- 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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- Identification and biosynthesis of tropone derivatives and sulfur volatiles produced by bacteria of the marine Roseobacter clade
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Bacteria of the Roseobacter clade are abundant marine bacteria and are important contributors to the global sulfur cycle. The volatiles produced by two of its members, Phaeobacter gallaeciensis and Oceanibulbus indolifex, were analyzed to investigate whether the released compounds are derived from sulfur metabolism, and which biosynthetic pathways are involved in their formation. Both bacteria emitted different sulfides and thioesters, including new natural compounds such as 5-methyl phenylethanethioate (16) and butyl methanesulfonate (21). The S-methyl alkanoates were identified by comparison with standards that were synthesized from the respective methyl alkanoates by a new method using an easily prepared aluminium/sulfur reagent. Phaeobacter gallaeciensis is also able to produce tropone (37) in large amounts. Its biosynthesis was investigated by various feeding experiments, showing that 37 is formed via a deviation of the phenylacetate catabolism. The unstable tropone hydrate 42 was identified as an intermediate of the tropone biosynthesis that was also released together with tropolone (38). The Royal Society of Chemistry 2010.
- Thiel, Verena,Brinkhoff, Thorsten,Dickschat, Jeroen S.,Wickel, Susanne,Grunenberg, Joerg,Wagner-Doebler, Irene,Simon, Meinhard,Schulz, Stefan
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experimental part
p. 234 - 246
(2010/04/29)
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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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- Single-crystal proton ENDOR studies of the [Fe4S4]3+ cluster: Determination of the spin population distribution and proposal of a model to interpret the1H NMR paramagnetic shifts in high-potential ferredoxins
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Proton ENDOR spectroscopy has been used in single crystals of the synthetic compound [N(C2D5)2[Fe4S4-(SCH 2C6D5)4], which is a good biomimetic model of the active sites of many four-iron-four-sulfur proteins. The eight protons of the four thiolate CH2 groups have been used in order to probe in detail the distribution of the unpaired electron spin population in a paramagnetic [Fe4S4]3+ center created by gamma irradiation in the crystals. The thus obtained hyperfine tensors of the eight protons constitute an original, abundant, and precise source of information on this oxidation state. They have been analyzed in two separate parts. From their anisotropic parts, it is possible to deduce the distribution of the unpaired spin population on the different iron and sulfur atoms with the help of a point-dipole model. Within the limitations of the simple and symmetric vectorial spin coupling model which involves two equivalent mixed-valence iron atoms and two equivalent ferric iron atoms, we find that this paramagnetic center is close to the |7/2,3,1/2) state, the first number representing the spin state of the mixed-valence pair, the second one the spin state of the ferric pair, and the last one the resulting spin of the cluster. This attribution is in contrast with recent proposals considering that the [Fe4S4]3+ spin state is |9/2,4,1/2). Finally, the analysis of the isotropic parts of the tensors leads us to propose a new quantitative model establishing the law existing between these isotropic couplings and two different parameters: a magnetic parameter which is the spin population on the adjacent iron and an angular parameter defining the orientation of each CH bond. This model seems indeed able to provide the basis of a quantitative interpretation of 1H paramagnetic shifts in the NMR spectra of high-potential proteins in their oxidized state. Through the variety of results obtained, the interest of the present study is also that it gives the capacity to unify the interpretations of results concerning the [Fe4S4]3+ state in the proteins and in model compounds which have been derived from the EPR, ENDOR, M?ssbauer, and NMR spectroscopies.
- Mouesca,Rius,Lamotte
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p. 4714 - 4731
(2007/10/02)
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- Active site dynamics of toluene hydroxylation by cytochrome P-450
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Rat liver cytochrome P-450 hydroxylates toluene to benzyl alcohol plus o-, m-, and p-cresol. Deuterated toluenes (C6D5CH3, C6D5CD3, PhCD(n)H(3-n)) were incubated under saturating conditions
- Hanzlik,Ling
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p. 3992 - 3997
(2007/10/02)
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- Skeletal Rearrangements on Chemical Ionization of Dibenzyl Ether and Derivatives
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Protonated molecular ions of dibenzyl ether, formed by chemical ionization using hydrogen and isobutane as reagent gases, undergo skeletal rearrangements to lose water and formaldehyde, both in the ion source and the flight path.The rearrangements have been elucidated by deuterium labelling and chemical substitution.The water lost contains the reagent proton and an aromatic hydrogen atom, and the aromatic hydrogen atoms have been shown to be mobile prior to the reaction.It is proposed that the skeletal rearrangement for water loss is initiated by protonation on the other oxygen atom, followed by benzyl migration.The formaldehyde loss contains benzylic hydrogen atoms exclusively, and it is proposed that the skeletal rearrangement is preceded by hydrogen rearrangement of an oxygen protonated molecular ion to a ring protonated molecular ion.Daughter ion structures are supported by comparisons of their collision induced dissociation spectra with those of isomeric ions prepared by alternative routes.
- Kingston, Eric E.,Shannon, James S.,Diakiw, Vladimir,Lacey, Michael J.
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p. 428 - 440
(2007/10/02)
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