Synthèse d'isoxazoles substitués en α de l'oxygène et d'isoxazoles substitués en α de l'azote et de l'oxygène par des chaînes alkyle ou alcényle

1991 ◽  
Vol 69 (4) ◽  
pp. 625-631 ◽  
Author(s):  
Jean-Claude Cherton ◽  
M. Lanson ◽  
D. Ladjama ◽  
N. Lefebvre ◽  
Z. Vossough ◽  
...  
Keyword(s):  
Oxygen Atom ◽  
Key Words ◽  
Dipolar Cycloaddition ◽  
Side Chains ◽  
Alternative Route ◽  
Methyl Group ◽  
Additional Step ◽  
Alkenyl Chain ◽  
Convenient Route

Two series of isoxazoles substituted by long alkyl or alkenyl chains in the α position with respect to the oxygen atom or in the α position with respect to the two heteroatoms have been synthesized. Starting from 3,5-dimethylisoxazole, the regioselective metalation/alkylation on the α-O methyl group was a very convenient route to a large variety of "α-O substituted isoxazoles". When applied to α-O methylated isoxazoles bearing an α-N alkenyl chain the same method provides an original unequivocal approach to 3,5-dialkenyl isoxazoles. An alternative route to these compounds, despite the formation of di-isoxazoline as by-product and an additional step corresponding to the oxidation of the intermediate isoxazoline, is the 1,3-dipolar cycloaddition, by using terminal dienes as dipolarophiles with alkenyl dipoles. Nevertheless, the cycloaddition between monoalkylated alcynes and alkylated dipoles remains the most straightforward synthesis of 3,5-dialkyl isoxazoles. Key words: isoxazoles, alkenyl side chains, metalation–alkylation, regioselectivity.

Synthèse d'isoxazoles substitués en α de l'azote par une chaine alkyle ou alcényle

1990 ◽  
Vol 68 (8) ◽  
pp. 1271-1276 ◽  
Author(s):  
Jean-Claude Cherton ◽  
Marc Lanson ◽  
Daïf Ladjama ◽  
Yvette Guichon ◽  
Jean-Jacques Basselier
Keyword(s):  
Vinyl Acetate ◽  
Nitrile Oxide ◽  
Side Chain ◽  
Dipolar Cycloaddition ◽  
Side Chains ◽  
Alkyl Side Chain ◽  
Magnesium Compounds ◽  
Convenient Route ◽  
General Method ◽  
Convenient Access

Several syntheses of special isoxazoles bearing a long alkyl or alkenyl side chain in the α position of the nitrogen are presented. A very convenient route in the case of an alkyl side chain is the classical 1,3-dipolar cycloaddition of a nitrile-oxide to a vinyl acetate. Although it is a rather long approach, the reaction of hydroxylamine with enone-epoxides represents a new and unequivocal method compatible with alkenyl side chains. The isomerisation of the easily synthesized isoxazoles bearing such substitutents α to the oxygen, by the reaction of their isoxazolium salts with hydroxylamine, is a fast and general method. Another very convenient access to "α-N substituted" isoxazoles is the coupling of magnesium compounds with 3-bromomethyl 5-methyl isoxazole. Keywords: isoxazoles, substitution in the α position of nitrogen.

Remarkable kinetic stability of α-thiocarbamoyl substituted 4-methoxybenzylcations

1998 ◽  
Vol 76 (12) ◽  
pp. 1910-1915 ◽  
Author(s):  
Robert A McClelland ◽  
Victoria E Licence ◽  
John P Richard ◽  
Kathleen B Williams ◽  
Shrong-Shi Lin
Keyword(s):  
Key Words ◽  
Strong Interaction ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Visible Absorption ◽  
Methyl Group ◽  
Thioamide Group ◽  
Azide Ion ◽  
Uv Visible ◽  
Leaving Groups

4-Methoxybenzyl cations bearing α-(N,N-dimethylcarbamoyl) and α-(N,N-dimethylthiocarbamoyl) substituents have been generated photochemically upon irradiation of precursors with pentafluorobenzoate or 4-methoxybenzoate leaving groups. The ions have been observed with flash photolysis in 40:60 acetonitrile:water and in 50:50 methanol:water, and rate constants were measured for their decay in solvent alone and for their capture by azide ion. The cations so studied and their lifetimes in 40% acetonitrile are 6, ArC+H-CONMe2, 0.6 μs; 2, ArC+H-CSNMe2, 7 ms; and 4, ArC+(CH3)-CSMe2, 6 ms, where Ar = 4-MeOC6H4. The cation 4 reacts with solvent by elimination of a proton from the α-methyl group, and the rate constant for solvent addition must be less than 1 s-1. The CSNMe2 substituted cations are 105-107-fold longer lived than analogs where the thioamide group has been replaced with an α-methyl. The UV-visible absorption spectra of these two cations also show significant differences from those of typical 4-methoxybenzyl cations. Thus, both the lifetimes and spectra point to a strong interaction of the benzylic centre with the thioamide group. Key words: flash photolysis, thiocarbamoyl stabilized carbocation, photosolvolysis.

Application of Laser-Excited Raman Spectroscopy to Organic Chemistry. II. Conformers of Some Isochromans

1970 ◽  
Vol 24 (1) ◽  
pp. 42-43 ◽  
Author(s):  
Stanley K. Freeman
Keyword(s):  
Organic Chemistry ◽  
Raman Spectroscopy ◽  
Oxygen Atom ◽  
Aromatic Ring ◽  
Raman Spectra ◽  
Liquid State ◽  
Methyl Group ◽  
Methyl Analog

Raman spectra of 4-methyl isochroman and its aromatic ring substituted derivatives indicate the presence of two conformers in the liquid state and only one in the solid, while the 1- and 3-methyl analog assume one conformation only in both states. The presence of a methyl group adjacent to the ring oxygen atom sterically prevents adoption of one of the two possible conformations due to 1,3-interaction. No such restriction is imposed on the 4-methyl compounds.

scholarly journals Synthesis of Novel 1,2,3-Triazole-Dihydropyrimidinone Hybrids Using Multicomponent 1,3-Dipolar Cycloaddition (Click)–Biginelli Reactions: Anticancer Activity

Synlett ◽  
2020 ◽  
Vol 31 (06) ◽  
pp. 615-621
Author(s):  
Elisabete P. Carreiro ◽  
Ana M. Sena ◽  
Adrián Puerta ◽  
José M. Padrón ◽  
Anthony J. Burke
Keyword(s):  
Breast Cancer ◽  
Lung Cancer ◽  
Heterocyclic Ring ◽  
Small Cell ◽  
Dipolar Cycloaddition ◽  
Cancer Cervix ◽  
Small Cell Lung ◽  
Methyl Group ◽  
Cancer Breast ◽  
Biginelli Reactions

In this work, 21 novel (1,4-disubstituted 1,2,3-triazole)-dihydropyrimidinone (1,2,3-trzl-DHPM) type hybrids were synthesized and characterized. These were divided into two types: hybrids A (5 in total) containing the dihydropyrimidinone heterocyclic ring decorated with a 1,4-disubstituted 1,2,3-triazole in the C-5 position [these compounds were accessed by a multicomponent copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) (or click)–Biginelli reactions with satisfactory yields (39–57%)] and hybrids B (16 in total) containing two 1,2,3-triazole units in the C-5 and C-6 methyl position of the DHPM. Hybrids B were synthesized via functionalization of the C-6 methyl group of hybrids A, a multistep sequence of reactions was used that included bromination, azidation, and a CuAAC. Hybrids B were obtained in very good to excellent yields (up to 99%). Some hybrids A and B were evaluated for their antiproliferative activity against different cancer cell lines that included A549 and SW1573 (non-small-cell lung), HBL-100 and T-47D (breast), HeLa (cervix) and WiDr (colon). Three of these hybrids were potent cell proliferation inhibitors of non-small-cell lung cancer, cervix cancer, breast cancer, and colon cancer.

Asymmetric synthesis of taxol arid taxotère side chains by enolate hydroxylation

1996 ◽  
Vol 74 (4) ◽  
pp. 621-624 ◽  
Author(s):  
Stephen Hanessian ◽  
Jean-Yves Sancéau
Keyword(s):  
Asymmetric Synthesis ◽  
Key Words ◽  
Side Chains ◽  
Key Words Taxol ◽  
Phosphoric Triamide ◽  
Enolate Hydroxylation

We report an asymmetric synthesis of the taxol and taxotère side chains by hydroxylation of enolates derived from N-substitued methyl 3-amino-3-phenyl propionate with the oxodiperoxymolybdenum (pyridine) (hexamethyl phosphoric triamide) complex (MoOPH). Key words: taxol and taxotère side chains, hydroxylation.

scholarly journals Cycloadditionen, XXI [1]. 2-Methyl-2,3-butadiensäure-arylester; Synthese und thermische Reaktivität / Cycloadditions, XXI [1] Aryl 2-methyl-2,3-butadienoates; Synthesis and Thermal Reactivity

1994 ◽  
Vol 49 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Gerhard Himbert ◽  
Dieter Fink ◽  
Martina Stürm
Keyword(s):  
Acid Chloride ◽  
Catalytic Amount ◽  
Diels Alder ◽  
Alternative Route ◽  
Substituted Phenols ◽  
Enol Ether ◽  
Methyl Group ◽  
Thermal Reactivity ◽  
Tricyclic Ketone

Abstract The substituted phenyl, 1-naphthyl or the 9-anthrylmethyl esters of the 2-methyl-(or 2-phenyl)-2,3-alkadienoic acids (see 4 a -g , 9 a -d and 12a,b) are synthesized by condensation of the allenic acids 2 a -d with the substituted phenols 3 a -g , with 1-naphthol (8) or with 9-anthrylmethanol (11) in the presence of dicyclohexyl carbodiimide (DCC) and a catalytic amount of 4-dimethylaminopyridine (DMAP). An alternative route is the reaction of the acid chloride la with the phenols 3 a -c (see formation of 4 a -c) in the presence of triethylamine. All these compounds (except 12a) undergo the intramolecular Diels-Alder (IMDA)-reaction to form the tricycles 6 a -g , 10 a-d and 13. The enol ether 6a is hydrolized during chromatography to give the tricyclic ketone 7. The influence of the geminal methyl group on the rate of the IMDA-reaction is investigated. 9-Anthryl-and (2,4,6-cycloheptatrien-1-on-2-yl)-2-methyl-2,3-butadienoate (15, 17), formed by reaction of 2-methyl-2,3-butadienoyl chloride (1a) with 9-anthrone (14) and 2-tropolone (16) isomerise spontaneously to the IMDA-products 19 and 18.

scholarly journals Synthesis of Some Biologically Important 3-Oxacepham Derivatives

1970 ◽  
Vol 5 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Mohammad Rafiqul Islam ◽  
Mohammad Nurnabi ◽  
AM Sarwaruddin Chowdhury ◽  
Mohammad Mehdi Masud
Keyword(s):  
Key Words ◽  
Full Text ◽  
Crystallographic Analysis ◽  
High Yield ◽  
Methyl Group ◽  
X Ray ◽  
Tert Butyl ◽  
Relative Stereochemistry

The 6H-oxathiazines 1a-e having imine moiety underwent [2+2] cycloaddition with phenoxyacetylchloride in the presence of Et3N to give β-lactam derivatives 2a-e in high yield. The X-ray crystallographic analysis revealed the relative stereochemistry that the substituents at C-2 and C-4 were cis configurated. The subtituents at C-6 and C-7 were also cis to each other. However, the 6H-oxathiazines 1f-i containing tert-butyl or methyl group at C-4 did not undergo the cycloaddition. Key words: Azetedinone, β-lactam, oxacepham, cycloaddition, imine, ketene, oxathiazine. Dhaka Univ. J. Pharm. Sci. Vol.5(1-2) 2006 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

Colicinogeny of O157:H7 enterohemorrhagic Escherichia coli and the shielding of colicin and phage receptors by their O-antigenic side chains

1991 ◽  
Vol 37 (2) ◽  
pp. 97-104 ◽  
Author(s):  
D. E. Bradley ◽  
S. P. Howard ◽  
H. Lior
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Hemolytic Uremic Syndrome ◽  
Key Words ◽  
Bloody Diarrhea ◽  
Enterohemorrhagic Escherichia Coli ◽  
Side Chains ◽  
Uremic Syndrome ◽  
O Antigens ◽  
Clinical Conditions

Twenty O157:H7 enterohemorrhagic Escherichia coli strains from patients with different clinical conditions were tested for colicinogeny and the presence of Verotoxin (VT) genes. From bloody diarrhea cases, 7/8 isolates and from hemolytic uremic syndrome cases 3/5 isolates all synthesized what appeared to be colicin D. The remaining strains, which included 7 from asymptomatic sources, were noncolicinogenic. The plasmid determining the colicin was found to be 1.4 kb larger than the 5.2-kb pColD. The colicin D protein had a molecular weight of about 90 000, whereas the O157 colicin was 87 000. The plasmid was designated pColD157 to reflect these differences. Of O157:H7 isolates 17/20 had genes for both of the Verotoxins VT1 and VT2, and the remaining 3/20 for VT1 only. There was no correlation between the presence of VT determinants and colicinogeny or symptoms. The O157:H7 strains exhibited significant resistance to other colicins and bacteriophages. Key words: O-antigens, enterohemorrhagic, colicin, Verotoxin, bacteriophages.

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