ChemInform Abstract: Formation of Glycosides by Epoxidation-Ring Closure of Open-Chain Hydroxyenol Ethers Obtained from Sugars.

ChemInform ◽  
1987 ◽  
Vol 18 (40) ◽  
Author(s):  
F. NICOTRA ◽  
L. PANZA ◽  
F. RONCHETTI ◽  
G. RUSSO ◽  
L. TOMA
Keyword(s):  
Ring Closure ◽  
Open Chain

Formation of glycosides by epoxidation-ring closure of open-chain hydroxyenol ethers obtained from sugars

1987 ◽  
pp. 1319 ◽  
Author(s):  
Francesco Nicotra ◽  
Luigi Panza ◽  
Fiamma Ronchetti ◽  
Giovanni Russo ◽  
Lucio Toma
Keyword(s):  
Ring Closure ◽  
Open Chain

scholarly journals A biomimetic approach to some specifically functionalized cyclic terpenoids.

2007 ◽  
Vol 54 (4) ◽  
pp. 679-693 ◽  
Author(s):  
Veaceslav Kulciţki
Keyword(s):  
Double Bond ◽  
Functional Groups ◽  
Ring Closure ◽  
Living Systems ◽  
Open Chain ◽  
Initial Substrate ◽  
Alpha Omega ◽  
Biomimetic Approach

The paper relates on the current advancements in the synthesis of complex cyclic terpenoids by superacidic induced cyclization of open chain precursors. It is shown that functional groups disposal in the initial substrate strongly influences the reaction outcome. Possible variations of the investigated compound structures include particularly alpha-functionalization and alpha,omega-bifunctionalization. This approach allowed a selective initiation of cyclization sequence from an internal double bond or suspending the ring closure cascade to partially cyclized compounds. The reported synthetic schemes are attempts to mimic the biogenetical processes postulated in the living systems.

scholarly journals Reverse C-glycosidase reaction provides C-nucleotide building blocks of xenobiotic nucleic acids

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Martin Pfeiffer ◽  
Bernd Nidetzky
Keyword(s):  
Synthetic Biology ◽  
Nucleic Acids ◽  
Enzymatic Reaction ◽  
Building Blocks ◽  
Cascade Reactions ◽  
Ring Closure ◽  
One Pot ◽  
Open Chain ◽  
Nucleotide Synthesis ◽  
Nucleotide Triphosphates

AbstractC-Analogues of the canonical N-nucleosides have considerable importance in medicinal chemistry and are promising building blocks of xenobiotic nucleic acids (XNA) in synthetic biology. Although well established for synthesis of N-nucleosides, biocatalytic methods are lacking in C-nucleoside synthetic chemistry. Here, we identify pseudouridine monophosphate C-glycosidase for selective 5-β-C-glycosylation of uracil and derivatives thereof from pentose 5-phosphate (d-ribose, 2-deoxy-d-ribose, d-arabinose, d-xylose) substrates. Substrate requirements of the enzymatic reaction are consistent with a Mannich-like addition between the pyrimidine nucleobase and the iminium intermediate of enzyme (Lys166) and open-chain pentose 5-phosphate. β-Elimination of the lysine and stereoselective ring closure give the product. We demonstrate phosphorylation-glycosylation cascade reactions for efficient, one-pot synthesis of C-nucleoside phosphates (yield: 33 – 94%) from unprotected sugar and nucleobase. We show incorporation of the enzymatically synthesized C-nucleotide triphosphates into nucleic acids by RNA polymerase. Collectively, these findings implement biocatalytic methodology for C-nucleotide synthesis which can facilitate XNA engineering for synthetic biology applications.

Intermediates from ring-opening reactions. Reactions of 2-chloro-5-nitropyridine and 2-chloro-3-nitropyridine with deuteroxide ion in selected solvents

1984 ◽  
Vol 62 (6) ◽  
pp. 1120-1123 ◽  
Author(s):  
John D. Reinheimer ◽  
Nicolas Sourbatis ◽  
Robert L. Lavallee ◽  
Douglas Goodwin ◽  
George L. Gould
Keyword(s):  
Ring Opening ◽  
Pyridine Ring ◽  
Ring Closure ◽  
Polar Solvents ◽  
Open Chain ◽  
Decomposition Products ◽  
Aqueous Sodium ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Kinetics Of

Open chain intermediates from the ring-opening reaction of aqueous sodium deuteroxide (2 mol) with 2-chloro-5-nitropyridine (1 mol) and 2-chloro-3-nitropyridine (1 mol) were isolated. These intermediates were purified, analyzed for elemental composition, and characterized by various spectrophotometric techniques. The intermediate formed from 2-chloro-5-nitropyridine and two equivalents of deuteroxide ion reacts with additional deuteroxide in D2O in various polar solvents to reclose the pyridine ring. The kinetics of the ring closure reaction are reported and are supplemented with observations of salt and solvent effects upon the rate of closure. In addition, a mechanism for the ring closure is presented. The intermediate formed from 2-chloro-3-nitropyridine did not undergo a similar ring closure when reacted with additional deuteroxide, but instead formed various decomposition products. A reason for the failure of this ring closure is suggested.

Kinetische Analyse zur Umwandlung von Oxirenen oder Thiirenen und ihren offenkettigen Valenzisomeren / Kinetic Analysis for the Conversion of Oxirenes or Thiirenes and their Open-Chain Valence Isomers

1980 ◽  
Vol 35 (8) ◽  
pp. 1040-1048 ◽  
Author(s):  
Herbert Meier ◽  
Heinz Kolshorn
Keyword(s):  
Experimental Data ◽  
Kinetic Models ◽  
Ring Opening ◽  
Product Distribution ◽  
Ring Closure ◽  
Quantitative Interpretation ◽  
Open Chain ◽  
Energy Profiles ◽  
Ring Opening Reactions ◽  
Kinetische Analyse

Abstract Ring closure and ring opening reactions possess an outstanding significance for the formation and reactivity of antiaromatic heterocycles like oxirenes and thiirenes. The valence isomerisations 2 ⇆ 1 ⇆ 2' can be controlled by the product distribution 2 → P/2' → P'. A quantitative interpretation of many experimental data, published in the last years, is given on the basis of a few kinetic models, which consider thermal and photochemical pathways. Possible energy profiles of single hypersurfaces (S0 or S1) and the transition between different hypersurfaces (S1 → S0) are the most important features of these models.

Fundamentals in the catalytic ring closure of open chain hydrocarbons

1939 ◽  
Vol 35 ◽  
pp. 921 ◽  
Author(s):  
Hugh S. Taylor ◽  
John Turkevich
Keyword(s):  
Ring Closure ◽  
Open Chain

Thermo- and photochromic dyes: indolino-benzospiropyrans. Part 1. UV–VIS spectroscopic studies of 1,3,3-spiro(2H-1-benzopyran-2,2′-indolines) and the open-chain merocyanine forms; solvatochromism and medium effects on spiro ring formation

1991 ◽  
Vol 69 (12) ◽  
pp. 1940-1947 ◽  
Author(s):  
Sam-Rok Keum ◽  
Mun-Suk Hur ◽  
Peter M. Kazmaier ◽  
Erwin Buncel
Keyword(s):  
Transition State ◽  
Ultraviolet Irradiation ◽  
Ground State ◽  
Phenyl Group ◽  
Spectroscopic Studies ◽  
Ring Closure ◽  
Medium Effects ◽  
Open Chain ◽  
Semi Empirical ◽  
Electronic Character

A kinetic and ultraviolet–visible study of a series of thermo- and photochromic dyes is reported. Ultraviolet irradiation of the indolino-benzospiropyran derivatives 1′–4′ leads to their transformation to the open-chain, colored merocyanine forms, which undergo thermal ring closure into the colorless spiro forms. The rate of this ring closure has been determined in different solvents. Plots of log (rate) vs. the solvent parameter ET are linear but are dependent on the nature of the substituent in the phenyl moiety, which yields information on the electronic character of the ground state (IIa↔IIb) and the transition state. The ring-closure process is characterized by a zwitterionic type transition state, TS3. The merocyanine dyes exhibit a significant solvatochromic effect, which unexpectedly shows sensitivity to substituents on the phenyl group. This observation finds explanation through semi-empirical molecular orbital (MOPAC) calculations. The MOPAC calculations also predict that the most stable configurational isomer of the merocyanines is the CTTC form. Key words: indolino-benzospiropyran–merocyanine interconversion, photochromic–solvatochromic dyes.

THE Hg 6(3P1) PHOTOSENSITIZED DECOMPOSITION OF CYCLOHEXENE VAPOR

1965 ◽  
Vol 43 (5) ◽  
pp. 1329-1337 ◽  
Author(s):  
G. R. De Maré ◽  
O. P. Strausz ◽  
H. E. Gunning
Keyword(s):  
Triplet State ◽  
Rate Constant ◽  
Bond Cleavage ◽  
Product Distribution ◽  
Ring Closure ◽  
Rate Equations ◽  
Open Chain ◽  
Fragmentation Reactions ◽  
Triplet Biradicals ◽  
Kinetic Features

The reaction follows the pattern established for the triplet state reactions of olefins in general. The major products, ethylene, 1,3-butadiene, vinylcyclobutane, cyclohexane, various C12-compounds, and polymer, can best be accounted for by the allylic C—H and C—C bond cleavage of the primary triplet biradicals and the ring closure and fragmentation reactions of the resulting open chain biradicals. At least three types of triplet state species must be involved in the mechanism. The rate equations, developed on the assumed mechanism, satisfactorily describe the observed product distribution and kinetic features of the system and permit the estimation of the elementary rate constant values and the lifetimes of the various transient biradicals involved. Preliminary experiments with cycloheptene indicate that vinylcyclopentane is an important product.

N-ACYLATED AMINO ACID IMINO CHLORIDES AND A QUALITATIVE STUDY OF RING CLOSURE AMONG N-ACYLAMINO ACID CHLORIDES

1957 ◽  
Vol 35 (9) ◽  
pp. 1031-1038 ◽  
Author(s):  
Edward Ronwin
Keyword(s):  
Amino Acid ◽  
Nitrogen Atom ◽  
Ring Closure ◽  
Acid Chlorides ◽  
Reaction Intermediates ◽  
Open Chain ◽  
Imino Acid ◽  
Infrared Spectral ◽  
Salt Forms ◽  
Predominant Product

Products have been isolated from the treatment of N-acylaminoacetonitriles with dry hydrogen chloride which are either the open-chain imino acid chlorides or the dissociated salt forms. These compound types have often been postulated as reaction intermediates but never isolated with an unsubstituted nitrogen atom. In the unsubstituted condition they are analogous to regular or oxygen acid chlorides.Several N-acylamino acids were treated with PCl5 and the reaction solutions were subjected to infrared spectral analyses. The results indicate that the open-chain acid chloride, rather than the azlactone salt, is the predominant product obtained with the compounds used in this investigation.

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