- Copper-catalyzed enantioselective 1,2-borylation of 1,3-dienes
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A highly enantioselective Cu-catalyzed borylation of 2-substituted 1,3-dienes is reported. The use of a chiral phosphanamine ligand is essential in achieving high chemo-, regio-, diastereo- and enantioselectivity. It provides access to a variety of homoallylic boronates in consistently high yield and enantiomeric excess with 2-aryl and 2-heteroaryl 1,3-dienes as well as sterically demanding 2-alkyl 1,3-dienes. Preliminary investigations based on a non-linear effect study point to a mechanism involving more than one metal center.
- Liu, Yangbin,Fiorito, Daniele,Mazet, Clément
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p. 5284 - 5288
(2018/06/21)
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- Structure-Function Studies of Artemisia tridentata Farnesyl Diphosphate Synthase and Chrysanthemyl Diphosphate Synthase by Site-Directed Mutagenesis and Morphogenesis
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The amino acid sequences of farnesyl diphosphate synthase (FPPase) and chrysanthemyl diphosphate synthase (CPPase) from Artemisia tridentata ssp. Spiciformis, minus their chloroplast targeting regions, are 71% identical and 90% similar. FPPase efficiently and selectively synthesizes the "regular" sesquiterpenoid farnesyl diphosphate (FPP) by coupling isopentenyl diphosphate (IPP) to dimethylallyl diphosphate (DMAPP) and then to geranyl diphosphate (GPP). In contrast, CPPase is an inefficient promiscuous enzyme, which synthesizes the "irregular" monoterpenes chrysanthemyl diphosphate (CPP), lavandulyl diphosphate (LPP), and trace quantities of maconelliyl diphosphate (MPP) from two molecules of DMAPP, and couples IPP to DMAPP to give GPP. A. tridentata FPPase and CPPase belong to the chain elongation protein family (PF00348), a subgroup of the terpenoid synthase superfamily (CL0613) whose members have a characteristic α terpene synthase α-helical fold. The active sites of A. tridentata FPPase and CPPase are located within a six-helix bundle containing amino acids 53 to 241. The two enzymes were metamorphosed into one another by sequentially replacing the loops and helices of the six-helix bundle from enzyme with those from the other. Chain elongation was the dominant activity during the N-terminal to C-terminal metamorphosis of FPPase to CPPase, with product selectivity gradually switching from FPP to GPP, until replacement of the final α-helix, whereupon cyclopropanation and branching activity competed with chain elongation. During the corresponding metamorphosis of CPPase to FPPase, cyclopropanation and branching activities were lost upon replacement of the first helix in the six-helix bundle. Mutations of active site residues in CPPase to the corresponding amino acids in FPPase enhanced chain-elongation activity, while similar mutations in the active site of FPPase failed to significantly promote formation of significant amounts of irregular monoterpenes. Our results indicate that CPPase, a promiscuous enzyme, is more plastic toward acquiring new activities, whereas FPPase is more resistant. Mutations of residues outside of the α terpene synthase fold are important for acquisition of FPPase activity for synthesis of CPP, LPP, and MPP.
- Lee, J. Scott,Pan, Jian-Jung,Ramamoorthy, Gurusankar,Poulter, C. Dale
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supporting information
p. 14556 - 14567
(2017/10/24)
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- Chelation versus Non-Chelation Control in the Stereoselective Alkenyl sp2 C?H Bond Functionalization Reaction
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A hydroxy group chelation-assisted stereospecific oxidative cross-coupling reaction between alkenes was developed under mild reaction conditions. In the presence of palladium catalyst, the alkenes tethered with hydroxy functionality can couple efficiently with electron-deficient alkenes to form the corresponding multi-substituted olefin products. The hydroxy group on the substrate could play dual roles in reaction, acting as the directing group for alkenyl C?H bond activation and controlling the stereoselectivity of the products.
- Liang, Qiu-Ju,Yang, Chao,Meng, Fei-Fan,Jiang, Bing,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 5091 - 5095
(2017/04/24)
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- Toward higher polyprenols under 'prebiotic' conditions
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Geraniol and isomers (C10) can be obtained by the condensation of C5 monoprenols at room temperature in the presence of montmorillonite K-10. It is also possible to obtain farnesol (C15) and isomers by condensation of geraniol with isopentenol. Despite the low yields achieved, these findings support the hypothesis that polyprenyl phosphates may have been formed in prebiotic conditions, and served as constituents of primitive membranes.
- Désaubry, Laurent,Nakatani, Yoichi,Ourisson, Guy
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p. 6959 - 6961
(2007/10/03)
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- Syntheses with organoboranes. VII, monohydroboration of conjugated dienes with catecholborane catalyzed by complexes of Nickel(II) chloride and Cobalt(II) chloride with diphosphines
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The monohydroboration of representative conjugated dienes 1-7 with catecholborane in the presence of SmI3, t-BuOSmI2, LaI3, Ti(OPr(i))4, iron(II), nickel(II) and cobalt(II) chloride complexes with dppe, dppp and dppb was examined. NiCl2(dppe), NiCl2(dppp) and CoCl2(dppp) shoned catalytic activity. The 1,2-addition products were obtained, no 1,4-addition was observed. The reactivity in the presence of NiCl2(dppe) decreased in the order acyclic dienes > cyclic dienes >>1-decene.
- Zaidlewicz, Marek,Meller, Jerzy
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p. 7279 - 7282
(2007/10/03)
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- Kinetic influences on enantioselectivity in asymmetric catalytic hydrogenation
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The influence of reaction conditions on enantioselectivity in the RuII-(binap)-catalyzed asymmetric hydrogenation of allylic alcohols is discussed. This work highlights the importance of considering kinetic influences in addition to the stereochemical aspects of the chiral catalytic environment in interpreting catalytic behavior in asymmetric hydrogenation reactions.
- Sun, Yongkui,Wang, Jian,LeBlond, Carl,Reamer, Robert A.,Laquidara, Joseph,Sowa Jr., John R.,Blackmond, Donna G.
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- ON THE ROLE OF THE PHOSPHATE RESIDUES IN GERANYL PYROPHOSPHATE BIOSYNTHESIS
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Phosphoric esters bearing a sulfonium group in the γ position are converted under basic conditions into allylic phosphates.
- Jacob, L.,Julia, M.,Pfeiffer, B.,Rolando, C.
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p. 4327 - 4330
(2007/10/02)
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- BIOMIMETIC ENTRY TO ACYCLIC TERPENE SYNTHESIS. A NOVEL REARRANGEMENT OF ALLYL ETHER CATALYZED BY ORGANOALUMINUM REAGENTS
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The intramolecular prenyltransfer reaction is accomplished by the rearrangement of allyl ethers with (2,6-di-tert-butyl-4-methylphenoxy)methylaluminum trifluoromethanesulfonate.The present method provides a simple and highly efficient synthesis of lavandulol.
- Yamamura, Yoshihiro,Umeyama, Kensuke,Maruoka, Keiji,Yamamoto, Hisashi
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p. 1933 - 1936
(2007/10/02)
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- CONDENSATIONS BIOMIMETIQUES: EDIFICATION DE SQUELETTES TERPENIQUES A PARTIR DE SYNTHONS ISOPRENIQUES
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The action of perchloric, trifluoroacetic and formic acids on the 1,1-(and 3,3-) dimethylallylic alcohols has been studied.In the presence of formic acid in dichloromethane 2-methyl-3-butene-2-ol (DMVC) has been condensed on the acetate of 3-methyl-3-butene-1-ol (IPA) giving geranylic and lavandulylic type 1,1-adducts.Saponification, dehydration, oxidation and isomerisation of the former type lead to citral.In the same medium, DMVC produces (after saponification) a C10 glycol which upon dehydration produces lavandulol in a convenient way.Geraniol and its acetate have been condensed with low yield on IPA giving farnesylic derivatives.
- Babin, Didier,Fourneron, Jean-Dominique,Julia, Marc
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p. 588 - 600
(2007/10/02)
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