- Aerobic C?C Bond Cleavage Catalyzed by Whole-Cell Cultures of the White-Rot Fungus Dichomitus albidofuscus
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Whole-cell cultures of the basidiomycetous white-rot fungus Dichomitus albidofuscus exhibit varying catalytic activity towards aromatic compounds depending on the growth stage. This study reveals the catalytic behavior of mature whole-cell cultures that effectively catalyze a C?C bond cleavage oxidizing toluene, benzaldehyde and acetophenone to phenol. The reaction products were analyzed by GC-MS and NMR techniques. To exclude the de novo formation of phenol by the fungus, its origin has been proven by bioconversion of benzaldehyde-d5. The key step involves an aerobic Baeyer-Villiger type rearrangement where the incorporation of oxygen into the product was confirmed based on isotope labelling experiments with 18O2. Intermediate esters were not found in reaction mixture presumably due to the detected esterase activity in the mycelium as well as in supernatant of the whole-cell cultures. As a result, the sequence of biocatalytic reactions catalyzed by D. albidofuscus for the degradation of toluene via C?C bond cleavage has been disclosed.
- Zhuk, Tatyana S.,Babkina, Valeriia V.,Zorn, Holger
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- Quantitative Difference in Solubility of Diastereomeric (2H/1H)-Isotopomers
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Many achiral organic compounds become chiral by an isotopic substitution of one of the enantiotopic moieties in their structures. Although spectroscopic methods can recognize the molecular chirality due to an isotopic substitution, the effects of isotopically chiral compounds in enantioselective reactions have remained unsolved because the small chirality arises only from the difference between the number of neutrons in the atomic nuclei. The difference between the diastereomeric isotopomers of reactive sources should be the key to these effects. However, the energy difference between them is difficult to calculate, even using present computational methods, and differences in physical properties have not yet been reported. Here, we demonstrate that the small energy difference between the diastereomeric isotopomers at the molecular level can be enhanced to appear as a solubility difference between the diastereomeric (2H/1H) isotopomers of α-aminonitriles, synthesized from an isotopically chiral amine, achiral aldehyde, and HCN. This small, but measurable, difference induces the chiral (d/l) imbalance in the suspended α-aminonitrile; therefore, a second enhancement in the solid-state chirality proceeds to afford a highly stereoimproved aminonitrile (>99% selectivity) whose handedness arises completely from the excess enantiomer of isotopically chiral amine, even in a low enantiomeric excess and low deuterium-labeling ratio. Because α-aminonitriles can be hydrolyzed to chiral α-amino acids with the removal of an isotope-labeling moiety, the current sequence of reactions represents a highly enantioselective Strecker amino acid synthesis induced by the chiral hydrogen (2H/1H) isotopomer. Thus, hydrogen isotopic chirality links directly with the homochirality of α-amino acids via a double enhancement of α-aminonitrile, the chiral intermediate of a proposed prebiotic mechanism.
- Kawasaki, Tsuneomi,Kubo, Hiroki,Nishiyama, Satoshi,Saijo, Taiki,Tokunaga, Yuji,Yokoi, Rintaro
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supporting information
p. 19525 - 19531
(2021/11/22)
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- Expeditious synthesis of phenanthridines through a Pd/MnO2-mediated C-H arylation/oxidative annulation cascade from aldehydes, aryl iodides and amino acids
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The expeditious construction of phenanthridine scaffolds via a Pd/MnO2-mediated C-H arylation/oxidative annulation cascade involving aldehydes, aryl iodides and amino acids is disclosed. This reaction proceeds smoothly involving the formation of multiple chemical bonds with the tolerance of a wide range of functional groups. The control experiments suggest a radical mechanism for C-N bond formation via MnO2-promoted oxidative annulation of imine compounds. The synthetic utility of this transformation has been demonstrated via the straightforward access to bioactive natural alkaloid trisphaeridine and its analogue.
- Fan, Jian,Li, Li,Xie, Meihua,Zhang, Jitan
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p. 2775 - 2778
(2020/03/13)
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- Biosynthesis of Benzylic Derivatives in the Fermentation Broth of the Edible Mushroom, Ischnoderma resinosum
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Employing isotope incubation studies, the biosynthetic pathway leading to a series of benzylic derivatives was elucidated in the fermentation broth of the edible mushroom Ischnoderma resinosum (P. Karst). Twenty-six hydroxy- and methoxy- benzylic derivatives were screened by gas chromatography-mass spectrometry (GC-MS) of which 13 were detected in the culture media. Results from the isotope incubation studies showed the transformation of both benzyl alcohol and benzoic acid into benzaldehyde. Benzaldehyde was then converted into 4-methoxybenzaldehyde via hydroxylation and subsequent methylation of the 4-C position. The resulting 4-methoxybenzaldehyde was then hydroxylated in the 3-C position followed by methylation into 3,4-dimethoxybenzaldehyde. Based on these findings, a novel metabolic scheme for the biosynthesis of benzylic derivatives in I. resinosum was proposed. The knowledge of the biosynthetic pathway was utilized to produce 4-hydroxy-3-methoxybenzaldehyde (vanillin) from 4-hydroxy-3-methoxybenzoic acid (vanillic acid). This is the first report to elucidate the biosynthetic pathway of benzyl derivatives and production of vanillin from I. resinosum.
- Wickramasinghe, Purni C. K.,Munafo, John P.
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p. 2485 - 2492
(2020/02/27)
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- Visible light-mediated intermolecular [2 + 2] photocycloaddition of 1-aryl-2-nitroethenes and olefins
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Despite the importance of cyclobutanes there are not many direct [2 + 2] photocycloaddition reactions which can be performed with visible light in the absence of a catalyst. A notable exception is the reaction of 1-aryl-2-nitroethenes and olefins which can be performed at a wavelength of λ = 419 nm or λ = 424 nm in CH2Cl2 as the solvent. In the present study, a total of 15 1-aryl-2-nitroethenes were found to undergo a [2 + 2] photocycloaddition with 2,3-dimethyl-2-butene (28-86% yield) and a set of 12 olefins was studied in their photocycloaddition to 1-phenyl-2-nitroethene (37-88% yield). All mechanistic results are in agreement with a triplet reaction pathway and with the intermediacy of a 1,4-diradical.
- Mohr, Lisa-Marie,Bauer, Andreas,Jandl, Christian,Bach, Thorsten
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supporting information
p. 7192 - 7203
(2019/08/07)
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- Generation of Donor/Donor Copper Carbenes through Copper-Catalyzed Diyne Cyclization: Enantioselective and Divergent Synthesis of Chiral Polycyclic Pyrroles
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The generation of metal carbenes from readily available alkynes represents a significant advance in metal carbene chemistry. However, most of these transformations are based on the use of noble-metal catalysts and successful examples of such an asymmetric version are still very scarce. Here a copper-catalyzed enantioselective cascade cyclization of N-propargyl ynamides is reported, enabling the practical and atom-economical construction of diverse chiral polycyclic pyrroles in generally good to excellent yields with wide substrate scope and excellent enantioselectivities (up to 97:3 e.r.). Importantly, this protocol represents the first copper-catalyzed asymmetric diyne cyclization. Moreover, mechanistic studies revealed that the generation of donor/donor copper carbenes is presumably involved in this 1,5-diyne cyclization, which is distinctively different from the related gold catalysis, and thus it constitutes a novel way for the generation of donor/donor metal carbenes.
- Hong, Feng-Lin,Wang, Ze-Shu,Wei, Dong-Dong,Zhai, Tong-Yi,Deng, Guo-Cheng,Lu, Xin,Liu, Rai-Shung,Ye, Long-Wu
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supporting information
p. 16961 - 16970
(2019/10/16)
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- Ruthenium(II)-Catalyzed Synthesis of Spirobenzofuranones by a Decarbonylative Annulation Reaction
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The first decarbonylative insertion of an alkyne through C?H/C?C activation of six-membered compounds is reported. The Ru-catalyzed reaction of 3-hydroxy-2-phenyl-chromones with alkynes works most efficiently in the presence of the ligand PPh3 to provide spiro-indenebenzofuranones. Unlike previously reported metal-catalyzed decarbonylative annulation reactions, in the present decarbonylative annulation reaction, the annulation occurs before extrusion of carbon monoxide.
- Kaishap, Partha P.,Duarah, Gauri,Sarma, Bipul,Chetia, Dipak,Gogoi, Sanjib
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p. 456 - 460
(2018/02/21)
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- Rhodium(III)-Catalyzed C-H Activation/Alkyne Annulation by Weak Coordination of Peresters with O-O Bond as an Internal Oxidant
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A redox-economic strategy has been developed, involved in an efficient Rh(III)-catalyzed oxidative C-H activation and alkyne annulation with perester as the oxidizing directing group. In this process, the cleavage of an oxidizing O-O bond as an internal oxidant is described for the first time. This reaction could be carried out under mild conditions and exhibits excellent regioselectivity and wide functional groups tolerance.
- Mo, Jiayu,Wang, Lianhui,Cui, Xiuling
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supporting information
p. 4960 - 4963
(2015/11/03)
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- Zinc-Catalyzed Alkyne Oxidation/C-H Functionalization: Highly Site-Selective Synthesis of Versatile Isoquinolones and β-Carbolines
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An efficient zinc(II)-catalyzed alkyne oxidation/C£H functionalization sequence was developed, thus leading to highly site-selective synthesis of a variety of isoquinolones and β-carbolines. Importantly, in contrast to the well-established gold-catalyzed intermolecular alkyne oxidation, over-oxidation can be completely suppressed in this system and the reaction most likely proceeds by a Friedel-Crafts-type pathway. Mechanistic studies and theoretical calculations are described.
- Li, Long,Zhou, Bo,Wang, Yong-Heng,Shu, Chao,Pan, Yi-Fei,Lu, Xin,Ye, Long-Wu
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p. 8245 - 8249
(2015/07/07)
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- Dual gold catalysis: Synthesis of polycyclic compounds via C-H insertion of gold vinylidenes
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New and interesting polycyclic compounds have been synthesized from non-conjugated diyne systems by dual gold catalysis. A quaternary carbon center in the backbone and the accompanying Thorpe-Ingold effect enabled the unprecedented insertion of sp3 and sp2 C-H bonds that for the first time were incorporated within the backbone of the diyne system and allowed the construction of complex polycyclic carbon scaffolds inaccessible by previous approaches in which the C-H bonds for the insertion were situated at the other end of the alkyne.
- Wieteck, Marcel,Tokimizu, Yusuke,Rudolph, Matthias,Rominger, Frank,Ohno, Hiroaki,Fujii, Nobutaka,Hashmi, A. Stephen K.
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supporting information
p. 16331 - 16336
(2015/01/09)
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- Concerning the potential reversibility of carbometalation in alkoxide-directed Ti(Oi-Pr)4-mediated reductive cross-coupling of homoallylic alcohols with aromatic imines
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In an attempt to understand the nature of selectivity in Ti-mediated reductive cross-coupling between homoallylic alcohols and imines, we investigated whether thermodynamic equilibration of the presumed organometallic intermediate plays a role in selectiv
- Takahashi, Masayuki,Micalizio, Glenn C.
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supporting information; experimental part
p. 3336 - 3338
(2010/08/06)
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- Synthesis and spectroscopic characterization of photo-affinity peptide ligands to study rhodopsin-G protein interaction
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G protein-coupled receptors (GPCRs) are involved in the control of virtually all aspects of our behavior and physiology. Activated receptors catalyze nucleotide exchange in heterotrimeric G proteins (composed of α-GDP, β and γ subunits) on the inner surfa
- Chen, Yihui,Herrmann, Rolf,Fishkin, Nathan,Henklein, Peter,Nakanishi, Koji,Ernst, Oliver P.
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experimental part
p. 831 - 838
(2009/09/30)
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- Synthesis of [2,3,4,5,6-2H5]phenyl glucosinolate
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Starting from commercially available [2,3,4,5,6-2H 5]benzoic acid, [2,3,4,5,6-2H5]phenyl glucosinolate was synthesized. Under negative-ion electrospray-ionization mass spectrometric conditions, this compound affords a peak at m/z 399. Since this m/z value is not known from the ions derived from natural glucosinolates, the [2,3,4,5,6-2H5]phenyl glucosinolate reported here is useful as an internal standard for the quantification of glucosinolates by negative-ion mass spectrometry (MS) and liquid chromatography (LC)/MS techniques. Copyright
- Bialecki, Jason B.,Ruzicka, Josef,Attygalle, Athula B.
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p. 711 - 715
(2008/02/11)
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- Isotope labeled 'HEA Moiety' in the synthesis of labeled HIV-protease inhibitors - Part 1
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[(S)-1′-((N-tert-Butyloxycarbonyl)amino)-2S-[2H 5]phenyl-ethyl]oxirane 11, made from [2H 5]-bromobenzene, was transformed into the HIV-protease inhibitors [2H5J-DPH 153893 and [2H5]-DPH 140
- Ekhato, I. Victor,Liao, Yuan,Plesescu, Mihaela
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p. 821 - 835
(2007/10/03)
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- Substantial 2H-magnetic isotope effects on the diastereoselectivity of triplet photocycloaddition reactions
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Magnetic isotope effects (MIE) on the diastereoselectivity of the triplet [2+2]-photocycloaddition of benzaldehyde with 2,3-dihydrofuran are described for four substrate combinations. The MIE results from H/D exchange at the reactive carbons of either the
- Griesbeck, Axel G.,Bondock, Samir,Cygon, Peter
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p. 9016 - 9017
(2007/10/03)
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- Reaction of magnesium pinacolone enolate with benzaldehyde: Polar or ET mechanism?
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The carbonyl-carbon kinetic isotope effect (KIE) and the substituent effect were measured for the reaction of magnesium pinacolone enolate (CH2=C(OMgBr)C(CH3)3, 1) with benzaldehyde. The results were compared with those for lithium enolate (CH2=C(OLi)C(CH3)3, 2). A normal carbonyl-carbon KIE, a medium-sized Hammett ρ value and the results of chemical probe experiments indicated that the reaction of 1 proceeds via the polar mechanism as in the reaction of 2.
- Yamataka, Hiroshi,Shimizu, Makoto,Mishima, Masaaki
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p. 127 - 129
(2007/10/03)
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- On the mechanism of addition of lithium pinacolone enolate to benzaldehyde: Polar or electron transfer?
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The carbonyl-carbon kinetic isotope effect (KIE) and the substituent effect were measured for the reaction of lithium pinacolone enolate (CH2=C(OLi)C(CH3)3) with benzaldehyde, and the results were compared with those for other lithium reagents such as MeLi, PhLi, and CH2=CHCH2Li. Ab initio MO calculations (HF/6-31+G*) were carried out to estimate the equilibrium IE on the addition to benzaldehyde. A carbonyl addition reaction, in general, proceeds by way of either a polar direct nucleophilic attack (PL) in a one-step or a two-step process going through a radical ion intermediate (eq 1). The carbonyl-carbon KIE is of primary nature for the PL or the RC rate-determining ET mechanism, while it is considered to be secondary for the ET rate-determining mechanism. The reaction of lithium pinacolone enolate with benzaldehyde gave a small positive KIE (12k/13k = 1.019), which is larger than the theoretical equilibrium IE (12K/13K = 1.006) determined by the MO calculations. Thus, there is a reaction-coordinate contribution to the observed KIE. This is in sharp contrast to the absence of KIE (12k/14k = 1.000) measured previously for the MeLi addition. Dehalogenation and enone-isomerization probe experiments showed no evidence of a single electron transfer to occur during the course of the reaction. The primary carbonyl-carbon KIE together with the substituent effect and chemical probe experiments led to the conclusion that the reaction of lithium pinacolone enolate with benzaldehyde proceeds via the polar mechanism.
- Yamataka, Hiroshi,Sasaki, Daizo,Kuwatani, Yoshiyuki,Mishima, Masaaki,Tsuno, Yuho
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p. 9975 - 9979
(2007/10/03)
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- Alkyl phenylglyoxylates as radical photoinitiators creating negative photoimages
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Alkyl phenylglyoxylates are shown to be efficient photoinitiators for acrylate polymerization. Benzoyl and phenyl radicals derived from intermolecular hydrogen abstraction are the initiating species. A negative photoimage system was developed based on thi
- Hu, Shengkui,Neckers, Douglas C.
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p. 1737 - 1740
(2007/10/03)
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- SELECTIVE MONO- OR DIMETALATION OF ARENES BY MEANS OF SUPERBASIC REAGENTS
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If employed in tetrahydrofuran, stoichiometric amounts of butyllithium and potassium tert-butoxide react with benzene under clean monometalation.In hexane suspension, however, considerable amounts of meta- and para-disubstituted by-products are obtained (approx. 10percent).They become preponderant if a three-fold excess of the metalating agent is used.Naphthalene leads under the same conditions to a mixture of two mono- and ten di-substituted derivatives. - Alkyl groups, as present in tert-butylbenzene, retard the metalation at both m- and p-positions, while trialkylsilyl groups deactivate only m-position.In either case exclusive monosubstitution occurs. - Perdeuterobenzene undergoes metalation and subsequent electrophilic mono- or disubstitution to afford isotope labeled compounds with moderate, though synthetically attractive yields.The kinetic isotope effects and product ratios can be taken as evidence for aggregate formation at the level of both the superbasic metalating reagent and the organometallic intermediates.
- Schlosser, Manfred,Choi, Jung Hoon,Takagishi, Sadahito
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p. 5633 - 5648
(2007/10/02)
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- Reactions of 1,4-Dihydro-3-(2H)benzoisoquinolinones with Aldehydes in the Presence of a Strong Base. Condensation and Aromatization as Competing Reactions
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In reactions of 1-phenyl-1,4-dihydro-3-(2H)benzoisoquinolinones with benzaldehyde in the presence of a strong base, the final result can be ring substitution with aromatization or only aromatization of the starting isoquinolinone, depending on the positio
- Hazai, L.,Deak, Gy.,Toth, G.,Volford, J.,Tamas, J.
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