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Alkyl Esters (alkyl + ester)
Selected AbstractsCrystallization Behavior of Poly(, -caprolactone) Grafted onto Cellulose Alkyl Esters: Effects of Copolymer Composition and Intercomponent MiscibilityMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 20 2008Ryosuke Kusumi Abstract Graft copolymers of CA and CB with PCL were prepared at compositions rich in PCL. Kinetic DSC data were analyzed in terms of a folded-chain crystallization formula expanded for a binary mixing system of amorphous/crystalline polymers. The order of crystallization rates was plain PCL,>,CA- g -PCL (DS,=,2.98),>,CB- g -PCL (DS,=,2.1,2.95),>,CA- g -PCL (DS,=,2.1,2.5), and the fold-surface free energy of the PCL crystals obeyed the reverse order. POM revealed a generally tardy growth of spherulites for all the graft copolymers. The slower crystallization process may be ascribed primarily to the compulsory effect of anchoring PCL chains onto the semi-rigid cellulose backbone. Intercomponent miscibility of the CA/PCL and CB/PCL pairs was also taken into consideration. [source] Removal of the Acyl Donor Residue Allows the Use of Simple Alkyl Esters as Acyl Donors for the Dynamic Kinetic Resolution of Secondary Alcohols.CHEMINFORM, Issue 38 2005Gerard K. M. Verzijl Abstract For Abstract see ChemInform Abstract in Full Text. [source] Mild Regeneration of the Carboxylic Group of Amino Acid Alkyl Esters by Aqueous Methanolic Sodium Hydrogen Carbonate via 5-Oxazolidinones.CHEMINFORM, Issue 2 2004Pietro Allevi Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Facile Conversion of Trialkylsilyl Esters to Alkyl Esters Mediated by Tetrabutylammonium Fluoride Trihydrate.CHEMINFORM, Issue 26 2001Takashi Ooi Abstract ChemInform 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. [source] Composition of alkyl esters in the cuticular wax on inflorescence stems of Arabidopsis thaliana cer mutantsTHE PLANT JOURNAL, Issue 2 2007Christine Lai Abstract Wax biosynthetic pathways proceed via the elongation of 16:0 acyl-CoA to very long-chain fatty acids (VLCFA), and by further modifications that include reduction to primary alcohols and formation of alkyl esters. We have analyzed the alkyl esters in the stem wax of ten cer mutants of Arabidopsis thaliana together with the corresponding wild types. Alkyl esters with chain lengths between C38 and C52 were identified, and the levels of esters ranged from 0.15 µg cm,2 in Wassilewskija (WS) to 1.20 µg cm,2 in cer2. Esters with even numbers of carbons prevailed, with C42, C44 and C46 favoured in the wild types, a predominance of C42 in cer2 and cer6 mutants, and a relative shift towards C46 in cer3 and cer23 mutants. The esters of all mutants and wild types were dominated by 16:0 acyl moieties, whereas the chain lengths of esterified alcohols were between C20 and C32. The alkyl chain-length distributions of the wild-type esters had a maximum for C28 alcohol, similar to the free alcohols accompanying them in the wax mixtures. The esterified alcohols of cer2, cer6 and cer9 had largely increased levels of C26 alcohol, closely matching the patterns of the corresponding free alcohols and, therefore, differing drastically from the corresponding wild type. In contrast, cer1, cer3, cer10, cer13 and cer22 showed ester alcohol patterns with increased levels of C30, only partially following the shift in chain lengths of the free alcohols in stem wax. These results provide information on the composition of substrate pools and/or the specificity of the ester synthase involved in wax ester formation. We conclude that alcohol levels at the site of biosynthesis are mainly limiting the ester formation in the Arabidopsis wild-type epidermis. [source] ChemInform Abstract: Chemoselective Removal of Acyloxy in 1-(Benzotriazole-1-yl)alkyl Esters and Its Application in the Preparation of ,-(Benzotriazole-1-yl)alcohols.CHEMINFORM, Issue 6 2009Xiaoxia Wang Abstract ChemInform 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. [source] Preparation of Optically Active (Acyloxy)alkyl Esters from Optically Active O-Acyl-,-hydroxy Acids.CHEMINFORM, Issue 43 2002Peter R. Guzzo Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Cleavage of Benzyloxycarbonyl-5-oxazolidinones to ,-Benzyloxycarbonylamino-,-alkyl Esters by Alcohols and Sodium Hydrogen Carbonate.CHEMINFORM, Issue 46 2001Pietro Allevi Abstract ChemInform 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. [source] Kinetics and mechanism of the reaction between maleic anhydride and fatty acid esters and the structure of the productsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2008Florina Stefanoiu Abstract Alkenyl succinic anhydrides (ASA) were obtained by reaction between maleic anhydride and high-oleic sunflower oil (HOSO) esters. A kinetics study of the maleinization of alkyl esters indicated that the maleinization reaction was second order overall and first order with respect to the individual reactants, and the activation energy was 77.2,±,3.3,kJ/mol in the investigated temperature range (185,225,°C). These results showed that the cis configuration and the central position of the double bond in HOSO esters facilitate the maleinization of the latter. On the contrary, the length of the linear ester moiety had no influence on the course of the maleinization reaction. Moreover, new evidence demonstrates that there are two different reaction mechanisms: ene-reaction and addition in allylic position with a 2,:,1 ratio, respectively. This ratio was constant throughout the reaction, thus indicating that these mechanisms are independent. [source] Reactions of 4-chloro-5h -1,2,3-dithiazole-5-thione with ,,,-unsaturated ,-amino esters: Formation of 2-[2-(1-alkenylsulfanyl-1-alkoxycarbonyl-2-amino)-1,2-dicyano-vinylsulfanyl]-3-amino-2-alkenoic alkyl estersJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2002Yong-Goo Chang Treatment of 4-chloro-5H -1,2,3-dithiazole-5-thione with alkyl 3-alkyl (or aryl)-3-amino-2-propenoates in the presence of pyridine (2 equivalents) in dichloromethane at reflux gave 2-[2-(1-alkenylsulfanyl-1-alkoxy-carbonyl-2-amino)-1,2-dicyanovinylsulfanyl]- 4 and-1,2-dicyanovinyldisulfanyl]-3-amino-2-alkenoic alkyl esters 7 in 16 to 60% and 8 to 48% yields, respectively. [source] Polymer-bound alkyltriazenes for mild racemization-free esterification of amino acid and peptide derivativesJOURNAL OF PEPTIDE SCIENCE, Issue 10 2004Joachim Smerdka Abstract A novel tool for polymer-assisted solution phase (PASP) esterification of amino acid and peptide derivatives has been developed. When treated with carboxylic acids, polymer-bound alkyltriazenes react with a loss of nitrogen and transfer of the alkyl moiety to the carboxylate anion to form the corresponding alkyl esters. There are no limitations with regard to either the protecting groups or the nature of the amino acid. Furthermore no racemization occurs at the chiral centers of the amino acids as demonstrated by chiral GC-MS analyses. Alkyltriazene-resins were also applied successfully to the esterification of peptide acids and other peptidic structures, such as tripalmitoyl- S -glyceryl-cysteine (Pam3Cys). The triazene-mediated esterification reaction is exceptionally mild, and there is no need for prior activation of the carboxy groups. This method is therefore particularly suitable for the alkylation of complex peptidomimetic structures prone to racemization and for acid-sensitive structures. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Drug substances presented as sulfonic acid salts: overview of utility, safety and regulationJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2009David P. Elder Abstract Objectives Controlling genotoxic impurities represents a significant challenge to both industry and regulators. The potential for formation of genotoxic short-chain alkyl esters of sulfonic acids during synthesis of sulfonic acid salts is a long-standing regulatory concern. This review provides a general overview of the utility of sulfonic acids as salt-forming moieties and discusses strategies for effectively minimizing the potential for alkyl sulfonate formation during the synthesis and processing of sulfonate salt active pharmaceutical ingredients. The potential implications of the recent establishment of a substantial human threshold dose for ethyl methanesulfonate for the safety assessment of alkyl sulfonates in general are also discussed. Key findings The formation of alkyl sulfonates requires highly acidic conditions, possibly combined with long reaction times and/or elevated temperatures, to generate significant amounts, and these conditions are most unlikely to be present in the synthesis of active pharmaceutical ingredient sulfonate salts. It is possible to design salt formation conditions, using a short-chain alcohol as solvent, to manufacture sulfonate salts that are essentially free of alkyl sulfonate impurities. Processes using non-acidic conditions such as ethanol recrystallization or wet granulation should not raise any concerns of alkyl sulfonate formation. Summary An understanding of the mechanism of formation of alkyl sulfonates is critical in order to avoid restricting or over-controlling sulfonic acid salts, which have many technical advantages as pharmaceutical counterions. Recent regulatory acceptance of a human threshold limit dose of 2 mg/kg per day for ethyl methanesulfonate, indicating that its toxicological risks have previously been considerably overestimated, could signal the beginning of the end over safety concerns on alkyl sulfonate residues, thus removing a major constraint from the exploitation of sulfonic acid counterions. [source] Ester prodrugs of morphine improve transdermal drug delivery: a mechanistic studyJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2007Jhi-Joung Wang Two alkyl esters of morphine, morphine propionate (MPR) and morphine enanthate (MEN), were synthesized as potential prodrugs for transdermal delivery. The ester prodrugs could enhance transdermal morphine delivery. The mechanisms of this enhancing effect were elucidated in this study. Both prodrugs were more lipophilic than their parent drug as evaluated by the skin/vehicle partition coefficient (log P) and capacity factor (log K,). The in-vitro skin permeation of morphine and its prodrugs from pH 6 buffer was in the order of MEN > MPR > morphine. MPR and MEN respectively enhanced the transdermal delivery of morphine by 2- and 5-fold. A contrary result was observed when using sesame oil as the vehicle. The prodrugs were stable against chemical hydrolysis in an aqueous solution, but were readily hydrolysed to the parent drug when exposed to skin homogenate and esterase. Approximately 98% MPR and ,75% MEN were converted to morphine in an in-vitro permeation experiment. The viable epidermis/dermis contributed to a significant resistance to the permeation of ester prodrugs. According to the data of skin permeation across ethanol-, ,-terpineol-, and oleic acid-pretreated skin, MEN was predominantly transported via lipid bilayer lamellae in the stratum corneum. The intercellular pathway was not important for either morphine or MPR permeation. [source] A variety of poly(m -benzamide)s with low polydispersities from inductive effect-assisted chain-growth polycondensationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Tomoyuki Ohishi Abstract Chain-growth polycondensation of 3-(alkylamino)benzoic acid alkyl esters 1 was investigated for obtaining poly(m -benzamide)s with defined molecular weights and low polydispersities. Polymerization conditions were first studied to find that ethyl 3-(octylamino)benzoate (1b) polymerized in a chain polymerization manner in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base and phenyl 4-methylbenzoate (2b) as an initiator in THF at 0 °C. The molecular weight of the polymer was controlled by the feed ratio of monomer to initiator. The polymerization of 1c,i with a variety of N -alkyl groups was then carried out under the established conditions to yield well-defined poly(m -benzamide)s, which showed higher solubility than those of the corresponding poly(p -benzamide)s. Furthermore, the 4-octyloxybenzyl group on the amide nitrogen in poly1i was removed by treatment with trifluoroacetic acid (TFA) to give N -unsubstituted poly(m -benzamide) (poly1j) with a low polydispersity, which is soluble in DMAc and DMSO, contrary to the para-substituted counterpart. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4990,5003, 2006 [source] A Novel, Facile Method for the Preparation of Uniform, Reactive Maleic Anhydride/Vinyl Acetate Copolymer Micro- and NanospheresMACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2004Chang-Min Xing Abstract Summary: A novel, stabilizer-free dispersion polymerization with alkyl esters as reaction media gives uniform alternating microspheres of maleic anhydride (MAn)/vinyl acetate (VAc) copolymer. The diameter of the copolymer microspheres could be precisely controlled from 80 to 750 nm by changing the monomer concentration or feed ratio. Moreover, this new type of copolymer microspheres with reactive anhydride groups on the surface has good solubility in common nontoxic solvents such as water and ethanol. SEM image of the powder surface of copolymer microspheres formed at [MAn],=,[VAc],=,1.5 M. [source] Composition of alkyl esters in the cuticular wax on inflorescence stems of Arabidopsis thaliana cer mutantsTHE PLANT JOURNAL, Issue 2 2007Christine Lai Abstract Wax biosynthetic pathways proceed via the elongation of 16:0 acyl-CoA to very long-chain fatty acids (VLCFA), and by further modifications that include reduction to primary alcohols and formation of alkyl esters. We have analyzed the alkyl esters in the stem wax of ten cer mutants of Arabidopsis thaliana together with the corresponding wild types. Alkyl esters with chain lengths between C38 and C52 were identified, and the levels of esters ranged from 0.15 µg cm,2 in Wassilewskija (WS) to 1.20 µg cm,2 in cer2. Esters with even numbers of carbons prevailed, with C42, C44 and C46 favoured in the wild types, a predominance of C42 in cer2 and cer6 mutants, and a relative shift towards C46 in cer3 and cer23 mutants. The esters of all mutants and wild types were dominated by 16:0 acyl moieties, whereas the chain lengths of esterified alcohols were between C20 and C32. The alkyl chain-length distributions of the wild-type esters had a maximum for C28 alcohol, similar to the free alcohols accompanying them in the wax mixtures. The esterified alcohols of cer2, cer6 and cer9 had largely increased levels of C26 alcohol, closely matching the patterns of the corresponding free alcohols and, therefore, differing drastically from the corresponding wild type. In contrast, cer1, cer3, cer10, cer13 and cer22 showed ester alcohol patterns with increased levels of C30, only partially following the shift in chain lengths of the free alcohols in stem wax. These results provide information on the composition of substrate pools and/or the specificity of the ester synthase involved in wax ester formation. We conclude that alcohol levels at the site of biosynthesis are mainly limiting the ester formation in the Arabidopsis wild-type epidermis. [source] Research and Development Trends in BiodieselASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2004V. Rudolph Biodiesel, a derivative from plant oils or animal fats, has gained widespread acceptance in recent years as a sustainable alternative fuel to petroleum diesel due to its environmental benefits and renewability. Although there are several different ways in which biodiesel can be used or formulated as a fuel such as direct blending, microemulsions and thermal cracking, the most widespread remains the alkyl esters of fatty acids obtained through transesterification of the oils or fats. In transesterification, triglycerides which are the main chemical in oils or fats are converted into esters through reaction with simple alcohols. The physical and chemical properties of the esters thus obtained are very similar to those of the petroleum diesel. This paper reviews the current technologies available for the transesterifications of vegetable oils and animal fats and identifies that the biggest factor deterring a greater market uptake of biodiesel is its cost. It concludes that, in addition to government policy framework, e.g. to reduce the pump price of biodiesel through fuel tax exemption, further technological development presents significant scope for improvement. At present, there are no suitable and developed transesterification technologies that can handle cheap, low-quality feedstocks including waste animal fats and spent cooking oils. These feedstocks contain high percentages of water and free fatty acids which are extremely detrimental to the yield and reaction rates of the transesterification processes. This paper also suggests some future research and development directions and requirements for more competitive biodiesel production. [source] Evidence for Spontaneous Release of Acrylates from a Transition-Metal Complex Upon Coupling Ethene or Propene with a Carboxylic Moiety or CO2CHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2007Michele Aresta Prof. Abstract The development of a new synthetic approach to acrylates based on the formation of alkyl esters of acrylic acids has been studied. A preformed Pd,COOMe moiety is used as a model system to investigate the insertion of an olefin into the PdC bond. The fast elimination of acrylate is observed. Density functional calculations support the experimental findings and allow the characterization of transition states along the reaction pathway. The first example of olefin/CO2 coupling with facile release of ethyl acrylate is also presented. [source] Asymmetric Hydrogenations One by One: Differentiation of up to Three ,-Ketocarboxylic Acid Derivatives Based on Ruthenium(II),Binap Catalysis,CHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2007Rainer Kramer Dipl.-Chem. Abstract Noyori-type reductions of pairs of ,-ketoamides and ,-ketoesters with elemental hydrogen (4,bar) proceeded substrate by substrate. When Et2NH2+[{RuCl(S)-binap}2](,-Cl)3, was employed as a catalyst in a methanol or ethanol solution, the substrates were reduced at room temperature in the order ,-ketopyrrolidide , ,-ketopiperidide , ,-keto(N,N -diethylamide) > ,-keto(alkyl esters) > ,-keto(oligofluoroalkyl esters). This is the first time that ,-ketoamides have been reduced asymmetrically (91 to >98,% ee) under such mild conditions. Monitoring the concentrations of these ,-ketocarboxyl acid derivatives and their respective hydrogenation products over the course of time showed that the most electron-rich substrate is captured by the catalyst preferentially and exothermically; whether this occurs reversibly or irreversibly remains to be determined. The hydrogenation product is subsequently formed. The last transformation includes the rate-determining step. The combination of these events explains why starting from appropriate mixtures of substrates a "first-choice substrate" reacted from early on while the "second-choice substrate" stayed virtually untouched over an extended period of time and reacted no earlier than after the "first-choice substrate" had disappeared. From then onward, however, the "second-choice substrate" also reacted relatively rapidly. [source] | ||||||||||||||||