Showing papers on "Alkylation published in 1987"
TL;DR: Several alkyl phosphorylcholines and related derivatives were tested against Leishmania donovani amastigotes in mouse peritoneal macrophages in vitro and ED50 values were determined in the range of 1-12 microM.
215 citations
TL;DR: In this article, the interstitial cations in the K10 montmorillonite were exchanged to obtain catalysts for Friedel-Crafts alkylation with halides, alcohols, and olefins.
Abstract: Catalysts are obtained by exchange of the interstitial cations in the K10 montmorillonite. They are applied to Friedel-Crafts alkylations with halides, alcohols, and olefins. They are quite effective even with unactivated hydrocarbons. Isomer distribution depends little on the catalyst used. Thermodynamic equilibration does not take place, the reactions appear to be kinetically controlled. Efficiency of the catalysts bears no apparent relation to that of the corresponding Lewis acids under homogeneous conditions, and it depends on the nature of the alkylating agent. Zr(IV) and Ti(IV), in general, give the best results.
186 citations
158 citations
TL;DR: Alkyl 2-chloroethoxymethylphosphine (DPHP) was used to give [2-(adenin-9-yl)ethoxy]methyl(diethoxymmethyl)phosphinates VIII and XIV, bearing the kidney protecting group on the phosphorus atom.
Abstract: Alkyl 2-chloroethoxymethyl(diethoxymethyl)phosphinates VII and XIII were prepared by reaction of silyl esters of dialkoxymethylphosphinic acid with 2-chloroethyl chloromethyl ether. Adenine was alkylated with VII and XIII to give [2-(adenin-9-yl)ethoxy]methyl(diethoxymethyl)phosphinates VIII and XIV , bearing the dialkoxymethyl protecting group on the phosphorus atom. Acid hydrolysis of compounds VIII and XIV afforded 9-(2-phosphinoethoxymethyl)adenine ( X ). Alkyl dialkoxymethylphosphinates V and XI reacted with paraformaldehyde to give hydroxymethylphosphinates XV and XIX which were converted into the synthons XVI , XVII and XVIII capable of introducing a protected hydroxymethylphosphino group on a hydroxy or amino group.
143 citations
TL;DR: A procedure is described which provides high yields of pyridylethylated cysteine during gas-phase sequencing of peptides and is particularly useful when subnanomole levels of material must be reduced and alkylated.
113 citations
TL;DR: Le tricarbonylnitrosyl ferrate du titre catalyse l'alkylation de carbonates allyliques par l'anion du malonate as mentioned in this paper.
Abstract: Le tricarbonylnitrosyl ferrate du titre catalyse l'alkylation de carbonates allyliques par l'anion du malonate
100 citations
TL;DR: In this article, the synthesis of (R)-and (S)-2-aminomethyl-1-ethylpyrrolidine precursors from (R) amines with 3,5-dichloro-2,6-dimethoxybenzoyl chloride is described.
Abstract: Radioactive labelled raclopride and its (R)-isomer were prepared by O-alkylation of the corresponding phenols with labelled methyl iodide. The syntheses of the two phenolic precursors from (R)- and (S)-2-aminomethyl-1-ethylpyrrolidine are described. Resolution of the racemic amine into the enantiomers was accomplished by fractional crystallization of the ditartrates. Coupling of the amines with 3,5-dichloro-2,6-dimethoxybenzoyl chloride, followed by dealkylation, led to the diphenolic precursors. Mono-alkylation of the corresponding precursor with [3H]methyl iodide furnished the potent dopamine-D2 ligand [3H]raclopride and its (R)-isomer. [11C]Methyl iodide was prepared from [11C]carbon dioxide. Subsequent reaction with phenolic (S)-precursor furnished [11C]raclopride which has been used in positron emission tomography (PET) studies of the human brain.
88 citations
TL;DR: In this article, the Na form of a commercial, pelleted X-type zeolite by ion exchange with alkali cations was used for side-chain alkylation of toluene with methanol.
83 citations
TL;DR: In this article, Cincanu et al. used dimethyl sulphoxide containing solid sodium hydroxide and methyl iodide to methylate simple neutral oligosaccharides.
Abstract: O-Methylation of simple neutral oligosaccharides is readily accomplished in dimethyl sulphoxide containing solid sodium hydroxide and methyl iodide [Cincanu I, Kerek F (1984) Carbohydr Res 131∶209-17]. This procedure has been extended to 2-acetamido-2-deoxy sugars and sialic acid-containing oligosaccharides. CompleteO-andN-methylation was in most cases achieved in 15 min. Esterification of carboxylic groups in uronic acids was fast and resulted in concomitant β-elimination. The method is also suitable for methylation of glycoproteins and glycosphingolipids. Polysaccharides can also be methylated by this technique. Analysis of the products by gas-liquid chromatography and mass spectrometry showed no degradation products.
72 citations
TL;DR: Results show that 2,5-dihydro-4-methyl-2-phenyl-1-5-benzothiazepine-3-carboxylic ester is a good starting point for designing dihydropyridine as well as diltiazem mimics.
Abstract: 2,5-Dihydro-4-methyl-2-phenyl-1,5-benzothiazepine-3-carboxylic acid esters, based on the structures of dihydropyridines and diltiazem, were synthesized from o-aminothiophenol and 2-(phenylmethylene)- 3-oxobutanoic acid esters. Biological evaluation in the potassium-depolarized rabbit aorta suggests that these compounds are calcium channel blockers. The in vitro activity was further confirmed by electrophysiological techniques. Structure-activity studies for the aromatic substitution showed that the 2-nitro derivative was the most potent (IC50 = 0.3 microM) compound in vitro while the ethyl ester was slightly better than the corresponding methyl ester. Replacement of sulfur with nitrogen atom provided 2,5-dihydro-4-methyl-2-(3-nitrophenyl)-1,5-benzodiazepine-3-carboxylic acid ethyl ester, which was only slightly less active than the corresponding benzothiazepine. Derivatization of the nitrogen in 2,5-dihydro-4-methyl- 2-(3-nitrophenyl)-1,5-benzothiazepine-3-carboxylic acid methyl ester with a (dimethylamino)ethyl group (present in diltiazem) provided 2,5-dihydro-5-[(dimethylamino)ethyl]- 4-methyl-2-(3-nitrophenyl)-1,5-benzo-thiazepine-3-carboxylic acid methyl ester, which was found to be equipotent to diltiazem in vitro. Radioligand binding studies using [3H]nitrendipine and [3H]diltiazem showed that the compound with the free nitrogen binds competitively into the dihydropyridine binding site while the molecule in which the nitrogen is alkylated with a (dimethylamino)ethyl group interacts competitively with both diltiazem and dihydropyridine binding sites. Our results therefore show that 2,5-dihydro-4-methyl-2-phenyl-1,5-benzothiazepine-3-carboxylic ester is a good starting point for designing dihydropyridine as well as diltiazem mimics.
66 citations
TL;DR: In this paper, the acid-catalysed (catalyst, 0.15 M p-toluenesulfonic acid in the reaction medium) alkylation of lignins with rnethano) or ethanol in dioxane (alcohol-dioxane) at 30°C has been studied by NMR spectroscopic methods.
Abstract: The acid-catalysed (catalyst, 0.15 M p-toluenesulfonic acid in the reaction medium) alkylation of lignins with rnethano) or ethanol in dioxane (alcohol-dioxane (2:1)) at 30°C has been studied by NMR spectroscopic methods. Complete alkylation required 4—6 days and resulted in the introduction of about one alkoxyl group in every second phenylpropane unit. The alkylation can be explained by etherification of benzy) alcohols (and, to a minute extent, cinnamyl alcohols), reetherification of benzyl ethers, esterification of carboxylic acids and formation of acetals from benzaldehydes, cinnamaldehydes and glyceraldehyde-2-aryl ethers. The methodology used permitted the conclusion that reactions other than alkylation occurred to only a minor extent. The wine-red colour acquired by the reaction mixture from lignin alkylation could be related to the occurrence of cinnamaldehyde groups. According to model compound studies, alkylation of arylglycerol-ß-aryl ethers resulted in a mixture of the erythro (60%) and threo (40%) forms of the benzyl ethers.
TL;DR: In this article, a bicyclic cyclopentenone was transformed into bicyclic lactams, which, after metalation and alkylation, gave high diastereomeric ratios of 2,2-dialkyl quaternary products, 29 and 12, respectively.
TL;DR: The CsX, RbX, and KX zeolites, which selectively alkylate the side chain of toluene with methanol, show formation of both unidentate and bidentate formates on the suface during the reaction as mentioned in this paper.
TL;DR: In this article, the authors presented methods by which enantiomerically pure 3-aminobutanoic acid derivatives can be prepared by adding dilithiated methyl- or ethyl-N-benzoyl-3aminobutoanoates to benzaldehyde to give products of l - and u, u -configuration respectively.
TL;DR: In this article, the azidoesters and the corresponding acid chlorides are shown to be interesting reagents for the nucleophilic and electrophilic amino-alkylation.
TL;DR: In this article, a LaY zeolite catalyst was used for the alkylation of isobutane with 1-butene, but it rapidly deteriorates due to the formation of carbonaceous deposits.
TL;DR: In this paper, the authors present CP-MAS NMR evidence both for dynamic and static carbocations which result from the reaction of propene in a H-Y zeolite.
Abstract: Zeolites in the hydrogen form are widely used for such acid-catalyzed reactions as the cracking of alkanes, alkene isomerization, alkylation, and the conversion of methanol to hydrocarbons. Although much of this chemistry can be explained via mechanisms involving carbocations, spectroscopic evidence for these intermediates in zeolites is limited. In the present study the authors present CP-MAS NMR evidence both for dynamic and static carbocations which result from the reaction of propene in a H-Y zeolite.
TL;DR: In this paper, the acidity and electronegativity of the zeolites were investigated and the most electropositive ones producing ethylbenzene and styrene, and most electrone-gative catalysing formation of xylenes.
TL;DR: In this article, the reaction of phenol with anisole was carried out over three X-, six Y-, a ZSM-5 and aZSM-11 zeolites, and over γ-Al 2 O 3, in a fixed-bed continuous reactor.
TL;DR: In this article, the hemin catalyst is converted to N-alkylhemin by addition to the alkene during the course of hemincatalyzed epoxidation of norbornene and other alkenes.
Abstract: During the course of hemin-catalyzed epoxidation of norbornene and other alkenes, the hemin catalyst is converted to N-alkylhemin by addition to the alkene.
TL;DR: In this paper, the association of (η 5 -indenyl)-Fe(CO) 2 − a CO was discussed and the authors proposed a method for preparation par association.
TL;DR: Optically active phenanthrones 7 and 12 were prepared using the asymmetric process involving Michael-type alkylation of chiral imines as discussed by the authors, and compound 12 was then transformed into the ring-C aromatic steroid 16.
TL;DR: The 1,2,3,4,4-tetrahydro-N-pivaloyl-isoquinoline-3-carboxylic acids 1d, 2d, and 3d, derived from (R)- or (S)-phenylalanine, dopa, and α-methyldopa, respectively, are doubly deprotonated with (tert-butyl)lithium in THF and alkylated at the 1-position.
Abstract: The 1,2,3,4-tetrahydro-N-pivaloyl-isoquinoline-3-carboxylic acids 1d, 2d, and 3d, derived from (R)- or (S)-phenylalanine, (S)-dopa, and (S)-α-methyldopa, respectively, are doubly deprotonated with (tert-butyl)lithium in THF and alkylated at the 1-position (products 5–10). The major diastereoisomers formed are the result of electrophilic attack from the face opposite to the carboxylate group (rel. topicity ul-1,3). Even the addition to benzaldehyd (7,8) is highly stereoselective (one of four diastereoisomers is formed exclusively (300-MHz 1H-NMR analysis)), if MgBr2 etherate is added prior to the electrophile. Some of the obtained amino-acid derivatives are decarboxylated by anodic oxidation in MeOH (11, 12, 17) and NaBH3CN reduction, and converted to the known 1-methyl- and 1-benzyltetrahydroisoquinolines (15, 16) of > 95% ee as well as to the phthalide isoquinoline alkaloid (+)-corlumine of ≥80% ee. The synthetic approach described here is compared with other methods of synthesizing enantiomerically pure 1-substituted tetrahydroisoquinolines (and thus an important group of alkaloids, Scheme 1).
TL;DR: Ortho-alkylation par l'intermediaire d'une transposition sigmatrope [2+3], les isopropylthio-1' alkyl-2' phenols obtenus peuvent se cycliser: on prepare de cette facon la coumarine, le chromanne, le dimethyl-2,2 chromene and l'α-tocopherol.
Abstract: Ortho-alkylation par l'intermediaire d'une transposition sigmatrope [2+3]; les isopropylthio-1' alkyl-2' phenols obtenus peuvent se cycliser: on prepare de cette facon la coumarine, le chromanne, le dimethyl-2,2 chromene et l'α-tocopherol