Intermolecular Methyl Group Exchange and Reversible P–Me Bond Cleavage at Cobalt(III) Dimethyl Halide Species

2013 ◽  
Vol 32 (3) ◽  
pp. 798-806 ◽  
Author(s):  
Hongwei Xu ◽  
Paul G. Williard ◽  
Wesley H. Bernskoetter
Keyword(s):  
Bond Cleavage ◽  
Methyl Group

scholarly journals Proteogenomics Reveals Novel Reductive Dehalogenases and Methyltransferases Expressed during Anaerobic Dichloromethane Metabolism

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Sara Kleindienst ◽  
Karuna Chourey ◽  
Gao Chen ◽  
Robert W. Murdoch ◽  
Steven A. Higgins ◽  
...  
Keyword(s):  
Amino Acid ◽  
Reductive Dechlorination ◽  
Bond Cleavage ◽  
Amino Acid Identity ◽  
Methyl Group ◽  
Acid Identity ◽  
Group Transfer ◽  
Degrading Bacterium ◽  
Chlorine Bond ◽  
Methyl Group Transfer

ABSTRACTDichloromethane (DCM) is susceptible to microbial degradation under anoxic conditions and is metabolized via the Wood-Ljungdahl pathway; however, mechanistic understanding of carbon-chlorine bond cleavage is lacking. The microbial consortium RM contains the DCM degrader “CandidatusDichloromethanomonas elyunquensis” strain RM, which strictly requires DCM as a growth substrate. Proteomic workflows applied to DCM-grown consortium RM biomass revealed a total of 1,705 nonredundant proteins, 521 of which could be assigned to strain RM. In the presence of DCM, strain RM expressed a complete set of Wood-Ljungdahl pathway enzymes, as well as proteins implicated in chemotaxis, motility, sporulation, and vitamin/cofactor synthesis. Four corrinoid-dependent methyltransferases were among the most abundant proteins. Notably, two of three putative reductive dehalogenases (RDases) encoded within strain RM’s genome were also detected in high abundance. Expressed RDase 1 and RDase 2 shared 30% amino acid identity, and RDase 1 was most similar to an RDase ofDehalococcoides mccartyistrain WBC-2 (AOV99960, 52% amino acid identity), while RDase 2 was most similar to an RDase ofDehalobactersp. strain UNSWDHB (EQB22800, 72% amino acid identity). Although the involvement of RDases in anaerobic DCM metabolism has yet to be experimentally verified, the proteome characterization results implicated the possible participation of one or more reductive dechlorination steps and methyl group transfer reactions, leading to a revised proposal for an anaerobic DCM degradation pathway.IMPORTANCENaturally produced and anthropogenically released DCM can reside in anoxic environments, yet little is known about the diversity of organisms, enzymes, and mechanisms involved in carbon-chlorine bond cleavage in the absence of oxygen. A proteogenomic approach identified two RDases and four corrinoid-dependent methyltransferases expressed by the DCM degrader “CandidatusDichloromethanomonas elyunquensis” strain RM, suggesting that reductive dechlorination and methyl group transfer play roles in anaerobic DCM degradation. These findings suggest that the characterized DCM-degrading bacteriumDehalobacterium formicoaceticumand “CandidatusDichloromethanomonas elyunquensis” strain RM utilize distinct strategies for carbon-chlorine bond cleavage, indicating that multiple pathways evolved for anaerobic DCM metabolism. The specific proteins (e.g., RDases and methyltransferases) identified in strain RM may have value as biomarkers for monitoring anaerobic DCM degradation in natural and contaminated environments.

scholarly journals Isotope labeling and infrared multiple-photon photodissociation investigation of product ions generated by dissociation of [ZnNO3(CH3OH)2]+: Conversion of methanol to formaldehyde

2019 ◽  
Vol 25 (1) ◽  
pp. 58-72
Author(s):  
Evan Perez ◽  
Theodore A Corcovilos ◽  
John K Gibson ◽  
Jonathan Martens ◽  
Giel Berden ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Isotope Labeling ◽  
Bond Cleavage ◽  
Neutral Loss ◽  
Density Functional Theory Calculations ◽  
Collision Induced Dissociation ◽  
Functional Theory ◽  
Methyl Group ◽  
Isotope Label

Electrospray ionization was used to generate species such as [ZnNO3(CH3OH)2]+ from Zn(NO3)2•XH2O dissolved in a mixture of CH3OH and H2O. Collision-induced dissociation of [ZnNO3(CH3OH)2]+ causes elimination of CH3OH to form [ZnNO3(CH3OH)]+. Subsequent collision-induced dissociation of [ZnNO3(CH3OH)]+ causes elimination of 47 mass units (u), consistent with ejection of HNO2. The neutral loss shifts to 48 u for collision-induced dissociation of [ZnNO3(CD3OH)]+, demonstrating the ejection of HNO2 involves intra-complex transfer of H from the methyl group methanol ligand. Subsequent collision-induced dissociation causes the elimination of 30 u (32 u for the complex with CD3OH), suggesting the elimination of formaldehyde (CH2 = O). The product ion is [ZnOH]+. Collision-induced dissociation of a precursor complex created using CH3-18OH shows the isotope label is retained in CH2 = O. Density functional theory calculations suggested that the “rearranged” product, ZnOH with bound HNO2 and formaldehyde is significantly lower in energy than ZnNO3 with bound methanol. We therefore used infrared multiple-photon photodissociation spectroscopy to determine the structures of both [ZnNO3(CH3OH)2]+ and [ZnNO3(CH3OH)]+. The infrared spectra clearly show that both ions contain intact nitrate and methanol ligands, which suggests that rearrangement occurs during collision-induced dissociation of [ZnNO3(CH3OH)]+. Based on the density functional theory calculations, we propose that transfer of H, from the methyl group of the CH3OH ligand to nitrate, occurs in concert with the formation of a Zn–C bond. After dissociation to release HNO2, the product rearranges with the insertion of the remaining O atom into the Zn–C bond. Subsequent C–O bond cleavage, with H transfer, produces an ion–molecule complex composed of [ZnOH]+ and O = CH2.

scholarly journals Mechanistic studies on C-19 demethylation in oestrogen biosynthesis

1982 ◽  
Vol 201 (3) ◽  
pp. 569-580 ◽  
Author(s):  
Muhammad Akhtar ◽  
Michael R. Calder ◽  
David L. Corina ◽  
J. Neville Wright
Keyword(s):  
Formic Acid ◽  
Bond Cleavage ◽  
Mechanistic Studies ◽  
Hydroxy Compound ◽  
Microsomal Preparation ◽  
Methyl Group ◽  
Cleavage Step ◽  
Compound Ii ◽  
Cumulative Evidence ◽  
Oxygen Atoms

Mechanistic aspects of the biosynthesis of oestrogen have been studied with a microsomal preparation from full-term human placenta. The overall transformation, termed the aromatization process, involves three steps using O2 and NADPH, in which the C-19 methyl group of an androgen is oxidised to formic acid with concomitant production of the aromatic ring of oestrogen: [Formula: see text] To study the mechanism of this process in terms of the involvement of the oxygen atoms, a number of labelled precursors were synthesized. Notable amongst these were 19-hydroxy-4-androstene-3,17-dione (II) and 19-oxo-4-androstene-3,17-dione (IV) in which the C-19 was labelled with2H in addition to18O. In order to follow the fate of the labelled atoms at C-19 of (II) and (IV) during the aromatization, the formic acid released from C-19 was benzylated and analysed by mass spectrometry. Experimental procedures were devised to minimize the exchange of oxygen atoms in substrates and product with oxygens of the medium. In the conversion of the 19-[18O] compounds of types (II) and (IV) into 3-hydroxy-1,3,5-(10)-oestratriene-17-one (V, oestrone), it was found that the formic acid from C-19 retained the original substrate oxygen. When the equivalent16O substrates were aromatized under18O2, the formic acid from both substrates contained one atom of18O. It is argued that in the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), the C-19 oxygen of the former remains intact and that one atom of oxygen from O2 is incorporated into formic acid during the conversion of the 19-oxo compound (IV) into oestrogen. This conclusion was further substantiated by demonstrating that in the aromatization of 4-androstene-3,17-dione (I), both the oxygen atoms in the formic acid originated from molecular oxygen. 10β-Hydroxy-4-oestrene-3,17-dione formate, a possible intermediate in the aromatization, was synthesized and shown not to be converted into oestrogen. In the light of the cumulative evidence available to date, stereochemical aspects of the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), and mechanistic features of the C-10–C-19 bond cleavage step during the conversion of the 19-oxo compound (IV) into oestrogen are discussed.

Metal−Metal Cooperativity Effects in Promoting C−H Bond Cleavage of a Methyl Group by an Adjacent Metal Center

1999 ◽  
Vol 121 (15) ◽  
pp. 3666-3683 ◽  
Author(s):  
Jeffrey R. Torkelson ◽  
Frederick H. Antwi-Nsiah ◽  
Robert McDonald ◽  
Martin Cowie ◽  
Justin G. Pruis ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Metal Center ◽  
Methyl Group ◽  
Metal Metal ◽  
Cooperativity Effects

scholarly journals Crystal structure of rubidium methyldiazotate

2017 ◽  
Vol 73 (2) ◽  
pp. 159-161 ◽  
Author(s):  
Tobias Grassl ◽  
Nikolaus Korber
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Natural Compound ◽  
Liquid Ammonia ◽  
Raw Materials ◽  
Bond Cleavage ◽  
New Approach ◽  
Methyl Group ◽  
Blue Solution ◽  
Gain Access

The title compound, Rb+·H3CN2O−, has been crystallized in liquid ammonia as a reaction product of the reductive ammonolysis of the natural compound streptozocin. Elemental rubidium was used as reduction agent as it is soluble in liquid ammonia, forming a blue solution. Reductive bond cleavage in biogenic materials under kinetically controlled conditions offers a new approach to gain access to sustainably produced raw materials. The anion is nearly planar [dihedral angle O—N—N—C = −0.4 (2)°]. The Rb+cation has a coordination number of seven, and coordinates to five anions. One anion is boundviaboth its N atoms, one by both O and N, two anions are bound by only their O atoms, and the last is boundviathe N atom adjacent to the methyl group. The diazotate anions are bridged by cations and do not exhibit any direct contacts with each other. The cations form corrugated layers that propagate in the (-101) plane.

High temperature catalytic hydrogenolysis and alkylation of anisole and phenol

1984 ◽  
Vol 62 (11) ◽  
pp. 2540-2545 ◽  
Author(s):  
R. K. M. R. Kallury ◽  
T. T. Tidwell ◽  
D. G. B. Boocock ◽  
D. H. L. Chow
Keyword(s):  
High Temperature ◽  
Bond Cleavage ◽  
Reactive Intermediates ◽  
Nickel Catalysts ◽  
Methyl Group ◽  
Catalytic Hydrogenolysis

Hydrogenation of phenol at 2.8 MPa pressure with MoO3–NiO–Al2O3 catalyst at 450 °C gave 60% benzene, 16% cyclohexane, and 7% methylcyclopentane, while anisole under the same conditions gave 60–70% less of each of these products and 52% methylated benzenes. In the presence of added methanol either phenol or anisole give 47–63% of methylbenzenes and 22% of methylated phenols. At 350–400 °C significant yields of cyclohexylbenzene and cyclohexylphenol were formed. The reactions are interpreted as involving electrophilic methylation or cyclotiexylation of phenol concurrent with ring hydrogenation and hydrogenolysis of C—O bonds. Cyclohexyl cations are proposed as reactive intermediates that act as cyclohexylating agents or rearrange to methylcyclopentyl cations, and the methylating species is derived from methanol or the methyl group of anisole. When phenol was reacted with H2 and CD3OH the methylated aromatic products were only partially deuterated, indicating exchange with the H2 atmosphere was occurring. Control experiments involving possible intermediates in the reaction are consistent with these conclusions. Nickel catalysts favour ring saturation over C—O bond cleavage.

scholarly journals Bond Activation in Iron(II) and Nickel(II) Complexes of Polypodal Phosphanes

2010 ◽  
Vol 65 (3) ◽  
pp. 238-250 ◽  
Author(s):  
Simon-Andreas Gentschow ◽  
Stephan W. Kohl ◽  
Walter Bauer ◽  
Frank W Heinemann ◽  
Dennis Wiedemann ◽  
...  
Keyword(s):  
Bond Activation ◽  
Close Contact ◽  
Bond Cleavage ◽  
X Ray Diffraction ◽  
Monodentate Ligand ◽  
Donor Ligand ◽  
Methyl Group ◽  
Intermolecular Mechanism ◽  
Cleavage Reactions ◽  
Iron Center

A pyridine-derived tetraphosphane ligand (donor set: NP4) has been found to undergo remarkably specific C-P bond cleavage reactions, thereby producing a ligand with an NP3 donor set. The reaction may be reversed under suitable conditions, with regeneration of the original NP4 ligand. In order to investigate the mechanism of this reaction, the NP3 donor ligand C5H3N[CMe(CH2PMe2)2][CMe2(CH2PMe2)] (11) was prepared, and its iron(II) complex 4 generated from Fe(BF4)2 ・6H2O, with methyl diethylphosphinite (7) as an additional monodentate ligand. Ligand 11 has, in addition to the NP3 donor set, one methyl group in close contact with the iron center, reminiscent of an agostic M・ ・ ・H-C interaction. Depending on the stoichiometric amount of iron(II) salt, a side product 15 is formed, which has a diethylphosphane ligand instead of the phosphinite 7 coordinated to iron(II). While attempts to deprotonate the metal-coordinated methyl group in 4 were unsuccessful, the reaction was shown to occur in an alternative complex (18), which is similar to 4 but has a trimethylphosphane ligand instead of the phosphinite 7. The reaction of complex 15 with CO gave two different products, which were both characterized by single-crystal X-ray diffraction. One (19) is the dicarbonyl iron(II) complex of the triphosphane ligand 11, the other (3) is the carbonyl iron(II) complex of the tetraphosphane C5H3N[CMe(CH2PMe2)2]2 (1). This suggests an intermolecular mechanism for the C-P bond formation in question.

Use of [13C-methyl]Tropinone to follow the fate of the methyl group during calystegine formation in root cultures of Solanum dulcamara (Solanaceae)

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
TA Bartholomeusz ◽  
R Molinié ◽  
A Roscher ◽  
AC Freydank ◽  
B Dräger ◽  
...  
Keyword(s):  
Root Cultures ◽  
Solanum Dulcamara ◽  
Methyl Group
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