- Catalytic α-Deracemization of Ketones Enabled by Photoredox Deprotonation and Enantioselective Protonation
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This study reports the catalytic deracemization of ketones bearing stereocenters in the α-position in a single reaction via deprotonation, followed by enantioselective protonation. The principle of microscopic reversibility, which has previously rendered this strategy elusive, is overcome by a photoredox deprotonation through single electron transfer and subsequent hydrogen atom transfer (HAT). Specifically, the irradiation of racemic pyridylketones in the presence of a single photocatalyst and a tertiary amine provides nonracemic carbonyl compounds with up to 97% enantiomeric excess. The photocatalyst harvests the visible light, induces the redox process, and is responsible for the asymmetric induction, while the amine serves as a single electron donor, HAT reagent, and proton source. This conceptually simple light-driven strategy of coupling a photoredox deprotonation with a stereocontrolled protonation, in conjunction with an enrichment process, serves as a blueprint for other deracemizations of ubiquitous carbonyl compounds.
- Chen, Shuming,Gao, Anthony Z.,Ivlev, Sergei I.,Meggers, Eric,Nie, Xin,Ye, Chen-Xi,Zhang, Chenhao
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supporting information
p. 13393 - 13400
(2021/09/03)
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- Cobalt-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carboxylic Acids by Homolytic H2 Cleavage
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The asymmetric hydrogenation of α,β-unsaturated carboxylic acids using readily prepared bis(phosphine) cobalt(0) 1,5-cyclooctadiene precatalysts is described. Di-, tri-, and tetra-substituted acrylic acid derivatives with various substitution patterns as well as dehydro-α-amino acid derivatives were hydrogenated with high yields and enantioselectivities, affording chiral carboxylic acids including Naproxen, (S)-Flurbiprofen, and a d-DOPA precursor. Turnover numbers of up to 200 were routinely obtained. Compatibility with common organic functional groups was observed with the reduced cobalt(0) precatalysts, and protic solvents such as methanol and isopropanol were identified as optimal. A series of bis(phosphine) cobalt(II) bis(pivalate) complexes, which bear structural similarity to state-of-the-art ruthenium(II) catalysts, were synthesized, characterized, and proved catalytically competent. X-band EPR experiments revealed bis(phosphine)cobalt(II) bis(carboxylate)s were generated in catalytic reactions and were identified as catalyst resting states. Isolation and characterization of a cobalt(II)-substrate complex from a stoichiometric reaction suggests that alkene insertion into the cobalt hydride occurred in the presence of free carboxylic acid, producing the same alkane enantiomer as that from the catalytic reaction. Deuterium labeling studies established homolytic H2 (or D2) activation by Co(0) and cis addition of H2 (or D2) across alkene double bonds, reminiscent of rhodium(I) catalysts but distinct from ruthenium(II) and nickel(II) carboxylates that operate by heterolytic H2 cleavage pathways.
- Chirik, Paul J.,Shevlin, Michael,Zhong, Hongyu
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supporting information
(2020/03/13)
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- Mechanistic Investigation of the Nickel-Catalyzed Carbonylation of Alcohols
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The carbonylation of alcohols represents a straightforward and atom-efficient methodology for the preparation of carboxylic acids. It is desirable to perform these reactions under precious metal-free and low-pressure conditions, with regioselectivity control. In this work, we present a detailed mechanistic study of a catalytic system based on NiI2, which can carbonylate benzylic alcohols in a highly regioselective manner to the corresponding branched carboxylic acids, core motifs for nonsteroidal drugs. The combination of catalytic amounts of nickel and iodide is crucial for efficient catalytic and regioselective conversion. Quantum-chemical computations were used to evaluate the underlying mechanistic processes. They revealed that a combination of two mechanisms is responsible for the observed reactivity and that the oxidative addition of alkyl halides to the Ni(0) species follows a radical oxidation pathway via two one-electron steps.
- Comba, Peter,Ghosh, Tamal,Hashmi, A. Stephen K.,Krieg, Saskia,Menche, Maximilian,Paciello, Rocco,Rück, Katharina S. L.,Sabater, Sara,Sch?fer, Ansgar,Schaub, Thomas
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supporting information
(2020/03/19)
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- Caesium fluoride-mediated hydrocarboxylation of alkenes and allenes: Scope and mechanistic insights
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A caesium fluoride-mediated hydrocarboxylation of olefins is disclosed that does not rely on precious transition metal catalysts and ligands. The reaction occurs at atmospheric pressures of CO2 in the presence of 9-BBN as a stoichiometric reductant. Stilbenes, β-substituted styrenes and allenes could be carboxylated in good yields. The developed methodology can be used for preparation of commercial drugs as well as for gram scale hydrocarboxylation. Computational studies indicate that the reaction occurs via formation of an organocaesium intermediate.
- Gevorgyan, Ashot,Obst, Marc F.,Guttormsen, Yngve,Maseras, Feliu,Hopmann, Kathrin H.,Bayer, Annette
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p. 10072 - 10078
(2019/11/14)
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- Electrogenerated Sm(II)-Catalyzed CO2 Activation for Carboxylation of Benzyl Halides
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Sm(II)-catalyzed carboxylation of benzyl halides is reported through the electrochemical reduction of CO2. The transformation proceeds under mild reaction conditions to afford the corresponding phenylacetic acids in good to excellent yields. This user-friendly and operationally simple protocol represents an alternative to traditional strategies, which usually proceeds through the C(sp3)-halide activation pathway.
- Bazzi, Sakna,Schulz, Emmanuelle,Mellah, Mohamed
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supporting information
p. 10033 - 10037
(2019/12/24)
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- SUBSTITUTED 3-HETEROARYLOXY-3-(HETERO)ARYL-PROPYLAMINES AS SEROTONIN TRANSPORTER AND SEROTONIN HT2C RECEPTOR MODULATORS
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The present invention relates to compounds compound according to Formula (1): and pharmaceutically acceptable salts, hydrates and solvates thereof. These compounds have serotonin (5-HT) transporter inhibitory effects and 5-HT 2C receptor antagonist or inverse agonist effects. The present invention also relates to pharmaceutical compositions comprising these compounds, and methods of using them for application in the prophylaxis or treatment of CNS disorders.
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Page/Page column 18; 32
(2014/04/04)
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- Ni-catalyzed direct carboxylation of benzyl halides with CO2
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A novel Ni-catalyzed carboxylation of benzyl halides with CO2 has been developed. The described carboxylation reaction proceeds under mild conditions (atmospheric CO2 pressure) at room temperature. Unlike other routes for similar means, our method does not require well-defined and sensitive organometallic reagents and thus is a user-friendly and operationally simple protocol for assembling phenylacetic acids.
- León, Thierry,Correa, Arkaitz,Martin, Ruben
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supporting information
p. 1221 - 1224
(2013/03/14)
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- Palladium complexes of bulky ortho-trifluoromethylphenyl-substituted phosphines: Unusually regioselective catalysts for the hydroxycarbonylation and alkoxycarbonylation of alkenes
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The reactions of the very bulky phosphine ligands containing both tert-butyl and ortho-trifluoromethylphenyl substituents with [PdCl 2(PhCN)2] have been studied, in order to assess the impact of steric and electronic effects on a ligand's coordination ability. The palladium complexes of tert-butyl(ortho-trifluoromethylphenyl)methyl phosphine and tert-butyl(ortho-trifluoromethylphenyl)(n-butyl)phosphine were characterised by X-ray crystallography and shown to be good precatalysts for the hydroxy- and alkoxycarbonylation of alkenes relative to Pd complexes of tricyclohexylphosphine and triphenylphosphine. A notable feature of Pd complexes of tert-butyl(ortho-trifluoromethylphenyl)methyl phosphine is significantly enhanced regioselectivity relative to previous state-of-the-art catalysts in the hydroxycarbonylation of styrene, even if lithium chloride co-catalysts are not used. These catalysts derived from large cone angle ligands consistently give higher regioselectivity in the alkoxycarbonylation of styrene using ethanol, n-propanol, and i-propanol as nucleophiles. These Pd complexes are also active in the Suzuki coupling of activated aryl chlorides, and in both carbonylation and Suzuki reactions, tert-butyl(ortho-trifluoromethylphenyl)methyl phosphine gives more productive catalysts than its bulkier analogues.
- Grabulosa, Arnald,Frew, Jamie J.R.,Fuentes, José A.,Slawin, Alexandra M.Z.,Clarke, Matthew L.
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experimental part
p. 18 - 25
(2010/12/20)
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- Dynamic enzymatic kinetic resolution of methyl 2,3-dihydro-1h-indene-1- carboxylate
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A new reaction setup for kinetic enzymatic resolution was established and is demonstrated for the case of the hydrolase-catalysed conversion of methyl 2,3-dihydro-1H-indene1-carboxylate (1) in conjunction with a base-catalysed racemisation. The system allows controlled racemisation, resulting in efficient dynamic kinetic resolution (DKR) of the title compound. Short reaction times and high enantio-selectivities were obtained with CAL-B and TBD (1,5,7-triazabicyclo[4,4.0]dec-5-ene). Compound (R)-1 (ee 95%) served as a starting material in a domino reaction that led to the biaryl indanyl ketone (R)-8, a lead compound for novel inhibitors of peptidyl-prolyl-cis/irans- isomerases, in 94 % ee. Wiley-VCH Verlag GmbH & Co. KGaA,.
- Pietruszka, Joerg,Simon, Robert Christian,Kruska, Fabian,Braun, Manfred
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experimental part
p. 6217 - 6224
(2010/03/26)
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- Indane modulators of glucocorticoid receptor, AP-1, and/or NF/kB activity and use thereof
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Novel non-steroidal compounds are provided that are useful in treating diseases associated with modulation of the glucocorticoid receptor, AP-1, and/or NF-κB activity including obesity, diabetes, inflammatory and immune diseases having the structure of formula (I): or enantiomers, diastereomers, or a pharmaceutically-acceptable salt, or hydrate, thereof, where X is -A1QA2-; Q is a bond, —C(═O)—, —OC(O)—, —C(═O)NR5—, —SOp—, —SOpNR5—, —C(O)O—, —NR5C(O)—, —OC(O)NR5—, —NR5C(O)O—, —S(O)pNR5C(O)—, —C(O)NR5S(O)p— —NR5S(O)p—, or —NR5C(═O)NR6—. Y is selected from hydrogen, C1-4alkyl, OR16, substituted C1-6alkyl, cycloalkyl, aryl, heterocyclo and heteroaryl. A1 and A2 are independently selected from a bond, C1-3alkylene, or C1-3alkenylene, and R1-R11 are defined herein. Also provided are pharmaceutical compositions, combinations, and methods of treating obesity, diabetes and inflammatory- or immune-associated diseases comprising said compounds.
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Page/Page column 51
(2008/06/13)
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- SULFONYL-SUBSTITUTED BICYCLIC COMPOUNDS AS MODULATORS OF PPAR
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Compounds as modulators of peroxisome proliferator activated receptors, pharmaceutical compositions comprising the same, and methods of treating disease using the same are disclosed.
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Page/Page column 60
(2015/10/07)
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- Catalytic enantioselective construction of all-carbon quaternary stereocenters: Synthetic and mechanistic studies of the C-acylation of silyl ketene acetals
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With the aid of an appropriate chiral catalyst, acyclic silyl ketene acetals react with anhydrides to furnish 1,3-dicarbonyl compounds that bear all-carbon quaternary stereocenters in good ee and yield. Mechanistic studies provide strong support for a catalytic cycle that involves activation of both the electrophile (anhydride → acylpyridinium) and the nucleophile (silyl ketene acetal → enolate).
- Mermerian, Ara H.,Fu, Gregory C.
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p. 5604 - 5607
(2007/10/03)
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- Unusual Tethering Effects in the Schmidt Reaction of Hydroxyalkyl Azides with Ketones: Cation-π and Steric Stabilization of a Pseudoaxial Phenyl Group
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The Lewis acid-promoted reactions of chiral 2-aryl-3-azido-1-propanols with 4-substituted cyclohexanones lead to iminium ethers and ultimately caprolactams (following a hydrolysis step). In this study, it is shown that these reactions afford variable ratios of products, depending on the electronic nature of the phenyl group. These results are interpreted in the context of a cation?π stabilizing effect in the product-determining reaction intermediate. Remarkably, the best selectivity was obtained when an azidopropanol reagent containing a quaternary center was used; a control experiment showed that the high selectivity observed in this result depended upon the free rotation of the pseudoaxial aromatic group in the intermediate that affords the major product. Copyright
- Katz, Christopher E.,Aube, Jeffrey
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p. 13948 - 13949
(2007/10/03)
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- Microbial deracemization of α-substituted carboxylic acids: Substrate specificity and mechanistic investigation
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A new enzymatic method for the preparation of optically active α-substituted carboxylic acids is reported. This technique is called deracemization reaction, which provides us with a route to obtain the enantiomerically pure compounds, theoretically in 100% yield starting from the racemic mixture. This means that the synthesis of a racemate is almost equal to the synthesis of the optically active compound, and this concept is entirely different from the commonly accepted one in the asymmetric synthesis. Using the growing cell system of Nocardia diaphanozonaria JCM3208, racemates of 2-aryl- and 2-aryloxypropanoic acid are deracemized smoothly and (R)-form-enriched products are recovered in high chemical yield (>50%). In addition, using optically active starting compounds and deuterated derivatives as well as inhibitors, we have disclosed the fact that a new type of enzyme takes part in this biotransformation, and that the reaction proceeds probably via the same mechanism as that in rat liver.
- Kato, Dai-Ichiro,Mitsuda, Satoshi,Ohta, Hiromichi
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p. 7234 - 7242
(2007/10/03)
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- Functional-Group-Directed Diastereoselective Hydrogenation of Aromatic Compounds. 21
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Diastereoselective liquid-phase hydrogenation of a series of monosubstituted indan substrates was studied on supported rhodium catalysts. Predominantly the cis-cis diastereomer, obtained by hydrogenation from the diastereoface opposite the substituent at the stereogenic center, and the cis-trans diastereomer, obtained by hydrogenation from the diastereoface on the same side as the substituent, were formed. The diastereoselectivity depends on the balance between steric repulsion and electronic attraction of the substituent with the surface of the catalyst. For alkoxy and carboxyl groups (acid, methyl ester, and amide), the steric repulsion dominated and the cis-cis diastereomer was obtained with moderately high selectivity. The diastereoselectivity obtained in the hydrogenation was influenced by the addition of bases to the reaction mixture. Addition of triethylamine caused a small increase in the selectivity to the cis-cis diastereomer in some substrates, whereas the addition of NaOH significantly increased the selectivity toward the cis-trans isomer in all substrates.
- Ranade, Vidyadhar S.,Consiglio, Giambattista,Prins, Roel
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p. 1132 - 1138
(2007/10/03)
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- Correlation of rates of uncatalyzed and hydroxide-ion catalyzed ketene hydration. A mechanistic application and solvent isotope effects on the uncatalyzed reaction
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Rates of hydration of a number of ketenes were measured in neutral and basic solution using flash photolytic techniques, and rate constants for their uncatalyzed, k(uc), and hydroxide-ion catalyzed, k(HO), reactions were determined. These results, plus additional data from the literature, were found to provide the remarkably good correlation log k(uc) = -3.21 + 1.14 log k(HO), which spans 10 orders of magnitude in reactivity and includes 31 ketenes. This good correlation implies that uncatalyzed and hydroxide-ion catalyzed ketene hydraton occur by similar reaction mechanisms, which for the hydroxide-ion catalyzed process is known to involve nucleophilic attack on the carbonyl carbon atom of the ketene. Rate constants for phenylhydroxyketene, on the other hand, do not fit this correlation, which suggests that the mechanistic assignment upon which these rate constants are based may not be correct. Solvent isotope effects on these uncatalyzed ketene hydrations are weak; most are less than k(H)/k(D) = 2. It is argued that these isotope effects are largely, if not entirely, secondary in nature and that they are consistent with both a reaction mechanism in which nucleophilic attack of a single water molecule on the ketene carbonyl carbon atom produces a zwitterionic intermediate and also a mechanism that avoids this intermediate by passing through a cyclic transition state involving several water molecules.
- Andraos, John,Kresge, A. Jerry
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p. 508 - 515
(2007/10/03)
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- Functional-Group-Directed Diastereoselective Hydrogenation of Aromatic Compounds
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Diastereoselective liquid phase hydrogenation of a series of monosubstituted indane and tetralin substrates was studied on supported rhodium catalysts. Predominantly the cis-cis diastereomer, obtained by hydrogenation from the diastereoface opposite the substituent (at the stereogenic center), and the cis-trans diastereomer, obtained by hydrogenation from the diastereoface on the same side as the substituent, were formed. The diastereoselectivity between the two isomers was dependent on the steric repulsion or the electronic attraction of the substituent with the surface of the catalyst. The hydroxyl group did not exhibit a strong attraction (haptophilicity), and the cis-cis diastereomer was obtained as the major product. The amino group exhibited a very high haptophilicity, yielding primarily the cis-trans diastereomer. The diastereoselectivity obtained in the hydrogenation of all the substrates was influenced on addition of bases to the reaction mixture. In the case of alcoholic substrates, the selectivity to the cis-trans diastereomer could be substantially increased with alkaline hydroxide additives.
- Ranade, Vidyadhar S.,Consiglio, Giambattista,Prins, Roel
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p. 8862 - 8867
(2007/10/03)
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- On the Conformation of the Substrate Binding to the Active Site during the Course of Enzymatic Decarboxylation
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The activation parameters of the enzymatic decarboxylation of malonic acid derivatives catalyzed by arylmalonate decarboxylase (AMDase) were obtained by means of kinetics. In order to understand the conformation of the substrate at the transition state, the activation entropy (ΔS?) for indane-1,1-dicarboxylic acid, a representative molecule that is conformationally restricted, was compared with those of phenylmalonic acid and ortho-chlorophenylmalonic acid, of which the aromatic ring can freely rotate. The obtained value for the former molecule was about 10 cal mol-1 K-1 smaller than those of the latter compounds, clearly indicating that a conformationally restricted substrate, such as the indane derivative, is entropically advantageous for enzymatic decarboxylation. These kinetic studies evidently disclose that the conformation of the substrate at the transition state in the course of AMDase-catalyzed decarboxylation should be synperiplanar with regard to ortho- and α-substituents.
- Kawasaki, Takayasu,Horimai, Emiko,Ohta, Hiromichi
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p. 3591 - 3594
(2007/10/03)
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- 1,4-disubstituted piperazines
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The compounds are 1,4-disubstituted piperazines useful for the treatment of disorders of central nervous system and neuroendocrine disorders. A compound disclosed is (R,S)-4-(benzodioxan-5-yl)-1-[(benzocyclobutan-1-yl)methyl]piperazine.
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- A Novel Method for the Synthesis of Methyl Indane-1-carboxylates by Ring Contraction of Tetralones Using Lead(IV) Acetate
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A smooth ring contraction of the tetralones takes place with lead(IV) acetate in presence of boron trifluoride etherate and methanol to afford methyl indane-1-carboxylates in satisfactory yields.The method is extended to five- and seven-membered cyclic aromatic ketones.
- Nongrum, F.M.,Myrboh, B.
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p. 845 - 846
(2007/10/02)
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- Synthesis of Novel Furan and Thiophene PAH'S Related to Acephenanthrylene
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The total syntheses of furan and thiophene PAH's related to acephenanthrylene are reported.Cyclobutanones which were obtained by addition of ketenes with 2,3-dihydrofuran or 2,3-dihydrothiophene regioselectively could be converted into angular PAH skeleton molecules by rearrangements with polyphosphoric acid. 2,3-Dichloro-5,6-dicyanobenzoquinone was applied for aromatization to achieve the formation of PAH's.
- Lee-Ruff, Edward,Chung, Ying-Sheng
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p. 1551 - 1554
(2007/10/02)
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- Asymmemtric Hydrolysis of (+/-)-α-Substituted Carboxylic Acid Esters with Microorganisms
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Microorganisms that hydrolyze methyl 2-phenylpropionate (1) or reduce 4-phenyl-2-butanone (3) were screened from 250 type cultures.Several Aspergilli and two bacteria hydrolyzed ester 1, and Asp. sojae IAM 2703 preferentially hydrolyzed (R)-isomer of (+/-)-1, whereas Bacillus subtilis var. niger IFO 3108 and Mycobacterium smegmatis ATCC 10143 preferentially hydrolyzed (S)-isomer.The hydrolysis of the related esters of 1 with these organisms was also examined.
- Iriuchijima, Shinobu,Keiyu, Atsuko
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p. 1389 - 1392
(2007/10/02)
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