scholarly journals Identification of the Tetrel Bonds between Halide Anions and Carbon Atom of Methyl Groups Using Electronic Criterion

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1083 ◽  
Author(s):  
Ekaterina Bartashevich ◽  
Yury Matveychuk ◽  
Vladimir Tsirelson
Keyword(s):  
Binding Energy ◽  
Carbon Atom ◽  
Molecular Complexes ◽  
Electron Donors ◽  
Methyl Groups ◽  
Geometrical Parameters ◽  
Halide Anion ◽  
Methyl Group ◽  
Electrophilic Site ◽  
Tetrel Bonds

The consideration of the disposition of minima of electron density and electrostatic potential along the line between non-covalently bound atoms in systems with Hal−···CH3–Y (Hal− = Cl, Br; Y = N, O) fragments allowed to prove that the carbon atom in methyl group serves as an electrophilic site provider. These interactions between halide anion and carbon in methyl group can be categorized as the typical tetrel bonds. Statistics of geometrical parameters for such tetrel bonds in CSD is analyzed. It is established that the binding energy in molecular complexes with tetrel bonds correlate with the potential acting on an electron in molecule (PAEM). The PAEM barriers for tetrel bonds show a similar behavior for both sets of complexes with Br− and Cl− electron donors.

Recent investigations on the nature of sterol intermediates in the biosynthesis of cholesterol

1972 ◽  
Vol 180 (1059) ◽  
pp. 125-146 ◽  
Keyword(s):  
Double Bond ◽  
Carbon Atom ◽  
Rat Liver ◽  
Liver Homogenate ◽  
Methyl Groups ◽  
Double Bonds ◽  
Animal Tissues ◽  
Methyl Group ◽  
Chromatographic Methods

Lanosterol(4,4,14α-trimethyl-cholesta-8,24-dien-3β-ol) has been proposed as the primary product of the cyclization of 2,3-epoxysqualene in animal tissues. Enzymic conversion of lanosterol to cholesterol requires reduction of the ∆ 24 double bond, removal of the three extra methyl groups, and shift of the nuclear double bond from ∆ 8 position to the ∆ 5 position. Until very recently, all of the proposed sterol intermediates in the biosynthesis of cholesterol possessed nuclear double bonds in the ∆ 8 , ∆ 7 , ∆ 5,7 or ∆ 5 positions. Consideration of possible mechanisms for the removal of the methyl group at carbon atom 14 of sterol precursors led to our demonstration of the presence of cholest-8(14)-en-3β-ol in animal tissues and establishment of the convertibility of this sterol to cholesterol in rat liver homogenate preparations. Reports (from other laboratories) of the stereospecific loss of the 15α-hydrogen of lanosterol upon enzymic conversion to cholesterol led to the demonstration of the convertibility of cholesta-8,14-dien-3β-ol, cholesta-7,14-dien-3β-ol, 14α-methyl-cholest-7-en-3β,15-diol, cholest-8(14)-en-3β,15α-diol, and cholest-8(14)-en-3β,15β-diol to cholesterol in rat liver preparations. We have recently developed chromatographic methods permitting the resolution of all of the C 27 sterols in question. The results of recent experiments directed towards an understanding of the detailed metabolism of these compounds are presented herein.

The biosynthesis of ephedrine

1989 ◽  
Vol 67 (6) ◽  
pp. 998-1009 ◽  
Author(s):  
Gunnar Grue-Sørensen ◽  
Ian D. Spenser
Keyword(s):  
Carbon Atom ◽  
Benzoic Acid ◽  
Pyruvic Acid ◽  
Nmr Spectra ◽  
Carbon Skeleton ◽  
Resonance Spectroscopy ◽  
Methyl Group ◽  
Acid Incorporation ◽  
Group A ◽  
C Nmr

It is shown by 13C nuclear magnetic resonance spectroscopy that the labelled C2 fragment of [2,3-13C2]pyruvic acid is transferred intact into the C-methyl group and the adjacent carbon atom of the Ephedra alkaloids, norephedrine, ephedrine, norpseudoephedrine, and pseudoephedrine, in growing plants of Ephedragerardiana. This finding serves to identify pyruvate as the elusive precursor of the aliphatic C2 terminus of the skeleton of the alkaloids. In earlier experiments with C-labelled substrates, label from [3-14C]pyruvic acid was incorporated mainly, but not exclusively, into the C-methyl group of ephedrine, and label from [2-14C]pyruvate was incorporated similarly into the carbon atom adjacent to the C-methyl group. A C6–C1 unit related to benzaldehyde or benzoic acid has long been known to generate the benzylic fragment of the carbon skeleton of the Ephedra alkaloids. It is likely that the carbon skeleton of ephedrine is generated from pyruvate and either benzaldehyde or benzoic acid, by a reaction analogous to the formation of acetoin or diacetyl from pyruvate and acetaldehyde or acetic acid, respectively. Keywords: biosynthesis of ephedrine, Ephedra alkaloids, 13C NMR spectra, ephedrine, biosynthesis of pyruvic acid, incorporation into ephedrine13C NMR spectra.

Net charges and valence AO's in the methylamines; the hydrogen basis set and the properties of nitrogen

1985 ◽  
Vol 63 (7) ◽  
pp. 1487-1491 ◽  
Author(s):  
Giuseppe Del Re ◽  
Sándor Fliszár ◽  
Michel Comeau ◽  
Claude Mijoule
Keyword(s):  
Basis Set ◽  
Basis Sets ◽  
Methyl Groups ◽  
Extended Form ◽  
Amine Nitrogen ◽  
Methyl Group ◽  
Net Charges ◽  
Extended Basis

Net charges and valence AO's for ammonia, methylamine, dimethylamine, and trimethylamine were calculated using extended basis sets. Superposition effects, evaluated by replacing Pople's standard 6-31G* basis by an extended form in which the basis of the ammonia H atoms and of the methyl groups of trimethylamine are retained in the treatment of each molecule, indicate that the quality of the treatment of amine nitrogen atoms is strongly dependent on the number of methyl groups. A new, augmented basis is proposed for the hydrogens, which appears to be reasonably well balanced: comparison with familiar (e.g., 6-31G*) calculations illustrates in what manner the treatment of nitrogen is worsened when even just one methyl group is replaced by hydrogen unless the impoverishment of the basis is suitably taken care of.

The Rates and Products of Addition of 4-Chlorobenzenesulfenyl Chloride to a Series of Side Chain Methyl Substituted Styrenes

1974 ◽  
Vol 52 (9) ◽  
pp. 1807-1812 ◽  
Author(s):  
George H. Schmid ◽  
Dennis G. Garratt
Keyword(s):  
Steric Hindrance ◽  
Side Chain ◽  
Methyl Groups ◽  
Methyl Group

The rates of addition and the product compositions have been determined for the addition of 4-chlorobenzenesulfenyl chloride to a series of seven side chain methyl substituted styrenes in 1,1,2,2-tetrachloroethane at 25°. Unlike the addition to the corresponding series of methylated ethylenes, the effect of the methyl groups is not cumulative. The effect of the methyl groups depends upon whether or not the β-methyl group is cis to the phenyl. When it is cis, the rate of addition is decreased compared to styrene and substitution of additional methyl groups has only a small effect on the rate of addition. In compounds lacking a cis-β-methyl group the rate of addition more closely resembles that for addition to the methylated ethylenes. Steric hindrance between the cis-methyl and phenyl groups is believed to be the cause of this difference in behavior between the ethylene and styrene series.

Transition metal-free C(sp3)–H bond coupling among three methyl groups

2017 ◽  
Vol 53 (38) ◽  
pp. 5346-5349 ◽  
Author(s):  
Yufeng Liu ◽  
Xi Zhan ◽  
Pengyi Ji ◽  
Jingwen Xu ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Methyl Groups ◽  
Methyl Ketones ◽  
Reaction Conditions ◽  
Methyl Group ◽  
Metal Free

A coupling of multiple C(sp3)–H bonds of the methyl group in methyl ketones with dimethyl sulfoxides was developed under transition metal-free reaction conditions.

scholarly journals Modulation of Methyl Group Metabolism by Streptozotocin-induced Diabetes and All-trans-retinoic Acid

2004 ◽  
Vol 279 (44) ◽  
pp. 45708-45712 ◽  
Author(s):  
Kristin M. Nieman ◽  
Matthew J. Rowling ◽  
Timothy A. Garrow ◽  
Kevin L. Schalinske
Keyword(s):  
Retinoic Acid ◽  
Diabetic Rats ◽  
Significant Decline ◽  
Methionine Synthase ◽  
Methyl Groups ◽  
Culture Studies ◽  
Methyl Group ◽  
Trans Retinoic Acid ◽  
All Trans Retinoic Acid ◽  
Streptozotocin Induced Diabetes

The hepatic enzyme glycineN-methyltransferase (GNMT) plays a major role in the control of methyl group and homocysteine metabolism. Because disruption of these vital pathways is associated with numerous pathologies, understanding GNMT control is important for evaluating methyl group regulation. Recently, gluconeogenic conditions have been shown to modulate homocysteine metabolism and treatment with glucocorticoids and/or all-trans-retinoic acid (RA)-induced active GNMT protein, thereby leading to methyl group loss. This study was conducted to determine the effect of diabetes, alone and in combination with RA, on GNMT regulation. Diabetes and RA increased GNMT activity 87 and 148%, respectively. Moreover, the induction of GNMT activity by diabetes and RA was reflected in its abundance. Cell culture studies demonstrated that pretreatment with insulin prevented GNMT induction by both RA and dexamethasone. There was a significant decline in homocysteine concentrations in diabetic rats, owing in part to a 38% increase in the abundance of the transsulfuration enzyme cystathionine β-synthase; treatment of diabetic rats with RA prevented cystathionine β-synthase induction. A diabetic state also increased the activity of the folate-independent homocysteine remethylation enzyme betaine-homocysteineS-methyltransferase, whereas the activity of the folate-dependent enzyme methionine synthase was diminished 52%. In contrast, RA treatment attenuated the streptozotocin-mediated increase in betaine-homocysteineS-methyltransferase, whereas methionine synthase activity remained diminished. These results indicate that both a diabetic condition and RA treatment have marked effects on the metabolism of methyl groups and homocysteine, a finding that may have significant implications for diabetics and their potential sensitivity to retinoids.

THE ANAEROBIC DISSIMILATION OF D-GLUCOSE-1-C14, D-ARABINOSE-1-C14, AND L-ARABINOSE-1-C14 BY AEROBACTER AEROGENES

1954 ◽  
Vol 32 (1) ◽  
pp. 147-153 ◽  
Author(s):  
A. C. Neish ◽  
F. J. Simpson
Keyword(s):  
Carbon Dioxide ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Carboxyl Groups ◽  
Methyl Groups ◽  
Carboxyl Group ◽  
Complete Conversion ◽  
Aerobacter Aerogenes ◽  
Methyl Group ◽  
Ethanol Acetic Acid

D-Glucose-1-C14, D-arabinose-1-C14, and L-arabinose-1-C14 were dissimilated anaerobically by Aerobacter aerogenes. The major products (2,3-butanediol, ethanol, acetic acid, lactic acid, formic acid, and carbon dioxide) were isolated and the location of C14 determined. The products from glucose were all labeled, mainly in the methyl groups, in agreement with the hypothesis that they were derived from methyl-labeled pyruvate formed by the reactions of the classical Embden–Meyerhof scheme for glycolysis. The products from both pentoses appeared to have been formed from pyruvate labeled in both the methyl and carboxyl groups with twice as much C14 in the methyl group as in the carboxyl group. This result may be explained quantitatively by a hypothesis assuming complete conversion of pentose to triose via a heptulose.

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