- Isoprenoid biosynthesis in Escherichia coli via the methylerythritol phosphate pathway: Enzymatic conversion of methylerythritol cyclodiphosphate into a phosphorylated derivative of (E)-2-methylbut-2-ene-1,4-diol
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A crude cell-free system from an Escherichia coli strain overexpressing the cluster containing the three genes yfgA, yfgB, and gcpE converted 2-C-methyl-D-erythritol 2,4-cyclodiphosphate (1) into a phosphorylated derivative of (E)-2-methylbut-2-ene-1,4-diol (6), which most probably represents a novel intermediate in the methylerythritol phosphate pathway for isoprenoid biosynthesis. The free diol 6 was accumulated by phosphatase treatment of the crude enzyme preparation and was identified by comparison with a synthetic reference.
- Seemann, Myriam,Campos, Narciso,Rodriguez-Concepción, Manuel,Iba?ez, Ester,Duvold, Tore,Tritsch, Denis,Boronat, Albert,Rohmer, Michel
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- Highly regioselective lipase-catalyzed acetylation and hydrolysis of acyclic α,ω-terpenediols and their diacetates
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Highly regioselective transformations of the acyclic α,ω-terpenediols and their diacetates to the monoacetates using lipase were accomplished. The acetylation of the α,ω-terpenediols gave regioselectively the ω-monoacetates 3, whereas the α-monoacetates 2 were obtained by hydrolysis of the α,ω-diacetates.
- Takabe, Kunihiko,Mase, Nobuyuki,Hisano, Takaya,Yoda, Hidemi
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p. 3267 - 3269
(2007/10/03)
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- Incorporation of 2-C-methyl-D-erythritol, a putative isoprenoid precursor in the mevalonate-independent pathway, into ubiquinone and menaquinone of Escherichia coli
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Incorporation of deuterium labelled 2-C-methyl-D-erythritol into isoprenoid side-chains of ubiquinone and menaquinone from Escherichia coli strongly supports the proposed intermediate role of this branched sugar derivative in the mevalonate independent pathway for isoprenoid biosynthesis via glyceraldehyde 3-phosphate and pyruvate.
- Duvold, Tore,Cali, Patrizia,Bravo, Jean-Michel,Rohmer, Michel
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p. 6181 - 6184
(2007/10/03)
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- Liquid-phase 1,4-Diacetoxylation of Conjugated Dienes with Tellurium(IV) Oxide and Alkali Metal Halides
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Oxidation of buta-1,3-diene, isoprene, and 2,3-dimethylbuta-1,3-diene with tellurium(IV) oxide and lithium bromide in acetic acid affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products).The product yield and selectivity for 1,4-isomers are high when an excess of LiBr is employed (LiBr/TeO2 = 5-10).The reaction also proceeds in the presence of NaBr, KBr, LiCl, HBr, or I2 in the place of LiBr, but both the selectivity for 1,4-isomers and the product yield are lower.The reaction hardly occurs using LiF, LiI, NaCl, Br2, and NH4Br as a halogen source.The reaction proceeds catalytically with respect to TeO2 to some extent when a re-oxidant such as H2O2 or t-BuOOH is used.In the cases of 2,5-dimethylhexa-2,4-diene, cyclopenta-1,3-diene, cyclohexa-1,3-diene, and cyclo-octa-1,3-diene the results are unsatisfactory in either the product yield or the selectivity for 1,4-isomers.Halogeno- and/or acetoxy-telluriation of a diene followed by acetolysis of the produced C-X (X = halogen) and C-Te bonds are proposed as one of the possible reaction pathways.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Patil, Suresh R.,Okano, Masaya
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p. 499 - 504
(2007/10/02)
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- Stereo-and Regioselective Palladium-Catalyzed 1,4-Diacetoxylation of 1,3-Dienes
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Palladium-catalyzed oxidation of 1,3-dienes in acetic acid using an oxidation system of MnO2 and catalytic amounts of p-benzoquinone selectively gives 1,4-diacetoxy-2-alkenes.The reaction proceeds with high stereo-and regioselectivity, and by ligand control the reaction can be made to take place with either cis or trans 1,4-diacetoxylation across the diene in cyclic systems.Also in an acyclic system the 1,4-relative stereochemistry can be controlled as shown by the stereoselective oxidation of (E,E)- and (E,Z)-2,4-hexadiene to their corresponding dl (>88percent dl) and meso (>95percent meso) diacetates 15 and 18, respectively.Evidence is provided that supports a mechanism involving a trans acetoxypalladation of the conjugated diene to give an intermediate (?-allyl)palladium complex, followed by either a cis or trans attack by acetate on the allyl group.The cis attack is best explained by a cis migration from a (?-allyl)palladium intermediate.The diacetoxylation reaction was applied to the preparation of a key intermediate for the synthesis of dl-shikimic acid.
- Baeckvall, Jan-E.,Bystroem, Styrbjoern E.,Nordberg, Ruth E.
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p. 4619 - 4631
(2007/10/02)
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- The Reactions of t-Butoxyl with Unsaturated Hydrocarbons: Structure and Reactivity of Allylic Radicals
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A radical trapping technique employing 1,1,3,3-tetramethylisoindolin-2-yloxyl (1) as scavenger has been used to study the reactions of t-butoxy radicals with propene, 2-methylpropene, but-1-ene, (E)- and (Z)-but-2-ene, 3-methylbut-1-ene, buta-1,3-diene and 2-methylbuta-1,3-diene.Relative rates of double bond addition and of allylic hydrogen abstraction have been measured and are discussed, as are the relative stabilities of the products formed.The allylic radicals generated in these systems react with (1) mainly by coupling at the more substituted terminus of the radical ? system.Substituent effects on this regioselectivity may be explained in terms of the electrophilicity of (1).
- Cuthbertson, Matthew J.,Rizzardo, Ezio,Solomon, David H.
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p. 1957 - 1973
(2007/10/02)
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- DIACETOXYLATION OF CONJUGATED DIENES WITH THALLIUM(III) ACETATE IN ACETIC ACID
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The reaction of conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2,5-dimethyl-2,4-hexadiene, 1,3-cyclopentadiene, and 1,3-cyclohexadiene with thallium(III) acetate in acetic acid at 10-65 deg C for 0.5-15 hr affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products) in 10-92 percent yields.The 1,2-addition products are predominantly formed in all cases examined except the case of 1,3-cyclopentadiene.The reaction is assumed to proceed through acetoxythallation and dethallation steps, the latter step being accompanied and/or followed by an attack of acetoxyl group.An initial attack of thallium moiety is proposed to occur mainly at C-1 and C-2 carbons in the cases of linear terminal dienes and cyclic dienes, respectively.
- Uemura, Sakae,Miyoshi, Haruo,Tabata, Akira,Okano, Masaya
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p. 291 - 295
(2007/10/02)
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- SELECTIVE 1,4-DIACETOXYLATION OF CONJUGATED DIENES WITH TELLURIUM(IV) OXIDE
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Oxidation of several linear conjugated dienes with tellurium(IV) oxide and lithium bromide in acetic acid affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products), 1,4-isomer being highly selectively produced when the ratio of LiBr/TeO2 is 5-10.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Okano, Masaya
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p. 5331 - 5334
(2007/10/02)
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