple linear terpene substrates. Recently, supramolecular structures have emerged as promising enzyme mimetics. In the present study, the hexameric resorcinarene capsule was utilized as an artificial cyclase to catalyze the cyclization of sesquiterpenes. With the cyclization reaction as the key step, the first total synthesis of the sesquiterpene natural product δ-selinene was achieved. This represents the first total synthesis of a sesquiterpene natural product that is based on the cyclization of a linear terpene precursor inside a supramolecular catalyst. To elucidate the reaction mechanism, detailed kinetic studies and kinetic isotope measurements were performed. Surprisingly, the obtained kinetic data indicated that a rate-limiting encapsulation step is operational in the cyclization of sesquiterpenes.
- Zhang, Qi,Tiefenbacher, Konrad
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supporting information
p. 12688 - 12695
(2019/08/12)
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- Stereochemical investigations on the biosynthesis of achiral (Z)-γ-bisabolene in Cryptosporangium arvum
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A newly identified bacterial (Z)-γ-bisabolene synthase was used for investigating the cyclisation mechanism of the sesquiterpene. Since the stereoinformation of both chiral putative intermediates, nerolidyl diphosphate (NPP) and the bisabolyl cation, is lost during formation of the achiral product, the intriguing question of their absolute configurations was addressed by incubating both enantiomers of NPP with the recombinant enzyme, which resolved in an exclusive cyclisation of (R)-NPP, while (S)-NPP that is non-natural to the (Z)-γ-bisabolene synthase was specifically converted into (E)-β-farnesene. A hypothetical enzyme mechanistic model that explains these observations is presented.
- Rinkel, Jan,Dickschat, Jeroen S.
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p. 789 - 794
(2019/04/17)
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- Structural and functional insights into asymmetric enzymatic dehydration of alkenols
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The asymmetric dehydration of alcohols is an important process for the direct synthesis of alkenes. We report the structure and substrate specificity of the bifunctional linalool dehydratase isomerase (LinD) from the bacterium Castellaniella defragrans that catalyzes in nature the hydration of β-myrcene to linalool and the subsequent isomerization to geraniol. Enzymatic kinetic resolutions of truncated and elongated aromatic and aliphatic tertiary alcohols (C5-C15) that contain a specific signature motif demonstrate the broad substrate specificity of LinD. The three-dimensional structure of LinD from Castellaniella defragrans revealed a pentamer with active sites at the protomer interfaces. Furthermore, the structure of LinD in complex with the product geraniol provides initial mechanistic insights into this bifunctional enzyme. Site-directed mutagenesis confirmed active site amino acid residues essential for its dehydration and isomerization activity. These structural and mechanistic insights facilitate the development of hydrating catalysts, enriching the toolbox for novel bond-forming biocatalysis.
- Nestl, Bettina M.,Geinitz, Christopher,Popa, Stephanie,Rizek, Sari,Haselbeck, Robert J.,Stephen, Rosary,Noble, Michael A.,Fischer, Max-Philipp,Ralph, Erik C.,Hau, Hoi Ting,Man, Henry,Omar, Muhiadin,Turkenburg, Johan P,Van Dien, Stephen,Culler, Stephanie J.,Grogan, Gideon,Hauer, Bernhard
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p. 275 - 281
(2017/02/23)
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- Isotope sensitive branching and kinetic isotope effects to analyse multiproduct terpenoid synthases from Zea mays
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Multiproduct terpene synthases TPS4-B73 and TPS5-Delprim from Zea mays exhibit isotopically sensitive branching in the formation of mono- and sesquiterpene volatiles. The impact of the kinetic isotope effects and the stabilization of the reactive intermediates by hyperconjugation along with the shift of products from alkenes to alcohols are discussed.
- Gatto, Nathalie,Vattekkatte, Abith,K?llner, Tobias,Degenhardt, J?rg,Gershenzon, Jonathan,Boland, Wilhelm
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supporting information
p. 3797 - 3800
(2015/03/30)
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- Biomimetic total synthesis of (-)-neroplofurol and (+)-ekeberin D4triggered by hydrolysis of terminal epoxides
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To accumulate the chemi cal basis of epoxide-opening cascade biogenesis, chemical syntheses of sesqui- and triterpenoids were performed. The biomi metic total syntheses of (-)-neroplofurol (1) and (+)-ekeberin D4(2) were accomplished by protic acid-catalyzed hydrolysis of the terminal epoxide from nerolidol diepoxide 3 and squalene tetraepoxide 4 through single and double 5-exo cyclizations in intermediates 5 and 6, respectively. This chemical reaction mimics the direct hydrolysis mechanism of epoxide hydrol ases, enzymes that catalyze an epoxide-opening reaction to finally produce vicinal diols.
- Kodama, Takeshi,Aoki, Shingo,Matsuo, Tomoki,Tachi, Yoshimitsu,Nishikawa, Keisuke,Morimoto, Yoshiki
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supporting information
p. 1662 - 1664
(2015/02/19)
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- Biosynthesis of the sesquiterpene botrydial in Botrytis cinerea. Mechanism and stereochemistry of the enzymatic formation of presilphiperfolan-8β-ol
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(Figure Presented) Presilphiperfolan-8β-ol synthase, encoded by theBcBOT2 gene from the necrotrophic plant pathogen Botrytis cinerea, cata lyzes the multistep cyclization of farnesyl diphosphate (2) to the tricyclic sesquiterpene alcohol presilphiperfolan-8β-ol (3), the preursor of the phytotoxin botrydial, a strain-dependent fungal virulence factor. Incubation of (1R)-[1-2H]farnesyl diphosphate (2b) with recombinant presilphiperfolan-8β-ol synthase gave exclusively (5R)-[5α-2H]-3b, while complementary incubation of (1S)-[1-2H]FPP (2c) gave (5S)-[5β-2H]-3c. These results establishedthat cyclization of farnesyl diphosphate involves displacement of the d iphosphate group from C-1 with net inversion of configuration and ruled out the proposed intermediacy of the cisoid conformer of nerolidyl diphosphate (9) in the cyclization. While not a mandatory intermediate, (3R)-nerolidyl diphosphate was shown to act as a substrate surrogate. Cyclization of [13,13,13-2H3] farnesyl diphosphate (2d) gave [14,14,14-2H3]-3d, thereby establishing that electrophilic attack takes place exclusively on the si face of the 12,13-double bond of 2. The combined results provide a detailed picture of theconformation of enzyme-bound farnesyl diphosphate at the active site of presilphiperfolan-8β-ol synthase.
- Wang, Chieh-Mei,Hopson, Russell,Lin, Xin,Cane, David E.
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supporting information; experimental part
p. 8360 - 8361
(2009/10/24)
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- The synthesis of (3R)-nerolidol
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The sesquiterpene natural product (3R)-nerolidol has been prepared in six steps starting from (3R)linalool.
- Cane, David E.,Ha, Hyun-Joon,McIlwaine, Douglas B.,Pascoe, Keith O.
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p. 7553 - 7554
(2007/10/02)
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- Alkylation du linalol sur les carbones C8 (et C6)
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Metallation of linalool α to the distal double bond with strong bases is described.The corresponding carbanions have been alkylated or oxidized to give mixtures of products resulting from attack at both carbon 8 (major product) and carbon 6 (minor product).
- Cuvigny, Therese,Julia, Marc,Rolando, Christian
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- (10R, 11R)-(+)-SQUALENE-10, 11-EPOXIDE: ISOLATION FROM LAURENCIA OKAMURAI AND THE ASYMMETRIC SYNTHESIS
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From a red alga Laurencia okamurai, (10R, 11R)-(+)-squalene-10, 11-epoxide 1 was isolated and its asymmetric synthesis has been achieved starting from trans, trans-farnesol.
- Kigoshi, Hideo,Ojika, Makoto,Shizuri, Yoshikazu,Niwa, Haruki,Yamada, Kiyoyuki
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p. 5413 - 5414
(2007/10/02)
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- Sur la stereochimie de la cyclisation du nerolidol an α-bisabolol
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The cyclisation of linalyl to α-terpinyl derivatives is known to take place with efficient transfer of chirality.Information was needed about the analogous cyclisation of nerolidyl to bisabolyl derivatives.This was made possible through the recent determination of the absolute configuration of bisabolol and epibisabolol.Hydrolysis of (+)(S) nerolidyl paranitrobenzoate has been carried out under the experimental conditons used for (-)(R) linalyl paranitrobenzoate.Strong asymmetric induction was observed about C4 (in the ring) but very little, if any, about C8 (in the chain).The cyclisation of (+)(S) nerolidol has been brought about by 90/10 aqueous formic acid.Under these experimental conditions very little asymmetric induction is observed about C8 or C4.This is explained by rapid racemisation of the starting material under the cyclisation conditions.
- Fourneron, Jean-Dominique,Julia, Marc
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p. 387 - 392
(2007/10/02)
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- Process for preparing stereospecific nerolidol and ester thereof
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A process for obtaining a stereospecific nerolidol at the Δ6 -position thereof by rectifying a mixture of Δ6 -cis-nerolidol and Δ6 -trans-nerolidol in rectification column having from 10 to 100 theoretical plates with a reflux ratio of from 2 to 200 at a temperature below 230° C. under reduced pressure to separate each stereospecific nerolidol from said mixture.
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- Isomerization of the unsaturated alcohols
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Unsaturated alcohols represented by the general formulas (I) and (II) below STR1 wherein R is a substituted or unsubstituted hydrocarbon radical, R2 and R3 are hydrogen or lower alkyl groups, and R and R2 may be linked together are mutually isomerized in the presence of a catalyst comprising a transition metal compound of Groups V, VI and VII of the Mendeleev Periodic Table.
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