- N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading
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We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N-heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α- and β-substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N-Mes-/N-2,4,6-trichlorophenyl 1,2,4-triazolium salt, and benzoic acid as co-catalyst, was developed. A whole series of α/β-substituted aliphatic aldehydes/enals hitherto not amenable to NHC-catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid-induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.
- Berkessel, Albrecht,Biswas, Animesh,Harnying, Wacharee,Sudkaow, Panyapon
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supporting information
p. 19631 - 19636
(2021/08/09)
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- Total Synthesis of (-)-Sinulariadiolide. A Transannular Approach
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The constrained tricyclic skeleton of the nor-cembranoid sinulariadiolide (1) with a nine-membered nexus was obtained by a cascade of transannular Michael reaction, carbonate elimination, butenolide formation, and spontaneous oxa-Michael addition of MeOH. The required macrocyclic precursor was prepared by ring-closing alkyne metathesis followed by trans-hydrostannation/carbonylation.
- Meng, Zhanchao,Fürstner, Alois
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supporting information
p. 805 - 809
(2019/01/23)
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- Divergent synthesis of four isomers of 6,7-dihydroxy-3,7-dimethyloct-2-enoic acid, esters and evaluation for the antifungal activity
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The four isomers of 6,7-dihydroxy-3,7-dimethyloct-2-enoic acid 2 were synthesized via the selective direct Sharpless asymmetry dihydroxylation of geraniol as the key step in 35.0%-48.0% overall yields with 91.9%-97.7% ee values for esters 4 and 31.3%-36.4% overall yields with 90.3-97.5% ee values for acids 2 using cis- and trans-geraniol as raw materials. Their structures were characterized by 1H, 13C NMR and HR-ESI-MS data. The in vivo bioassay results showed that the chiral acid (Z, S)-2 was a good lead compound with 80%-100% inhibitory rates against P. cubensis, E. graminis, P. sorghi and C. gloeosporioides at the concentration of 400μg/mL.
- Wang, Weiwei,Zhang, Xiaoteng,Zhao, Yu,Liu, Xinlei,Zhang, Zhenhua,Wang, Mingan
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- PLANT OR MICROORGANISM-DERIVED CAROTENOID-OXYGEN COPOLYMER COMPOSITIONS, METHODS OF IDENTIFYING, QUANTIFYING AND PRODUCING SAME AND USES THEREOF
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The present invention relates to carotenoid-oxygen copolymers, compositions, methods of identifying and quantifying carotenoid-oxygen copolymers in food and related sources, and methods of producing compositions comprising same. In one aspect the method of identifying and quantifying carotenoid-oxygen copolymers comprises an analysis of a low molecular weight marker compound in said sources. In another aspect the present invention provides a method of preparing compositions comprising said carotenoid-oxygen copolymers and/or enhancing levels of said copolymers in food sources in a sufficient and practically useful concentration to have beneficial effects in animals and humans, including beneficial immunological and health effects.
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- Molecular iodine as efficient co-catalyst for facile oxidation of alcohols with hypervalent(III) iodine
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A simple and mild procedure for the facile oxidation of alcohols to ketones and acids using a catalytic quantity of molecular iodine in combination with (diacetoxyiodo)benzene in acetonitrile is described. Direct oxidative methyl esterification of alcohols is also reported in methanol as solvent. Oxidation of alcohols is induced by iodonium ion generated in situ by the chemical oxidation of molecular iodine with (diacetoxyiodo)benzene. Georg Thieme Verlag Stuttgart.
- Karade,Tiwari,Huple
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p. 2039 - 2042
(2007/10/03)
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- Molecular recognition of α,β-unsaturated carbonyl compounds using aluminum tris(2,6-diphenylphenoxide) (ATPH): Structural and conformational analysis of ATPH complexes and application to the selective vinylogous aldol reaction
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Various α,β-unsaturated carbonyl compounds were coordinated with aluminum tris(2,6-diphenylphenoxide) (ATPH) to give the corresponding Lewis acid-base complexes in a distinctive coordination fashion (selective coordination). ATPH recognizes carbonyl substrates and subsequently orients itself as it forms a stable complex through selective coordination with the carbonyl oxygen. Selective coordination also confers a conformational preference to each carbonyl compound under the steric and electronic influence of ATPH, which enables the vinylogous aldol reaction of α,β-unsaturated carbonyl compounds to give the corresponding γ-aldol products with different regio- and stereoselectivities.
- Saito, Susumu,Nagahara, Takashi,Shiozawa, Masahito,Nakadai, Masakazu,Yamamoto, Hisashi
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p. 6200 - 6210
(2007/10/03)
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- Structure elucidation, enantioselective analysis, and biogenesis of nerol oxide in Pelargonium species
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A novel enantioselective synthesis of nerol oxide (3,6-dihydro-4-methyl- 2-(2-methyl-1-propenyl)2H-pyran) was used for the determination of the absolute configuration at C-2. The order of elution of the enantiomers on octakis-(2,3-di-O-butyryl-6-O-tert-butyldimethylsilyl)-γ-cyclodextrin in OV 1701-vi as the chiral stationary phase in enantioselective GC was determined as (2R) before (2S). Enantioselective multidimensional GC/MS (enantio- MDGC/MS) was used for the determination of the enantiomeric ratios of nerol oxide in different geranium oils. As a result, in all investigated oils nerol oxide occurs as a racemate. The biogenesis of nerol oxide in Pelargonium species was investigated by feeding experiments using deuterium-labeled neryl glucoside as the precursor. The Pelargonium plants were able to convert the fed precursor into racemic nerol oxide, which has to be considered as a 'natural racemate'.
- Wuest, Matthias,Reindl, Juergen,Fuchs, Sabine,Beck, Thomas,Mosandl, Armin
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p. 3145 - 3150
(2007/10/03)
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- Substrate specificity for the epoxidation of terpenoids and active site topology of house fly cytochrome P450 6A1
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Heterologous expression in Escherichia coli, purification, and reconstitution of house fly P450 6A1 and NADPH-cytochrome P450 reductase were used to study the metabolism of terpenoids. In addition to the epoxidation of cyclodiene insecticides demonstrated previously [Andersen et al. (1994) Biochemistry 33, 2171-2177], this cytochrome P450 was shown to epoxidize a variety of terpenoids such as farnesyl, geranyl, and neryl methyl esters, juvenile hormones I and III, and farnesal but not farnesol or farnesoic acid. P450 6A1 reconstituted with NADPH-cytochrome P450 reductase and phosphatidylcholine did not metabolize α-pinene, limonene, or the insect growth regulators hydroprene and methoprene. The four geometric isomers of methyl farnesoate were metabolized predominantly to the 10,11-epoxides, but also to the 6,7-epoxides and to the diepoxides. The 10,11-epoxide of methyl (2E,6E)-farnesoate was produced in a 3:1 ratio of the (10S) and (10R) enantiomers. Monoepoxides of methyl farnesoate were metabolized efficiently to the diepoxides. Methyl farnesoate epoxidation was strongly inhibited by a bulky substituted imidazole. The active site topology of P450 6A1 was studied by the reaction of the enzyme with phenyldiazene to form a phenyl-iron complex. Ferricyanide-induced in situ migration of the phenyl group showed formation of the N-phenylprotoporphyrinporphyrin IX adducts in a 17:25:33:24 ratio of the N(B):N(A):N(C):N(D) isomers. These experiments suggest that metabolism of xenobiotics by this P450, constitutively overexpressed in insecticide-resistant strains of the house fly, is not severely limited by stereochemically constrained access to the active site.
- Andersen, John F.,Walding, Jennifer K.,Evans, Philip H.,Bowers, William S.,Feyereisen, Rene
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p. 156 - 164
(2007/10/03)
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- OZONOLYSIS OF ALKENES AND THE REACTIONS OF POLYFUNCTIONAL COMPOUNDS LIII.SYNTHESIS OF THE ESTERS OF 2,3-DIHYDRO DERIVATIVES OF TRI-, DI-, AND MONOPRENOIC ACIDS
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The esters of the 2,3-dihydro derivatives of geranylgeranic, farnesylic, and geranic acids (di-, sesqui-, and monoterpenoid acids) were synthesized from the products from ozonolysis of 1,5,9-trimethyl-1E,5E,9E-cyclododecatriene.
- Odinokov, V. N.,Kukovinets, O. S.,Sakharova, N. I.,Tolstikov, G. A.
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- ACTIVATION AND SYNTHETIC APPLICATION OF THIOSTANNANES. PROTECTION OF CARBOXYL GROUPS WITH α-METHYLCINNAMYL ALCOHOL AS A MEANS OF CHEMODIFFERENTIATION AND SELECTIVE ACTIVATION
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α-Methylcinnamyl (MEC) esters are converted into parent carboxylic acids under mild conditions, various functions being tolerated including acetoxy, siloxy, MEM, and so on.Furthermore, MEC esters are transformed into other esters through CsF-promoted alkylation of intermediary organotin carboxylates.
- Sato, Tsueno,Otera, Junzo,Nozaki, Hitoshi
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p. 2959 - 2962
(2007/10/02)
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- THE PHOTOCHEMISTRY OF METHYL GERANATE, A MODEL CHROMOPHORE FOR INSECT JUVENILE HORMONE ANALOGS
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The irradiation of methyl geranate (3) in ether using 254 nm lamps produces methyl 5-methyl-2-isopropenyl-4-hexenoate (13), 1,6,6-trimethyl-endo-5-carbomethoxybicyclo-hexane (11), methyl 2-isopropenyl-5-methylcyclopentanecarboxylate (12) and methyl (3Z)-3,7-dimethyl-3,6-octadienoate (14).Photolysis run in water or in ether in the presence of base generates two additional dienes: methyl 3-methylene-7-methyl-6-octaenoate (16) and methyl (3E)-3,7-dimethyl-3,6-octadienoate (17).The photolysis of methyl (2E, 6E)-3,7-dimethyl-2,6-nonadienoate (4a) in ether procedures all Z/E isomers, 4a - 4d.
- Freeman, Peter K.,Siggel, Lorenz,Chamberlain, Paul H.,Clapp, Gary E.
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p. 5051 - 5064
(2007/10/02)
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- The Kinetics of Photochemical Deconjugation Reactions of Methyl Geranate
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The photochemical transformations of methyl geranate are analyzed in terms of the depedence of quantum yield upon base, 1,2-dimethylimidazole, concentration.The dependence of quantum yield of deconjugated esters methyl (3Z)-3,7-dimethyl-3,6-octadienoate (12), methyl 3-methylene-7-methyl-6-octenoate (13), and methyl (3E)-3,7-dimethyl-3,6-octadienoate (14) and the ratio of (13)/(12) and (13)/(14) upon base concentration, as well as the dependence of the ratios (methyl 2-isopropenyl-5-methylcyclopentanecarboxylate (15): deconjugated ester) (10)/(12), (10)/(13) and (10)/(14) upon the reciprocal of the base concentration, are consistent with relative rate constant ratios for (sigmatropic shift)/(dienol deprotonation) for photodienols 15, (precursor of 13), 17 (precursor of 12) and 19 (precursor of 14), of 72, 1.0 and 85.
- Freeman, Peter K.,Siggel, Lorenz
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p. 5065 - 5074
(2007/10/02)
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- Nuclear Synthons: Mesyltriflone as an Olefin Polyanion Equivalent
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Mesyltriflone (CF3SO2CH2SO2CH3) is developed as a nuclear synthon reagent capable first of multiple constructions such as alkylations then of Ramberg-Baecklund elimination to a substituted olefin.The alkylations are clean and regiospecific, often amenable to one-pot operation, and in most cases the elimination is smooth.A variety of examples is presented to establish the scope of the method, and the mechanism and stereochemistry are discussed.
- Hendrickson, James B.,Boudreaux, Gerald J.,Palumbo, Paul S.
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p. 2358 - 2366
(2007/10/02)
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- PALLADIUM DICHLORIDE CATALYZED COPE REARRANGEMENT OF FUNCTIONALIZED ACYCLIC 1,5-DIENES
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The cope rearrangement of acyclic 1,5-dienes having an electronwithdrawing group at carbon-3 and an alkyl substituent at carbon-2 is effectively catalyzed by palladium dichloride.This reaction can be employed to achieve clean γ-allylation of vinyl esters and acids.
- Overman, Larry E.,Renaldo, Alfred F.
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p. 3757 - 3760
(2007/10/02)
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- OXIDATION OF α,β-UNSATURATED ALDEHYDES
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A variety of methods for the conversion of α,β-unsaturated aldehydes to the corresponding acids have been explored.The best approach uses sodium chlorite and gives the desired transformation even in systems where steric hindrance and/or sensitive functionality are present.
- Bal, Balkrishna S.,Childers, Wayne E.,Pinnick, Harold W.
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p. 2091 - 2096
(2007/10/02)
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- A NOVEL METHOD FOR THE TERPENE SYNTHESIS BY THE RING-OPENING REACTION OF β-METHYL-β-PROPIOLACTONE
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A new route for the terpene synthesis is investigated, which undergoes via terpene carboxylic acids as key intermediates obtained by the regiospecific ring opening of β-methyl-β-propiolactone with cuprate or with a Grignard reagent in the presence of a copper catalyst.
- Fujisawa, Tamotsu,Sato, Toshio,Kawara, Tatsuo,Noda, Atsunari,Obinata,Toshiyuki
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p. 2553 - 2554
(2007/10/02)
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- Manufacture of poly-(cis)-isoprenols
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γ-Alkylation of 2-butynoic acid utilizing lithium 2,2,6,6-tetramethylpiperidide and 1-bromo-3-methyl-2-butene, followed by esterification of the resulting 7-methyloct-6-en-2-ynoic acid and treatment of the ester with lithium dimethyl cuprate, yields methyl (Z)-3,7-dimethylocta-2,6-dienoate. The ester is reduced to (Z)-3,7-dimethylocta-2,6-dien-1-ol, commonly known as nerol, which is useful as perfume agent.
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