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1.
NIS/TfOH mediated glycosidation of methyl 3,4,6-tri-O-benzyl-α-d-mannopyranoside with phenyl 2-O-acetyl-3,4,6-tri-O-benzyl-1-thio-α-d-mannopyranoside furnished the corresponding disaccharide derivative in excellent yield and α-selectivity. Zémplen deacetylation of the same followed by reaction with BSP/Tf2O-preactivated phenyl 4,6-O-benzylidene-2,3-di-O-benzyl-1-thio-α-d-mannopyranoside generated methyl 4,6-O-benzylidene-2,3-di-O-benzyl-β-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzyl-α-d-mannopyranoside in very good yield and excellent β-selectivity. Pd/C catalyzed hydrogenation of the latter finally afforded the repeating trisaccharide of Escherichia coli 8 O-antigen as its methyl glycoside. 相似文献
2.
The trisaccharide 2-O-(α-L-fucopyranosyl)-3-O-(α-D-galactopyranosyl)-D-galactose has been synthesised stereospecifically using the imidate procedure. Allyl 3-O-benzoyl-4,6-O-benzylidene-β-D-galactopyranoside was first α-L-fucosylated by 1-O-(N-methyl)-acetimidyl-2,3,4-tri-O-benzyl-β-L-fucopyranose then, after O-debenzoylation, α-D-galactosylated by 1-O-(N-methyl)-acetimidyl 2,3,4,6-tetra-O-benzyl-β-D-galactopyranose. The resulting tri-saccharide has also been obtained from allyl 2-O-benzoyl-4,6-O-benzylidene-β-D-galactopyranoside after α-D-galactosylation, O-debenzoylation and α-L-fucosylation. The glycosylations were performed at room temperature in nitromethane in the presence of p-toluenesulfonic acid. Deallylation followed by catalytic hydrogenolysis gave the B blood-group antigenic determinant. The allyl group was also selectively transformed into hydroxyethyl group. 相似文献
3.
《Tetrahedron: Asymmetry》1999,10(20):4029-4035
New disaccharide chiral phosphines, such as 4,6-O-benzylidene-2-(diphenylphosphino)-2-deoxy-α-d-altropyranosyl-(1,1)-4,6-O-benzylidene-2-(diphenylphosphino)-2-deoxy-α-d-altropyranoside 1 and 2-(diphenylphosphino)-2-deoxy-4,6-O-isopropylidene-α-d-altropyranosyl-(1,1)-2-(diphenylphosphino)-2-deoxy-4,6-O-isopropylidene-α-d-altropyranoside 9, were prepared from α,α-trehalose. We also succeeded in the synthesis of polyhydroxy chiral diphosphine 2-(diphenylphosphino)-2-deoxy-α-d-altropyranosyl-(1,1)-2-(diphenylphosphino)-2-deoxy-α-d-altropyranoside 5 by deprotection of isopropylidene groups. 相似文献
4.
Jitka Moravcova Petr KocalkaAnne Imberty David SykoraMiroslav Fris 《Tetrahedron letters》2003,44(49):8797-8800
Treatment of methyl 2,3-di-O-benzyl-4,6-O-benzylidene-α(β)-d-glucopyranoside with triethyl phosphite and trimethylsilyl trifluoromethanesulfonate affords the seven-membered phostone arising from the attack of reagents on the acetal protecting group. 相似文献
5.
The trisaccharide derivative methyl 2-O-[4,6-di-O-acetyl-3-O-(2,3,4,6-tetra-O-benzyl-α-D-gal-actopyranosyl)-2-deoxy-2-phthalimido-β-D-gluco-pyranosyl]-4,6-O-benzylidene-β-D-mannopyranoside (12) was obtained when 3-O-(2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-4,6-di-Oacetyl-2-deoxy-2-phtha-limido-β-D-glucopyranosyl trichloroacetimidate (8) was allowed to react with methyl 3-O-benzyl-4,6-O-benzylidene-β-D-mannopyranoside (11) in presence of trimethylsilyl triflate. Removal of protecting groups then gave the desired trisaccharide. 相似文献
6.
Methyl-2-acetamido-4,6-di-O-acetyl-3-S-acetyl-2-deoxy-3-thio-α-D-mannopy-ranoside has been synthesized by conversion of methyl 2-amino-2-deoxy-4,6-O-benzylidene-α-D-altropyranoside into the corresponding 3-O-methanesulfony1-2-N-[(methylthio)thiocarbonyl]derivative followed by intramolecular displacement of the 3-O-methanesulfonyloxy group with the (methylthio)thiocarbamoyl group. 相似文献
7.
Federico G. De las Heras Ana San Félix Ana Calvo-Mateo Piedad Fernández-Resa 《Tetrahedron》1985,41(18):3867-3873
Reaction of methyl 2-acetamido-4,6--benzylidene-2-deoxy-α---hexopyranosid-3-ulose with Me3SiCN afforded methyl 2-acetamido-4,6--benzylidene-3--cyano-2-deoxy-3--trimethylsilyl-α--- Reaction of ethyl 4,6-di--acetyl-2,3-anhydro-α--mannopyranoside with Me3SiCN gave the corresponding ethyl 4,6-di--acetyl-2--cyano-2-deoxy-α--glucopyranoside. Reaction of methyl 4,6--benzylidene-2,3-anhydro-α--allopyranoside or methyl 4,6--benzylidene-2,3-di--tosyl-α--glucopyranoside with Me3SiCN at - 75° or - 50° gave the corresponding methyl 6--[(R)-cyano phenyl methyl]-α--glyco-pyranosides with high or total regio and stereoselectivity. 相似文献
8.
SHI Ji-Cheng WEN Ting-Bin WU Da-Xu LU Ge-Tan HONG Mao-ChunLIU Qiu-Tian KANG Bei-ShengState Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou Fujian ChinaWANG Han-Qing LU Shi-JieLanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou Gansu China 《中国化学》1996,14(5):454-461
Methyl 3-deoxy-3-(diphenylphosphino)-4,6-O-benzylidene-α-D-altropyranoside (1) and methyl 2-deoxy-2-(diphenylphosphino)-4,6-O-benzylidene-α-D-altropyranoside (2) were prepared from methyl 2,3-anhydro-4,6-O-benzylidene-O-D-mannopyranoside and methyl 2,3-anhydro-4,6-O-benzyl-idene-α-D-allopyranoside,respectively,via regioselective and stcreospecific ring-opening reactions in high yields.Compounds 1 and 2 were oxidized to give the corresponding phosphine oxides (3 and 4). 相似文献
9.
H. M. Zuurmond P. A.M. van der Klein J. de Wildt G. A. van der Marel J. H. van Boom 《Journal of carbohydrate chemistry》2013,32(2):323-339
Abstract DAST-assisted rearrangement of 3-O-allyl-4-O-benzyl-α-l-rhamnopyranosyl azide followed by treatment of the generated fluorides with ethanethiol and BF3·OEt2 gave glycosyl donor ethyl 3-O-allyl-2-azido-4-O-benzyl-2,6-dideoxy-1-thio-α/β-l-glucopyranoside. Stereoselective glycosylation of methyl 4,6-O-benzylidene-2-deoxy-2-phthalimido-β-D-glucopyranoside with ethyl 3-O-allyl-2-azido-4-O-benzyl-2,6-dideoxy-1-thio-α/β-l-glucopyranoside, under the agency of NIS/TfOH afforded methyl 3-O-(3-O-allyl-2-azido-4-O-benzyl-2,6-dideoxy-α-l-glucopyranosyl)-4,6-O-benzyli-dene-2-deoxy-2-phthalimido-β-D-glucopyranoside. Removal of the allyl function of the latter dimer, followed by condensation with properly protected 2-azido-2-deoxy-glucosyl donors, in the presence of suitable promoters, yielded selectively methyl 3-O-(3-O-[6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-D-glucopyranosyl]-2-azido-4-O-benzyl-2,6-dideoxy-α-l-glucopyranosyl)-4,6-O-benzylidene-2-deoxy-2-phthalimido-β-D-glucopyranoside. Deacetylation and subsequent glycosylation of the free HO-6 with phenyl 2,3,4,6-tetra-O-benzoyl-1-seleno-β-D-glucopyranoside in the presence of NIS/TfOH furnished a fully protected tetrasaccharide. Deprotection then gave methyl 3-O-(3-O-[6-O-{β-D-glucopyranosyl}-2-acetamido-2-deoxy-β-D-glucopyranosyl)-2-acetamido-2,6-dideoxy-α-L-glucopyranosyl)-2-acetamido-2-deoxy-β-D-glucopyranoside. 相似文献
10.
《Tetrahedron: Asymmetry》2001,12(14):2031-2041
Novel, potentially bioactive, fluorinated branched-chain monosaccharides were obtained by reaction of diethylaminosulphur trifluoride (DAST) with a series of methyl 3-C-cyano-3-ethoxycarbonyl-β-d-glucopyranoside derivatives, including the 4,6-O-benzylidene derivative and their 3-C-(N-protected aminomethyl) reduction products, as well as the phenyl 3-C-cyano-3-ethoxycarbonyl-1-thio-α-d-(and β-d-)glucopyranosides. The absolute configuration at C(3) was unambiguously assigned for all compounds on the basis of X-ray crystallographic analysis of methyl 4,6-O-benzylidene-3-C-cyano-3-deoxy-3-ethoxycarbonyl-β-d-glucopyranoside, corroborating the previous tentative assignment by other authors for the 4,6-unprotected compound. The course of the fluorination depended on the reaction temperature and the substitution pattern of the substrate. Thus, for methyl 3-C-cyano-3-ethoxycarbonyl-β-d-glucopyranoside, fluorination occurred exclusively at C(6), but for the phenylthio analogue, a 2-deoxy-2-phenylthio-α-d-manno-configured glycosyl fluoride and its 6-fluoro derivative were obtained, resulting from the expected rearrangement reaction, whilst starting from the phenylthio α anomer, only the unrearranged 6-fluoro compound was formed. Rearrangement was also observed in the fluorination of methyl 4,6-O-benzylidene-3-C-(N-protected aminomethyl)-β-d-glucopyranoside, which led to the 2-O-methyl-α-d-mannopyranosyl fluoride derivative as the sole product. This methodology may constitute a simple route to enantiopure conformationally constrained cyclic fluorinated β-amino acids having the α carbon atom shared with a pyranose ring, although only moderate yields were achieved, particularly in the fluorination step. 相似文献
11.
Langqiu ChenFanzuo Kong 《Tetrahedron letters》2003,44(18):3691-3695
Glycosylation of 4-methoxyphenyl 2,3,6-tri-O-benzoyl-β-d-glucopyranoside (2) with isopropyl 3-O-allyl-2,4,6-tri-O-benzoyl- (9) or 6-O-allyl-2,3,4-tri-O-benzoyl-1-thio-β-d-galactopyranoside (7) as the donor, afforded an α- and β-linked mixture, whereas with isopropyl 3-O-chloroacetyl-2-O-benzoyl-4,6-O-benzylidene- (13) and isopropyl 3-O-allyl-2-O-benzoyl-4,6-O-benzylidene-1-thio-β-d-galactopyranoside (15) as the donor, glycosylation of 2 gave α-linked products only, indicating that 4,6-O-benzylidenation led to α-stereoselectivity in spite of the C2 ester capable of neighboring group participation. Using 15 as the donor, glycosylation of mannose derivatives with 2- or 3-OH's, glucose with 2- or 3-OH's, galactose with 2-, or 3-, or 4-OH's, glucosamine and glucuronic acid with a 4-OH, and a lactose derivative with a 4-OH, also furnished α-linked products. However, when using 15 as the donor, glycosylation of aglycon alcohol or sugars with 6-OH's yielded normal β-linked products. 相似文献
12.
The structure of some rearrangement ions in the electron impact induced fragmentation of methyl 4,6-O-benzylidene-2,3-di-O-methyl-α-D -glucopyranoside and phenyl 4,6-O-benzylidene-2,3-di-O-methyl-β-D -glucopyranoside have been investigated using high resolution, deuterium labelling and linked scan (B,E) techniques. Shifts of methoxyl groups from C-2 and C-3 to C-1 have been confirmed. 相似文献
13.
Examination of the PMR spectral changes (expressed as shift gradients of individual protons) wrought by graduated addition of the paramagnetic lanthanide complex tris [1,1,1,2,2,3,3-heptafluoro- 7,7-dimethyloctane-4,6-dionato]europium(III) [Eu(fod)3] permitted assignment of the configuration at tertiary alcoholic centers of certain sugar derivatives. The configurations of the tertiary position of 3- C-(1,3-dithian-2-yl)-1,2:5,6-di-O-isopropylidene-α-d-allofuranose (1), lethyl of 4,6-O-benzylidene-2- deoxy-3-C-(dithian-2-yl)-α-d-ribo-hexopyranoside (2) and the corresponding 3-C-butyl compound (2a), and methyl 2-C-(1,3-dithian-2-yl)-3,4-O-isopropylidene-δ-d-ribopyranoside (3) were assigned by comparison with reference spectra. The proton shift-gradients for 5-C-benzoyloxymethyl-2,3-O- cyclohexylidene-1-O-p-tolylsulfonyl-1(R),2(S),3(S),5(R)-cyclohexanetetrol (4), taken in conjunction with the spin-spin coupling values, permit direct assignment of relative stereochemistry in the latter compound. 相似文献
14.
Hans Peter Wessel Rudolf Minder Michel Trumtel 《Journal of carbohydrate chemistry》2013,32(8):1283-1306
Abstract Four derivatives of β-maltosyl-(1→4)-trehalose were prepared, each with two deoxy functions in one of the constitutive disaccharide building blocks. 2,3-Di-O-acetyl-4,6-dideoxy-4,6-diiodo-α-D-galactopyranosyl- (1→4) ?1,2,3,6-tetra-O-acetyl-D-glucopyranose (3) was employed as a precursor for the 4?,6?-dideoxygenated tetrasaccharide 9: coupling of 3 with 2,3,6-tri-O-benzyl-α-D-glucopyranosyl 2,3,6-tri-O-benzylidene-α-D-glucopyranoside (4) furnished the tetrasaccharide 5 which was deiodinated and deprotected to yield the target tetrasaccharide 9. Secondly, the dideoxygenated maltose derivative 3-deoxy-4,6-O-isopropylidene-2-O-pivaloyl-β-D-glucopyranosyl- (1→4) ?1,6-anhydro-3-deoxy-2-O-pivaloyl-β-D-glucopyranose (10) was ring-opened to the anomeric acetate 11. A [2+2] block synthesis with 4 in TMS triflate mediated glycosylation gave a tetrasaccharide which was deprotected to the 3″,3?-dideoxygenated analogue of β-maltosyl-(1→4)-trehalose. For the third tetrasaccharide, 2,3,2″,3′-tetra-O-benzyl-α,α-trehalose was iodinated at the primary positions and deiodinated in the presence of palladium-on-carbon, then this acceptor was selectively glycosylated with hepta-O-acetyl-maltosyl bromide (20). Removal of protective groups furnished the maltosyl trehalose tetrasaccharide deoxygenated at positions C-6 and C-6′. to prepare a 3,3′-dideoxygenated trehalose, the free hydroxyl groups of 2-O-benzyl-4,6-O-(R)-benzylidene-α-D-glucopyranosyl 2-O-benzyl-4,6-O-(R)-benzylidene-α-D-glucopyranoside (25) were reduced by Barton-McCombie deoxygenation. One of the benzylidene groups was opened reductively with sodium cyanoborohydride. The resulting free hydroxyl group at the 4′-position was glycosylated in a Koenigs-Knorr reaction with 20 to yield the 3,3′-dideoxygenated tetrasaccharide 32, the fourth target oligosaccharide, after deprotection. 相似文献
15.
Reaction of methyl 4,6-O-benzylidene-3(2)-deoxy-hexopyranosid-2(3)-ulose (1) with various arylamines under Bargellini reaction conditions was investigated. A series of unique enaminoketones 3-12 was obtained unexpectedly under basic conditions in 52-72% yield. 相似文献
16.
《Tetrahedron: Asymmetry》1999,10(23):4539-4551
New chiral monoaza-15-crown-5 derivatives anellated to methyl-4,6-O-benzylidene-α-d-glucopyranoside 2a, 2e, 2g–i and to methyl-4,6-O-benzylidene-α-d-galactopyranoside 3a, 3e, 3i have been synthesized. These crown ethers showed significant asymmetric induction as phase transfer catalysts in the Michael addition of 2-nitropropane to chalcone (87% ee), in the Darzens condensation of phenacyl chloride with benzaldehyde (71% ee) and in the self-condensation of phenacyl chloride (64% ee) to give 14. The absolute configurations of (−)-(2R,3S)-epoxy-3-(4-chlorophenyl)-1-phenyl-1-propanone 12 and (−)-4-chloro-(2R,3S)-epoxy-1,3-diphenyl-1-butanone 14 have also been determined by X-ray diffraction. 相似文献
17.
Kosuke Kakita Toshifumi Tsuda Noritoshi Suzuki Seiichi Nakamura Hisanori Nambu Shunichi Hashimoto 《Tetrahedron》2012,68(25):5005-5017
TMSOTf-promoted glycosidation of 2-azido-4,6-O-benzylidene-2-deoxygalactosyl diphenyl phosphates with fluorenylmethoxycarbonyl (Fmoc)-protected serine and threonine derivatives in THF/Et2O (1:1) gave glycosyl amino acids in high yields and with excellent levels of α-selectivity (α/β=94:6–95:5). The synthetic utility of the present glycosidation method was demonstrated by a stereoselective synthesis of mucin-type glycopeptide core 5 and core 7 building blocks, which are suitable for Fmoc-based solid-phase synthesis of O-glycopeptides. 相似文献
18.
Abstract Conformational investigations using 1D TOCSY and ROESY 1H NMR experiments on 1,3,4,6-tetra-O-acetyl-2-C-(4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hexopyranosyl)-2-deoxy-β-D-glucopyranose (8) and related disaccharides showed that for steric reasons the C-linked hexopyranosyl ring occurs in the usually unfavoured 1C4 conformation and reconfirmed the structure of 1,3,4,6-tetra-O-acetyl-2-C-(4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranosyl)-2-deoxy-β-D-glucopyranose (5). Glycosylation of 2,3,6-tri-O-benzyl-α-D-glucopyranosyl 2,3-di-O-benzyl-4,6-(R)-O-benzylidene-α-D-glucopyranoside (13) with acetate 8 using trimethylsilyl triflate as a catalyst afforded the α-D-linked tetrasaccharide 14. A remarkable side product in this reaction was the unsaturated tetrasaccharide 2,3,6-tri-O-benzyl-4-O-[4,6-di-O-acetyl-2,3-dideoxy-2-C-(4,6-di-O-acetyl-2,3-dideoxy-β-D-erythro-hexopyranosyl)-α-D-erythro-hex-2-enopyranosyl]-α-D-glucopyranosyl 2,3-di-O-benzyl-4,6-(R)-O-benzylidene-α-D-glucopyranoside (16) where in the C-linked hexopyranosyl ring an isomerization to the β-anomer had taken place to allow for the favoured 4C1 conformation. The tetrasaccharide 14 was deacetylated and hydrogenolyzed to form the fully deprotected tetrasaccharide 18. The 1 C 4 conformation of the C-glycosidic pyranose of this tetrasaccharide was maintained as shown by an in depth NMR analysis of its peracetate 19. 相似文献
19.
Convenient synthesis of d-rubranitrose from d-glucose was achieved by using simple and novel methods for deoxygenation and construction of functionalized branched-chain structures. The total yield of d-rubranitrose from methyl 4,6-O-benzylidene-α-d-glucopyranoside (1) was 4.9%. 相似文献
20.
Boris A. Trofimov Lidiya N. Parshina Anatolii P. Tantsyrev Oksana V. Vysotskaya Nina K. Gusarova 《Tetrahedron》2007,63(47):11661-11665
Vinyl ethers, promising chiral carbohydrate synthons, have been synthesized by the addition of glucose acetals (1,2:5,6-di-O-isopropylidene-α-d-glucofuranose, methyl 4,6-O-benzylidene-α-d-glucopyranoside, 1,2-O-cyclohexylidene-α-d-glucofuranose, methyl α-d-glucopyranoside) to acetylene under atmospheric and elevated pressures in an autoclave in the presence of superbase catalytic systems (KOH-DMSO, t-BuOK-DMSO). The complete vinylation of 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose and methyl α-d-glucopyranoside has been realized under elevated pressure of acetylene in the system KOH-THF as well. 相似文献