Preparation of E-Secolupane Acids and Lactones

2003 ◽  
Vol 68 (4) ◽  
pp. 751-778 ◽  
Author(s):  
Iva Tišlerová ◽  
Eva Klinotová ◽  
Jiří Klinot ◽  
Jan Sejbal ◽  
Martin Rejzek ◽  
...  
Keyword(s):  
Dicarboxylic Acids ◽  
Epoxide Ring ◽  
Carboxylic Group ◽  
Reaction Conditions ◽  
Dioic Acid ◽  
Hydroxymethyl Group ◽  
Nmr Techniques ◽  
Derivatives Of ◽  
Ring Conformations ◽  
C Nmr

Anhydrides of 3β,28-diacetoxy-21,22-secolup-18-ene-21,22-dioic acid (1) and (19R)-3β,28-diacetoxy-18β,19-epoxy-21,22-secolupane-21,22-dioic acid (11) undergo alkaline hydrolysis yielding the corresponding dicarboxylic acids. Depending on reaction conditions, these acids are further transformed yielding various lactones, liberating C-28 hydroxymethyl group, or undergoing decarboxylation leading to nor derivatives. This method has been used to prepare a diverse series of E-secolupane derivatives including lactonoacids (e.g. 2 and 15), lactones (4, 16 and 17), 28-nor derivatives (3 and 6) and 21,28-dinor derivatives (12 and 13). Derivatives of (19R)-3β,28-dihydroxy-18β,19-epoxy-21,22-secolupane-21,22-dioic acid 21,28-lactone (15c), bearing a free carboxylic group, are labile and can only be isolated as the corresponding dilactones 17. The C-22 carboxylic group forms a β-lactone by a nucleophilic α-directed attack on the C-18 epoxide ring carbon atom resulting in (19R)-3β,19-dihydroxy-21,22-secolupane-21,28:22,18α-dilactone (17b) and related derivatives. The structure and stereochemistry of the compounds discussed in this contribution were derived from IR, MS, 1H and 13C NMR spectra (1D and 2D COSY, TOCSY, NOESY, HSQC, HMBC). Using these NMR techniques and measuring the solvent influence on the IR carbonyl stretching frequencies of the dilactones 17, an equilibrium between the two E-ring conformations was shown to exist.

scholarly journals Switchable highly regioselective synthesis of 3,4-dihydroquinoxalin-2(1H)ones from o-phenylenediamines and aroylpyruvates

2017 ◽  
Vol 13 ◽  
pp. 1350-1360 ◽  
Author(s):  
Juraj Dobiaš ◽  
Marek Ondruš ◽  
Gabriela Addová ◽  
Andrej Boháč
Keyword(s):  
Regioselective Synthesis ◽  
Reaction Conditions ◽  
Reaction Selectivity ◽  
Pharmaceutical Applications ◽  
Wide Range ◽  
Nmr Techniques ◽  
Derivatives Of ◽  
Optimal Reaction

3-Acylmethylidene-3,4-dihydroquinoxalin-2(1H)-ones are compounds which possess a wide range of physical and pharmaceutical applications. These compounds can be easily prepared by cyclocondensation of o-phenylenediamines and aroylpyruvates. Unsymmetrically substituted o-phenylenediamines can be obtained form regioisomeric mixtures of 3,4-dihydroquinoxalin-2(1H)-ones. It is often quite difficult to get a pure regioisomer and determine its structure without controlling the reaction selectivity and exploitation of complex NMR techniques (HSQC, NOESY, HMBC). This article examines the regioselectivity of the cyclocondensation between six monosubstituted o-phenylenediamines (-OMe, -F, -Cl, -COOH, -CN, -NO2) and the derivatives of p-chlorobenzoylpyruvate (ester or acid) which we studied. Six regioisomeric 3,4-dihydroquinoxalin-2(1H)-one pairs were selectively prepared and characterised. Based on our experiences, a simplified methodology for determining the structure of the regioisomers was proposed. We developed two general and highly selective methodologies starting from the same o-phenylenediamines and activated 4-chlorobenzoylpyruvates (ester or acid) enabling switching of 3,4-dihydroquinoxalin-2(1H)-one regioselectivity in a predictable manner. For comparison, all regioselective cyclocondensations were performed with the same standardized conditions (DMF, rt, 3 days), differing only by the additives p-TsOH or HOBt/DIC (hydroxybenzotriazole/N,N’-diisopropylcarbodiimide). Both selected methods are simple, general and highly regioselective (72–97%). A mechanism for the regioselectivity was also proposed and discussed. This study can be used as a guide when choosing the most optimal reaction conditions for the synthesis of the desired 3,4-dihydroquinoxalin-2(1H)-one regioisomers with the best selectivity. The demonstrated methodologies in this article may also be applied to differently substituted 3,4-dihydroquinoxalin-2(1H)-ones in general, which could expand the synthetic impact of our results.

scholarly journals Heterocyclic Hypervalent Iodine(III) Compounds with Fused Benziodazole and Tetrazole Rings (I-Substituted Tetrazolo[1,5-b][1,2]Benziodazoles)

2020 ◽  
Author(s):  
Rajesh Kumar ◽  
Kapil Dev Sayala ◽  
Lejla Lejla Camdzic ◽  
Maxime Siegler ◽  
Avichal Vaish ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hypervalent Iodine ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Reaction Conditions ◽  
Thermal Stabilities ◽  
X Ray ◽  
X Ray Crystallography ◽  
Derivatives Of ◽  
C Nmr

A series of heterocyclic hypervalent (HV) iodine(III) compounds containing fused tetrazole and benziodazole rings, i.e., derivatives of benziodazolotetrazole (BIAT) with various ligands (L) attached to the iodine atom (BIAT-L) were prepared and studied. They were characterized by <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy, ESI-HRMS, and X-ray crystallography. The thermal stabilities of all BIAT derivatives (L= Cl, OH, OAc, OMe) were studied and the degradation patterns as well as the enthalpies of degradation were measured by thermal gravimetric analysis coupled with differential scanning calorimetry. The reaction of various alkenes with BIAT-Cl in the presence of Cu(OTf)<sub>2</sub> at room temperature yielded chloro-tetrazolylated products. The oxidation of thioanisole with BIAT-Cl under various reaction conditions is also reported.

scholarly journals Heterocyclic Hypervalent Iodine(III) Compounds with Fused Benziodazole and Tetrazole Rings (I-Substituted Tetrazolo[1,5-b][1,2]Benziodazoles)

2020 ◽  
Author(s):  
Rajesh Kumar ◽  
Kapil Dev Sayala ◽  
Lejla Lejla Camdzic ◽  
Maxime Siegler ◽  
Avichal Vaish ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hypervalent Iodine ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Reaction Conditions ◽  
Thermal Stabilities ◽  
X Ray ◽  
X Ray Crystallography ◽  
Derivatives Of ◽  
C Nmr

A series of heterocyclic hypervalent (HV) iodine(III) compounds containing fused tetrazole and benziodazole rings, i.e., derivatives of benziodazolotetrazole (BIAT) with various ligands (L) attached to the iodine atom (BIAT-L) were prepared and studied. They were characterized by <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy, ESI-HRMS, and X-ray crystallography. The thermal stabilities of all BIAT derivatives (L= Cl, OH, OAc, OMe) were studied and the degradation patterns as well as the enthalpies of degradation were measured by thermal gravimetric analysis coupled with differential scanning calorimetry. The reaction of various alkenes with BIAT-Cl in the presence of Cu(OTf)<sub>2</sub> at room temperature yielded chloro-tetrazolylated products. The oxidation of thioanisole with BIAT-Cl under various reaction conditions is also reported.

scholarly journals Catalytic Hydrogenation Products of Aromatic and Aliphatic Dicarboxylic Acids

2019 ◽  
Vol 31 (5) ◽  
pp. 1137-1142
Author(s):  
Sunil B. Shinde ◽  
Raj M. Deshpande
Keyword(s):  
Benzoic Acid ◽  
Catalytic Hydrogenation ◽  
Phthalic Acid ◽  
Dicarboxylic Acids ◽  
Carboxylic Group ◽  
Reaction Conditions ◽  
Aromatic Dicarboxylic Acids ◽  
Aliphatic Dicarboxylic Acids ◽  
Lower Temperature ◽  
Al2o3 Catalyst

Hydrogenation of aromatic dicarboxylic acids gave 100 % selectivity to respective cyclohexane dicarboxylic acid with 5 % Pd/C catalyst. 5 % Ru/C catalyst was observed to give over hydrogenation products at 493 K and at lower temperature (453 K) the selectivity for cyclohexane dicarboxylic acids was increased. Hydrogenation of phthalic acid with Ru-Sn/Al2O3 catalyst was observed to give phthalide instead of 1,2-benzene dimethanol or 2-hydroxy methyl benzoic acid. Ru-Sn/Al2O3 catalyst selectively hydrogenated the carboxylic group of cyclohexane dicarboxylic acids to give cyclohexane dimethanol. Use of proper catalysts and reaction conditions resulted in desired products.

Thermal cyclocondensations of 3-N(4- and 5-benzimidazolyl and benztriazolyl)amino derivatives of 2-propenoic acid

1987 ◽  
Vol 52 (12) ◽  
pp. 2918-2925 ◽  
Author(s):  
Viktor Milata ◽  
Dušan Ilavský
Keyword(s):  
Uv Spectra ◽  
Propenoic Acid ◽  
Amino Derivatives ◽  
Derivatives Of ◽  
C Nmr ◽  
Ir And Uv Spectra

The cyclization of 3-N(4- and 5-benzimidazolyl and benztriazolyl)amino-2-cyano- and 2-ethoxycarbonyl-2-propenoate esters Ia, b-IVa, b under the conditions of the Gould-Jacobs reaction leads to angularly ring-fused substituted imidazo or triazolo[4,5-f] (V, VI) and [4,5-h] (VII, VIII) quinolines, respectively. The esters Vb-VIIIb have been transformed into the corresponding chloroderivatives Vc-VIIIc. 3-N(5-Benzimidazolyl and 5-benztriazolyl)amino-2-cyano-2-propenenitriles are cyclized in the presence of aluminium(III) chloride to give the aminoquinolines Vd, VId. The structure of the products has been characterized by their 1H, 13C NMR, IR, and UV spectra.

Cleavage of the Epimines of 1,6-Anhydrohexoses with Fluoride Anion

2005 ◽  
Vol 70 (12) ◽  
pp. 2075-2085 ◽  
Author(s):  
Jiří Kroutil ◽  
Klára Jeništová
Keyword(s):  
Fluoride Anion ◽  
Ring Cleavage ◽  
Protecting Group ◽  
Reaction Conditions ◽  
Aziridine Ring ◽  
Cleavage Reactions ◽  
Derivatives Of ◽  
Fluoro Derivatives

Aziridine ring cleavage reactions of five N-nosylepimines (2-6) having D-talo, D-galacto, D-manno, and D-allo configurations with potassium hydrogendifluoride under various reaction conditions have been performed. The cleavage regioselectively afforded diaxial isomers of vicinal amino-fluoro derivatives of 1,6-anhydro-β-D-gluco- and mannopyranose 7-11 in 51-94% yields. Removal of 2-nitrobenzenesulfonyl protecting group with benzenethiol has been attempted in the case of compound 10.

A review of lignin hydrogen peroxide oxidation chemistry with emphasis on aromatic aldehydes and acids

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ajinkya More ◽  
Thomas Elder ◽  
Zhihua Jiang
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidative Degradation ◽  
Reaction Medium ◽  
Dicarboxylic Acids ◽  
Aromatic Aldehydes ◽  
Product Distribution ◽  
Reaction Conditions ◽  
Alkaline Conditions ◽  
The Stability ◽  
Oxidation Chemistry

Abstract This review discusses the main factors that govern the oxidation processes of lignins into aromatic aldehydes and acids using hydrogen peroxide. Aromatic aldehydes and acids are produced in the oxidative degradation of lignin whereas mono and dicarboxylic acids are the main products. The stability of hydrogen peroxide under the reaction conditions is an important factor that needs to be addressed for selectively improving the yield of aromatic aldehydes. Hydrogen peroxide in the presence of heavy metal ions readily decomposes, leading to minor degradation of lignin. This degradation results in quinones which are highly reactive towards peroxide. Under these reaction conditions, the pH of the reaction medium defines the reaction mechanism and the product distribution. Under acidic conditions, hydrogen peroxide reacts electrophilically with electron rich aromatic and olefinic structures at comparatively higher temperatures. In contrast, under alkaline conditions it reacts nucleophilically with electron deficient carbonyl and conjugated carbonyl structures in lignin. The reaction pattern in the oxidation of lignin usually involves cleavage of the aromatic ring, the aliphatic side chain or other linkages which will be discussed in this review.

Flavon- and Flavonolglycosides from Achillea pannonica Scheele

2001 ◽  
Vol 56 (7-8) ◽  
pp. 521-525 ◽  
Author(s):  
Denata Kasaj ◽  
Liselotte Krenn ◽  
Sonja Prinz ◽  
Antje Hüfner ◽  
Shi Shan Yuc ◽  
...  
Keyword(s):  
Methanolic Extract ◽  
2D Nmr ◽  
Flavonoid Glycosides ◽  
Spectroscopic Methods ◽  
Esi Ms ◽  
Aerial Parts ◽  
Nmr Techniques ◽  
Chemotaxonomic Study ◽  
First Time ◽  
C Nmr

The detailed investigation of a methanolic extract of aerial parts of Achillea pannonica SCHEELE. within a chemotaxonomic study led to the isolation of 6 flavonoid glycosides. Besides rutin, apigenin-7-O-glucopyranoside, luteolin-7-O-glucopyranoside, apigenin-7-O-rutinoside and acacetin-7-O-rutinoside, an unusual flavondiglucoside was isolated. Its structure was established by UV, 1HNMR and 13C NMR spectroscopic methods including 2D-NMR techniques and ESI-MS as luteolin-7,4′-O-β-diglucoside. This substance is reported for the first time in the genus Achillea. Chemotaxonomic aspects are discussed briefly

scholarly journals Enzymatic synthesis and phosphorolysis of 4(2)-thioxo- and 6(5)-azapyrimidine nucleosides by E. coli nucleoside phosphorylases

2016 ◽  
Vol 12 ◽  
pp. 2588-2601 ◽  
Author(s):  
Vladimir A Stepchenko ◽  
Anatoly I Miroshnikov ◽  
Frank Seela ◽  
Igor A Mikhailopulo
Keyword(s):  
Purine Nucleoside Phosphorylase ◽  
Reaction Conditions ◽  
E Coli ◽  
No Formation ◽  
Structural Peculiarities ◽  
Substrate Properties ◽  
Nucleoside Phosphorylases ◽  
Derivatives Of

The trans-2-deoxyribosylation of 4-thiouracil (4SUra) and 2-thiouracil (2SUra), as well as 6-azauracil, 6-azathymine and 6-aza-2-thiothymine was studied using dG and E. coli purine nucleoside phosphorylase (PNP) for the in situ generation of 2-deoxy-α-D-ribofuranose-1-phosphate (dRib-1P) followed by its coupling with the bases catalyzed by either E. coli thymidine (TP) or uridine (UP) phosphorylases. 4SUra revealed satisfactory substrate activity for UP and, unexpectedly, complete inertness for TP; no formation of 2’-deoxy-2-thiouridine (2SUd) was observed under analogous reaction conditions in the presence of UP and TP. On the contrary, 2SU, 2SUd, 4STd and 2STd are good substrates for both UP and TP; moreover, 2SU, 4STd and 2’-deoxy-5-azacytidine (Decitabine) are substrates for PNP and the phosphorolysis of the latter is reversible. Condensation of 2SUra and 5-azacytosine with dRib-1P (Ba salt) catalyzed by the accordant UP and PNP in Tris∙HCl buffer gave 2SUd and 2’-deoxy-5-azacytidine in 27% and 15% yields, respectively. 6-Azauracil and 6-azathymine showed good substrate properties for both TP and UP, whereas only TP recognizes 2-thio-6-azathymine as a substrate. 5-Phenyl and 5-tert-butyl derivatives of 6-azauracil and its 2-thioxo derivative were tested as substrates for UP and TP, and only 5-phenyl- and 5-tert-butyl-6-azauracils displayed very low substrate activity. The role of structural peculiarities and electronic properties in the substrate recognition by E. coli nucleoside phosphorylases is discussed.

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