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Robert A Field - One of the best experts on this subject based on the ideXlab platform.
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synthesis of apiose containing oligosaccharide fragments of the plant cell wall fragments of rhamnogalacturonan ii side chains a and b and apiogalacturonan
Organic and Biomolecular Chemistry, 2011Co-Authors: Sergey A Nepogodiev, Margherita Fais, David L Hughes, Robert A FieldAbstract:Fragments of pectic polysaccharides rhamnogalacturonan-II (RG-II) and apiogalacturonan were synthesised using p-tolylthio apiofuranoside derivatives as key building blocks. Apiofuranose thioglycosides can be conveniently prepared by cyclization of the corresponding dithioacetals possessing a 2,3-O-Isopropylidene Group, which is required for preservation of the correct (3R) configuration of the apiofuranose ring. The remarkable stability of this protecting Group in apiofuranose derivatives requires its replacement with a more reactive protecting Group, such as a benzylidene acetal which was used in the synthesis of trisaccharide β-Rhap-(1→3′)-β-Apif-(1→2)-α-GalAp-OMe. The X-ray crystal structure of the protected precursor of this trisaccharide has been elucidated.
Barry V L Potter - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of the enantiomers of myo-inositol 1,2,4,5-tetrakisphosphate, a regioisomer of myo-inositol 1,3,4,5-tetrakisphosphate
Journal of The Chemical Society-perkin Transactions 1, 1997Co-Authors: Stephen J. Mills, Barry V L PotterAbstract:Routes for the synthesis of racemic myo-inositol 1,2,4,5-tetrakisphosphate DL-Ins(1,2,4,5)P4 5ab and the chiral antipodes D- and L-myo-inositol 1,2,4,5-tetrakisphosphate 5a and 5b, respectively, are described. For the synthesis of racemate 5ab, 3,6-di-O-benzoyl-1,2:4,5-di-O -Isopropylidene-myo-inositol 7ab is prepared in two steps from myo-inositol. The ketals are hydrolysed under acidic conditions to give DL-1,4-di-O-benzoyl- myo-inositol 8ab. Phosphitylation of compounds 8ab using chloro(diethoxy)phosphine in the presence of base, followed by oxidation and a three-step deprotection strategy, gives DL-Ins(1,2,4,5)P4 5ab.The chiral tetrakisphosphates 5a and 5b are synthesized using a different route. The 4,5-Isopropylidene Group of DL-3,6-di-O -benzyl-1,2:4,5-di-O-Isopropylidene-myo -inositol 13ab are selectively removed under mild acidic conditions to give diol 14ab. p-Methoxybenzylation at the 4,5-positions followed by acid hydrolysis of the cis-Isopropylidene ketal affords cis-diol 16ab. Selective coupling of (S)-(+)-O -acetylmandelic acid with diol 16ab at the equatorial hydroxy Group provides two diastereoisomers 18 and 19, which are separated by chromatography. Basic hydrolysis of the individual diastereoisomers provides the enantiomers 16a and 16b. Acidic hydrolysis gives D- and L-3,6-di-O-benzyl- myo-inositol 20a and 20b, respectively. Phosphitylation and oxidation of tetraols 20a and 20b gives the fully blocked derivatives, which are deprotected to give tetrakisphosphates 5a and 5b, respectively. The absolute configuration of compound 20a is established by a chemical method. DL-1,2:4,5-Di-O -Isopropylidene-myo-inositol 12ab is coupled to (S)-(+)-O -acetylmandelic acid to give a mixture of bis-esters 26 and 27 and crystallisation of the mixture of diastereoisomers affords pure isomer 27. Basic hydrolysis gives the pure enantiomer 12a (for which the absolute configuration is known) and benzylation followed by acid hydrolysis gives tetraol 20a with the same physical properties as compound 20a prepared by a different route described previously. D-Ins(1,2,4,5)P4 5a is a potent mobiliser of intracellular Ca2+ ions in permeabilised platelets, while L-Ins(1,2,4,5)P4 5b is inactive.
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synthesis of l scyllo inositol 1 2 4 trisphosphate scyllo inositol 1 2 4 5 tetrakisphosphate and phosphorothioate and dl 2 deoxy 2 fluoro myo inositol 1 4 5 trisphosphate optical resolution of dl 1 o allyl 3 6 di o benzyl 4 5 o Isopropylidene scyllo
Journal of The Chemical Society-perkin Transactions 1, 1996Co-Authors: Dethard Lampe, Changsheng Liu, Mary F Mahon, Barry V L PotterAbstract:Routes for the synthesis of scyllo-inositol tris-and tetrakis-phosphates and 2-deoxy-2-fluoro-myo-inositol 1,4,5-trisphosphate from myo-inositol have been devised. For DL-scyllo-inositol 1,2,4-trisphosphate, DL-1-O-allyl 1–3,6-di-O-benzyl-4,5-O-Isopropylidene-scyllo-inositol was prepared from the triflate of DL-1-O-allyl-3,6-di-O-benzyl-4–5-O-Isopropylidene-myo-inositol by inversion at C-2. Removal of the Isopropylidene Group and phosphorylation gave the protected trisphosphate. Deblocking with sodium in liquid ammonia afforded racemic scyllo-inositol 1,2,4-trisphosphate. DL-1-O-Allyl-3,6-di-O-benzyl-4,5-O-Isopropylidene-scyllo-inositol was resolved into its enantiomers by means of the crystalline 2-O-camphanate ester. The structure of one diastereoisomer, 1D-O-allyl-3,6-di-O-benzyl-2-O-[(–)-camphanate]-4,5–0-Isopropylidene-scyllo-inositol was determined by single-crystal X-ray crystallography. 1D-(+)-1-O-Allyl-3,6-di-O-benzyl-4,5-O-Isopropylidene-scyllo-inositol was used to prepare 1L(–)-scyllo-inositol 1,2,4-trisphosphate in a fashion analogous to the racemic modification. DL-1-O-Allyl-3,6-di-O-benzyl-scyllo-inositol was isomerised to the (Z)-prop-1-enyl derivative. The propenyl Group was then removed to give the meso-1,4-di-O-benzyscyllo-inositol. Phosphitylation followed by oxidation or sulfoxidation gave the fully protected tetrakis-phosphate or -phosphorothioate, respectively. After deblocking and purification, scyllo-inositol 1,2,4,5-tetrakisphosphate and scyllo inositol 1,2,4,5-tetrakisphosphorothioate were obtained. DL-1-O-Allyl-3,6-di-O-benzyl-4,5-O-Isopropylidene-scyllo-inositol was isomerised to the 1-O-[(Z)-prop-1-enyl] derivative which was converted into the 2-O-triflate. Displacement of the triflate using tetrabutylammonium fluoride proceeded with inversion of configuration to give DL-3,6-di-O-beflzyl-2-deoxy-2-fluoro-4,5-O-Isopropylidene-1-O-([(Z)-prop-1-eny]-myo-inositol. Removal of propenyl and Isopropylidene Groups afforded DL-3,6-di-O-benzyl-2-deoxy-2-fluoro-myo-inositol, which was phosphitylated and the product oxidised to give the fully protected 2-fluoro trisphosphate. Deprotection furnished DL-2-deoxy-2-fluoro-myo-inositol 1,4,5-trisphosphate. These compounds will be useful probes for investigation of the polyphosphoinositide pathway of cellular signalling.
Sergey A Nepogodiev - One of the best experts on this subject based on the ideXlab platform.
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synthesis of apiose containing oligosaccharide fragments of the plant cell wall fragments of rhamnogalacturonan ii side chains a and b and apiogalacturonan
Organic and Biomolecular Chemistry, 2011Co-Authors: Sergey A Nepogodiev, Margherita Fais, David L Hughes, Robert A FieldAbstract:Fragments of pectic polysaccharides rhamnogalacturonan-II (RG-II) and apiogalacturonan were synthesised using p-tolylthio apiofuranoside derivatives as key building blocks. Apiofuranose thioglycosides can be conveniently prepared by cyclization of the corresponding dithioacetals possessing a 2,3-O-Isopropylidene Group, which is required for preservation of the correct (3R) configuration of the apiofuranose ring. The remarkable stability of this protecting Group in apiofuranose derivatives requires its replacement with a more reactive protecting Group, such as a benzylidene acetal which was used in the synthesis of trisaccharide β-Rhap-(1→3′)-β-Apif-(1→2)-α-GalAp-OMe. The X-ray crystal structure of the protected precursor of this trisaccharide has been elucidated.
Margherita Fais - One of the best experts on this subject based on the ideXlab platform.
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synthesis of apiose containing oligosaccharide fragments of the plant cell wall fragments of rhamnogalacturonan ii side chains a and b and apiogalacturonan
Organic and Biomolecular Chemistry, 2011Co-Authors: Sergey A Nepogodiev, Margherita Fais, David L Hughes, Robert A FieldAbstract:Fragments of pectic polysaccharides rhamnogalacturonan-II (RG-II) and apiogalacturonan were synthesised using p-tolylthio apiofuranoside derivatives as key building blocks. Apiofuranose thioglycosides can be conveniently prepared by cyclization of the corresponding dithioacetals possessing a 2,3-O-Isopropylidene Group, which is required for preservation of the correct (3R) configuration of the apiofuranose ring. The remarkable stability of this protecting Group in apiofuranose derivatives requires its replacement with a more reactive protecting Group, such as a benzylidene acetal which was used in the synthesis of trisaccharide β-Rhap-(1→3′)-β-Apif-(1→2)-α-GalAp-OMe. The X-ray crystal structure of the protected precursor of this trisaccharide has been elucidated.
Shigeo Nakamura - One of the best experts on this subject based on the ideXlab platform.
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preparation and characterization of fluorine containing aromatic condensation polymers 4 preparation and characterization of fluorine containing aromatic polyazomethines and copolyazomethines from perfluoroIsopropylidene Group containing aromatic dia
Macromolecular Chemistry and Physics, 1994Co-Authors: Yasuo Saegusa, Minoru Kuriki, Shigeo NakamuraAbstract:A series of novel fluorine-containing aromatic homopolyazomethines and copolyazomethines were synthesized by solution polycondensation of perfluoroIsopropylidene (perfluoropropane-2,2-diyl) Group-containing aromatic diamines, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane (4,4′-[1,1,1,3,3,3-hexafluoropropane-2,2-diylbis(1,4-phenyleneoxy)]dianiline (1a)) and 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane (4,4′-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)dianiline (1b)), and/or the corresponding analogous Isopropylidene Group-containing aromatic diamines, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (4,4′-[Isopropylidenebis(1,4-phenyleneoxy)]dianiline (1c)) and 2,2-bis(4-aminophenyl)propane (4,4′-Isopropylidenedianiline (1d)), with terephthalaldehyde (2a) and isophthaladehyde (2b). The effect of fluorine substitution on the synthesis and properties of these polymers was investigated by comparison with those of the corresponding homopolyazomethines but without fluorine. Film-forming fluorine-containing polyazomethines with reduced viscosities up to ηred = 0,44 dL · g−1 were obtained in high yields by using m-cresol as reaction medium. Incorporation of perfluoroIsopropylidene Groups in the polyazomethine backbone greatly enhanced the solubility of the polymers in various organic solvents including chloroform and tetrahydrofuran. Their thermal stability was also successfully improved by the introduction of fluorine, and both the temperatures of 5% and 10% weight loss in air increased monotonically with the increase of the fluorine content. The surface properties of the films or the contact angles formed by water and diiodomethane were, however, scarcely affected by fluorine substitution. The mechanical properties of the films, such as tensile strength and initial modulus, fairly decreased by the modification.
