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Acid Building Blocks (acid + building_block)
Kinds of Acid Building Blocks Selected AbstractsSilylene/Oxazolidinone Double-Locked Sialic Acid Building Blocks for Efficient Sialylation Reactions in DichloromethaneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Shinya Hanashima Abstract We describe efficient sialylation reactions in CH2Cl2 with the use of silylene/oxazolidinone double-locked sialic acid building blocks. The building blocks were synthesized from 4,5-oxazolidinone-protected phenylthiosialoside. In sialylation reactions towards primary and relatively reactive secondary hydroxy groups on the galactosides, the double-locked building blocks provided desired coupling products in good yields with excellent ,-selectivities. In the sialylation reaction with the C3-OH of the galactoside, the double-locked building blocks expressed significantly better ,-selectivity in comparison with the results obtained by using the oxazolidinone-locked building block. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] De Novo Synthesis of Uronic Acid Building Blocks for Assembly of Heparin OligosaccharidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2007Alexander Adibekian Abstract An efficient de novo synthesis of uronic acid building blocks is described. The synthetic strategy relies on the stereoselective elongation of thioacetal protected dialdehydes 12,a and 17. The dialdehydes are prepared from D -xylose, a cheap and commercially available source. A highly stereoselective MgBr2,OEt2 -mediated Mukaiyama aldol addition to C4-aldehyde 12,a is performed to obtain D -glucuronic acid building block 16, whereas L -iduronic acid building block 22 is prepared by MgBr2,OEt2 -mediated cyanation of C5-aldehyde 17. Synthesis of a heparin disaccharide demonstrates the utility of the de novo strategy for the assembly of glycosaminoglycan oligosaccharides. [source] O -Glycosyl Amino Acids by 2-Nitrogalactal Concatenation , Synthesis of a Mucin-Type O -GlycanEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2003Gottfried A. Winterfeld Abstract Base-promoted Michael-type addition of N -Boc- and N -Fmoc-protected serine and threonine esters to 2-nitrogalactal derivatives 2 and 26 led highly selectively to ,-glycosides 4a,d and 27a,c, respectively. Ensuing transformation of threonine derivative 4d and serine derivatives 4a,b resulted in compounds useful as lysine and dipeptide mimetics. 6- O -Desilylation of 27a,c, then 6- O -sialylation, and transformation of the nitro group of the galactose moiety into a 2-acetamido functionality, afforded N -Boc-protected serine and threonine tert -butyl esters 31a,c carrying the O -protected STN -antigen at the hydroxy group. The threonine derivative 31c was then transformed into the N -Fmoc-protected amino acid building block 33, which was employed for the synthesis of mucin repeating unit partial structure Ac-GS(STN)-TAPPAHG-NH2 (1). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] De Novo Synthesis of Uronic Acid Building Blocks for Assembly of Heparin OligosaccharidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2007Alexander Adibekian Abstract An efficient de novo synthesis of uronic acid building blocks is described. The synthetic strategy relies on the stereoselective elongation of thioacetal protected dialdehydes 12,a and 17. The dialdehydes are prepared from D -xylose, a cheap and commercially available source. A highly stereoselective MgBr2,OEt2 -mediated Mukaiyama aldol addition to C4-aldehyde 12,a is performed to obtain D -glucuronic acid building block 16, whereas L -iduronic acid building block 22 is prepared by MgBr2,OEt2 -mediated cyanation of C5-aldehyde 17. Synthesis of a heparin disaccharide demonstrates the utility of the de novo strategy for the assembly of glycosaminoglycan oligosaccharides. [source] A Novel Heavy-Atom Label for Side-Specific Peptide Iodination: Synthesis, Membrane Incorporation and X-ray ReflectivityCHEMPHYSCHEM, Issue 9-10 2009Philipp E. Schneggenburger Abstract A novel iodine peptide label for X-ray analysis of membrane-active peptide structures is applied to solid-phase peptide synthesis. The resulting pore-structured labeled peptide as well as a non-labeled reference were reconstituted in lipid bilayer stacks (see scheme). The results indicate the exhibition of a membrane-spanning ,5.6 -double helical peptide structure and illustrate the quality of the new label. Structural parameters, such as conformation, orientation and penetration depth of membrane-bound peptides and proteins that may function as channels, pores or biocatalysts, are of persistent interest and have to be probed in the native fluid state of a membrane. X-ray scattering in combination with heavy-atom labeling is a powerful and highly appropriate method to reveal the position of a certain amino acid residue within a lipid bilayer with respect to the membrane normal axis up to a resolution of several Ångstrøm. Herein, we report the synthesis of a new iodine-labeled amino acid building block. This building block is intended for peptide incorporation to provide high intensities for electron density difference analysis of X-ray reflectivity data and improve the labeling potential for the lipid bilayer head-group and water region. The novel building block as well as the commercially available non-iodinated analogue, required for X-ray scattering, was implemented in a transmembrane peptide motif via manual solid-phase peptide synthesis (SPPS) following the fluorenylmethyloxycarbonyl (Fmoc)-strategy. The derived peptides were reconstituted in lipid vesicles as well as in highly aligned multilamellar lipid stacks and investigated via circular dichroism (CD) and X-ray reflectivity. Thereby, it has been revealed that the bulky iodine probe neither causes conformational change of the peptide structure nor lamellar disordering of the membrane complexes. [source] Silylene/Oxazolidinone Double-Locked Sialic Acid Building Blocks for Efficient Sialylation Reactions in DichloromethaneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Shinya Hanashima Abstract We describe efficient sialylation reactions in CH2Cl2 with the use of silylene/oxazolidinone double-locked sialic acid building blocks. The building blocks were synthesized from 4,5-oxazolidinone-protected phenylthiosialoside. In sialylation reactions towards primary and relatively reactive secondary hydroxy groups on the galactosides, the double-locked building blocks provided desired coupling products in good yields with excellent ,-selectivities. In the sialylation reaction with the C3-OH of the galactoside, the double-locked building blocks expressed significantly better ,-selectivity in comparison with the results obtained by using the oxazolidinone-locked building block. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis, and Helix or Hairpin-Turn Secondary Structures of ,Mixed' ,/, -Peptides Consisting of Residues with Proteinogenic Side Chains and of 2-Amino-2-methylpropanoic Acid (Aib)HELVETICA CHIMICA ACTA, Issue 9 2006Dieter Seebach Abstract Twelve peptides, 1,12, have been synthesized, which consist of alternating sequences of , - and , -amino acid residues carrying either proteinogenic side chains or geminal dimethyl groups (Aib). Two peptides, 13 and 14, containing 2-methyl-3-aminobutanoic acid residues or a ,random mix' of ,-, ,2 -, and ,3 -amino acid moieties were also prepared. The new compounds were fully characterized by CD (Figs.,1 and 2), and 1H- and 13C-NMR spectroscopy, and high-resolution mass spectrometry (HR-MS). In two cases, 3 and 14, we discovered novel types of turn structures with nine- and ten-membered H-bonded rings forming the actual turns. In two other cases, 8 and 11, we found 14/15 -helices, which had been previously disclosed in mixed ,/, -peptides containing unusual , -amino acids with non-proteinogenic side chains. The helices are formed by peptides containing the amino acid moiety Aib in every other position, and their backbones are primarily not held together by H-bonds, but by the intrinsic conformations of the containing amino acid building blocks. The structures offer new possibilities of mimicking peptide,protein and protein,protein interactions (PPI). [source] Synthetic dsDNA-Binding Peptides Using Natural Compounds as ModelHELVETICA CHIMICA ACTA, Issue 6 2006Filip Borgions Abstract We have developed a series of short DNA-binding peptides containing newly synthesized, unnatural as well as natural amino acid building blocks. By a combinatorial-library approach, oligopeptides were developed with moderate dsDNA-binding affinities. Two strategies were used to further enhance the binding affinity of the lead peptides: Ac-Arg-Ual-Sar-Chi-Chi-Chi-Arg-NH2 and Ac-Arg-Cbg-Cha-Chi-Chi-Tal-Arg-NH2. Site-selective amino acid substitutions increased the binding affinities up to 2,×,10,5,M. Further enhancement of the binding affinities could be achieved by coupling of an acridine intercalating unit, using linker arms of different length and flexibility. With the introduction of a new lysine-based acridine unit, different types of oligopeptide,acridine conjugates were designed using known dsDNA-binding ligands as model compounds. The binding capacities of these new oligopeptide,acridine conjugates have been investigated by a fluorescent intercalator (ethidium bromide) displacement (FID) assay. With the synthesis of the dipeptide,acridine conjugates, binding affinities in the low micromolar range were obtained (6.4,×,10,6,M), which is similar to the binding strength of the well-known DNA binder Hoechst 33258. [source] Expediting the Fmoc solid phase synthesis of long peptides through the application of dimethyloxazolidine dipeptidesJOURNAL OF PEPTIDE SCIENCE, Issue 1 2004Dr Peter White Abstract This paper describes the step-wise Fmoc solid phase synthesis of a 95-residue peptide related to FAS death domain. Attempts to prepare this peptide employing conventional amino acid building blocks failed. However, by the judicious use of dimethyloxazolidine dipeptides of serine and threonine, the peptide could be readily prepared in remarkable purity by applying single 1 h coupling reactions. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd. [source] Synthesis and secondary structure of loop 4 of myelin proteolipid protein: effect of a point mutation found in Pelizaeus-Merzbacher diseaseCHEMICAL BIOLOGY & DRUG DESIGN, Issue 3 2005E. Trifilieff Abstract:, To study the effects of a point mutation found in Pelizaeus-Merzbacher disease (PMD) on the physicochemical and structural properties of the extracellular loop 4 of the myelin proteolipid protein (PLP), we synthesized the peptide PLP(181,230)Pro215 and one mutant PLP(181,230)Ser215 with regioselective formation of the two disulphide bridges Cys200 -Cys219 and Cys183 -Cys227. As conventional amino acid building blocks failed to give crude peptides of good quality we had to optimize the synthesis by introducing pseudoproline dipeptide building blocks during the peptide elongation. In peptide Pro215 the first bridge Cys200,Cys219 was obtained after air oxidation, but in peptide Ser215 because of aggregation, dimethyl sulfoxide (DMSO) oxidation had to be used. The second bridge Cys183,Cys227 was obtained by iodine oxidation of both Cys (acetamidomethyl, Acm)-protected peptides. The secondary structures of the parent and mutant loops were analysed by circular dichroism (CD) in the presence of trifluoroethanol (TFE) and sodium dodecyl sulphate (SDS) as a membrane mimetic. Analysis of the spectra showed that the content of , -helix and , -sheet varied differently for both peptides in TFE and SDS solutions, demonstrating the sensitivity of their conformation to the environment and the differences in their secondary structure. The ability of both peptides to insert into the SDS micelles was assayed by intrinsic tryptophan fluorescence. [source] De Novo Synthesis of Uronic Acid Building Blocks for Assembly of Heparin OligosaccharidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2007Alexander Adibekian Abstract An efficient de novo synthesis of uronic acid building blocks is described. The synthetic strategy relies on the stereoselective elongation of thioacetal protected dialdehydes 12,a and 17. The dialdehydes are prepared from D -xylose, a cheap and commercially available source. A highly stereoselective MgBr2,OEt2 -mediated Mukaiyama aldol addition to C4-aldehyde 12,a is performed to obtain D -glucuronic acid building block 16, whereas L -iduronic acid building block 22 is prepared by MgBr2,OEt2 -mediated cyanation of C5-aldehyde 17. Synthesis of a heparin disaccharide demonstrates the utility of the de novo strategy for the assembly of glycosaminoglycan oligosaccharides. [source] | ||||||||||