共查询到20条相似文献,搜索用时 31 毫秒
1.
Asuka Nishikawa Shintaro Saito Yuichi Hashimoto Kenji Koga Ryuichi Shirai 《Tetrahedron letters》2001,42(52)
Efficient synthesis of l-α-phosphatidyl-d-myo-inositol 3,5-bisphosphate was achieved from 1,2,5,6-diisopropylidene-d-glucose by utilizing ring-closing metathesis and catalytic OsO4 dihydroxylation. 相似文献
2.
Ilko Bald Helga D. Flosadttir Janina Kopyra Eugen Illenberger Oddur Inglfsson 《International journal of mass spectrometry》2009,280(1-3):190
We present a detailed, collaborative study on the fragmentation of deprotonated native d-ribose and d-fructose and the isotopically labelled 1-13C-d-ribose, 5-13C-d-ribose and C-1-d-d-ribose. The fragmentation is studied in a matrix assisted laser desorption/ionization time of flight mass spectrometer (MALDI ToF MS), both in in-source decay (ISD) and post-source decay (PSD) mode and compared with fragmentation through dissociative electron attachment (DEA). Fragmentation of deprotonated monosaccharides formed in the MALDI process, as well as their transient molecular anions formed upon electron attachment are characterized by loss of different numbers of H2O and CH2O units. Two different fragmentation pathways leading to cross-ring cleavage are identified. Metastable decay of deprotonated d-ribose proceeds either via an X-type cleavage yielding fragment anions at m/z = 119, 100 and 89, or via an A-type cleavage resulting in m/z = 89, 77 and 71. A fast and early metastable cross-ring cleavage of deprotonated d-ribose observed in in-source decay is dominated by X-type cleavage leading mainly to m/z = 100 and 71. For dissociative electron attachment to d-ribose a sequential dissociation was identified that includes metastable decay of the dehydrogenated molecular anion leading to m/z = 89. All other fragmentation reactions in DEA to d-ribose are likely to proceed directly and on a faster timescale (below 400 ns). 相似文献
3.
The title compound has been synthesized via two proline-catalyzed aldol addition reactions of 2,2-dialkyl-1,3-dioxan-5-ones: the first addition to 1,3-dithiane-2-carboxaldehyde, followed by reduction to the corresponding diol, protection of the OH groups and dithiane hydrolysis afforded a protected d-ribose that was used in the second aldol addition reaction. 相似文献
4.
Tsonko Kolev Bojidarka B. Koleva Michael Spiteller William S. Sheldrick Heike Mayer-Figge 《Journal of Molecular Structure》2008,879(1-3):30-39
Benzamidinium d-glucuronate (1) crystallizes in the orthorhombic space group P212121 and exhibits a 3 D network with molecules linked by moderate intermolecular hydrogen bonds (HNH…O(solvent) 2.993 Å, HNH…OCO 2.894 Å, HNH…O(cycle) 2.844 Å, OH…NH2 2.931 Å, OH…O(solvent) 2.894, 2.924 and 2.715 Å (stronger)) with participation of cations, anions and solvent molecules. The IR-band assignment of carbohydrate moieties is elucidated by a comparison between the types and bond lengths of intermolecular interactions with participation of OH groups in d-glucuronate and linear polarized IR-(IR-LD) spectroscopic data. Experimental results are supported by theoretical ab initio calculations of benzamidinium cation and d-glucuronate anion. 相似文献
5.
Two five-coordinate copper(II) complexes, formulated as [Cu(La)2Cl]BF4 (1) and [Cu(Lb)2Cl]BF4 (2) having d-(+)-1,2,2-trimethylcyclopentane-1,3-diamine (La) and d,l-1,2,2-trimethylcyclopentane-1,3-diamine (Lb) ligands, have been synthesized and characterized. X-ray diffraction studies of 1 and 2 demonstrate that they crystallize in the different space groups (P212121 for 1 and Pnma for 2), although they have identical unit cell volumes, due to the use of enantiomeric and racemic diamine ligands. One dimensional (1D) hydrogen-bond-sustained dimeric zigzag chains are formed by means of eight-membered N2H2CuBF2 as well as 10-membered N2H4ClBF2 hydrogen-bonded cycles. Thermal analyses for 1 and 2 are also described herein. 相似文献
6.
The title homoazasugar, also referred as (2R,5S)-bis(hydroxymethyl)-(3R,4R)-dihydroxypyrrolidine, has been synthesized by addition of 2-lithiothiazole to the 2,3,5-tri-O-benzyl-d-arabinofuranose-derived nitrone---hydroxylamine mixture followed by reductive N-dehydroxylation and conversion of the thiazole ring into the hydroxymethyl group. 相似文献
7.
Knut M. Haldorsen 《Journal of chromatography. A》1978,150(2)
Pentavalent vanadium in sulphuric acid can be used for the quantitative analysis of sugars. The yellow pentavalent vanadium is reduced by carbohydrates to the blue tetravalent form, and either the consumption of vanadium(V) or the amount of vanadium(IV) formed can be measured. For model studies, different d-fructose-d-glucose-sucrose mixtures were used. The monosaccharides were separated from the disaccharide by thin-layer chromatography. Owing to the great difference in reactivity between aldohexoses and ketohexoses, d-fructose and d-glucose can be determined separately without prior separation. The method enables 10 μg of each sugar to be determined. 相似文献
8.
A stereoselective total synthesis of ophiocerin D is reported by a combination of a ‘chiron’ approach and an asymmetric synthesis, from d-xylose. Of the four stereogenic centers, the vic diols C3/C4 and C5/C6 were obtained by Sharpless asymmetric dihydroxylation and from d-xylose, respectively. 相似文献
9.
Stephen G. Davies Ai M. FletcherEmma M. Foster James A. LeePaul M. Roberts James E. ThomsonMichael A. Waul 《Tetrahedron》2014
A range of the methyl glycosides of 2-deoxy-2-aminohexoses, comprising d-allosamine, d-mannosamine, d-idosamine and d-talosamine, were prepared from the corresponding d-aldopentoses via a seven step synthetic sequence. The doubly diastereoselective conjugate addition of the requisite antipode of lithium N-benzyl-N-(α-methylbenzyl)amide and in situ enolate oxidation with the requisite antipode of camphorsulfonyloxaziridine (CSO) was used as the key, stereodefining step. Sequential reduction of the resultant α-hydroxy-β-amino esters and oxidative cleavage of the C(1)–C(2) diol unit furnished the corresponding α-amino aldehydes. Subsequent N- and O-deprotection gave the target compounds (as mixtures of anomers) in good yield and high diastereoisomeric purity. 相似文献
10.
A key intermediate corresponding to a rare sugar framework has been synthesized, starting from d-xylose, an inexpensive carbohydrate. This approach gave access to new elaborated sugar moieties for structure–activity relationships in the KRN research. 相似文献
11.
Odile Meyer Jean-Franois Hoeffler Catherine Grosdemange-Billiard Michel Rohmer 《Tetrahedron》2004,60(52):12153-12162
An optimised gram scale synthesis allows the production of 1-deoxy-d-xylulose and 1-deoxy-d-xylulose 5-phosphate with possible deuterium labelling at C-5. Such substrates are required for investigations on the mevalonate-independent 2-C-methyl-d-erythritol 4-phosphate pathway for isoprenoid biosynthesis in bacteria and chloroplasts of phototrophic eukaryotes and for the biosynthesis of vitamins B1 (thiamine diphosphate) and B6 (pyridoxol phosphate) in bacteria. 相似文献
12.
Xuequan Lu 《Tetrahedron letters》2005,46(18):3165-3168
The preparations of d-ribo- and l-lyxo-phytosphingosines (1, 2) are described. Chelation-controlled addition of tetradecylmagnesium bromide to pentylidene-protected d-threitol aldehyde 6 afforded the key intermediate tetrol 7, providing the desired l-lyxo stereochemistry of phytosphingosine. Inversion at C4 of intermediate 7 provided the d-ribo stereochemistry. 相似文献
13.
New phosphine-imine and phosphine-amine chiral ligands which were easily prepared from d-gluco-, d-galacto- and d-allosamine furnished a high level of enantiomeric excess (up to 99%) in the Pd(0)-catalysed asymmetric allylic alkylation of racemic 1,3-diphenyl-2-propenyl acetate with malonates. 相似文献
14.
Starting from a single suitable functionalised epoxide, a highly efficient stereoselective synthesis of d-erythro-sphingosine and d-lyxo-phytosphingosine is described. The approach allows the formal preparation of all stereoisomers of these sphingoid structures. 相似文献
15.
Omprakash P. Bande Vrushali H. Jadhav Vedavati G. Puranik Dilip D. Dhavale Marco Lombardo 《Tetrahedron letters》2009,50(49):6906-6908
Intramolecular N-alkylation of 2,3-O-isopropylidene-5-O-methanesulfonyl-6-O-t-butyldimethylsilyl-d-mannofuranose-oxime 7 afforded a five-membered cyclic nitrone 9, which on N–O bond reductive cleavage followed by deprotection of –OTBS and acetonide functionalities gave 1,4-dideoxy-1,4-imino-l-allitol (DIA) 3. Addition of allylmagnesium chloride to nitrone 9 afforded α-allylated product 10a in high diastereoselectivity providing an easy entry to N-hydroxy-C1-α-allyl-substituted pyrrolidine iminosugar 4a after removal of protecting group, while N–O bond reductive cleavage in 10a afforded C1-α-allyl-pyrrolidine iminosugar 4b. 相似文献
16.
Regio- and stereoselective cycloaddition of methyl acrylate to C-glycosyl nitrones derived from d-galactose and d-glucose, giving 5-methoxycarbonyl-3-(pentoglycos-5-yl or pentitol-1-yl)isoxazolidines, is reported. Transformation of one of them into a 4-hydroxy-2-(pentoglycos-5-yl)pyrrolidine derivative, potentially useful in a route to polyhydroxy-perhydroazaazulenes, was achieved. 相似文献
17.
Transport characterisation of a PIM system used for the extraction of Pb(II) using d2ehpa as carrier
German Salazar-Alvarez Ana Nelly Bautista-Flores Eduardo Rodríguez de San Miguel Mamoun Muhammed Josefina de Gyves 《Journal of membrane science》2005,250(1-2):247-257
The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulose triacetate as polymeric support, bis-(2-ethylhexyl)-phosphoric acid (d2ehpa) as carrier, and tris-(2-butoxyethyl)phosphate as plasticiser (tbep), is investigated. The influence of some of the aqueous and membrane components on the permeability of Pb(II) was studied. The maximum flux obtained with these membranes is 3.5×10−6 mol m−2 s−1, which is of the same order of magnitude of those reported for supported liquid membranes and is in the upper range of those reported for polymeric inclusion membranes. Aqueous and membranes resistances were determined from a model that describes the transport mechanism across the membranes using the stoichiometric relationship and the extraction equilibrium constant value of 6.2×10−4 determined independently by solid–liquid extraction. An activation energy of 11 kJ mol−1 was also determined for Pb(II) migration, which suggest that the transport of Pb(II) is controlled by a membrane diffusion mechanism. Membrane characterisation was performed using several techniques including atomic force microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and thermal analysis. 相似文献
18.
19.
Intramolecular nitrone–olefin cycloaddition in a mannose template followed by N–O cleavage, quaternization of the resulting amine, and finally oxidative elimination of the amino group affords, after deprotection, ent-gabosine E in enantiomerically pure form. 相似文献
20.
Ram Kripal Pragya Singh Har Govind 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):357-362
EPR studies are carried out on Cr3+ ions doped in d-gluconic acid monohydrate (C6H12O7·H2O) single crystals at 77 K. From the observed EPR spectra, the spin Hamiltonian parameters g, |D| and |E| are measured to be 1.9919, 349 (×10−4) cm−1 and 113 (×10−4) cm−1, respectively. The optical absorption of the crystal is also studied at room temperature. From the observed band positions, the cubic crystal field splitting parameter Dq (2052 cm−1) and the Racah interelectronic repulsion parameter B (653 cm−1) are evaluated. From the correlation of EPR and optical data the nature of bonding of Cr3+ ion with its ligands is discussed. 相似文献