Preparation Of Alkyl Research Articles

A Shortcut to the Synthesis of Peptide Thioesters.

Peptide thioesters serve as fundamental building blocks for the synthesis of proteins and cyclic peptides. Classically, methods to synthesize thioesters have been based on acid-labile amino-protecting groups for which final side-chain deprotection required the use of hazardous hydrogen fluoride (HF). Alternative protection schemes based on base-labile amino-protecting groups have become preferred methods but are not suitable due to the lability of thioester bonds toward bases. In this method, we employ a trifluoracetic acid/trimethylsilyl bromide (TFA/TMSBr) protocol using a hydroxymethyl resin obviating the need for HF. TFA/TMSBr is volatile enough to be easily removed yet less hazardous than HF, making it more practical for general peptide chemists. We describe optimized cleavage procedures and appropriate protecting group schemes and discuss in situ neutralization protocols. The method is relatively simple, straightforward, and easily scalable, allowing the facile preparation of alkyl and aryl thioesters.

"Single-pot" approach towards the preparation of alkyl and polyfluoroalkyl organo-silica monolithic capillaries for reversed-phase liquid chromatography.

Organo-silica monolithic capillary columns were prepared using thermally initiated polymerization of mixtures containing 3-(methacryloyloxy)propyltrimethoxysilane as the silicon-containing monomer, an aqueous acid catalyst, ethylene dimethacrylate as the cross-linker, a functional monomer selected from the group comprising octadecyl methacrylate, trifluoroethyl methacrylate, pentafluoropropyl methacrylate, and heptadecafluorodecyl methacrylate, toluene as the porogen, and 2,2'-azobisisobutyronitrile as the initiator. The permeability of the monoliths was controlled by varying the composition of the polymerization mixture. Chromatographic properties of resulting monolithic 100μm i.d. capillaries were evaluated utilizing four sets of probe compounds under isocratic elution conditions in the reversed-phase mode. Baseline separation of alkylbenzenes and the best steric selectivity were achieved using the octadecyl methacrylate monolithic column verifying that its surface was the most hydrophobic. In contrast, separation of a mixture containing polar compounds was observed using columns prepared in the absence of the functional monomer due to the presence of residual surface silanols at the pore surface. Polyfluoroalkyl stationary phases, especially those with a high number of fluorine atoms, exhibited the highest selectivity towards fluorine-containing analytes.

ChemInform Abstract: Copper(I)/Ligand‐Catalyzed 5‐endo Radical Cyclization—Aromatization of 2,2,2‐Trichloroethyl Vinyl Ethers: Synthesis of 2,3‐Difunctionalized 4‐Chlorofurans.

Copper(I)/ligand-catalyzed one pot synthesis of highly substituted 2,3-difunctionalized-4-chlorofurans has been reported. The reaction proceeds via a Cu(I)-catalyzed regioselective 5-endo-trig radical cyclization of 2,2,2-trichloroethyl vinyl ethers followed by the base-promoted dehydrochlorination. The success of the kinetically disfavored 5-endo cyclization was attributed to the formation of captodatively stabilized radical intermediate in the cyclization step and relatively high reaction temperature. Synthetic application of this protocol was also demonstrated in the preparation of alkyl and aryl substituted 4-chlorofuranonapthoquinones.

Copper(I)/Ligand-Catalyzed 5-endo Radical Cyclization-Aromatization of 2,2,2-Trichloroethyl Vinyl Ethers: Synthesis of 2,3-Difunctionalized 4-Chlorofurans.

Copper(I)/ligand-catalyzed one pot synthesis of highly substituted 2,3-difunctionalized-4-chlorofurans has been reported. The reaction proceeds via a Cu(I)-catalyzed regioselective 5-endo-trig radical cyclization of 2,2,2-trichloroethyl vinyl ethers followed by the base-promoted dehydrochlorination. The success of the kinetically disfavored 5-endo cyclization was attributed to the formation of captodatively stabilized radical intermediate in the cyclization step and relatively high reaction temperature. Synthetic application of this protocol was also demonstrated in the preparation of alkyl and aryl substituted 4-chlorofuranonapthoquinones.

ChemInform Abstract: Copper‐Free Asymmetric Allylic Alkylation of Trisubstituted Cyclic Allyl Bromides Using Grignard Reagents.

AbstractA regio‐ and enantioselective method for the preparation of alkyl‐, allyl‐substituted benzothiopyran and tetralone derivatives is developed.

Preparation of alkyl 11‐anilino‐10‐hydroxy undecanoates and evaluation of their antioxidant activity

A novel class of 10‐undecenoic acid‐based alkyl 11‐anilino‐10‐hydroxy undecanoates were prepared by reacting n‐alkyl (C1 and C4) and iso alkyl (C3, C4, and C8) epoxy undecanoates with aniline under catalyst‐free reaction conditions. The synthesized products were characterized by 1H NMR, IR, GC, and GC‐MS and evaluated for their antioxidant activity using rancimat and differential scanning calorimetry (DSC) methods. The effect of antioxidants was studied at 0.25 and 0. 5% concentrations using rancimat method and at 0.5% in DSC analysis by adding in a lubricant base stock, namely epoxy karanja fatty acid 2‐ethylhexyl esters. All the products exhibited good antioxidant properties at 0.25% concentration and enhanced antioxidant activity with the increased antioxidant concentration at 0.5%. The results obtained from isothermal DSC correlated well with those based on the rancimat method. n‐Butyl 11‐anilino‐10‐hydroxy undecanoate (4c) exhibited the best stabilizing effect on lubricant base stock with longest induction time compared to butylated hydroxytoluene (BHT) and other products. The data indicate that the synthesized products are potential antioxidants for lubricant formulations.

Sulfuric Acid Catalyzed Preparation of Alkyl and Alkenyl Camptothecin Ester Derivatives and Antitumor Activity against Human Xenografts Grown in Nude Mice

Camptothecin-20-propinate (CZ48) and other camptothecin ester derivatives were prepared by the esterification reac-tions of camptothecin or 9-nitrocamptothecin with the corresponding acylating agents such as organic acid anhydride or chloride with concentrate sulfuric acid as the catalyst. The sulfuric acid-catalyzed reactions gave high yields of camptothecin ester products.Among the 11 compounds prepared by this method, camptothecin-20-O-propionate, camptothecin-20-O-crotonate, and 9-nitrocamptothecin-20-O-propionate showed good anticancer activity against various types of human tumors grown as xenografts in nude mice. The methodology developed for the preparation of camptothecin esters in this article can be applied to a wide scope of other ester derivatives.

ChemInform Abstract: Cleavage of Ethers and Geminal Diacetates Using the Boron Triiodide N, N-Diethylaniline Complex.

Abstract The boron triiodide-N,N-diethylaniline complex, generated in situ from borane:N,N-diethylaniline and iodine cleaves ethers and regenerates carbox-aldehydes from the corresponding geminal diacetate derivatives under mild conditions in good yields. Recently a simple procedure for the preparation of alkyl and alkenyl iodides in good yields using boron triiodide-N,N-diethylaniline complex and acetic acid was reported.1 This prompted us to report our results on the cleavage of ethers and regeneration of aldehydes from geminal diacetates using the boron triiodide-N,N-diethylaniline reagent.

Synthesis of substituted phthalocyanines

This review summarizes the synthetic strategies for substituted phthalonitriles and phthalocyanines. Preparation of alkyl-, aryl-, halo-, nitro-, alkoxy-, aryloxy-, alkylthio-, arylthio-, and amino- substituted phthalocyanines along with the derivatives of phthalocyanine carboxylicand sulfoacids is overviewed. Influence of the substituents on the position of Q-band in UV-vis spectra of substituted phthalocyanines is also briefly discussed.

ChemInform Abstract: One‐Pot, Three‐Step Preparation of Alkyl and Aryl Alkylcarbamates from S‐Methyl N‐Alkylthiocarbamates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Preparation of Alkyl and Aryl Chlorodifluoromethyl Ethers Using BrF3

AbstractBoth alkyl and aryl chlorothioformates could readily be obtained from the corresponding alcohols and thiophosgene. These families of compounds were treated with BrF3 to form the corresponding alkyl and aryl chlorodifluoromethyl ethers in 60–85 % yields. The method is suitable for constructing a variety of aliphatic as well as electron‐deficient aromatic chlorodifluoromethyl ethers. The reactions proceed under mild conditions and short reaction times. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Preparation of Alkyl 4,5-Dihydro-2H-benz[g]indazole-2-carboxylates and Methyl 4,5-Dihydro-2H-benz[e]indazole-2-carboxylates from Dilithiated 1-Tetralone or 2-Tetralone Carboalkoxyhydrazones and Aromatic Esters

Dilithiated 1-tetralone or 2-tetralone carboalkoxyhydrazones were prepared in excess lithium diisopropylamide and condensed with a variety of aromatic esters followed by acid cyclization of C-acylated intermediates to give substituted dihydrobenzindazoles, alkyl 4,5-dihydro-2H-benz[g]indazole-2-carboxylates and methyl 4,5-dihydro-2H-benz[e]indazole-2-carboxylates. These fused-ring heterocyclic products have considerable application potential.

No-carrier-added synthesis of aliphatic and aromatic radioselenoethers via selenocyanates

Various aliphatic and aromatic [ 75Se]selenoethers were prepared at the no-carrier-added (n.c.a.) level using a new radiosynthetic pathway, based on the formation of alkyl[ 75Se]selenocyanates as intermediates. Using one-pot model reactions of elemental 75Se, sodium cyanide and various alkylbromides in ethanol, the preparation of alkyl[ 75Se]selenocyanates was examined and optimized. Purification of these 75Se-labeled intermediates and subsequent conversion with alkyl and aryl lithium or Grignard compounds in anhydrous diethyl ether yielded radioselenoethers with radiochemical yields of up to 55% (related to 75Se 0) within an overall reaction time of 20 min. This is the first method described to obtain n.c.a. arylselenoethers.

A New Synthetic Route to Alkyl Terminated Silicon Nanoparticles.

ABSTRACTThis paper describes the preparation of alkyl terminated silicon nanoparticles that are air and moisture stable by the oxidation of magnesium silicide with bromine and then the subsequent termination with an alkyl Grignard reagent. The nanoparticles have been characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and fluorescence spectroscopy.

Preparation of alkyl (R)-(-)-3-hydroxybutyrate by acidic alcoholysis of poly-(R)-(-)-3-hydroxybutyrate.

An efficient method for the preparation of optically active alkyl (R)-(-)-3-hydroxybutyrates by chemical depolymerization of biopolymer, poly-(R)-(-)-(3-hydroxybutyrate), was established. This method consists of simple recovery of poly-(R)-(-)-(3-hydroxybutyrate) from bacterial cells followed by acidic alcoholysis. When poly-(R)-(-)-(3-hydroxybutyrate) was purified by a simple digestion method that used 0.2 N sodium hydroxide, alkyl (R)-(-)-hydroxybutyrates were most efficiently produced by alcoholysis with anhydrous hydrochloric acid.

One-step preparation of alkyl β-d-glucosaminide by the transglycosylation of chitosan and alcohol using purified exo-β-d-glucosaminidase

Alkyl β-d-glucosaminides (RGlcN) were prepared by the novel direct transglycosylation reaction of chitosan and alcohol using the purified exo-β-d-glucosaminidase from the chitosan-assimilating strain, Penicillium funiculosum KY616. Using the exo-β-d-glucosaminidase, versatile synthetic intermediates, short and medium chain RGlcNs, were prepared in a maximum yield of higher than 480 mg/g-chitosan when chitosan and an alcohol were incubated at a temperature of 30 °C for 2 d.

Preparation of alkyl α- and β- d-glucopyranosides, thermotropic properties and X-ray analysis

Monohydrates of heptyl to decyl α- d-glucopyranosides as obtained from product mixtures of the Fischer glucosylation were crystallized from water at the Krafft point. The results of the single-crystal X-ray analysis of anhydrous α anomers and their monohydrates provide for a better understanding of crystal formation and stability of their hydrates. The preparation of alkyl β- d-glucopyranosides—without concomitant formation of α anomers as by-products—has been described. The thermotropic properties have been investigated for the α compounds and their monohydrates, and for the β- d-glucopyranosides.

ChemInform Abstract: Preparation of Alkyl 3‐Methylalka‐2,4‐dienoates from γ,δ‐Unsaturated β‐Keto Esters via the Corresponding Conjugated Unsaturated 3‐Enol Phosphates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Preparation of alkyl 3-methylalka-2,4-dienoates from γ,δ-unsaturated β-keto esters via the corresponding conjugated unsaturated 3-enol phosphates

Methylation of α,β,γ,δ-unsaturated-β-substituted enol phosphates with lithium dimethyl cuprate gave a mixture of (2 E,4 E)- and (2 Z,4 E) alkyl 3-methylalka-2,4-dienoates and unsubstituted alkyl alka-2,4-dienoates. An improved synthesis is described for ethyl β-safranate and the insect growth regulator hydroprene.

ChemInform Abstract: Alkoxylation at the meta Position to the Hydroxyl Group of L‐Tyrosine: Preparation of Alkyl (S)‐2,4‐Dialkoxyphenylalaninates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.