- A novel low-molecular-mass pumpkin polysaccharide: Structural characterization, antioxidant activity, and hypoglycemic potential
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The novel natural low-molecular-mass polysaccharide (SLWPP-3) from pumpkin (Cucurbia moschata) was separated from the waste supernatant after macromolecular polysaccharide production and purified using a DEAE cellulose-52 column and gel-filtration chromatography. Chemical and instrumental studies revealed that SLWPP-3 with a molecular mass of 3.5 kDa was composed of rhamnose, glucose, arabinose, galactose and uronic acid with a weight ratio of 1: 1: 4: 6: 15, and primarily contained →3,6)-β-D-Galp-(1→, →4)-α-GalpA-(1→(OMe), →4)-α-GalpA-(1→, →2,4)-α-D-Rhap-(1→, →3)-β-D-Galp-(1→, →4)-α-D-Glcp, and →4)-β-D-Galp residues in the backbone. The branch chain passes were connected to the main chain through the O-4 atom of glucose and O-3 atom of arabinose. Physiologically, the ability of SLWPP-3 to inhibit carbohydrate-digesting enzymes and DPPH and ABTS radicals, as well as protect pancreatic β cells from oxidative damage by decreasing MDA levels and increasing SOD activities, was confirmed. The findings elucidated the structural types of pumpkin polysaccharides and revealed a potential adjuvant natural product with hypoglycemic effects.
- Huang, Linlin,Li, Fei,Li, Quanhong,Liang, Li,Wei, Yunlu,Yu, Guoyong
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- Chemical synthesis method of L-xylose
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The invention discloses a novel chemical synthesis method of L-xylose. According to the novel chemical synthesis method, 2, 2-dimethoxypropane protects hydroxyl of L-(-)2,3-dihydroxypropionaldehyde, and then a product is coupled with (1-bromovinyl)trimethylsilane so as to establish a basic framework of a target product; after production of 99% of ee is guaranteed by a sharpless epoxidation or Jacobsen-Katsuki expoxidation method, a three-membered ring is opened by protecting groups to guarantee that the configuration thereof is unchanged; then, the hydroxyl group produced by selectively removing one protecting group is oxidized into an aldehyde group; finally, the remaining protecting groups are removed to obtain the target product L-xylose, and the total yield is 46-48%. By the novel chemical synthesis method, the condition is mild, raw materials are cheap and easy to obtain, and a synthesis thought and the synthesis method are provided for chemical synthesis of a series of aldoses.
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- Method for preparing amino alcohol derivative
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The invention provides a method for preparing an amino alcohol derivative. The method is characterized in that substitution reaction is carried out on ester groups of dihydric alcohol carboxylic esteror polyhydric alcohol carboxylic ester to obtain the amino alcohol derivative, wherein the amidogen is derived into sulfonamido, and at least one carboxylic ester group remains. The method for preparing the amino alcohol derivative has the advantages that the raw materials are cheap and obtained easily, the use quantity of catalysts is low, the reaction condition is simple, and the selectivity ofproducts is high.
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Paragraph 0099; 0100; 0101
(2018/11/22)
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- Discovery and characterization of family 39 glycoside hydrolases from rumen anaerobic fungi with polyspecific activity on rare arabinosyl substrates
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Enzyme activities that improve digestion of recalcitrant plant cell wall polysaccharides may offer solutions for sustainable industries. To this end, anaerobic fungi in the rumen have been identified as a promising source of novel carbohydrate active enzymes (CAZymes) that modify plant cell wall polysaccharides and other complex glycans. Many CAZymes share insufficient sequence identity to characterized proteins from other microbial ecosystems to infer their function; thus presenting challenges to their identification. In this study, four rumen fungal genes (nf2152, nf2215, nf2523, and pr2455) were identified that encode family 39 glycoside hydrolases (GH39s), and have conserved structural features with GH51s. Two recombinant proteins, NF2152 and NF2523, were characterized using a variety of biochemical and structural techniques, and were determined to have distinct catalytic activities. NF2152 releases a single product, β1,2-arabinobiose (Ara2) from sugar beet arabinan (SBA), and β1,2-Ara2 and α-1,2-galactoarabinose (Gal-Ara) from rye arabinoxylan (RAX). NF2523 exclusively releases α-1,2-Gal-Ara from RAX, which represents the first description of a galacto-(-1,2)-arabinosidase. Both β-1,2-Ara2 and α-1,2-Gal-Ara are disaccharides not previously described within SBA and RAX. In this regard, the enzymes studied here may represent valuable new biocatalytic tools for investigating the structures of rare arabinosyl-containing glycans, and potentially for facilitating their modification in industrial applications.
- Jones, Darryl R.,Uddin, Muhammed Salah,Gruninger, Robert J.,Pham, Thi Thanh My,Thomas, Dallas,Boraston, Alisdair B.,Briggs, Jonathan,Pluvinage, Benjamin,McAllister, Tim A.,Forster, Robert J.,Tsang, Adrian,Selinger, L. Brent,Abbott, D. Wade
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p. 12606 - 12620
(2017/08/02)
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- Isolation, purification and structural characterization of a water-soluble polysaccharide HM41 from Halenia elliptica D. Don
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A water-soluble polysaccharide, HM41, was obtained from Halenia elliptica D. Don by acidic ethanol fractionation and gel filtration. Its homogeneity was confirmed by chromatography using multiple systems. HM41 was composed of rhamnose (Rha), arabinose (Ara), xylose (Xyl), mannose (Man), galactose (Gal), glucose (Glc) with a molar ratio of 1.0:5.5:1.8:3.0:9.4:21. The average molecular weight of HM41 was approximately 1.17 × 104. Periodate oxidation, Smith degradation, methylation and GC, IR, NMR, XRD, GC-MS analysis were used for the structural analysis of HM41. Its main chain was composed mainly of β-(1 → 4)Gal, β-(1 → 4)Glc and β-(1 → 6)Glc. β-(1 → 4)Gal were substituted at 6-O and on average there were 14 branches among 23 main chain residues; (1 → 4)Glc had no branch; (1 → 6)Glc were substituted at 3-O and on average there were 9 branches among 14 main chain residues. The side chain was composed of (1 → 3,6)-Rha, (1 → 4)/(1 → 5)-Ara, (1 → 4)/(1 → 5)-Xyl, (1 → 4,6)-Man and (1 → 2)-Glc. The terminal residue was composed of Ara, Xyl, Man, Gal, and Glc. Then, we demonstrated that HM and HM41 had strong scavenging activities in vitro hydroxyl. Overall, HM and HM41 may have potential applications in the antioxidants for medical and food industry.
- Liu, Chun-Lan,Li, Yang,Xu, Gui-Yun,Li, Ya-Shuang
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p. 979 - 983
(2016/06/13)
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- Isolation and characterization of a hyperbranched proteoglycan from Ganoderma Lucidum for anti-diabetes
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Presently, an efficient protein tyrosine phosphatase 1B (PTP1B) inhibitor, named FYGL-n, was isolatedfrom Ganoderma Lucidum and characterized for its structure and bioactivity. Structure and chain con-formation of FYGL-n based on both chemical and spectroscopic analysis showed that FYGL-n was ahyperbranched heteropolysaccharide bonded with protein via both serine and threonine residues by O-type glycoside, and showed a sphere observed by AFM. Specifically, monosaccharide compositionindicated that FYGL-n consisted of D-arabinose, D-galactose, L-rhamnose and D-glucose in a mole ratio of 0.08:0.21:0.24:0.47, with a molecular mass of 72.9 kDa. The analysis of amino acids in FYGL-n indicatedthat there were 16 common amino acids, among which aspartic acid, glycine, serine, alanine, glutamicacid and threonine were the dominant components. Also it was demonstrated that FYGL-n could inhibitthe PTP1B activity on a competitive mechanism in vitro.
- Pan, Deng,Wang, Linqiang,Chen, Congheng,Hu, Bingwen,Zhou, Ping
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supporting information
p. 106 - 114
(2015/02/19)
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- I2/ionic liquid as a highly efficient catalyst for per-O-acetylation of sugar under microwave irradiation
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A practical and highly efficient approach was developed to synthesize peracetylated sugar derivatives using a recyclable iodine/PEG400-based ionic liquid catalyst (I2/IL). The peracetylated sugars were readily obtained in a few minutes in excellent yields (90%-99%, 13 examples) on a multi-gram scale (50.0 mmol) by the reaction of sugar and acetic anhydride under microwave irradiation in the absence of a volatile organic solvent. The desired product was easily obtained by simple extraction with toluene from the reaction mixture, and I2/ILs can be readily recovered and reused at least six times without obvious loss in the yield. When the scale of the per-O-acetylation reaction was increased to 50.0 mmol, the desired product was still obtained in 90% yield after five recycles.
- Xiong, Xingquan,Yi, Chao,Han, Qian,Shi, Lin,Li, Sizhong
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p. 237 - 243
(2015/09/28)
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- Characterization of the chemical diversity of glycosylated mycosporine-like amino acids in the terrestrial cyanobacterium Nostoc commune
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Mycosporine-like amino acids (MAAs) are UV-absorbing pigments, and structurally unique glycosylated MAAs are found in the terrestrial cyanobacterium Nostoc commune. In this study, we examined two genotypes of N. commune colonies with different water extract UV-absorption spectra. We found structurally distinct MAAs in each genotype. The water extract from genotype A showed a UV-absorbing spectrum with an absorption maximum at 335 nm. The extract contained the following compounds: 7-O-(β-arabinopyranosyl)-porphyra-334 (478 Da), pentose-bound shinorine (464 Da), hexose-bound porphyra-334 (508 Da) and porphyra-334 (346 Da). The water extract from genotype B showed a characteristic UV-absorbing spectrum with double absorption maxima at 312 and 340 nm. The extract contained hybrid MAAs (1050 Da and 880 Da) with two distinct chromophores of 3-aminocyclohexen-1-one and 1,3-diaminocyclohexen linked to 2-O-(β-xylopyranosyl)-β-galactopyranoside. A novel 273-Da MAA with an absorption maximum at 310 nm was also identified in genotype B. The MAA consisted of a 3-aminocyclohexen-1-one linked to a γ-aminobutyric acid chain. These MAAs had potent radical scavenging activities in vitro and the results confirmed that the MAAs have multiple roles as a UV protectant and an antioxidant relevant to anhydrobiosis in N. commune. The two genotypes of N. commune exclusively produced their own characteristic glycosylated MAAs, which supports that MAA composition could be a chemotaxonomic marker for the classification of N. commune.
- Nazifi, Ehsan,Wada, Naoki,Asano, Tomoya,Nishiuchi, Takumi,Iwamuro, Yoshiaki,Chinaka, Satoshi,Matsugo, Seiichi,Sakamoto, Toshio
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p. 154 - 168
(2015/02/18)
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- Silica-supported boric acid catalyzed synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, esters and amides
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Silica-supported boric acid (H3BO3-SiO2) has been established as a green, efficient and recyclable catalyst for the synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, and acetylation of alcohols, phenols, amines and thiols under solvent free conditions. The main features of the present method include clean reaction, mild conditions, low loading of environment friendly catalyst and easy workup procedure. The catalyst can be recycled at least five times without any significant loss in activity.
- Kumar, Vishal,Singh, Chitra,Sharma, Upendra,Verma, Praveen K.,Singh, Bikram,Kumar, Neeraj
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- New 9,19-cycloartenol glycosides isolated from the roots of Cimicifuga simplex and their anti-inflammatory effects
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Two new cycloartenol triterpene saponins, 3β,16α-dihydroxy-12-acetoxy-16,22-cyclo-23-ketone-24R,25-epoxy-cycloartane-3-O-β-d-galactopyranoside (1), 3β,16α-dihydroxy-12-acetoxy-16,22-cyclo-23-ketone-24R,25-epoxy-cycloartane-7-ene-3-O-β-d-xylopyranoside (2), were isolated from the ethyl acetate soluble fraction of the roots of Cimicifuga simplex Wormsk. Their structures were established by detailed spectroscopic analysis, including extensive 2D NMR data. Their anti-proinflammatory activities were also carried out by LPS-stimulated IL-6, IL-23 and TNF-α genes expression in RAW cells in vitro using Q-PCR method.
- Su, Yang,Wu, Lun,Wang, Qiuhong,Yang, Bingyou,Kuang, Haixue
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supporting information
p. 5688 - 5691
(2015/01/08)
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- Enumeration of hydroxyl groups of sugars and sugar alcohols by aqueous-based acetylation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
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RATIONALE The properties of carbohydrates are determined in part by the number and stereochemical arrangement of their hydroxyl groups. To facilitate their analysis, rapid methods are needed to identify and enumerate hydroxyl groups in sugars and polyalcohols, especially methods that are water-based. METHODS The present report details the results of an alternative method for identification and enumeration of hydroxyl groups in aqueous media. It employs vinyl acetate to selectively derivatize hydroxyl groups in analytes, followed by analysis of the reaction mixtures by matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF-MS). RESULTS The method has been applied to several single and multi-component mixtures of monosaccharides and polyalcohols. The O-acetylated products were analyzed without chromatographic separation or purification by MALDI-TOF-MS. The mass spectra revealed consecutive ion peaks that are separated by 42 mass units as a consequence of displacement of one hydroxyl hydrogen by one acetyl group. CONCLUSIONS A rapid and aqueous-based method is described to enumerate the hydroxyl groups in carbohydrates. The number of ion peaks due to derivatized products is determined by MALDI-TOF-MS, and corresponds to the number of free hydroxyl groups in the analyte. The method is applicable to both single and multi-component mixtures. Published 2011. This article is a US Government work and is in the public domain in the USA. Published 2012. This article is a US Government work and is in the public domain in the USA.
- Adeuya, Anthony,Price, Neil P.J.
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experimental part
p. 1372 - 1376
(2012/08/08)
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- Extraction, purification, characterization and hypoglycemic activity of a polysaccharide isolated from the root of Ophiopogon japonicus
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In this research, a water-soluble polysaccharide (OJP1) extracted with hot water from the roots of Ophiopogon japonicus which is a traditional Chinese medicinal herb was precipitated with 95% ethanol and purified by DEAE-52 cellulose anion-exchange and Sephadex G-100 gel filtration chromatography. The high performance gel permeation chromatography (HPGPC) analysis showed that the average molecular weight (Mw) of OJP1 was 35.2 kDa. Monosaccharides analysis revealed that the OJP1 is composed of Ara, Glc, Gal with a relative molar ratio of 1:16:8. Pharmaceutical experiments showed OJP1 can significantly reduce blood glucose level, increase the insulin level and remediating destruction of pancreatic islets in STZ-induced diabetic rats compared with the diabetic control group. The study shows that OJP1 has an anti-diabetic effect on STZ-induced diabetic rats, and has potential use as an anti-diabetic agent. Copyright
- Chen, Xiaoming,Jin, Jing,Tang, Jia,Wang, Zhongfu,Wang, Junjun,Jin, Liqin,Lu, Jianxin
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experimental part
p. 749 - 754
(2011/06/27)
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- 1-Phenylprop-2-ynyl acetate: A useful building block for the stereoselective construction of polyhydroxylated chains
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(R)- or (S)-1-phenylprop-2-ynyl acetate was added stereoselectively to aldehydes to afford 4-hydroxy-1-phenylalk-2-ynyl acetates. The transformation of such adducts into the corresponding allylic 1,4-diacetates allowed a highly efficient transfer of chirality from C1 to C3 by a regio- and stereoselective [3,3]-sigmatropic rearrangement. The obtained unsaturated 1,2-diacetates were useful synthetic intermediates whose double bond and/or phenyl group were transformed in different aldehydes, acids, or esters.
- Ariza, Xavier,Garcia, Jordi,Georges, Yohan,Vicente, Mar
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p. 4501 - 4504
(2007/10/03)
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- Prebiotic carbohydrate synthesis: Zinc-proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
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Zn-proline catalyzed aldolisation of glycoladehyde gave mainly tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose. The Royal Society of Chemistry 2005.
- Kofoed, Jacob,Reymond, Jean-Louis,Darbre, Tamis
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p. 1850 - 1855
(2007/10/03)
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- Regioselective benzylation of pentitols, tetritols, and some hexitols via their stannyl ether derivatives: Versatile synthesis of monobenzylalditols
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The xylitol, ribitol and D-arabinitol were transformed into their tributylstannyl ether derivatives by reaction with bis-tributyltin oxide [(nBu3Sn)2O I] and azeotropic removal of water. Subsequent benzyl etherification, using BnBr with solvent or under free solvent conditions, led regioselectively to primary mono-O-benzylalditol derivatives in satisfactory yields for a direct regioselective synthesis (~ 52%). This etherification when applied to tetritols and some hexitols exhibits similar behaviour. With pentitols, an analogous study carried out with the n-dibutyltin oxide [nBu2SnO (II)] as the activating reagent showed contrasting results as regards regioselectivity.
- Halila, Sami,Benazza, Mohammed,Demailly, Gilles
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p. 467 - 483
(2007/10/03)
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- New phenylphenalenones from banana fruit
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Six new phenylphenalenone derivatives were isolated from unripe banana, Musa acuminata, fruit that had been wounded followed by inoculation with Colletotrichum musae. Absolute configurations of optically active phenylphenalenone derivatives were elucidated by their chemical conversion to L-arabitol pentaacetate. Antifungal activities against C. musae and a biosynthetic pathway of phenylphenalenones are also discussed.
- Kamo, Tsunashi,Hirai, Nobuhiro,Iwami, Kumiko,Fujioka, Daie,Ohigashi, Hajime
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p. 7649 - 7656
(2007/10/03)
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- Reaction of sugar allyltins with aldehydes. A remarkable difference in reactivity between furanose and pyranose organometallic derivatives
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The reaction of organometallic derivatives of monosaccharides with aldehydes catalyzed with BF3·OEt2 was studied. A significant difference in reactivity between the pyranosidic and furanosidic and allyltins was noted. The former reacted readily with aldehydes affording precursors of higher carbon sugars with very high stereoselectivity, while the latter underwent rearrangement with elimination of the stannyl moiety prior to reaction with the aldehyde.
- Jarosz, Slawomir,Skora, Stanislaw,Szewczyk, Katarzyna,Ciunik, Zbigniew
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p. 1895 - 1905
(2007/10/03)
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- Chemoenzymatic synthesis of trans-4,5-dihydroxycyclopent-2-enones: Conversion to D-1-deoxynojirimycin
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(4R,5S)-trans-4,5-Bis(tert-butyldimethylsilyloxy)cyclopent-2-enone 8 and (4R,5S)-trans-4,5-di(benzyloxy)cyclopent-2-enone 20 are prepared by equilibration of the corresponding cis derivatives; enone 8 is transformed into the glucosidase inhibitor, D-1-deoxynojirimycin 14.
- Johnson,Nerurkar,Golebiowski,Sundram,Esker
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p. 1139 - 1140
(2007/10/02)
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- Acetolysis of 2,4-O-benzylidene-L-ribo-hex-5-enitol derivative
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Acetolysis of (Z)-1,3-di-O-acetyl-2,4-O-benzylidene-5,6-dideoxy-6-C-(2,4-dichlorophenyl)-L-ribo-hex-5-enitol afforded, besides 2-C--3,4,6-tri-O-acetyl-2-deoxy-β-D-allo- and -gluco-hexopyranosylbenzene, (E)-1,2,3,4-tetra-O-acetyl-5,6-dideoxy-6-C-(2,4-dichlorophenyl)-D-lyxo- and -L-ribo-hex-5-enitol as main products.The rate of this reaction as well as the ratio of the products depends on the chirality of C-3.This was confirmed by acetolysis of the corresponding L-erythro-pent-4-enitol derivative.
- Kuszmann, Janos,Podanyi, Benjamin
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p. 217 - 226
(2007/10/02)
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- Asymmetric dihydroxylation of chiral olefins. High control of diastereofacial selection
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Highly diastereoselective dihydroxylation of 4,5-dihydroxy-2-pentenoate with osmium tetroxide using chiral N,N′-dialkyl-2,2′-bipyrrolidine ligands (1) is described. Either syn or anti selection was achieved for acetate (2d) and methyl ether (2e) by employing the enantiomeric ligands.
- Oishi, Tohru,Iida, Kyo-Ichiro,Hirama, Masahiro
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p. 3573 - 3576
(2007/10/02)
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- Chelation Control in the Aldol Reaction of Tetronic Acid. Application to the Synthesis of Pentoses, Arabitol and Ribitol
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The aldol reaction of lithium enolates of tetronates with (R)-2,3-O-cyclohexylideneglyceraldehyde afforded the chelation controlled products stereoselectively.The conversion of the aldol products into arabitol and ribitol was also described.
- Honda, Toshio,Hayakawa, Tomohisa,Kondoh, Hirotsune,Okuyama, Akihiko,Tsubuki, Masayoshi
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p. 1861 - 1864
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF POLYHYDROLXYLATED NATURAL PRODUCTS I. EFFICIENT PREPARATION OF L-ARABINITOL
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A new approach to sugar synthesis is demonstrated through the synthesis of L-arabinitol.Reduction of allylic β-ketosulfoxides followed by hydroxylation of the double bond in the resulting allylic β-ketosulfoxides are the two important asymmetric steps involved in the process.
- Solladie, Guy,Hutt, Jean,Frechou, Catherine
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- Stereospecific hydroxylation of chiral allylic β-hydroxysulfoxides: asymmetric synthesis of L-arabinitol
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Chiral allylic β-hydroxysulfoxides 2 have been hydroxylated by the osmium tetroxide catalyzed reaction.The reaction can be highly stereoselective depending on the nature of the substituent linked to the double bond and the configurations of the sulfoxide and hydroxylic groups.The diastereoselectivity can be as high as 90 percent.This methodology was applied to the asymmetric synthesis of L-arabinitol.
- Solladie, Guy,Frechou, Catherine,Hutt, Jean,Demailly, Gilles
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p. 827 - 836
(2007/10/02)
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- Stereoselective Synthesis of β,γ-Unsaturated- and β,γ-Epoxy Glycerol Derivatives starting with Glyceraldehyde and their Use in the Synthesis of Alditols
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Highly stereoselective addition of vinylcopper and vinylcuprate compounds to glyceraldehyde acetonide affords both syn- and anti-β,γ-unsaturated glycerol derivatives, respectively, which can readily be converted into all the possible steric isomers of the β,γ-epoxy glycerol derivatives, which are useful intermediates in the synthesis of alditols.
- Kusakabe, Masato,Sato, Fumie
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p. 989 - 991
(2007/10/02)
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- ON STEREOCHEMISTRY OF OSMIUM TETRAOXIDE OXIDATION OF ALLYLIC ALCOHOL SYSTEMS. EMPIRICAL RULE
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An empirical formulation is presented to predict the stereochemistry of major osmylation products of allylic alcohols and their derivatives.
- Cha, J. K.,Christ, W. J.,Kishi, Y.
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p. 2247 - 2256
(2007/10/02)
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- EQUILIBRATION OF ALDITOL ANHYDRIDES IN ACETIC ACID
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Dehydration of pentitols in acetic acid containing an acidic catalyst parallels that in aqueous sulfuric acid; 1,4(2,5)-dehydration occurs with inversion of configuration at C-2 or C-4.Acetylated alditols undergo similar processes via intermediates having free hydroxyl groups.Configurational inversion of 1,4- or 1,5-anhydroalditols is attributed to intermediate acyloxonium ions that are also proposed as intermediates in the structural isomerisation.Drastic treatment of each alditol gives equilibrium mixtures.The equilibrium concentrations are used to calculate free-energy differences.
- Wisniewski, Andrzej,Gajdus, Jerzy,Sokolowski, Janusz,Szafranek, Janusz
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- Regioselective and Stereoselective Methods for the Synthesis of the Pentitols
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Several different approaches to the stereoselective synthesis of xylitol (1), as well as the other two pentitols, ribitol (2) and DL-arabinitol DL-(3), from the (Z)- and (E)-1-hydroxypentadienes (4) and (5) and the (Z)- and (E)-4,5-epoxypent-2-enals (6) and (7) are described.They rely upon either (a) epoxidations of allylic C=C double bonds followed by stereospecific (anti) and sometimes regioselective epoxide cleavages, or (b) syn-hydroxylations of allylic C=C double bonds.Employing approach (a), the (Z)-isomers (4) and (6) do not afford any ribitol (2) among the products and the (E)-isomers do not afford any xylitol (1).The consequences are reversed when approach (b) is adopted.The most convenient synthesis of xylitol (1) starts from the (Z)-isomer (6) of 4,5-epoxypent-2-enal.The formyl group in (6) is reduced, provided acidic work-up conditions are employed, to yield (Z)-(4RS)-4,5-epoxy-1-hydroxypent-2-ene (9), which is characterised as its acetate (10).Opening of the epoxide ring in (10) with acetate ion gives the triacetate (11), which is deacetylated to afford a key intermediate, (Z)-(4RS)-1,4,5-trihydroxypent-2-ene (12).Epoxidation of (12) with peracids (e.g. p-nitroperbenzoic acid) yields (t-butyl hydroperoxide with catalytically active Ti4+, V5+, and Mo6+ complexes fails) two epoxides (13) and (14), arbitrarily named isomers A (13) and B (14) subsequently shown to have the relative stereochemistries (2S,3R,4R) and (2R,3R,4R), respectively.Epoxide ring opening with acetate ion in acetic anhydride of the more abundant isomer B (14), obtained with 70percent diastereoselectivity, yields xylitol penta-acetate (16) as the major product (>80percent diastereoselectivity) along with small and trace amounts of the other two pentitol penta-acetates.Epoxide ring opening of isomer A with acetate ion in acetic anhydride is not a straightforward reaction for the most part and has been found to involve the intermediacy of an isolatable bicyclic orthoester (23) en route to some of the xylitol penta-acetate (16) formed as the principal stable product during this reaction.These variations of approach (a) constitute stereoselective syntheses of xylitol (1), which are claimed to be acceptable on a laboratory scale.They provide a slightly better route than an alternative one involving the transformations (4) -> (33) -> (34) -> (39) -> (16) -> (1), starting from (Z)-1-hydroxypenta-2,4-diene (4), principally because this particular precursor is less readily accessible than (Z)-4,5-epoxypent-2-enal (6).By contrast, the (E)-isomer (5) of 1-hydroxypenta-2,5-diene is obtainable in high yield from the reduction of vinyl acrylic acid and the analogous transformations (26) -> (27) -> (28) -> DL-(5) -> DL-(3)> provide a highly stereoselective (91percent) synthetic route to DL-arabinitol DL-(3).Osmium-catalysed syn-hydroxylation of (E)-(4RS)-triacetoxypent-2-ene (22), prepared from (E)-4,5-epoxypent-2-enal (7) in two steps (20) -> (22)>, provides yet another...
- Holland, David,Stoddart, J. Fraser
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p. 1553 - 1571
(2007/10/02)
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- ON STEREOCHEMISTRY OF OSMIUM TETROXIDE OXIDATION OF ALLYLIC ALCOHOL SYSTEMS: EMPIRICAL RULE
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An empirical formulation is presented to predict the stereochemistry of major osmylation products of allylic alcohols and their derivatives.
- Cha, J. K.,Christ, W. J.,Kishi, Y.
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p. 3943 - 3946
(2007/10/02)
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- STEREOSELECTIVE EPOXIDATION OF DIVINYLMETHANOL: A SYNTHETIC APPROACH TO THE PENTITOLS
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Peroxy-acid epoxidation of divinylmethanol (9), followed by acetylation afforded the acetylated monoepoxides 1 and 2 having the erythro (53percent) and threo (47percent) configurations.Peroxy-acid epoxidation of 1 and 2 yielded the acetylated diepoxides 3 (erythro-erythro, 36percent) and 4 (erythro-threo, 64percent) (from 1), and 4 (erythro-threo, 47percent) and 5 (threo-threo, 53percent) (from 2).Relative configurational assignments were made to 1-5 on the basis of (a) (1)H-n.m.r. chemical-shift and coupling-constant data, (b) the observation that 1 gave only 3 and 4, and that 2 gave only 4 and 5 on epoxidation, and (c) the fact that 3-5 separately undergo epoxidering opening preferentially at their primary carbon atoms with acetate ion in acetic anhydride, to afford the penta-acetates of ribitol, DL-arabinitol, and xylitol, respectively, as major products.Epoxide-ring formation favours the erythro configuration when either peroxy acids or tert-butyl hydroperoxide with catalitically active Ti(4+), V(5+), or Mo(6+) complexes are employed as epoxidation reagents.However, the diastereoselectivities characterising the epoxidations and the regioselectivities governing the epoxide-ring openings are not sufficiently high to constitute an attractive synthesis of euther ribitol, DL-arabinitol, or xylitol from divinylmethanol.
- Holland, David,Stoddart, J. Fraser
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p. 207 - 220
(2007/10/02)
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- Synthesis of Saccharides and Related Polyhydroxylated Natural Products. 1. Simple Alditols
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A new approach to sugar synthesis is demonstrated through syntheses of tetritols, pentitols, and hexitols; titanium-catalyzed asymmetric epoxidation and a new selective opening reaction of 2,3-epoxy alcohols play essential roles.
- Katsuki, T.,Lee, A. W. M.,Ma, P.,Martin, V. S.,Masamune, S.,et al.
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p. 1373 - 1378
(2007/10/02)
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- SYNTHESES OF AMINOCYCLITOLS AND AMINOCYCLITOL-OLIGOGLYCOSIDES FROM URONIC ACIDS AND GLUCURONIDE-SAPONINS BY MEANS OF AN ELECTROLYTIC DECARBOXYLATION REACTION
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By use of the electrolytic decarboxylation reaction as the key step, aminocyclitols (6b, 7b, 8b, 10b, 14b) and aminocyclitol-oligoglycosides (e.g. 18) have been conveniently synthesized from uronic acids (1, 9, 12) and glucuronide-saponins (e.g. 15).The conversions include the first syntheses of optically active D-neo- and L-neo-nitrocyclitols (10, 14).
- Kitagawa, Isao,Kamigauchi, Toshiyuki,Shirakawa, Kiyoharu,Ikeda, Yoshiharu,Ohmori, Hidenobu,Yoshikawa, Masayuki
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p. 349 - 354
(2007/10/02)
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- DEGRADATION OF 2-DEOXYALDOSES BY ALKALINE HYDROGEN PEROXIDE
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Reaction of 2-deoxy-D-arabino-hexose, 2-deoxy-D-lyxo-hexose, and 2-deoxy-D-erythro-pentose with alkaline hydrogen peroxide in the presence of magnesium hydroxide afforded the corresponding 2-deoxyaldonic acid, the 1,4-lactone, and the 1-O-formyl derivative of the next lower alditol.The 2-deoxyaldonic acids were separeted in 60-80 percent yields, as new, crystalline lithium salts.The 1,4-lactones were obtained under conditions that precluded intermediate formation of the free acids; preasumbly, the reaction proceeded by way of an intermediate, furanosyl hydroperoxide, which was converted into the lactone by elimination of water.With an excess of alkaline hydrogen peroxide, in the absence of magnesium hydroxide, the substrates were degraded to formic acid, with concurrent decomposition of hydrogen peroxide.It is shown that decomposition of hydrogen peroxide is catalyzed by hydroperoxide anion, and that is takes place by both a chain, and a non-chain, process.The decomposition reactions afford an abundant source of hydroxyl radical capable of oxidizing a wide variety of compounds.
- Isbell, Horace S.,Frush, Harriet L.,Naves, Renee,Soontracharoen, Preeda
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p. 111 - 122
(2007/10/02)
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