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Gram Scale (gram + scale)
Selected AbstractsChemInform Abstract: Integrated Biocatalytic Synthesis on Gram Scale: The Highly Enantioselective Preparation of Chiral Oxiranes with Styrene Monooxygenase.CHEMINFORM, Issue 50 2001Andreas Schmid 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] Asymmetric Synthesis of ES-285, an Anticancer Agent Isolated from Marine SourcesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2009Ana C. Allepuz Abstract The asymmetric synthesis of (2S,3R)-2-amino-3-octanedecanol hydrochloride (ES-285·HCl) was achieved in eight steps in ca. 38,% overall yield from the N -benzylimine-derived from (R)-2,3- O -isopropylidene glyceraldehyde, which is easily available on gram scale from the inexpensive precursor D -mannitol. Highly diastereoselective addition of methylmagnesium bromide to the N -benzylimine was the key step to create the vic -amino alcohol moiety with the appropriate configuration. Regioselective ring opening of an intermediate aminoepoxide enabled the introduction of the long hydrocarbon chain at C4.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] An Efficient Enantioselective Method for Asymmetric Friedel,Crafts Alkylation of Indoles with ,,,-Unsaturated AldehydesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2009Liang Hong Abstract The Lewis base-Lewis base bifunctional catalytic system has been developed and successfully applied to the asymmetric Friedel,Crafts alkylation of indoles with ,,,-unsaturated aldehydes. The reactions are promoted by chiral diphenylprolinol trimethylsilyl ether in the presence of triethylamine. By this protocol, optically active 3-substituted indoles can be obtained in an organocatalytic process that is free of Lewis or protic acid in high yields with up to 98% ee. Besides, this reaction could be carried out on a gram scale without any loss in the enantioselectivity. [source] A Practical Transition Metal-Free Aryl-Aryl Coupling Method: Arynes as Key IntermediatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17-18 2007Frédéric Abstract Upon treatment of various aryllithium intermediates with 1,2-dibromobenzene or 1-bromo-2-iodobenzene, dissymmetrical ortho,ortho, -di-, tri- and even tetrasubstituted bromo- or iodobiaryls become readily available. The crucial steps in all these reactions were the nucleophilic addition of the organolithium precursor to a transient aryne species released from it by ,-elimination of a lithium halide and, stabilization of the resulting 2-biaryllithium intermediate by in situ transfer of bromine or iodine from the starting material. This straightforward transition metal-free access to biaryls allows the preparation of highly valuable halobiaryls on a gram scale in excellent yields. These precursors can be subsequently functionalized by highly regioselective halogen/metal permutations into a vast variety of target molecules. This was demonstrated in the synthesis of several mono- and diphosphine ligands. [source] Rapid and efficient microwave assisted method for the regioselective synthesis of 8,8,-methylene-bis-4-oxo-1H and 2H -chromeno[4,3- C]pyrazolesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2007Adki Nagaraj The ethyl ester of 5,5,-methylene-bis-salicyclic acid 3 was prepared by the esterification of 5,5,-methylene-bis-salicylic acid 2. The compound 3 on reacting with ethylacetoacetate yields 6,6,-methylenebis-(3-acetyl-4-hydroxycoumarin) 4. The compound 4 was regioselectively converted into either 8,8,-methylene-bis-(4-oxo-1H -chromeno[4,3- c]pyrazoles) 6 or 8,8,-methylene-bis(-4-oxo-2H -chromeno[4,3- c]-pyrazoles) 7 under microwave irradiation. High yields are achieved even on a gram scale, while reaction times are considerably shortened compared to conventional heating conditions. [source] Influence of solvent quality on successive solution fractionation (SSF) efficiency of high-density polyethylenePOLYMER INTERNATIONAL, Issue 4 2009Vincent Stéphenne Abstract BACKGROUND: Preparative successive solution fractionation (SSF) is a powerful technique for obtaining narrow-dispersity fractions on a multi-gram scale of high-density polyethylene (HDPE). In a previous paper, the operative separation mechanisms during SSF of a broad HDPE in cyclohexanone were studied. Two mechanisms, and not only one as expected from the literature, contribute to the separation of HDPE molecules according to their molar mass (MM). The very low MM chains are separated by a solid,liquid (S,L) mechanism, while the longer chains are isolated by a liquid,liquid (L,L) phase separation. In the present paper, the influence of a poorer solvent, diphenyl ether, is reported. RESULTS: It is shown that the relative importance of the S,L mechanism with respect to the L,L one is altered by the use of this solvent. The L,L temperature range is increased in diphenyl ether while the S,L transition temperature remains unchanged. Consequently, the SSF efficiency is improved. Large amounts (on a gram scale) of narrow-dispersity fractions are isolated, mainly by the L,L mechanism. Polydispersities are about 1.5 (compared to 2.0 for cyclohexanone) and a broader MM range of closer molar mass distribution fractions is available. CONCLUSION: This work demonstrates that the use of diphenyl ether, a poorer solvent than cyclohexanone (always used as SSF solvent for polyethylene in the literature), leads to an improvement of SSF efficiency for an essentially linear HDPE. The differences of behaviour during the separation with cyclohexanone or diphenyl ether are explained by the establishment of a phase diagram. Copyright © 2009 Society of Chemical Industry [source] Recombinant murine growth hormone from E. coli inclusion bodies: Expression, high-pressure solubilization and refolding, and characterization of activity and structureBIOTECHNOLOGY PROGRESS, Issue 3 2010Amber Haynes Fradkin Abstract We expressed recombinant murine growth hormone (rmGH) in E. coli as a cost-effective way to produce large quantities (gram scale) of the protein for use in murine studies of immunogenicity to therapeutic proteins. High hydrostatic pressure was used to achieve high solubility and high refolding yields of rmGH protein produced in E. coli inclusion bodies. A two-step column purification protocol was used to produce 99% pure monomeric rmGH. Secondary and tertiary structures of purified rmGH were investigated using circular dichroism and 2D-UV spectroscopy. The purified rmGH produced was found to be biologically active in hypophysectomized rats. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Graphite-Supported Gold Nanoparticles as Efficient Catalyst for Aerobic Oxidation of Benzylic Amines to Imines and N -Substituted 1,2,3,4-Tetrahydroisoquinolines to Amides: Synthetic Applications and Mechanistic StudyCHEMISTRY - AN ASIAN JOURNAL, Issue 10 2009Man-Ho So Abstract Selective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43,100,%) and product yields (66,99,%) (19,examples). Oxidation of N -substituted 1,2,3,4-tetrahydroisoquinolines in the presence of aqueous NaHCO3 solution gave the corresponding amides in good yields (83,93,%) with high selectivity (up to amide/enamide=93:4) (6,examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o -phenylenediamines with benzaldehydes under aerobic conditions (8,examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N -benzylidene(phenyl)methanamine without significant loss of catalytic activity and selectivity. This protocol "AuNPs/C+O2" can be scaled to the gram scale, and 8.9,g (84,% isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10,g 1,2,3,4-tetrahydroisoquinoline in a one-pot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed. [source] Induction of a Melanoma-Specific Antibody Response by a Monovalent, but not a Divalent, Synthetic GM2 NeoglycopeptideCHEMMEDCHEM, Issue 4 2009S. Bay Dr. Abstract Human tumor cell-specific antibodies were induced in mice after immunization with a synthetic glycopeptide, which is based on the GM2 ganglioside carbohydrate moiety produced on a gram scale in bacteria. Such neoglycopeptides represent a promising cancer vaccine strategy for active immunotherapy targeting carbohydrates. The GM2 ganglioside represents an important target for specific anticancer immunotherapy. We designed and synthesized a neoglycopeptide immunogen displaying one or two copies of the GM2 tetrasaccharidic moiety. These glycopeptides were prepared using the Huisgen cycloaddition, which enables the efficient ligation of the alkyne-functionalized biosynthesized GM2 with an azido CD4+ T,cell epitope peptide. It is worth noting that the GM2 can be produced on a gram scale in bacteria, which can be advantageous for a scale-up of the process. We show here for the first time that a fully synthetic glycopeptide, which is based on a ganglioside carbohydrate moiety, can induce human tumor cell-specific antibodies after immunization in mice. Interestingly, the monovalent, but not the divalent, form of GM2 peptide construct induced antimelanoma antibodies. Unlike traditional vaccines, this vaccine is a pure chemically-defined entity, a key quality for consistent studies and safe clinical evaluation. Therefore, such carbohydrate,peptide conjugate represents a promising cancer vaccine strategy for active immunotherapy targeting gangliosides. [source] Chiral synthesis of secondary alcohols using Geotrichum candidumCHIRALITY, Issue 9 2002Kaoru Nakamura Abstract Chiral synthesis of secondary alcohols of both the (S)- and (R)-enantiomer with extremely high enantioselectivities (up to >99% ee) using a biocatalyst, Geotrichum candidum, is reviewed. Resting cell and dried-cell preparation using acetone were applied to oxidation, reduction, and deracemization reactions. Many methods to improve the reactivity and enantioselectivity of the reactions were developed. For example, additives such as secondary alcohols and hydrophobic resin (AmberliteÔ XAD) were used in nonaqueous reaction media such as organic and supercritical solvents as well as in aqueous ones. As a result, optically pure alcohols of both enantiomers were synthesized on a gram scale. Chirality 14:703,708, 2002. © 2002 Wiley-Liss, Inc. [source] Enantioselective Synthesis of Non-Natural Aromatic ,-Amino AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2004Andreas Krebs Abstract We present two complementary methods for the stereoselective synthesis of non-natural ,-amino acids with aromatic or heteroaromatic side chains. One approach is based on the chemical transformation of methionine, whereas the other applies the stereoselective Myers alkylation of glycine. The resulting product types differ in the linker length between glycine and the aromatic substituent. Since methionine and pseudoephedrine are available in both absolute configurations, R - or S -configured enantiopure amino acids with either C2 or C3 linkers can be obtained on gram scales. In each case the key step of the synthesis is hydroboration of the unsaturated building blocks 9 and 17, followed by palladium-catalyzed Suzuki cross-coupling with aryl halides. Attention must in certain cases be paid to the stereochemical integrity when basic Suzuki conditions are applied. Our initial difficulties are reported as well as the final "racemization-proof" procedures. The protecting groups chosen for the ,-amino acids should be compatible with solid-phase peptide synthesis. This was confirmed by the successful synthesis of a series of tripeptides. [source] | ||||||||||||||||||||||