- Polymer-supported ferric chloride as a heterogeneous catalyst for chemoselective deprotection of acetonides
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Acetonides undergo chemoselective deprotection to afford the corresponding 1,2-diols in excellent yields using polymer (PVP)-supported ferric chloride as a heterogeneous catalyst in acetonitrile-dichloromethane at room temperature.
- Chari, M. Adharvana,Syamasundar
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- Thermal and Lewis acid promoted intramolecular Diels-Alder reaction of furanose tethered 1,3,9-decatriene systems: A synthetic and computational investigation
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The intramolecular Diels-Alder (IMDA) reaction of furanose tethered 1,3,9-decatrienes (4a-4r) was investigated under thermal conditions and in the presence of a Lewis acid. The stereoselectivity was determined by establishing the structures of adducts through single crystal X-ray diffraction and 1H NMR spectroscopy. It was found that contrary to expectations, the thermal IMDA reaction of (3E) and (3Z)-1,3,9-decatrienes proceeded with nearly equal rate and furnished IMDA adducts (6-25) with moderate stereoselectivity. In some cases, rearranged products (9, 12, 17 and 24) arising out of a 1,5-sigmatropic shift, cis-trans isomerization followed by IMDA reaction were formed. In contrast, a Lewis acid promoted IMDA reaction afforded only one adduct albeit in lower yields. Not surprisingly, cis-boat transition states were favored over trans-boat transition states. Experimental results were corroborated with transition state modeling of these reactions by applying density functional theory based electronic structure calculations.
- Kalmode, Hanuman P.,Maity, Dilip K.,Bhate, Prakash M.
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- Hydrogen isotopic profile in the characterization of sugars. Influence of the metabolic pathway
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The site-specific natural hydrogen isotope ratios of plant metabolites determined by 2H nuclear magnetic resonance (SNIF-NMR method) can provide powerful criteria for inferring mechanistic and environmental effects on biosynthetic pathways. This work examines the potential of isotopic profiles for the main constituents of carbohydrates, glucose and fructose, to distinguish different photosynthetic pathways. An appropriate analytical strategy, involving three suitable isotopic probes, has been elaborated with a view to measuring simultaneously, in conditions devoid of isotopic perturbations, all (or nearly all) of the carbon-bound hydrogen isotope ratios. It is shown that the type of photosynthetic metabolism, either C3 (sugar beet, orange, and grape), C4 (maize and sugar cane), or CAM (pineapple), and the physiological status of the precursor plant exert strong influences on the deuterium distribution in the sugar molecules. Consequently, this isotopic fingerprint may be a rich source of information for the comparison of mechanisms in metabolic pathways. In addition, it can provide complementary criteria to ethanol as a probe for the origin of sugars.
- Zhang, Ben-li,Billault, Isabelle,Li, Xiaobao,Mabon, Francoise,Remaud, Gerald,Martin, Maryvonne L.
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- Chiron approach for the synthesis of (1S,2R,5R,7S)-2-hydroxy-exo-brevicomin
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(1S,2R,5R,7S)-2-Hydroxy-exo-brevicomin ent-1 was synthesized from 1,2;5,6-di-O-isopropylidene-d-glucose in seven steps. The key reaction in our synthesis is the formation of bicyclic ketal 7 under acid mediated acetal exchange of a 1,2-acetonide of d-glucose derivative 6.
- Gautam,Kumar, D. Naveen,Rao, B. Venkateswara
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- Quantification of deuterium isotopomers of tree-ring cellulose using nuclear magnetic resonance
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Stable isotopes in tree rings are important tools for reconstruction of past climate. Deuterium (D) is of particular interest since it may contain climate signals and report on tree physiology. Measurements of the D/H ratio of tree-ring cellulose have proven difficult to interpret, presumably because the D/H ratio of the whole molecule blends the abundances of the seven D isotopomers of cellulose. Here we present a method to measure the abundance of the D isotopomers of tree-ring cellulose by nuclear magnetic resonance spectroscopy (NMR). The method transforms tree-ring cellulose into a glucose derivative that gives highly resolved, quantifiable deuterium NMR spectra. General guidelines for measurement of D isotopomers by NMR are described. The transformation was optimized for yield and did not alter the original D isotopomer abundances, thus, conserving the original signals recorded in wood cellulose. In the tree-ring samples tested, the abundances of D isotopomers varied by approximately ±10% (2% standard error). This large variability can only be caused by biochemistry processes and shows that more information is present in D isotopomer abundances, compared to the D/H ratio. Therefore, measurements of the D isotopomer distribution of tree rings may be used to obtain information on long-term adaptations to environmental changes and past climate change.
- Betson, Tatiana R.,Augusti, Angela,Schleucher, Juergen
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- INTERACTION BETWEEN ACETONE AND SOME CARBOHYDRATE BENZENEBORONATES: SELECTIVE ACETONOLYSIS OF 2-PHENYL-1,3,2-DIOXABOROLANES
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Treatment of D-glucitol 1,3:2,4:5,6-tris(benzeneboronate), D-mannitol 1,2:3,4:5,6-tris(benzeneboronate), and α-D-glucofuranose 1,2:3,5-bis(benzeneboronate) with acidified acetone, followed by chromatography using lyotropic solvents, gives 5,6-O-isopropylidene-D-glucitol, 1,2-O-isopropylidene-D-mannitol, and 1,2-O-isopropylidene-α-D-glucofuranose, respectively, in yields of 43-78percent.
- Griffiths, Chridtopher J.,Weigel, Helmut
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- A Warburg effect targeting vector designed to increase the uptake of compounds by cancer cells demonstrates glucose and hypoxia dependent uptake
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Glycoconjugation to target the Warburg effect provides the potential to enhance selective uptake of anticancer or imaging agents by cancer cells. A Warburg effect targeting group, rationally designed to facilitate uptake by glucose transporters and promote cellular accumulation due to phosphorylation by hexokinase (HK), has been synthesised. This targeting group, the C2 modified glucose analogue 2-(2-[2-(2-aminoethoxy)ethoxy]ethoxy)-D-glu-cose, has been conjugated to the fluorophore nitrobenzoxadiazole to evaluate its effect on uptake and accumulation in cancer cells. The targeting vector has demonstrated inhibition of glucose phosphorylation by HK, indicating its interaction with the enzyme and thereby confirming the potential to facilitate an intracellular trapping mechanism for compounds it is conjugated with. The cellular uptake of the fluorescent analogue is dependent on the glucose concentration and is so to a greater extent than is that of the widely used fluorescent glucose analogue, 2-NBDG. It also demonstrates selective uptake in the hypoxic regions of 3D spheroid tumour models whereas 2-NBDG is distributed primarily through the normoxic regions of the spheroid. The increased selectivity is consistent with the blocking of alternative uptake pathways.
- Glenister, Alexandra,Simone, Michela I.,Hambley, Trevor W.
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- A mild and convenient approach for selective acetonide cleavage involved in carbohydrate synthesis using PPA-SiO2
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Here, we report a highly selective, efficient and rapid method for the selective cleavage of primary acetonide using silica supported polyphosphoric acid (PPA-SiO2) for various carbohydrate substrates. Corresponding diols were obtained in good to excellent yields within 30 min using PPA-SiO2. Overall, PPA-SiO2 was found to be a useful catalyst for selective acetonide cleavage in carbohydrate substrates which may expand its utility in organic synthesis.
- Nikam, Rahul R.,Gore, Kiran R.
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- Acetalation studies. Part IX. Reaction of sucrose and some related sugars with acetone in the presence of iodine; a novel cleavage-isopropylidenation method
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An efficient cleavage-isopropylidenation reaction of sucrose, catalyzed by iodine, is described.Related D-fructofuranosyl-containing oligosaccharides and their individual monosaccharide units were treated in a similar manner to yield isopropylidenated monosaccharide derivatives.The reaction conditions are particularly mild and selective.Some mechanistic aspects of the procedure are also discussed.
- Verhart, Cor G. J.,Caris, Brigitte M. G.,Zwanenburg, Binne,Chittenden, Gordon J. F.
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- Synthesis and antimicrobial activity of (?)-cleistenolide and analogues
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Using the “chiral pool” approach, two modified total syntheses of the biologically active δ-lactone cleistenolide (1) have been achieved starting from D-glucose. These approaches also enabled the preparation of novel analogues and derivatives of natural product 1. The applied strategy for the synthesis of 1 involves: the initial degradation of the chiral precursor for a single C-atom, C2-fragment chain extension using Z-selective Wittig reaction, and the final δ-lactonization. All tested cleistenolide analogues displayed antimicrobial activity against a panel of nine microbial strains, most of them superseding the activity of cleistenolide itself, and, in some cases, coming close in value to the observed minimal inhibitory concentrations of chloramphenicol. Increased lipophilicity of the derivatives and the non-sterically congested conjugated lactone moiety were a prerequisite for analogues with high inhibitory activity against S. aureus and, in general, Gram-positive bacteria.
- Benedekovi?, Goran,Popsavin, Mirjana,Radulovi?, Niko S.,Stojanovi?-Radi?, Zorica,Farkas, Sándor,Francuz, Jovana,Popsavin, Velimir
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- Diastereoisomerically pure, (S)-O-1,2-O-isopropyli dene-(5-O-α-d-glucofuranosyl) t-butanesulfinate: Synthesis, crystal structure, absolute configuration and reactivity
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The reaction of t-butylmagnesium chlorides with diastereomerically pure (R)-1,2-Oisopropylidene-3,5-O-sulfinyl-α-d-glucofuranose (R)-4 was found to be stopped at the stage of the corresponding, diastereoisomerically pure 1,2-O-isopropylidene-(5-O-α-d-glucofuranosyl) t-butanesulfinate (S)-10 for which the crystal structure and the (S)-absolute configuration was determined by X-ray crystallography. Comparison of the absolute configurations of the starting sulfite (R)-4, and t-butanesulfinate (S)-10 (which crystallizes in the orthorhombic system, space group P212121, with the single compound molecule present in the asymmetric unit), clearly indicates that the reaction of nucleophilic substitution at the stereogenic sulfur atom in the sulfite (R)-4 occurs with the full inversion of configuration via the trigonal bipyramidal sulfurane intermediate 4c in which both the entering and leaving groups are located in apical positions.
- B?aszczyk, Jaros?aw,Bujnicki, Bogdan,Chmielewski, Marek,Drabowicz, Józef
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- Nascent-HBr-Catalyzed Removal of Orthogonal Protecting Groups in Aqueous Surfactants
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Organic reactions in the aqueous environment have recently emerged as a promising research area. The generation of nascent-HBr from the slow hydrolysis of the dispersed catalyst, benzyl bromide, with the interior water present in the hydrophobic core of the confined micellar medium in aqueous surfactant is described for the first time. The sustained-release nascent-HBr enabled the chemoselective cleavages of acid-sensitive orthogonal functionalities present in carbohydrates, amino alcohols, and hydroxylated acyclic compounds in good to excellent yields.
- Bera, Smritilekha,Gupta, Shilpi,Mondal, Dhananjoy
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- Diastereoselective Synthesis of Salacinol-Type α-Glucosidase Inhibitors
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A facile and highly diastereoselective approach toward the synthesis of potent salacinol-type α-glucosidase inhibitors, originally isolated from plants of the genus "Salacia", was developed using the S-alkylation of thiosugars with epoxides in HFIP (～90%, dr, α/β = ～ 26/1). The dr ratio of the product was significantly improved by the protocol as compared to that of the conventional S-alkylation of thiosugars (dr, α/β = ～ 8/1). The protocol could be used for gram scale synthesis of the desired compounds. The 3′-O-benzylated salacinol analogs, which are the most potent in vitro inhibitors to date, were synthesized and evaluated in vivo; all analogs suppressed blood glucose levels in maltose-loaded mice, at levels comparable to those of the antidiabetic agent, voglibose.
- Ishikawa, Fumihiro,Jinno, Kazumi,Kinouchi, Eri,Ninomiya, Kiyofumi,Marumoto, Shinsuke,Xie, Weijia,Muraoka, Osamu,Morikawa, Toshio,Tanabe, Genzoh
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supporting information
p. 185 - 193
(2018/02/19)
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- A containing double c type methylene the saccharification composition escapes the propylidene catalytic method
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The invention provides a method for catalyzing the propylidene removal of a dual-propylidene sugar compound, and belongs to the field of sugar compounds. According to the method, the propylidene removal of the dual-propylidene sugar compound is catalyzed by adopting a novel catalyst silica gel loaded sulfuric acid-glacial acetic acid contained in a loading type solid acid, and a post processing method is simplified; the dual-propylidene sugar compound is dissolved into an organic solvent, the silica gel loaded sulfuric acid-glacial acetic acid is added, and a product is obtained through post processing after the reaction is completed. Compared with the traditional process, the method provided by the invention is safe in operation and less in side reaction by adopting the novel catalyst silica gel loaded sulfuric acid-glacial acetic acid, can carry out quantitative catalysis, is simple in step processing and has less harmfulness on the environment in a process from the reaction to the post processing, and the catalyst is recyclable.
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Paragraph 0034-0037
(2016/10/10)
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- A concise total synthesis of cleistenolide
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A concise total synthesis of cleistenolide has been achieved from D-glucose. The synthesis of cleistenolide proceeds in six steps from D-glucose diacetonide in 42.5% overall yield. Selective benzoylation and Still-Gennari olefination are the key reactions involved in the synthesis.
- Reddy, A. Bal,Kumara Swamy,Yadav, Jhillu Singh
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p. 788 - 790
(2016/07/29)
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- 6-Azido-6-deoxy-l-idose as a Hetero-Bifunctional Spacer for the Synthesis of Azido-Containing Chemical Probes
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The design of 6-azido-6-deoxy-l-idose for use as a hetero-bifunctional spacer is reported. The hemiacetal at one terminus is an equivalent of an aldehyde and can react with nucleophiles, such as amino groups and electron-rich aromatics. The azido group at the other terminus bio-orthogonally undergoes a Hüisgen [3+2] cycloaddition with an acetylene. The idose derivative exhibited a higher level of reactivity towards oxime formation than a corresponding glucose derivative. The13C NMR spectrum of the uniformly13C-labeled 6-azido-idose indicated that the acyclic forms of the sugar totaled 0.3 % of all the isomers, whereas those of glucose totaled 0.01 %. The larger population of the acyclic forms of the idose derivative would result in higher reactivity towards electrophilic addition in comparison with glucose derivatives. Finally, we prepared a C-idosyl epigallocatechin gallate (EGCG) that bears an azido group through C-glycosylation of EGCG with 6-azido-idose. This glycosyl form of the C-idosyl EGCG exhibited a cytotoxicity against U266 cells that was comparable to that of EGCG. These results suggested that the EGCG derivative could be used as an effective chemical probe for the elucidation of EGCG biological functions.
- Hamagami, Hiroki,Kumazoe, Motofumi,Yamaguchi, Yoshiki,Fuse, Shinichiro,Tachibana, Hirofumi,Tanaka, Hiroshi
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supporting information
p. 12884 - 12890
(2016/08/30)
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- Synthesis and oxidation of thioglicosides underlain by neomenthanethiol, D-glucose, and D-fructose
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Synthesis of sulfides proceeding from neomenthanethiol, 1,2-O-isopropylidene-α-D-glucofuranose and 2,3:4,5-di-O-isopropylidene- β-D-fructopyranose was performed to get 65 and 54% yield respectively. Oxidation of the sulfides afforded diastereomeric sulfoxides in the yields from 40 to 53%, and diastereomeric excess (de) up to 36%. After removing the isopropylidene protection from 1-deoxy-1-[(1S,2S,5R)-2-isopropyl-5- methylcyclohexylsulfanyl]-2,3:4,5-di-O-isopropylidene-β-D-fructopyranose a water-soluble sulfide was obtained.
- Pestova,Izmest'Ev,Rubtsova,Kuchin
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p. 670 - 677
(2014/07/08)
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- N-Thiocarbonyl iminosugars: Synthesis and evaluation of castanospermine analogues bearing oxazole-2(3H)-thione moieties
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A straightforward and efficient synthetic route to a new class of glycosidase inhibitors containing an oxazole-2(3H)-thione moiety has been devised. The approach involves the formation of α-hydroxy ketones, which, after condensation with thiocyanic acid, leads to the formation of the heterocycle. By exploiting the ability of the nitrogen atom of oxazoline-2-thione precursors to act as nucleophiles in intramolecular addition, castanospermine analogues could be readily prepared in good overall yields. Glycosidase inhibitory activity compared to oxazolidinethione analogues showed a strong influence of the double bond, for example with pseudoiminosugar 19, by suppressing α-glucosidase inhibition and introducing, to a moderate level, β-glucosidase inhibitory activity. Reactivities showed the propensity of oxazole-2(3H)-thiones - especially when fused on carbohydrate frames - to convert into 1,3-oxazolidine-2-thione aminals through nucleophilic addition to the double bond, leading to unexpected tricyclic structure 21. Oxazole-2(3H)-thione moieties have been anchored onto carbohydrates in a five-step sequence that allows access to castanospermine analogues. Copyright
- Silva, Sandrina,Sanchez-Fernandez, Elena M.,Ortiz Mellet, Carmen,Tatibouet, Arnaud,Pilar Rauter, Amelia,Rollin, Patrick
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p. 7941 - 7951
(2014/01/06)
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- Ultrasound-assisted selective deprotection of terminal acetonides catalyzed by silica-supported boron trifluoride
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An efficient and convenient method for the selective cleavage of terminal acetonides is described. Treatment of terminal acetonides in the presence of a wide range of functional groups with silica-supported boron trifluoride as a catalyst furnished the corresponding diols in 82-95% yield under ultrasound irradiation conditions. The acid-labile p-methoxybenzyl group as a protecting group remained intact under the conditions employed to the present deprotection condition. Copyright Taylor & Francis Group, LLC.
- Xiong, Junlong,Yan, Shiqiang,Ding, Ning,Zhang, Wei,Li, Yingxia
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p. 184 - 192
(2013/07/27)
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- Lewis acid-assisted olefin cross-metathesis reaction: An efficient approach for the synthesis of glycosidic-pyrroloquinolinone based novel building blocks of camptothecin and evaluation of their antitumor activity
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A series of glycosidic-pyrroloquinolinone based novel building blocks of camptothecin (2a-g) were synthesized via Lewis acid-assisted olefin cross-metathesis reaction using Ti(OiPr)4 30 mol % and 10 mol % of Grubb's second generation catalyst with good to excellent yields. Most of these compounds exhibited significant growth inhibitory effects on all the tested cancer cell lines and three compounds (2c, 2d and 2e) showed potent cytotoxic activity.
- Nagarapu, Lingaiah,Gaikwad, Hanmant K.,Bantu, Rajashaker,Ganesh Kumar,Pombala, Sujitha
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p. 1287 - 1291
(2012/03/27)
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- Synthesis from d-altrose of (5 R,6 R,7 R,8 S)-5,7-dihydroxy-8- hydroxymethylconidine and 2,4-dideoxy-2,4-imino-d-glucitol, azetidine analogues of swainsonine and 1,4-dideoxy-1,4-imino-d-mannitol
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Ring closure of a 3,5-di-O-triflate derived from d-altrose with benzylamine allowed the formation of both monocyclic and bicyclic azetidine analogues of swainsonine.
- Araújo, Noelia,Jenkinson, Sarah F.,Martínez, R. Fernando,Glawar, Andreas F. G.,Wormald, Mark R.,Butters, Terry D.,Nakagawa, Shinpei,Adachi, Isao,Kato, Atsushi,Yoshihara, Akihide,Akimitsu, Kazuya,Izumori, Ken,Fleet, George W. J.
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supporting information; experimental part
p. 4174 - 4177
(2012/10/23)
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- Useful methods for the synthesis of isopropylidenes and their chemoselective cleavage
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A catalytic amount of phosphotungstic acid (PTA) has been found to be a very effective catalyst for isopropylidenation of 1,2-diols and their deprotection at room temperature. The ease of handling, cost and activity of the catalyst, good to excellent yields and chemoselectivity for deprotection are some of the highlights of the reported method.
- Vanlaldinpuia, Khiangte,Bez, Ghanashyam
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supporting information; experimental part
p. 3759 - 3764
(2011/08/06)
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- Metal-free deprotection of terminal acetonides by using tert -butyl hydroperoxide in aqueous medium
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Employing aqueous tert-butyl hydroperoxide (70%) as an inexpensive reagent a useful methodology for the regioselective and chemoselective deprotection of terminal acetonide groups in aqueous medium is developed. A variety of acetonide derivatives on reaction with aqueous tert-butyl hydroperoxide in water:tert-butanol (1:1) furnish the corresponding acetonide deprotected diols in good yields. A large number of acid labile protecting functional groups and other functional moieties were found to be unaffected under the conditions employed for the present deprotection. This method has been successfully applied to sugar derivatives. Georg Thieme Verlag Stuttgart.
- Maddani, Mahagundappa R.,Prabhu, Kandikere R.
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supporting information; experimental part
p. 821 - 825
(2011/06/28)
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- Stereodivergent access to polyhydroxylated 10-azabicyclo[4.3.1]decanes as new calystegine analogues
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A rapid and stereodivergent access to polyhydroxylated 10- azabicyclo[4.3.1]decanes as new calystegine analogues by way of a double benzotriazolyl/carbon nucleophile exchange followed by a ring-closing metathesis was achieved. Preliminary evaluation of the new compounds as glucocerebrosidase inhibitors was also performed.
- Chagnault, Vincent,Compain, Philippe,Lewinski, Krzysztof,Ikeda, Kyoko,Asano, Naoki,Martin, Olivier R.
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supporting information; experimental part
p. 3179 - 3182
(2009/09/05)
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- Zeolite catalyzed selective deprotection of di- and tri-O-isopropylidene sugar acetals
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H-Beta zeolite, a microporous solid acid, is demonstrated to be an efficient catalyst for the selective deprotection of cyclic as well as acyclic O-isopropylidene sugar acetals derived from d-glucose, d-xylose, d-mannose, and d-mannitol in aqueous MeOH at room temperature. A notable observation is the conversion of d-mannitol triacetonide into 1,2:3,4-di-O-isopropylidene-d-mannitol (48%) and 3,4-O-isopropylidene-d-mannitol (36%) brought about in 6 h by H-beta zeolite and the non-occurrence of any hydrolysis in the case of H-ZSM-5 catalyzed reaction in 24 h under the same conditions.
- Bhaskar, Pallooru Muni,Mathiselvam, Manoharan,Loganathan, Duraikkannu
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p. 1801 - 1807
(2008/12/21)
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- MW-assisted Er(OTf)3-catalyzed mild cleavage of isopropylidene acetals in Tricky substrates
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Erbium(III) trifluoromethane sulfonate is proposed as a very gentle Lewis acid catalyst in a MW-assisted chemoselective method for the cleavage of isopropylidene acetals in awkward substrates by using pure water as the solvent.
- Procopio, Antonio,Gaspari, Marco,Nardi, Monica,Oliverio, Manuela,Romeo, Roberto
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p. 1961 - 1964
(2008/09/19)
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- Rhodium-catalyzed decarbonylation of aldoses
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(Chemical Equation Presented) A catalytic procedure is described for decarbonylation of unprotected aldoses to afford alditols with one less carbon atom. The reaction is performed with the rhodium complex Rh(dppp)2Cl in a refluxing diglyme-DMA solution. A slightly improved catalyst turnover is observed when a catalytic amount of pyridine is added. Under these conditions most hexoses and pentoses undergo decarbonylation into the corresponding pentitols and tetrols in isolated yields around 70%. The reaction has been applied as the key transformation in a five-step synthesis of L-threose from D-glucose.
- Monrad, Rune Nygaard,Madsen, Robert
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p. 9782 - 9785
(2008/03/17)
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- First synthesis of 4a-carba-β-d-galactofuranose
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The synthesis of 4a-carba-β-d-galactofuranose is described starting from diacetone glucose. The key ring-closure step was carried out by metathesis to form a cyclopentene. Catalytic hydrogenation of the C{double bond, long}C double bond gave the galacto configured saturated carbahexofuranose with excellent diastereoselectivity.
- Frigell, Jens,Cumpstey, Ian
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p. 9073 - 9076
(2008/03/27)
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- Mild, efficient, and selective cleavage of trityl ethers with antimony trichloride
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Selective detritylation is quite crucial in synthetic chemistry. A mild and efficient procedure for selective hydrolysis of trityl ethers in the presence of other frequently used hydroxy protecting groups: TBDPS, Bz, Bn, Ac and Ts with antimony trichloride was described and 5′-trityl uridine was detritylated smoothly too. Copyright Taylor & Francis Group, LLC.
- Wu, Qinpei,Wang, Yuan,Chen, Wei,Liu, Hua
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p. 1361 - 1366
(2007/10/03)
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- Sulfuric acid immobilized on silica: an efficient reusable catalyst for selective hydrolysis of the terminal O-isopropylidene group of sugar derivatives
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Sulfuric acid immobilized on silica proved to be an efficient catalyst for selective hydrolysis of the terminal O-isopropylidene group of sugar derivatives. The method is very simple and economic for large-scale synthesis in which the catalyst is recovered and reused for several runs. Reactions with di-O-isopropylidene derivatives of d-glucose, d-mannose, d-fructose and l-sorbose led to the formation of the corresponding mono-O-isopropylidene derivatives in good to excellent yields.
- Rajput, Vishal Kumar,Roy, Bimalendu,Mukhopadhyay, Balaram
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p. 6987 - 6991
(2007/10/03)
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- Nucleoside synthesis from 3-alkylated sugars: Role of 3β-oxy substituents in directing nucleoside formation
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Using Vorbrueggen's protocol, reaction of persilylated uracil with xylofuranose derivatives having 3β-oxy-3α-alkyl substitution produced both α- and β-nucleosides. Only the β-nucleosides were formed from substrates having the reverse stereochemistry at C-3 or lacking the 3-alkyl substituent. Participation of the 3β-oxy substituent in stabilizing the incipient C-1 carbonium ion (or oxonium ion) intermediate has been suggested from analysis of energy-minimized conformations. The Royal Society of Chemistry 2006.
- Sahabuddin, Sk.,Ghosh, Ramprasad,Achari, Basudeb,Mandal, Sukhendu B.
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p. 551 - 557
(2008/02/02)
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- Synthesis of [18F]-6-deoxy-6-fluoro-D-glucose ([ 18F]6FDG), a potential tracer of glucose transport
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With the goal of developing a PET radioligand for the in vivo assessment of glucose transport, 6-deoxy-6-[18F]fluoro-D-glucose ([ 18F]6FDG) was prepared in two steps from 18F-. Starting with D-glucose, the tosyl- and mesyl-derivatives of 3,5-O-benzylidene-1,2-O-isopropylidene-α-D-glucofuranose were prepared by known methods. Reaction of either of these precursors with 18F - resulted in the formation of 3,5-O-benzylidene-6-deoxy-O-[ 18F]-fluoro-1,2-O-isopropylidene-α-D-glucofuranose in high yield. Subsequent hydrolysis resulted in the production of [18F]6FDG. Under optimal conditions, [18F]6FDG is produced 60-70 min after end of bombardment (EOB) in 71 ± 12% yield (decay corrected, based upon fluoride) with a radiochemical purity of ≥96%. Preliminary experiments have indicated that [18F]6FDG may be a more representative in vivo tracer for the glucose transporter than 2FDG. Copyright
- Neal, Timothy R.,Schumann, William C.,Berridge, Marc S.,Landau, Bernard R.
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p. 845 - 854
(2007/10/03)
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- Selective deprotection of terminal isopropylidene acetals and trityl ethers using HClO4 supported on silica gel
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Terminal isopropylidene acetals are selectively cleaved to the corresponding 1,2-diols in good to excellent yields in 6-24 h at room temperature by using the 'HClO4?SiO2' reagent system. Likewise, trityl ethers are readily cleaved to the corresponding alcohols in good to excellent yields within 2-3 h at room temperature. Work-up involves merely filtration of the reagent followed by purification of the crude product.
- Agarwal, Aditi,Vankar, Yashwant D.
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p. 1661 - 1667
(2007/10/03)
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- Chemoselective hydrolysis of terminal isopropylidene acetals in acetonitrile using molecular iodine as a mild and efficient catalyst
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A simple, mild and efficient method for deprotection of acetonides in the presence of molecular iodine is described. Acid labile protecting groups such as PMB, OMe, OBn, allyl and propargyl are compatible with the reaction conditions, while TBS, TBDPS, TMS and THP ethers were unstable under the same conditions.
- Yadav,Satyanarayana,Raghavendra,Balanarsaiah
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p. 8745 - 8748
(2007/10/03)
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- Synthesis and biological evaluation of branched and conformationally restricted analogs of the anticancer compounds 3′-C-ethynyluridine (EUrd) and 3′-C-ethynylcytidine (ECyd)
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The synthesis of branched and conformationally restricted analogs of the anticancer nucleosides 3′-C-ethynyluridine (EUrd) and 3′-C- ethynylcytidine (ECyd) is presented. Molecular modeling and 1H NMR coupling constant analysis revealed that the furanose rings of all analogs except the LNA analog are conformationally biased towards South conformation, and are thus mimicking the structure of ECyd. All target nucleosides were devoid of anti-HIV or anticancer activity.
- Hrdlicka, Patrick J.,Andersen, Nicolai K.,Jepsen, Jan S.,Hansen, Flemming G.,Haselmann, Kim F.,Nielsen, Claus,Wengel, Jesper
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p. 2597 - 2621
(2007/10/03)
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- Allyl, methallyl, prenyl, and methylprenyl ethers as protected alcohols: Their selective cleavage with diphenyldisulfone under neutral conditions
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Diphenyldisulfone is a mild and efficient reagent for selective cleavage of methylprenyl (2,3-dimethylbut-2-en-1-yl), prenyl (3-methylbut-2-en1-yl), and methallyl (2-methylallyl) ethers. These reaction conditions are compatible with the presence of other protecting groups such as acetals, acetates, and allyl, benzyl, and TBDMS ethers. Exposure of 2,3-dimethylbut-2-en-1-yl and 3-methylbut-2-en1-yl ethers to diphenyldisulfone led to the formation of 2,3-dimethylbuta-1,3-diene and isoprene, respectively. 2-Methylallyl ethers undergo isomerization to 2-methylpropenyl ethers, which are easily hydrolyzed into the corresponding free alcohols and isobutyraldehyde.
- Markovic, Dean,Vogel, Pierre
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p. 2693 - 2696
(2007/10/03)
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- Chemoselective deprotection of acid labile primary hydroxyl protecting groups under CBr4-photoirradiation conditions
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The CBr4-photoirradiation in methanol generates a controlled source of HBr, which can chemoselectively deprotect commonly used hydroxyl-protecting groups in saccharides and nucleosides, such as tert-butyldimethylsilyl, isopropylidene, benzylidene and triphenyl ethers in the presence of other acid-labile functional groups. Graphical Abstract.
- Chen, Ming-Yi,Patkar, Laxmikant N.,Lu, Kuo-Cheng,Lee, Adam Shih-Yuan,Lin, Chun-Cheng
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p. 11465 - 11475
(2007/10/03)
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- Introduction of a carbohydrate moiety into the structure of thiourea compounds targeting HIV-1 reverse transcriptase
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We developed a novel approach to introduce a carbohydrate moiety into the structure of thiourea compounds targeting the NNI binding pocket of the HIV-1 reverse transcriptase. The described method involves the synthesis of an amino-substituted carbohydrate moiety which is then condensed with various thiocarbonylimidazole derivatives of substituted aromatic amines.
- Goud, P. Mallikarjun,Venkatachalam,Uckun
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p. 1185 - 1193
(2007/10/03)
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- The synthesis of L-gulose and L-xylose from D-gluconolactone
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L-Gulose, an essential component for the antibiotic and antitumor activities of bleomycin A2, was synthesized in 47% yield from D-glucono-1,5-lactone. The effective cleavage of acetonides by SnCl2 in the presence of tert-butyldimethylsilyl ethers was of importance in the course of synthesis. Elaboration of D-glucono-1,5-lactone that includes a step of oxidative degradation by Dess-Martin periodinane also afforded a respectable yield of L-xylose.
- Yang, Wen-Bin,Patil, Sachindra S,Tsai, Cheng-Hsin,Lin, Chun-Hung,Fang, Jim-Min
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p. 253 - 259
(2007/10/03)
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- A highly efficient, mild, and selective cleavage of beta-methoxyethoxymethyl (MEM) ethers by cerium(III) chloride in acetonitrile.
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[structure: see text]. A highly selective cleavage of MEM ethers has been achieved in high yields using CeCl3.7H2O in refluxing acetonitrile under mild and neutral reaction conditions. The method is very rapid and compatible with other hydroxyl protecting groups such as Bn, TBDPS, Ac, Me, Tr, PMB, benzylidene, THP, MOM, BOM, and NHAc present in the substrate.
- Sabitha,Babu,Rajkumar,Srividya,Yadav
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p. 1149 - 1151
(2007/10/03)
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- Yb(OTf)3·H2O: A novel reagent for the chemoselective hydrolysis of isopropylidene acetals
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A facile chemoselective hydrolysis of terminal isopropylidene acetals has been achieved using a catalytic amount of Yb(OTf)3·H2O in acetonitrile at ambient temperature.
- Yadav,Reddy, B. V. Subba,Reddy, K. Srinivasa
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p. 430 - 431
(2007/10/03)
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- The role of the C-3 substituent in the asymmetric dihydroxylation of hexo-5-enofuranosides
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Asymmetric dihydroxylation of vinyl furanosides 1-6 by use of OsO4, AD-mix-α and β is described yielding the corresponding hexofuranose sugars. Vinyl furanosides 2 and 3, with an ester group at C-3, and vinyl manno furanoside 5 on asymmetric dihydroxylation with AD-mix α exhibited high R diastereoselectivity at C-5. Reversal in diastereoselectivity at C-5 was observed for the 3-deoxy vinyl furanoside 6 giving furanosaccharide 6S with the S configuration at C-5.
- Mereyala, Hari Babu,Goud, P. Mallikarjun,Gadikota, Rajendrakumar Reddy,Maddala, Rama Krishna,Reddy, K. Ramasubba
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p. 1201 - 1210
(2007/10/03)
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- An efficient, selective hydrolysis of terminal isopropylidene acetal protection by Zn(NO3)2·6H2O in acetonitrile
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Di-O-isopropylidene sugar derivatives (1a-9a) on treatment with a solution of Zn(NO3)2·6H2O in acetonitrile, undergo regioselective hydrolysis to furnish the corresponding diols (1b-9b) in excellent yields.
- Vijayasaradhi,Singh, Jaimala,Aidhen, Indrapal Singh
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p. 110 - 112
(2007/10/03)
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- Mild selective hydrolysis of acetals in carbohydrates
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A simple and inexpensive methodology for the selective hydrolysis of acetals using hydrogen chloride as catalyst is described.
- Gomes Cioletti, Alessandra,Alves, Ricardo José,De Souza Filho, José Dias,Gomes Chaves, Josiano,Fontes Prado, Maria Auxiliadora
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p. 2019 - 2028
(2007/10/03)
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- Synthesis of an enantiomeric 2,5-di-(E)-propenyltetrahydrofuran-3,4-diol derivative
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For total synthesis of a novel bioactive δ-lactone antibiotic FD-211, a key intermediate, a 2,5-di-(E)-propenyltetrahydrofuran-3,4-diol derivative, was synthesized from diacetone D-glucose.
- Suzuki, Eiju,Takao, Ken-Ichi,Tadano, Kin-Ichi
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p. 519 - 523
(2007/10/03)
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- Regioselective deprotection of p-methoxybenzyl ethers of furanose derivatives
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Reaction of per-p-methoxybenzylated hexofuranoses and pentofuranoses with either a catalytic amount of tin chloride dihydrate (SnCl2·2H2O) or 0.5-10% solution of trifluoroaoetic acid in dichloromethane afforded regioselectively the corresponding monosaccharide derivatives having a single free hydroxyl group at C(5) in good yields.
- Bouzide, Abderrahim,Sauve, Gilles
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p. 2883 - 2886
(2007/10/03)
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- Microwave thermolysis V : A rapid and selective method for the cleavage of THP ethers, acetals and acetonides using clay supported ammonium nitrate 'Clayan' in dry media
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The deprotection of a variety of tetrahydropyranyl ethers (THP), acetonides and acetals into their parent compounds using clay supported ammonium nitrate 'Clayan' under microwave irradiation is described. The ecofriendly nature of the reagent and non solvent conditions are the important features of the procedure.
- Meshram,Sumithra,Reddy,Ganesh,Yadav
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p. 2807 - 2815
(2007/10/03)
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- Synthesis of 1,2-O-isopropylidene-3,5-O-propylidene-α-D-glucofuranose as a convenient precursor of both 6-O-alkyl and 6-O-glycidyl-D-glucose amphiphiles
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1,2-O-Isopropylidene-3,5-O-propylidene-α-D-glucofuranose (3) was synthesized by conversion of 3-O-allyl-1,2-O-isopropylidene-α-D-glucofuranose (1) into its 3-O-prop-1-enyl isomer (2), followed by rapid acid-catalysed intramolecular acetalation in an aprotic solvent. The diacetal 3 was used as the precursor of 6-O-alkyl and 6-O-glucidyl-D-glucose amphiphiles, which show thermotropic and lyotropic liquid-crystalline properties. Copyright (C) 1997 Elsevier Science Ltd.
- Vanbaelinghem, Laurence,Gode, Paul,Goethals, Gerard,Martin, Patrick,Ronco, Gino,Villa, Pierre
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- Solvolytic behaviors of O-benzoyl, cyclic O,O-thionocarbonate, and O,S- thiolcarbonate groups in 3-O-benzoyl-1,2-O-isopropylidene-α-d-glucofuranose derivatives
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O-Benzoyl, cyclic thionocarbonate, and thiolcarbonate groups in 5,6-O- thiono-, 5,6-O,S-thiol-, and 5,6-S,O-thiolcarbonates of 3-O-benzoyl-1,2-O- isopropylidene-α-D-glucofuranoses behaved differently on solvolysis under alkaline conditions. Generally, the 3-O-benzoyl group was the most vulnerable to NaOH in water or MeOH, while thionocarbonate and thiolcarbonate groups were more reactive than the O-benzoyl group toward methanolysis with NaOMe. In particular, methanolysis of the 5,6-S,O- thiolcarbonate with NaOMe gave a thiirane derivative very rapidly.
- Tsuda, Yoshisuke,Shibayama, Kenji
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p. 1476 - 1479
(2007/10/03)
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- SYNTHESIS OF MONOESTERS AS SURFACTANTS AND DRUGS FROM D-GLUCOSE
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We have synthesized a series of monoesters from D-glucose corresponding to the structures 3-O-acyl, 6-O-acyl-1,2-O-isopropylidene-α-D-glucofuranose and 3-acyl-D-glucose, following the sequence of reactions : D-glucose -> diacetone glucose -> acylation -> partial or total deprotection.These compounds were prepared as either potential non-ionic surfactants (fatty acid esters and perfluoroalkylated ester) or antitumour drugs (n-butyric esters).Results concerning surface activity, toxicity and antitumour effects are reported.A novel method for obtaining partially deprotected 6-O-acyl esters from their corresponding 3-O-acyl isomers is reported.Deprotection conditions have been studied and a higher selectivity in partial deprotection has been achieved.We have given particular attention to the choice of solvents and reagents in order not to limit the extent to which the products might be applied.
- Goueth, Pierre Y.,Gogalis, Pascalis,Bikanga, Raphael,Gode, Paul,Postel, Denis,et al.
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p. 249 - 272
(2007/10/02)
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- Virtual 1H-1H spin-spin coupling in a linear five-spin system on the pyranose rings of some glucuronides
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In the 1H NMR spectra of methyl 2,3,4-tri-O-acetyl-β-D-glucopyranosyluronate-(1 -> 3)-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (6) and methyl 2,3,4-tri-O-acetyl-β-D-glucopyranosyluronate-(1 -> 6)-1,2:3,5-di-O-isopropylidene-α-D-glucofuranose (7), which were obtained by the reaction of 1,2;5,6-di-O-isopropylidene-α-D-glucofuranose (1) with methyl 2,3,4-tri-O-acetyl-α-D-glucopyranosyluronate bromide (5) in the presence of Hg(CN)2 in 1:1 benzene-nitromethane at 45 deg C, protons on both β-D-glucopyranosyluronate rings were observed as very complex signals that could not be interpreted by first-order analysis.Similar complex signals were also observed for the protons on the β-D-glucopyranosyluronate rings that were sugar components of some triterpenoidal glycosides (13-15).These complex signals were determined to be due to virtual long-range spin-spin coupling in the linear five-spin system on the glucopyranosyluronate rings of the glucuronides by 1H, 13C, H-C COSY, 1D HOHAHA, and spin-simulation spectroscopies.
- Saito, Setsuo,Sasaki, Yuka,Furumoto, Takako,Sumita, Shigeya,Hinomoto, Tohru
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