- 2-Diphenylarsino-, 2-diphenylphosphinyl-, and 2-triphenylstannyl-derivatives of methyl 4,6-O-benzylidene-2-deoxy-α-D-altropyranoside. Crystal structure of the phosphinyl derivative
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Reaction of methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside (3) with PhnMLi gives methyl 4,6-O-benzylidene-2-deoxy-2-M-α-D-altropyranoside (4; M=Ph2As, Ph2P or Ph3Sn).Compound (4, M=Ph2P) is readily oxidised in air to the phosphinyl derivative (4, M=Ph2P(O)).Characterisation of (4, M=Ph2As, Ph2P(O), or Ph3Sn) was achieved by NMR spectroscopy, including solid state NMR spectroscopy, for (4, M=Ph2As) and (4, M=Ph3Sn), and by X-ray crystallography for .In the solid state both the benzylidene and pyranose rings in , adopt chair conformations.The pentavalent phosphorus atom has a distorted tetrahedral geometry with C-P-C valency angles in the narrow range from 105.7(3) to 106.0(3) deg and the C-P-O valency angles ranging from 111.3(3) to 115.6(2) deg; the P-Caryl bond lengths are 1.808(5) and 1.815(6) Anagstroem, while the P-Calkyl bond length is slightly larger, being 1.829(6) Angstroem.Intermolecular H-bonding, involving HO and O(P) centres, links the molecules in the crystal.Keywords: Tin; Phosphorus; Arsinic; Pyranosides; Crystal structure
- Brown, Martyn A.,Cox, Philip J.,Howie, R. Alan,Melvin, Olga A.,Taylor, Oonah J.,Wardell, James L.
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Read Online
- A Domino Epoxide Ring-Opening Xanthate Migration Reaction: An Alternative Entry to Thiosugars
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A sterereospecific and efficient synthesis of thiosugars derived from levoglucosenone and methyl α-d-glucopyranoside was developed by a domino epoxide ring opening- xanthate migration to afford 1,3-oxathiolane-2-thiones in high yields. The stereochemical outcome of the new C–S bond was defined by the configuration of the starting materials. The 1,3-oxathiolane-2-thiones were subsequently submitted to a second tandem reaction affording the corresponding 2,3-episulfide alcohols. The thiosugars obtained are useful building blocks for the synthesis of thiooligosaccharides with potential biological properties.
- Comba, María B.,Mangione, María I.,Suárez, Alejandra G.,Sarotti, Ariel M.,Spanevello, Rolando A.
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supporting information
p. 6848 - 6856
(2018/12/11)
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- Diaminohexopyranosides as ligands in half-sandwich ruthenium(II), rhodium(III), and iridium(III) complexes
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The syntheses of methyl 2,3-diamino-4,6-O-benzylidene-2,3-dideoxy-α-d-hexopyranosides of glucose, mannose, gulose, and talose and methyl 2-amino-4,6-benzylidene-2,3-dideoxy-3-tosylamido-α-d-glucopyranoside are exhaustively presented, as well as their application as ligands in half-sandwich ruthenium(II), rhodium(III), and iridium(III) complexes. The complex formation occurs highly diastereoselectively, creating a stereogenic metal center. The molecular structures of the ligands and their complexes were investigated by X-ray structure analysis, NMR spectroscopy, polarimetry, and DFT methods. The diamino monosaccharide complexes have been subjected to antitumor activity studies. In vitro tests of a few ruthenium complexes against different cancer cell types showed antiproliferative activities 4-10 times lower than that of cisplatin.
- B?ge, Matthias,Fowelin, Christian,Bednarski, Patrick,Heck, Jürgen
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p. 1507 - 1521
(2015/05/13)
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- SUGAR-LINKER-DRUG CONJUGATES
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The present disclosure relates to sugar-linker-drug conjugates, of the formula [A-B-]n-L-D, wherein A is a saccharide; B is a spacer, n is an integer selected from 1 to 3; L is a linker group and D is a drug having a chemically reactive functional group selected from the group consisting of a primary or secondary amine, hydroxyl, sulfhydryl, carboxyl, aldehyde and ketone. Pharmaceutical compositions comprising the conjugates and methods of using thern are also provided.
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Paragraph 0237
(2014/09/29)
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- SACCHARIDE CONJUGATES
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This invention relates to compounds comprising a saccharide conjugated to an imaging agent or a reporter group, compositions comprising them and methods of using them. Specifically BLM-disaccharide and BLM-monosaccharide conjugates containing different linker groups and an imaging agent or a reporter group are provided for the targeting and imaging of tumors.
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Paragraph 0228; 0230
(2014/10/04)
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- Synthesis of ribo-hexopyranoside- and altrose-based azacrown ethers and their application in an asymmetric Michael addition
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The synthesis of four new ribo-hexopyranoside-based chiral lariat ethers of monoaza-15-crown-5 type and two altropyranoside-based crown ethers were elaborated. Our syntheses utilized the regioselective ring opening of the oxiran moiety of the 2,3-anhydro sugars by nucleophilic reagents to afford the key intermediates. The reaction of methyl-2,3-anhydro-4,6-O-benzylidene-α-d- mannopyranoside with ethanolamine is especially of interest to afford a 3-substituted altropyranoside. One of the ribo-hexopyranoside-based lariat ethers with a 4-methoxyphenyl substituent induced an enantioselectivity of 80% when used as catalyst in the Michael addition of diethyl acetamidomalonate to trans-β-nitrostyrene under phase transfer catalytic conditions.
- Rapi, Zsolt,Bakó, Péter,Keglevich, Gy?rgy,Sz?llsy, áron,Drahos, László,Hegeds, László
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- AN EFFICIENT AND SCALABLE PROCESS FOR THE MANUFACTURE OF FONDAPARINUX SODIUM
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The present invention relates to a process for the synthesis of the Factor Xa anticoagulent Fondaparinux and related compounds. The invention relates, in addition, to efficient and scalable processes for the synthesis of various intermediates useful in the synthesis of Fondaparinux and related compounds.
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- A scalable approach to obtaining orthogonally protected β-d-idopyranosides
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A practical method to obtain orthogonally protected d-idopyranose from d-galactose has been developed, which is the first method to enable synthesis of the challenging β-d-idopyranoside linkage. The method relies on a key double inversion at O-2 and O-3 in an easily prepared d-galactose derivative, which proceeds regio- and stereoselectively through a 2,3-anhydrotalopyranoside; reaction using a selection of alkoxides affords exclusively the 3-O-alkylidopyranoside, which can be used to generate an orthogonally protected monosaccharide. The process is scalable and requires minimal purification, so it could be used to produce building blocks to aid in the synthesis of various β-idopyranose-containing oligosaccharide targets to further probe their biological functions.
- Hevey, Rachel,Morland, Alizee,Ling, Chang-Chun
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p. 6760 - 6772
(2012/09/25)
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- Synthesis of 3-amido-3-deoxy-β-d-talopyranosides: All-cis-substituted pyranosides as lectin inhibitors
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3-Deoxy-3-amino-β-d-talopyranosides have been synthesized for the first time. The amines were obtained from galactopyranosides through 2,3-anhydrogulosides that were opened to idosides followed by an oxidation/reductive amination sequence. From the amines, 11 corresponding 3-deoxy-3-arylamido-β-talopyranosides have been synthesized and evaluated as inhibitors against galectin-1, -2, -3, -4C, -4N, -7, -8N and -9N. The synthesized talosamides showed selectivity for Galectin-4C with three of the monosaccharides having dissociation constants at around 100 μM against the lectin, which is more than two orders of magnitude better than methyl β-galactoside and significantly better than the previous best galectin-4C monosaccharide inhibitor.
- ?berg, Christopher T.,Noresson, Ann-Louise,Leffler, Hakon,Nilsson, Ulf J.
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experimental part
p. 9164 - 9172
(2011/12/03)
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- Base-promoted rearrangement of sugar epoxides to unsaturated sugars
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(Chemical Equation Presented) A simple and efficient method for rearranging 2,3-anhydro carbohydrates to unsaturated sugars has been developed. The exceptionally mild reaction conditions and high stereoselectivity should make this an attractive method for the preparation of unsaturated carbohydrate derivatives.
- Wang, Yuan,Li, Qin,Cheng, Shuihong,Wu, Yanfen,Guo, Dongjie,Fan, Qiu-Hua,Wang, Xiaofang,Zhang, Li-He,Ye, Xin-Shan
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p. 5577 - 5579
(2007/10/03)
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- Enantioselective synthesis of phyllanthurinolactone, a leaf-closing substance of Phyllanthus urinaria L., and its analogs toward the development of molecular probes
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We report enantioselective synthesis of phyllanthurinolactone (1), a leaf-closing substance of Phyllanthus urinaria L., and its analogs with sugars other than D-glucose. Structure-activity relationship study using them revealed that the structure of the sugar moiety did not affect their bioactivity at all. This result is very important for the development of molecular probes based on the structure of 1.
- Urakawa, Yoshifumi,Sugimoto, Takanori,Sato, Hirotaka,Ueda, Minoru
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p. 5885 - 5888
(2007/10/03)
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- Synthetic approach to tetrahydrofuran units and five-membered ring lactones fused to hexopyranosides
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A stereoselective synthesis of the miharamycin sugar moiety epimer at C-3′ was accomplished in high yield starting from an appropriate (Z)-Wittig product, synthesized by Wittig reaction of a 4,6-O-benzylidene protected hexopyranosid-3-ulose with [(ethoxycarbonyl)methylene]triphenylphosphorane followed by iodine promoted isomerisation of the (E)-Wittig product formed. Reduction of the (Z)-isomer obtained in quantitative yield, cyclisation and dihydroxylation with osmium tetroxide, gave the target molecule containing a cis-fused tetrahydrofuran ring in its structure. Synhesis of five-membered rings trans-fused to the hexopyranosidic units succeeded via two different synthetic pathways. Stereoselective Reformatsky reaction of a 2,6-di-O-pivaloyl protected hexopyranosid-3-ulose, followed by cyclisation with dimethylzinc gave a 3,4-trans-fused lactone. The approach using the reaction of 2,3-and 3,4-epoxides with the dianion of phenylselenoacetic acid led to low yield but novel phenylseleno derivatives of trans-fused five-membered rings, namely a phenylselenolactone 2,3-trans-fused to a 4,6-O-benzylidene-hexopyranoside and a phenylselenolactenol 3,4-trans-fused to a 6-O-pivaloyl-hexopyranoside.
- Rauter, Amelia P.,Oliveira, Olga,Canda, Tana,Leroi, Estelle,Ferreira, Humberto,Ferreira, Maria J.,Ascenso, Jose A.
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p. 257 - 273
(2007/10/03)
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- Synthesis of a carbon analogue of N-acetylmannosamine via acetolysis on a relatively stable ozonide
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After a 2-methylpropenyl group was added to a carbohydrate framework through regioselective opening of a glucose-derived epoxide, hydrolysis or acetolysis of the methyl glycoside in various derivatives was problematic. Ozonolysis of the olefin followed by brief treatment with dimethyl sulfide gave a mixture of diastereomeric ozonides that proved to be stable for weeks at room temperature. Acetolysis of these ozonides at low temperature allowed selective cleavage of the methyl glycoside in the presence of the 1,2,4-trioxolane as well as selective formation of the α-acetate.
- Chen, Liqiang,Wiemer, David F.
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p. 7561 - 7564
(2007/10/03)
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- Application of focused microwaves to the scale-up of solvent-free organic reactions
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A series of typical solvent-free reactions have been safely and beneficially scaled-up to several hundred grams in a larger batch reactor (Synthewave 1000) with yields equivalent to those obtained under similar conditions (temperature, reaction time) in laboratory-scale experiments (Synthewave 402). They concern potassium acetate alkylation, regioselective phenacylation of 1,2,4-triazole, deethylation of 2-ethoxy-anisole, and typical examples in carbohydrate chemistry (peracetylation, glycosylation, saponification, halogenation, and epoxidation of D-glucopyranosides).
- Cleophax,Liagre,Loupy,Petit
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p. 498 - 504
(2013/08/07)
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- Enantiospecific approach to a quinane skeleton related to pentalenolactones
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A novel and general approach has been delineated for the enantiomerically pure synthesis of the angularly fused tricyclic system of the pentalenolactone family of compounds. D-Glucose is used as starting material and a diasteroselective Diels-Alder reaction sets the elements for the ring junctions.
- Pellegrinet, Silvina C.,Spanevello, Rolando A.
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p. 8623 - 8626
(2007/10/03)
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- One-pot conversion of 1,2-diols to epoxides: Convenient preparation of methyl 2,3-anhydro-5-O-trityl-β-D-lyxofuranoside and methyl 2,3,-anhydro-4,6-O-benzylidene-α-D-mannopyranoside
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Tosyl chloride and sodium hydride are used to convert some 1,2-diols to epoxides in one-pot in enantiomerically/diastereomerically pure form.
- Srinivasa Murthy,Gaitonde,Prahlada Rao
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p. 285 - 289
(2007/10/02)
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- An alternative synthesis of methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside using carbonate esters
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New simple routes to the title epoxide, using carbonate esters of methyl 4,6-O-benzylidene-α-D-glucopyranoside, are described.Some mechanistic aspects of the reactions are discussed.
- Raajimakers, Harry W. C.,Zwanenburg, Binne,Chittenden, Gordon J. F.
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p. 185 - 192
(2007/10/02)
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- Chemistry of oxo-sugars. (2). Regio- and stereo-selective synthesis of methyl D-hexopyranosiduloses and identification of their forms existing in solutions
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Sixteen oxo derivatives of methyl D-hexopyranosides with various regio-and stereo-chemistries were selectively synthesized by direct oxidation of non-protected methyl glycosides by the bistributyltin oxide-bromine method or by oxidation of partially protected glycosides followed by deprotection. The forms of these oxoglycosides existing in pyridine-d5 and in H2O (D2O) were investigated by means of 13C-NMR spectroscopy, and it was found that interconversion between oxo and hydrate forms of oxoglycosides readily takes place.
- Liu,Sato,Tsuda
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p. 491 - 501
(2007/10/02)
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- Reactions of Some Pyranoside Diol Monotriflates with Nucleophiles and Bases
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Reaction of pyranoside diol (equatorial) monotriflates with soft, nonbasic nucleophiles is a useful way to make axial heteroatom-substituted and "epimerized" pyranosides, particularly where a fused acetal ring inhibits ring contraction.Among the substrates examined (1,2,3,4,35), only 4 shows a strong tendency to give ring-contracted products.The reaction of 1-3 with more basic nucleophiles (F(1-), t-BuO(1-)) leads to the anhydrosugars 8, 25, and 26, respectively.The SN2 reaction of 35 with tetra n-butylammonium iodide forms the basis for a new synthesis of the Cerny epoxide 32.
- Knapp, Spencer,Naughton, Andrew B. J.,Jaramillo, Carlos,Pipik, Brenda
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p. 7328 - 7334
(2007/10/02)
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- CYCLOADDITION OF CHIRAL AZOMETHINE YLIDES FROM AMINOSUGAR N-OXIDES. ENANTIOSELECTIVE SYNTHESIS OF 3,4-DISUBSTITUTED PYRROLIDINES
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The base deprotonation method, applied to amino-sugar N-oxides prepared from methyl 2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside (8) and methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside (9), allows the easy generation of complex and very reactive sugar azomethine ylides.Fair yields of the major diastereomeric pyrrolidines resulting from cycloaddition to stilbene are thus obtained with good asymmetric induction.The easy elimination of the chiral appendage as starting epoxides gives access to the enantiomerically enriched 3,4-diphenylpyrrolidines.
- Chastanet, Jacqueline,Fathallah, Hassana,Negron, Guillermo,Roussi, Georges
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p. 1565 - 1572
(2007/10/02)
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- Lithium aluminium hydride reduction of glycopyranoside-monosulfonates: Formation of branched furanosides
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Lithium aluminum hydride reduction of glycopyranoside-monotosylates caused three reactions: (1) stereospecific 1,2-shift, producing branched furanosides (path A), (2) reductive O-S bond cleavage, producing the original glycosides (path B), and (3) reductive removal of the tosyloxy group, producing deoxyglycosides (path C). The path A reaction was particularly evident for the monotosylates at 2-O, 3-O, and 4-O: for example, methyl 2-O-tosyl-α-D-xylopyranoside gave methyl 2-deoxy-2-C-(hydroxymethyl)-α-D-α-erythrofuranoside in 60% yield. This reaction opens a new and efficient route to branched glycofuranosides of natural and unnatural type. Stereo-electronic requirements of this reaction in relation to the balance of the other two reactions are discussed.
- Tsuda,Nishimura,Ito
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p. 1983 - 1989
(2007/10/02)
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- The 'Off-template' Problem: Towards a General Solution
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Wittig reaction of the t-butyldimethylsilylated C-3 ketone methyl 4,6-O-benzylidene-2-O-(t-butyldimethylsilyl)-α-D-ribo-hexopyranosid-3-uloside leads exclusively to C-2 alkenes, providing an efficient synthesis of these potentially useful intermediates.Alternatively, the corresponding t-butyldiphenylsilyl ether, prepared with complete regiospecificity from methyl 4,6-O-benzylidene-α-D-glucopyranoside, gives a C-3 alkene on oxidation and Wittig reaction.Deprotection, hydrogenation and cyclization of this product leads to the cis-fused butyrolactone, methyl 4,6-O-benzylidene-3-deoxy-3-(ethoxycarbonyl)-2,3-butyrolactone-α-D-allopyranoside, which is alkylated stereospecifically to give methyl 4,6-O-benzylidene-3-deoxy-3-(prop-2-yloxycarbonyl)-2,3-butyrolacto-α-D-allopyranoside.This procedure provides a general solution of the 'off-template' problem of carbohydrate-based natural product synthesis.
- Rashid, Abdul,Taylor, G. Mark,Wood, William W.,Alker, David
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p. 1289 - 1296
(2007/10/02)
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- SYNTHESIS OF STEREOSPECIFICALLY LABELLED CARBOHYDRATES III1,2: PREPARATION OF (3S)- AND (3R)-3-2H1PARATOSE
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Two synthetic pathways producing methyl 3,6-dideoxy-α-D-ribo-hexose (methyl paratose) labeled stereospecifically with deuterium at the 3S (1) and 3R (2) position, respectively, are described.
- Russell, Raymond N.,Liu, Hung-wen
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p. 5729 - 5732
(2007/10/02)
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- REACTIONS OF PHENYL CHLOROSULFATE AT OH-2 AND OH-3 OF ALDOHEXOPYRANOSE DERIVATIVES. COMPETING SUBSTITUTION AND DISPLACEMENT REACTIONS
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Reactions of phenyl chlorosulfate-sodium hydride with methyl 4,6-O-benzylidenealdohexopyranosides are characterized by a variety of nucleophilic substitution and displacement processes involving OH-2 and -3 of the glycosides.Depending on such factors as the relative rates of substitution of these two hydroxyl groups and their configurations, as well as temperature and stoichiometry, the products may be mono- or di-phenylsulfates (or both), 2,3-cyclic sulfates, or 2,3-oxiranes.For example, in the reaction of methyl 4,6-O-benzylidene-α-D-glucopyranoside with two equivalents of phenyl chlorosulfate at +25deg, the products were the 2,3-disulfate (10percent), 2,3-cyclic sulfate (77percent), and 2,3-allo epoxide (4percent), whereas, at -25deg, by far the major product was the 2-phenylsulfate (79percent).Intramolecular displacement was so readily facilitated in the reaction of methyl 4,6-O-benzylidene-α-D-altropyranoside that the only products obtained were the 2,3-anhydro-manno- (major) and -allo-pyranosides.Conformations of the 2,3-cyclic sulfates are considered on the basis of their n.m.r. characteristics.
- Abdel-Malik, Magdy M.,Perlin, Arthur S.
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- Tripyranoside Precursors for Ansamycins. Pyranosidic Homologation. 6.
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The primary and secondary alcohols of the dipyranoses 6 and 9a are used as implements for elaborating the upper pyranoside rings of the tripyranoses 27 and 28, respectively.Compounds 27 contains seven of the eight chiral centers of rifamycin S, while 28 fixes seven of the nine chiral centers of streptovaricin A.For the synthetic procedures, the primary alcohol is oxidized to an aldehyde, which is subjected to olefination with a phosphorane of the type PH3P=CHCH(OR)2.Treatment with pyridinium p-toluenesulfonate, specifically, in the presence of an alcohol causes cycliz ation with secondary the alcohol, resulting in a hexenepyranoside, which is glycositated in situ by the alcohol.The resulting hexenepyranoside is then epoxidized, and for this process, a new procedure was developed that involves hydroxylation with osmium tetroxide and treatment of the cis diol so formed with phosgene iminium chloride (Viehe's salt> to give a chloro carbamate, which then reacts with methoxide to give the desired epoxide.Opening of the ring with dimethylmagnesium then completes the requirements for the upper ring.
- Fraser-Reid, Bert,Molino, Bruce F.,Magdzinski, Leon,Mootoo, David R.
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p. 4505 - 4511
(2007/10/02)
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- The Synthesis and Attempted Cyclization of Some α-Acyloxy Carbohydrate Epoxides
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The preparation of eight α-acyloxy carbohydrate epoxides is described, together with attempts to cyclize these compounds.
- Jones, Keith,McEvoy, John,Wood, William W.,Scott, Ian L.
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p. 1774 - 1790
(2007/10/02)
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- Phase Transfer-Catalyzed Preparation of Oxiranes
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Oxiranes 3 are prepared in 70-85percent yields by treating 1,2-diols 1 with one molar equivalent of p-toluenesulfonyl (2) or methanesulfonyl chloride (2') under phase transfer conditions.
- Szeja, W.
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p. 983 - 985
(2007/10/02)
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- A Contribution to the Structural Assignment of Positional Isomers of Bis-galacto and Bis-manno Crown Ethers
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A structural assignment to the positional isomers of bis-galacto 3/4 and bis-manno crown ethers 6/7 is not possible using spectroscopic data only.Crown ethers 3 and 6 with a 3/3' and 2/2'conjunction of the two sugar moieties are available rationally via the "half crowns" 11 and 13 and are thus identifiable.
- Hain, Wolfgang,Lehnert, Rudolf,Walz, Bernhard,Schroeder, Gerhard
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p. 1046 - 1051
(2007/10/02)
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- DESULFONYLOXYLATION OF SOME SECONDARY p-TOLUENESULFONATES OF GLYCOSIDES BY LITHIUM TRIETHYLBOROHYDRIDE; A HIGH-YIELDING ROUTE TO 2- AND 3-DEOXY SUGARS
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Lithium triethylborohydride (LTBH) reacts readily with p-toluenesulfonates of methyl 4,6-O-benzylidene-α-D-glucopyranoside (4) to give deoxyglycosides in >90percent yield.Thus, the 2,3-ditosylate (1) and the 3-monotosylate (2) thereof afford methyl 4,6-O-benzylidene-2-deoxy-α-D-ribo-hexopyranoside (7) in highly regio- and stereo-selective reactions that proceed via methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside (6), and the 2-monotosylate (8) of 4 gives the 3-deoxy-α-D-arabino isomer (12) of 7 via the corresponding 2,3-anhydro-α-D-mannopyranoside 11.In the series of the corresponding β anomers, the 3-monotosylate 14 and the 2-monotosylate 16 are similarly desulfonyloxylated, with equal ease, but furnish mixtures of regioisomeric deoxyglycosides, namely, the 3- and 2-deoxy-β-D-ribo derivatives 20 and 21, and the 2- and 3-deoxy-β-D-arabino derivatives 22 and 23, respectively.It could be shown that this difference is due to the failure of the intermediary, β-glycosidic epoxides 18 and 19 (the anomers of 6 and 11) to obey the Fuerst-Plattner rule in their reductive ring-opening with LTBH.The β-glycosidic 2,3-ditosylate 15 reacts less readily, and gives 20-23, with 20 preponderating.The 2-O-methyl-3-O-tosyl-β-D-glucopyranoside 24 is partly desulfonylated and partly desulfonyloxylated, whereas its 3-O-methyl-2-O-tosyl isomer 27 undergoes desulfonylation exclusively.The reductions of 1, 2, and 8 by LTBH are compared with those previously effected by lithium aluminum hydride, which are slower, involve considerable desulfonylation, and afford lower yields of deoxyglycosides, with the main products differing from those obtained by the action of LTBH.Mechanistic differences associated with the two reductants are discussed.
- Baer, Hans H.,Hanna, Hanna R.
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- SELECTIVE ESTERIFICATION OF METHYL 4,6-O-BENZYLIDENE-α-D- AND β-D-GALACTOPYRANOSIDE IN A CATALYTIC TWO-PHASE SYSTEM
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Selective tosylation of methyl 4,6-O-benzylidene-α-D- (1) and β-D-galactopyranoside (8) in a catalytic two-phase system (CTP system) yields preferentially 2-O-p-toluenesulfonate and 3-O-p-toluenesulfonate, respectively.In the course of unimolar benzoylation of 1 and 8, under similar conditions, a migration of the acyl group takes place and an equilibrium mixture is obtained.Esterification of 1 and 8 with benzoyl chloride under CTP conditions, in presence of an aqueous sodium hydroxide solution, saturated with sodium perchlorate, afforded in preponderant yields 2-O-benzoate and 3-O-benzoate, respectively.
- Szeja, Wieslaw
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p. 1803 - 1808
(2007/10/02)
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- Epoxidation with Triphenylphosphine and Diethyl Azodicarboxylate. II Methyl 4,6-O-Benzylidene-D-aldohexopyranosides
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Epoxidation of the conformationally rigid diaxial diol methyl 4,6-O-benzylidene-α-D-altropyranoside with triphenylphosphine and diethyl azodicarboxylate proceeds in high yield under very mild conditions to give the corresponding 2,3-anhydro-D-mannoside.By contrast, the corresponding diequatorial diol, methyl 4,6-O-benzylidene-α-D-glucopyranoside, undergoes epoxidation only under forcing conditions and gives the D-allo isomer.Evidence is presented for the formation of a cyclic phosphorane intermediate in the latter case.
- Guthrie, R. D. (Gus),Jenkins, Ian D.
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p. 1997 - 2000
(2007/10/02)
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- A ONE-STEP PREPARATION OF 2,3-ANHYDRO-4,6-O-BENZYLIDENE-α-D-ALLOPYRANOSIDE AND -GULOPYRANOSIDE
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Methyl 4,6-O-benzylidene-α-D-glucopyranoside reacted with diethyl azodicarboxylate and triphenylphosphine to give methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside and -mannopyranoside with the former predominant, while allyl 4,6-O-bezylidene-α-D-galactopyranoside selectively afforded the corresponding 2,3-anhydroguloside.
- Mitsunobu, Oyo,Kudo, Takashi,Nishida, Mitsuru,Tsuda, Nobuo
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p. 1613 - 1614
(2007/10/02)
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