Reaction of N-methyl-N-(2,4-dinitrophenyl)glycine methylamide with methoxide

1989 ◽  
Vol 54 (2) ◽  
pp. 430-439 ◽  
Author(s):  
Vladimír Macháček ◽  
Miloslav Sebránek ◽  
Vojeslav Štěrba
Keyword(s):  
Equilibrium Constant ◽  
Half Life ◽  
Sodium Methoxide ◽  
Side Reactions ◽  
Subsequent Reduction ◽  
Rearrangement Product ◽  
Smiles Rearrangement ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

The side reactions of N-methyl-N-(2,4-dinitrophenyl)glycine methylamide with methanolic sodium methoxide reversibly give the spiro adduct (spiro[(1,3-dimethyl-5-imidazolidone)-2,1'-(2',4'-dinitrobenzenide)]) and irreversibly produce N-methyl-2-nitroso-4-nitroaniline which undergoes subsequent reduction. The diazolidine ring of the spiro adduct is opened by action of methanolic hydrogen chloride, whereby the Smiles rearrangement is completed. The rearrangement product-2-methylamino-N-methyl-N-(2,4-dinitrophenyl)acetamide hydrochloride-is present in the form of a mixture of Z and E isomers (ratio 1.9). The equilibrium constant of formation of the spiro adduct from 2-methylamino-N-methyl-N-(2,4-dinitrophenyl)acetamide hydrochloride is by 9 orders of magnitude lower than that found for the analogous trinitrophenylderivative. The rate-limiting step of the transformation of the Z-isomer into the spiro adduct consists in the isomerization Z ⇄ E. The E-isomer is cyclized with a half-life shorter than 1 ms.

Base-catalyzed formation of spiro adduct from N-methyl-N-(2,4,6-trinitrophenyl)glycinamide, the smiles rearrangement of the amide in methanol

1988 ◽  
Vol 53 (3) ◽  
pp. 601-618 ◽  
Author(s):  
Jaromír Kaválek ◽  
Vladimír Macháček ◽  
Makky M. M. Hassanien ◽  
Vojeslav Štěrba
Keyword(s):  
Proton Transfer ◽  
Equilibrium Constant ◽  
Ammonium Salt ◽  
Aliphatic Amine ◽  
Reaction Pathway ◽  
Smiles Rearrangement ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

The reaction of N-methyl-N-(2,4,6-trinitrophenyl)glycinamide (Ic with methoxide in methanol produces the spiro adduct IIc(A). In methanolic acetate buffers, the equilibrium is rapidly established between the spiro adduct IIc(A) and the dipolar ion of 2-methylamino-N-(2,4,6-trinitrophenyl)acetamide (IIIc(Z)). The equilibrium constant of the reaction IIIc(Z) ⇆ IIc(A) + H+ is by eight orders of magnitude greater than that of the analogous cyclization of 2-methylamino-N-methyl-N-(2,4,6-trinitrophenyl)acetamide to the spiro adduct. In chloracetate buffers, the dipolar ion is protonated to give 2-methylammonium-N-(2,4,6-trinitrohenyl)acetamide IIIc(K). The kinetics of the reversible reaction IIIc(Z) ⇆ IIc(A) + H+ has been studied in acetate buffers, aliphatic amine – ammonium salt buffers, and methoxide solutions. In all cases, the rate-limiting step was the proton transfer with half-lives in milliseconds. In more basic methanolic buffers (pH > 10) the rate-limiting step consists in the formation of spiro adduct from the zwiterion IIIc(Z) resulting from the protonation of the anion IIIc(A). n acetate buffers, the second reaction pathway via the cation IIIc(K) is predominant.

Wavelet Based Structural Analysis of Electroless Deposits in the Diffusion Limited Regime

1994 ◽  
Vol 367 ◽  
Author(s):  
A. Arneodo ◽  
F. Argoul ◽  
A. Kuhn ◽  
J.F. Muzy
Keyword(s):  
Electroless Deposition ◽  
Side Reactions ◽  
Statistical Features ◽  
Diffusion Limited ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Fractal Patterns ◽  
Rate Limiting ◽  
Comparative Structural Characterization

AbstractWe discuss the actual relevance of thin gap geometry electrodeposition to generate fractal patterns that mimic the morphology of Witten and Sander's diffusion-limited aggregates (DLA). Eliminating migration and convection, as well as electrochemical side reactions, we show that electroless deposition is a good candidate to meet the requirements for diffusion to be the rate limiting step of the growth process. We use the wavelet transform microscope to achieve a comparative structural characterization of both experimental electroless deposits and numerical DLA clusters. The fact that five-fold symmetry and Fibonacci hierarchical ordering are found as common predominant statistical features is, to our knowledge, the first demonstration, relying on an appropriate structural fractal analysis, of the existence of DLA morphologies in an experimental context.

scholarly journals The rate-limiting step in yeast PGK1 mRNA degradation is an endonucleolytic cleavage in the 3'-terminal part of the coding region.

1992 ◽  
Vol 12 (7) ◽  
pp. 2986-2996 ◽  
Author(s):  
P Vreken ◽  
H A Raué
Keyword(s):  
Half Life ◽  
Rnase H ◽  
Start Codon ◽  
Wild Type ◽  
Coding Region ◽  
Endonucleolytic Cleavage ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Nuclease Mapping ◽  
Rate Limiting

Insertion of an 18-nucleotide-long poly(G) tract into the 3'-terminal untranslated region of yeast phosphoglycerate kinase (PGK1) mRNA increases its chemical half-life by about a factor of 2 (P. Vreken, R. Van der Veen, V. C. H. F. de Regt, A. L. de Maat, R. J. Planta, and H. A. Raué, Biochimie 73:729-737, 1991). In this report, we show that this insertion also causes the accumulation of a degradation intermediate extending from the poly(G) sequence down to the transcription termination site. Reverse transcription and S1 nuclease mapping experiments demonstrated that this intermediate is the product of shorter-lived primary fragments resulting from endonucleolytic cleavage immediately downstream from the U residue of either of two 5'-GGUG-3' sequences present between positions 1100 and 1200 close to the 3' terminus (position 1251) of the coding sequence. Similar endonucleolytic cleavages appear to initiate degradation of wild-type PGK1 mRNA. Insertion of a poly(G) tract just upstream from the AUG start codon resulted in the accumulation of a 5'-terminal degradation intermediate extending from the insertion to the 1100-1200 region. RNase H degradation in the presence of oligo(dT) demonstrated that the wild-type and mutant PGK1 mRNAs are deadenylated prior to endonucleolytic cleavage and that the half-life of the poly(A) tail is three- to sixfold lower than that of the remainder of the mRNA. Thus, the endonucleolytic cleavage constitutes the rate-limiting step in degradation of both wild-type and mutant PGK1 transcripts, and the resulting fragments are degraded by a 5'----3' exonuclease, which appears to be severely retarded by a poly(G) sequence.

Solvolysis kinetics and mechanism of 3-methyl-1,3-thiazolidine-2,4-dione

1981 ◽  
Vol 46 (12) ◽  
pp. 3097-3103 ◽  
Author(s):  
Vladimír Macháček ◽  
Vojeslav Štěrba ◽  
Helena Zahradníčková
Keyword(s):  
Sodium Methoxide ◽  
Kinetics And Mechanism ◽  
Hydrolysis Kinetics ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Reaction Proceeds ◽  
One Step ◽  
Rate Limiting ◽  
Kinetics Of

The hydrolysis kinetics of 3-methyl-1,3-thiazolidine-2,4-dione have been studied in aqueous buffers and dilute NaOH solutions. The reaction proceeds via two base-catalyzed steps having different rates. In sodium methoxide solutions 3-methyl-1,3-thiazolidine-2,4-dione undergoes one-step methanolysis giving methyl thioglycolate anion as the final product. The rate-limiting step consists in decomposition of the anion CH3NCOSCH2COOCH3.

The rate-limiting step in yeast PGK1 mRNA degradation is an endonucleolytic cleavage in the 3'-terminal part of the coding region

1992 ◽  
Vol 12 (7) ◽  
pp. 2986-2996
Author(s):  
P Vreken ◽  
H A Raué
Keyword(s):  
Half Life ◽  
Rnase H ◽  
Start Codon ◽  
Wild Type ◽  
Coding Region ◽  
Endonucleolytic Cleavage ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Nuclease Mapping ◽  
Rate Limiting

Insertion of an 18-nucleotide-long poly(G) tract into the 3'-terminal untranslated region of yeast phosphoglycerate kinase (PGK1) mRNA increases its chemical half-life by about a factor of 2 (P. Vreken, R. Van der Veen, V. C. H. F. de Regt, A. L. de Maat, R. J. Planta, and H. A. Raué, Biochimie 73:729-737, 1991). In this report, we show that this insertion also causes the accumulation of a degradation intermediate extending from the poly(G) sequence down to the transcription termination site. Reverse transcription and S1 nuclease mapping experiments demonstrated that this intermediate is the product of shorter-lived primary fragments resulting from endonucleolytic cleavage immediately downstream from the U residue of either of two 5'-GGUG-3' sequences present between positions 1100 and 1200 close to the 3' terminus (position 1251) of the coding sequence. Similar endonucleolytic cleavages appear to initiate degradation of wild-type PGK1 mRNA. Insertion of a poly(G) tract just upstream from the AUG start codon resulted in the accumulation of a 5'-terminal degradation intermediate extending from the insertion to the 1100-1200 region. RNase H degradation in the presence of oligo(dT) demonstrated that the wild-type and mutant PGK1 mRNAs are deadenylated prior to endonucleolytic cleavage and that the half-life of the poly(A) tail is three- to sixfold lower than that of the remainder of the mRNA. Thus, the endonucleolytic cleavage constitutes the rate-limiting step in degradation of both wild-type and mutant PGK1 transcripts, and the resulting fragments are degraded by a 5'----3' exonuclease, which appears to be severely retarded by a poly(G) sequence.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting
Sign in / Sign up

Export Citation Format

Share Document