- 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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- 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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supporting information
p. 789 - 794
(2019/04/17)
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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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- 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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- A Tellurium Transposition Route to Allylic Alcohols: Overcoming Some Limitations of the Sharpless-Katsuki Asymmetric Epoxidation
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Good yields of enantiomeric allylic alcohols can be obtained in high enantiomeric excess (ee) by combining Sharpless-Katsuki asymmetric epoxidation process (SAE) with tellurium chemistry.The advantages of the tellurium process are as follows: (1) the 50percent yield limitation on the allylic alcohol in the Sharpless kinetic resolution (SKR) can be overcome; (2) allylic tertiary alcohols which are unsatisfactory substrates in the SKR can be obtained in high optical purity; (3) optically active secondary allylic alcohols with tertiary alkyl substituents (e.g. tert-butyl) at C-1 can be obtained in high ee; (4) optically active sterically congested cis secondary alcohols can be obtained in high ee; and (5) the nuisance of the slow SAE of some vinyl carbinols can be avoided.The key step in the reaction sequence is either a stereospecific 1,3-transposition of double bond and alcohol functionalities or an inversion of the alcohol configuration with concomitant deoxygenation of the epoxide function in epoxy alcohols.Trans secondary allylic alcohols can be converted to cis secondary allylic alcohols by way of erythro epoxy alcohols (glycidols); threo glycidyl derivatives are converted to trans secondary allylic alcohols.These transformations are accomplished by the action of telluride ion, generated in situ from the element, on a glycidyl sulfonate ester.Reduction of elemental Te is conveniently done with rongalite (HOCH2SO2Na) in an aqueous medium.This method is satisfactory when Te2- is required to attack at primary carbon site of a glycidyl sulfonate.In cases where Te2- is required to attack a secondary carbon site, reduction of the tellurium must be done with NaBH4 or LiEt3BH.Elemental tellurium is precipitated during the course of the reactions and can be recovered and reused.
- Dittmer, Donald C.,Discordia, Robert P.,Zhang, Yanzhi,Murphy, Christopher K.,Kumar, Archana,et al.
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p. 718 - 731
(2007/10/02)
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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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- ISOLATION OF (10R,11R)-(+)-SQUALENE-10,11-EPOXIDE FROM THE RED ALGA LAURENCIA OKAMURAI AND ITS ENANTIOSELECTIVE SYNTHESIS
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(10R,11R)-(+)-Squalene-10,11-epoxide 1 has been isolated from the red alga Laurencia okamurai.On the basis of the spectral data and comparison to the racemic compound prepared from squalene, assigment of the planar structure was made.The enantioselective synthesis of 1 was performed, which determined the absolute stereochemistry of 1.
- Kigoshi, Hideo,Ojika, Makoto,Shizuri, Yoshikazu,Niwa, Haruki,Yamada, Kiyoyuki
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p. 3789 - 3792
(2007/10/02)
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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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