- Acceleration and deceleration factors on the hydrolysis reaction of 4,6-O-benzylidene acetal group
-
The benzylidene acetal group is one of the most important protecting groups not only in carbohydrate chemistry but also in general organic chemistry. In the case of 4,6-O-benzylidene glycosides, we previously found that the stereochemistry at 4-position altered the reaction rate constant for hydrolysis of benzylidene acetal group. However, a detail of the acceleration or deceleration factor was still unclear. In this work, the hydrolysis reaction of benzylidene acetal group was analyzed using the Arrhenius and Eyring plot to obtain individual parameters for glucosides (Glc), mannosides (Man), and galactosides (Gal). The Arrhenius and Eyring plot indicated that the pre-exponential factor (A) and ΔS? were critical for the smallest reaction rate constant of Gal among nonacetylated substrates. On the other hand, both Ea/ΔH? and A/ΔS? were influential for the smallest reaction rate constant of Gal among diacetylated substrates. All parameters obtained suggested that the rate constant for hydrolysis reaction was regulated by protonation and hydration steps along with solvation. The obtained parameters support wide use of benzylidene acetal group as orthogonal protection of cis- and trans-fused bicyclic systems through the fast hydrolysis of the trans-fused benzylidene acetal group.
- Maki, Yuta,Kajihara, Yasuhiro,Nomura, Kota,Okamoto, Ryo,Izumi, Masayuki,Mizutani, Yasuhisa
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p. 15849 - 15856
(2021/01/18)
-
- Exploration of the Fluoride Reactivity of Aryltrifluoroborate on Selective Cleavage of Diphenylmethylsilyl Groups
-
The first known report on the fluoride catalytic reactivity of potassium aryltrifluoroborate is described. The fluoride reactivity of phenyltrifluoroborate was controlled by substituents on the trifluoroborate-attached benzene, such as the methoxy group a
- Fujiki, Katsumasa,Tanaka, Katsunori
-
supporting information
p. 4616 - 4620
(2020/07/06)
-
- Conformational analysis of the disaccharide methyl a-d-mannopyranosyl-(1→3)-2-O-acetyl-β-D-manno-pyranoside monohydrate
-
The crystal structure of methyl β-d-mannopyranosyl-(1→3)-2-O-acetyl-β-d-mannopyranoside monohydrate, C15H26O12.H2O, (II), has been determined and the structural parameters for its constituent β-d-mannopyranosyl residue compared with those for methyl β-d-mannopyranoside. Mono-O-acetylation appears to promote the crystallization of (II), inferred from the difficulty in crystallizing methyl β-d-mannopyranosyl-(1→3)-β-d-mannopyranoside despite repeated attempts. The conformational properties of the O-acetyl side chain in (II) are similar to those observed in recent studies of peracetylated mannose-containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C O bond of the acetyl group. The C2—O2 bond in (II) elongates by ≈0.02 ? upon O-acetylation. The phi (φ) and psi () torsion angles that dictate the conformation of the internal O-glycosidic linkage in (II) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated (II) using the statistical program MA'AT, with a greater disparity found for (? = ≈16°) than for φ (? = ≈6°).
- Zhang, Wenhui,Wu, Qingquan,Oliver, Allen G.,Serianni, Anthony S.
-
p. 610 - 615
(2019/06/14)
-
- Synthesis and O-Glycosidic Linkage Conformational Analysis of 13C-Labeled Oligosaccharide Fragments of an Antifreeze Glycolipid
-
NMR studies of two 13C-labeled disaccharides and a tetrasaccharide were undertaken that comprise the backbone of a novel thermal hysteresis glycolipid containing a linear glycan sequence of alternating [βXylp-(1→4)-βManp-(1→4)]n dimers. Experimental trans-glycoside NMR J-couplings, parameterized equations obtained from density functional theory (DFT) calculations, and an in-house circular statistics package (MA'AT) were used to derive conformational models of linkage torsion angles φ and ψ in solution, which were compared to those obtained from molecular dynamics simulations. Modeling using different probability distribution functions showed that MA'AT models of φ in βMan(1→4)βXyl and βXyl(1→4)βMan linkages are very similar in the disaccharide building blocks, whereas MA'AT models of ψ differ. This pattern is conserved in the tetrasaccharide, showing that linkage context does not influence linkage geometry in this linear system. Good agreement was observed between the MA'AT and MD models of ψ with respect to mean values and circular standard deviations. Significant differences were observed for φ, indicating that revision of the force-field employed by GLYCAM is probably needed. Incorporation of the experimental models of φ and ψ into the backbone of an octasaccharide fragment leads to a helical amphipathic topography that may affect the thermal hysteresis properties of the glycolipid.
- Zhang, Wenhui,Meredith, Reagan,Yoon, Mi-Kyung,Wang, Xiaocong,Woods, Robert J.,Carmichael, Ian,Serianni, Anthony S.
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p. 1706 - 1724
(2019/02/14)
-
- Binding of the Bacterial Adhesin FimH to Its Natural, Multivalent High-Mannose Type Glycan Targets
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Multivalent carbohydrate-lectin interactions at host-pathogen interfaces play a crucial role in the establishment of infections. Although competitive antagonists that prevent pathogen adhesion are promising antimicrobial drugs, the molecular mechanisms underlying these complex adhesion processes are still poorly understood. Here, we characterize the interactions between the fimbrial adhesin FimH from uropathogenic Escherichia coli strains and its natural high-mannose type N-glycan binding epitopes on uroepithelial glycoproteins. Crystal structures and a detailed kinetic characterization of ligand-binding and dissociation revealed that the binding pocket of FimH evolved such that it recognizes the terminal α(1-2)-, α(1-3)-, and α(1-6)-linked mannosides of natural high-mannose type N-glycans with similar affinity. We demonstrate that the 2000-fold higher affinity of the domain-separated state of FimH compared to its domain-associated state is ligand-independent and consistent with a thermodynamic cycle in which ligand-binding shifts the association equilibrium between the FimH lectin and the FimH pilin domain. Moreover, we show that a single N-glycan can bind up to three molecules of FimH, albeit with negative cooperativity, so that a molar excess of accessible N-glycans over FimH on the cell surface favors monovalent FimH binding. Our data provide pivotal insights into the adhesion properties of uropathogenic Escherichia coli strains to their target receptors and a solid basis for the development of effective FimH antagonists.
- Sauer, Maximilian M.,Jakob, Roman P.,Luber, Thomas,Canonica, Fabia,Navarra, Giulio,Ernst, Beat,Unverzagt, Carlo,Maier, Timm,Glockshuber, Rudi
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supporting information
p. 936 - 944
(2019/01/11)
-
- Structure-Based Design of a Monosaccharide Ligand Targeting Galectin-8
-
Galectin-8 is a β-galactoside-recognising protein that has a role in the regulation of bone remodelling and is an emerging new target for tackling diseases with associated bone loss. We have designed and synthesised methyl 3-O-[1-carboxyethyl]-β-d-galacto
- Bohari, Mohammad H.,Yu, Xing,Kishor, Chandan,Patel, Brijesh,Go, Rob Marc,Eslampanah Seyedi, Hadieh A.,Vinik, Yaron,Grice, I. Darren,Zick, Yehiel,Blanchard, Helen
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p. 1664 - 1672
(2018/08/01)
-
- A green and convenient method for regioselective mono and multiple benzoylation of diols and polyols
-
An efficient method for regioselective benzoylation of diols and polyols was developed. The benzoylation is catalyzed by only 0.2 equiv of benzoate anion in acetonitrile with the addition of a stoichiometric amount of benzoic anhydride under very mild condition, leading to high yields. Compared with all other methods, this method shows particular advantage in regioselective multiple benzoylation of polyols, and in avoiding the use of any metal-based catalysts and any amine bases, which is more environment-friendly.
- Zhang, Xiaoling,Ren, Bo,Ge, Jiantao,Pei, Zhichao,Dong, Hai
-
supporting information
p. 1005 - 1010
(2016/02/03)
-
- Wittig Reaction: Domino Olefination and Stereoselectivity DFT Study. Synthesis of the Miharamycins' Bicyclic Sugar Moiety
-
2-O-Acyl protected-d-ribo-3-uloses reacted with [(ethoxycarbonyl)methylene]triphenylphosphorane in acetonitrile to afford regio- and stereoselectively 2-(Z)-alkenes in 10-60 min under microwave irradiation. This domino reaction is proposed to proceed via tautomerization of 3-ulose to enol, acyl migration, tautomerization to the 3-O-acyl-2-ulose, and Wittig reaction. Alternatively, in chloroform, regioselective 3-olefination of 2-O-pivaloyl-3-uloses gave (E)-alkenes, key precursors for the miharamycins' bicyclic sugar moiety.
- Cachatra, Vasco,Almeida, Andreia,Sardinha, Jo?o,Lucas, Susana D.,Gomes, Ana,Vaz, Pedro D.,Florêncio, M. Helena,Nunes, Rafael,Vila-Vi?osa, Diogo,Calhorda, Maria José,Rauter, Amélia P.
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supporting information
p. 5622 - 5625
(2015/12/01)
-
- SUGAR-LINKER-DRUG CONJUGATES
-
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.
- -
-
Paragraph 0217
(2014/09/29)
-
- SACCHARIDE CONJUGATES
-
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.
- -
-
Paragraph 0210
(2014/10/04)
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- Selective 4,6-O-benzylidene formation of methyl α-d-mannopyranoside using 2,6-dimethylbenzaldehyde
-
While methyl α-d-glucopyranosides and α-d-galactopyranosides selectively form 4,6-O-benzylidenes when reacted with excess benzaldehyde in the presence of acid catalyst methyl α-d-mannopyranosides does not exhibit the same selectivity because of the cis-ar
- Liotta, Louis J.,Chalmers, Jennifer F.,Falco Marshall, Jessica N.,Ferreira, Timothy E.,Mullen, Hannah E.,Pace, Nicholas J.
-
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- Organocatalysis for the acid-free O-arylidenation of carbohydrates
-
Methyl glycopyranosides of glucose, galactose, and mannose, their 2,3-di-O-benzyl-protected derivatives, as well as the unprotected sugars react with p-methoxybenzaldehyde dimethyl acetal (3) and with benzaldehyde dimethyl acetal (7) as reagents in the presence of thiourea 1 or squaramide 2 as the organocatalyst to afford regioselectively 4,6-O-arylidenated derivatives 5 and 8. With an excess amount of 3 or 7, diarylidenated derivatives are also obtained. In situ formation of acetals of type 3 and 7 from corresponding aldehydes 10 and 13 in the presence of an orthoester and organocatalyst 1 or 2 can be used to generate 5 and 8 directly from the aldehydes. Some substrates also lead to mixed orthoesters with this procedure. The reaction courses are discussed. A squaramide catalyzes the 4,6-O-arylidenation of glucose, mannose, and galactose with the use of arenecarbaldehyde dimethyl acetals or arenecarbaldehydes and orthoesters as the reagents. Glycoside derivatives also undergo this reaction. Copyright
- Geng, Yiqun,Faidallah, Hassan M.,Albar, Hassan A.,Mhkalid, Ibrahim A.,Schmidt, Richard R.
-
supporting information
p. 7035 - 7040
(2013/11/06)
-
- Mannose-binding geometry of pradimicin A
-
Pradimicins (PRMs) and benanomicins are the only family of non-peptidic natural products with lectin-like properties, that is, they recognize D-mannopyranoside (Man) in the presence of Ca2+ ions. Coupled with their unique Man binding ability, t
- Nakagawa, Yu,Doi, Takashi,Taketani, Takara,Takegoshi,Igarashi, Yasuhiro,Ito, Yukishige
-
supporting information
p. 10516 - 10525
(2013/08/23)
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- Chiral copper(II) complex-catalyzed reactions of partially protected carbohydrates
-
Catalyst-controlled regioselective functionalization of partially protected saccharide molecules is a highly important yet under-developed area of carbohydrate chemistry. Such reactions allow for the reduction of protecting group manipulation steps required in syntheses involving sugars. Herein, an approach to these processes using enantiopure copper-bis(oxazoline) catalysts to control couplings of electrophiles to various partially protected sugars is reported. In a number of cases, divergent regioselectivity was observed as a function of the enantiomer of catalyst that is used.
- Allen, C. Liana,Miller, Scott J.
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supporting information
p. 6178 - 6181
(2014/01/17)
-
- 2,4,6-Trichloro-1,3,5-triazine (TCT) mediated one-pot sequential functionalisation of glycosides for the generation of orthogonally protected monosaccharide building blocks
-
Orthogonally protected monosaccharide building blocks have been prepared using TCT in a one-pot multicomponent transformation. The process involves successive steps of arylidene acetalation, esterification and regioselective reductive acetal cleavage. High regioselectivity, scope for using a broad range of substrates, functional group tolerance, mild reaction conditions, easy handling process and wide application range are a few advantages of the current process.
- Tatina, Madhubabu,Yousuf, Syed Khalid,Mukherjee, Debaraj
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supporting information; experimental part
p. 5357 - 5360
(2012/07/30)
-
- Acceptor-influenced and donor-tuned base-promoted glycosylation
-
Base-promoted glycosylation is a recently established stereoselective and regioselective approach for the assembly of di- and oligosaccharides by using partially protected acceptors and glycosyl halide donors. Initial studies were performed on partially methylated acceptor and donor moieties as a model system in order to analyze the key principles of oxyanion reactivities. In this work, extended studies on base-promoted glycosylation are presented by using benzyl protective groups in view of preparative applications. Emphases are placed on the influence of the acceptor anomeric configuration and donor reactivities.
- Boettcher, Stephan,Matwiejuk, Martin,Thiem, Joachim
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scheme or table
p. 413 - 420
(2012/05/05)
-
- CARBOHYDRATE-MEDIATED TUMOR TARGETING
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Tumors can be selectively targeted via compounds provided herein according to the formula, or a pharmaceutically acceptable salt thereof, wherein RA and RB are as defined herein. Tumors can be imaged or targeted for therapeutic treat
- -
-
Page/Page column 49-50
(2011/02/24)
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- Environmentally benign preparation of benzylidene acetal of carbohydrate derivatives in PEG 600
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An environmentally benign preparation of benzylidene acetal of carbohydrate derivatives catalyzed by HClO4-SiO2 in PEG 600 as solvent has been developed. Yields were excellent in every case. Copyright Taylor & Francis Group, LLC.
- Sau, Abhijit,Misra, Anup Kumar
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experimental part
p. 41 - 46
(2012/01/17)
-
- FeCl3 mediated arylidenation of carbohydrates
-
Glycosides and thioglycosides based on monosaccharides in reaction with benzaldehyde dimethylacetal or p-methoxybenzaldehyde dimethyl acetal undergo FeCl3-catalyzed (20 mol %) regioselective 4,6-O-arylidenation producing the corresponding acetals in high yields. FeCl3 also mediates acetalation of glycosides and thioglycosides of cellobiose, maltose, and lactose affording the corresponding 4′,6′-O-benzylidene acetals, which were isolated after their acetylation in situ with acetic anhydride and pyridine. The combined yields (two steps) of these final products are also high (61-84%). The procedure is applicable to a wide variety of functional groups including -OBn.
- Basu, Nabamita,Maity, Sajal K.,Roy, Soumik,Singha, Shuvendu,Ghosh, Rina
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experimental part
p. 534 - 539
(2011/04/27)
-
- A unique approach to the synthesis of a dengue vaccine and the novel tetrasaccharide that results
-
An approach to the development of a dengue vaccine by synthesizing the hexasaccharide epitope on the viral surface is examined. The stereochemical and structural challenges include the synthesis of a β-mannoside bond. Synthesis of this bond is approached
- Jalsa, Nigel Kevin,Singh, Gurdial
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scheme or table
p. 867 - 874
(2009/09/30)
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- Synthesis of |β-(1→2)-linked oligomannosides
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β-(1→2)-Linked oligomannosides constitute an important class of carbohydrate structures located on the cell surface of several Candida species, including C. albicans. As a result of the immunostimulating properties of such compounds, the upscaling of their synthesis is relevant. In this paper, a highly stereoselective synthesis of |β-(1→2)-linked oligomannosides was performed by further development of and modifications to the methodologies described earlier in the literature. In addition to the synthesis of fully deprotected β-(1→2)-linked mannobiose and mannotriose, some preliminary modifications to the oligosaccharide core, resulting in close analogues with biological potential, are presented. The fully deprotected products form potential targets for screening against C. albicans and may also result in new model structures for vaccine development.
- Polakova, Monika,Roslund, Mattias U.,Ekholm, Filip S.,Saloranta, Tiina,Leino, Reko
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experimental part
p. 870 - 888
(2009/07/17)
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- Synthesis of DIvalent 2,2′-linked mannose derivatives by homodimerization
-
Several studies have implicated (1 → 2)-linked mannans as biologically relevant compounds. Recently, there has been a growing interest in the synthesis of multivalent carbohydrate assemblies due to their ability to target multiple receptors simultaneously. In the present work, a protective group strategy, based on the methodology originally developed by Crich, has been utilized for the homodimerization of olefinic carbohydrates, allowing a highly diastereoselective synthesis of some divalent structures. Furthermore, it is shown that divalent donors may undergo coupling reactions without losses in stereoselectivity or efficiency. The strategies described may potentially be applied to the synthesis of diverse neoglycoconjugates and oligosaccharides. Georg Thieme Verlag Stuttgart.
- Ekholm, Filip S.,Polakova, Monika,Pawlowicz, Agnieszka J.,Leino, Reko
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experimental part
p. 567 - 576
(2009/07/18)
-
- Synthesis of pentasaccharide and heptasaccharide derivatives and their effects on plant growth
-
Two oligosaccharide derivatives, β-D-Glcp-(1-6)-β-D-Glcp-(1-6)- β-D-Glcp-(1-6)-β-D-Glcp-(1-4)-α-D-ManpOMe (1) and β-D-Glcp-(1-6)-β-D-Glcp-(1-6)-β-D-Glcp-(1-6)-β-D-Glcp-(1-6) -β-D-Glcp-(1-6)-β-D-Glcp-(1-4)-α-D-ManpOMe (2), have been synthesized efficiently using a convergent glycosylation strategy of 2 + 3 and 2 + 5.1,6-Anhydro-β-D-glucopyranose, which was prepared from cotton pyrolysis, was applied as a key synthon in the synthesis, significantly simplifying the preparation. The bioassay suggested that these two oligosaccharides can both stimulate the growth of maize cultured in liquid medium at a concentration of 3 ppm.
- Liu, Hongmei,Cheng, Shuihong,Liu, Jun,Du, Yuguang,Bai, Zhihui,Du, Yuguo
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scheme or table
p. 5634 - 5638
(2010/03/30)
-
- Truly catalytic and chemoselective cleavage of benzylidene acetal with phosphomolybdic acid supported on silica gel
-
Phosphomolybdic acid supported on silica gel provides a truly catalytic method for the chemoselective cleavage of benzylidene acetals having sensitive functional groups under mild conditions. It is easy to perform on large scale owing to minimal catalyst loading (0.5 mol-%). Several sensitive functional groups such as TBDPS ether, -OMs, -OAc, allyl ether, N-Boc, N-Fmoc and N-Cbz are stable under the reaction conditions. In addition, benzylidene acetal is selectively cleaved in the presence of isopropylidene ketal. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Kumar, Ponminor Senthil,Kumar, Gaddale Devanna Kishore,Baskaran, Sundarababu
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supporting information; scheme or table
p. 6063 - 6067
(2009/05/27)
-
- Regioselective esterification of vicinal diols on monosaccharide derivatives via Mitsunobu reactions
-
(Chemical Equation Presented) We have carried out a series of esterification reactions of secondary alcohols derived from D-glucose, D-mannose, and D-galaclose via the Mitsunobu reaction. The benzoylation reaction of vicinal diols derived from monosacchar
- Wang, Guijun,Ella-Menye, Jean-Rene,St. Martin, Michael,Yang, Hao,Williams, Kristopher
-
body text
p. 4203 - 4206
(2009/05/30)
-
- An iodocyclization approach toward diastereoselective synthesis of highly functionalized tetrasubstituted tetrahydrofurans with 2,5-trans and 2,5-cis relationships from pyranoside derived acyclic oximes
-
An efficient method to obtain novel tetrasubstituted tetrahydrofurans with C2 and C5 substitution in trans- and cis-relative configurations has been reported.
- Kumar, Vikas,Gauniyal, Harsh Mohan,Shaw, Arun K.
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p. 2069 - 2078
(2008/02/11)
-
- Synthesis and biophysical characterization of G-rich oligonucleotides conjugated with sugar-phosphate tails
-
A number of 5′-and 3′-glycoconjugates of the oligonucleotide 5′d(TGGGAG)3′ have been synthesized, exploiting fully automated, online phosphoramidite-based solid phase strategy, as potential anti-HIV-1 agents. The thermodynamic stability of the resulting quadruplexes has been investigated by thermal denaturation studies, via a detailed CD Q1 analysis. Copyright Taylor & Francis Group, LLC.
- D'Onofrio,Erra,Di Fabio,Iadonisi,Petraccone,De Napoli,Barone,Balzarini,Giancola,Montesarchio
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p. 1225 - 1229
(2008/09/20)
-
- Shortcut synthesis of β-cyclomannin from β-cyclodextrin
-
(Diagram presented) β-Cyclomannin, a cyclic oligosaccharide consisting of seven α-D-mannosides connected together by the (1→4) glycoside linkage, has been efficiently synthesized by the OsO4 oxidation of heptakis(2,3-didehydroxy)-β-cyclodextrin
- Fukudome, Makoto,Shiratani, Tomonori,Nogami, Yasuyoshi,Yuan, De-Qi,Fujita, Kahee
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p. 5733 - 5736
(2008/02/11)
-
- An efficient stereoselective dihydroxylation of glycals using a bimetallic system, RuCl3/CeCl3/NaIO4
-
A catalytic dihydroxylation reaction on glycals has been developed using a bimetallic oxidizing system to furnish sugar 1,2-diols in a highly setroselective manner.
- Tiwari, Pallavi,Misra, Anup Kumar
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p. 2911 - 2913
(2007/10/03)
-
- Synthesis of benzylidenated hexopyranosides in ionic liquids
-
The synthesis of 4,6-O-benzylidenated monosaccharides and disaccharides has been studied using ionic liquids as a unique solvent alternative. An examination of several imidazolium ionic liquids indicates that the benzylidenation of hexopyranosides in 3-bu
- Zhang, Jianguo,Ragauskas, Arthur J.
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p. 2812 - 2815
(2007/10/03)
-
- One-pot acetalation-acetylation of sugar derivatives employing perchloric acid immobilised on silica
-
Perchloric acid immobilised on silica gel has been used as an efficient promoter for per-O-acetylation, and acetalation and subsequent O-acetylation of glycosides and thioglycosides in one-pot using stoichiometric reagents.
- Mukhopadhyay, Balaram,Russell, David A.,Field, Robert A.
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p. 1075 - 1080
(2007/10/03)
-
- Stereoselective entry to β-linked C-disaccharides using a carbon-ferrier reaction
-
(Matrix presented) The synthesis of unsaturated β-linked C-disaccharides by the Lewis acid-mediated reaction of 3-O-acetylated glycals with monosaccharide-derived alkenes is described. Deprotection and selective hydrogenation of an exocyclic carbon-carbon
- Gemmell, Natasha,Meo, Paul,Osborn, Helen M. I.
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p. 1649 - 1652
(2007/10/03)
-
- Solid phase peptide templated glycosidic bond formation
-
Glycosylation reactions performed between a glycosyl donor and acceptor covalently linked to a peptide template both in the solution and solid phase give similar yields and product distributions. The adoption of a solid phase approach opens the way for the synthesis of libraries of peptide templates in an attempt to screen for particular peptide sequences that effect complete regio-and stereochemical control during glycosidic bond formation, whilst the use of second generation donors allows the possibility of an iterative approach.
- Tennant-Eyles, Richard J.,Davis, Benjamin G.,Fairbanks, Antony J.
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p. 1201 - 1210
(2007/10/03)
-
- Synthetic studies on ciguatoxin: A highly convergent synthesis of the GHIJKLM ring system based on b-alkyl suzuki coupling
-
Access to polycyclic polyethers is facilitated by a synthetic strategy involving two-step B-alkyl Suzuki coupling reactions for the stereo-selective construction of the polyether skeleton. Thus, a convergent synthetic route to the heptacyclic GHIJKLM ring system 1 of ciguatoxin, a marine algal toxin implicated in ciguatera fish poisoning, was developed. Bn = benzyl.
- Takakura, Hiroyuki,Noguchi, Katsuhiko,Sasaki, Makoto,Tachibana, Kazuo
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p. 1090 - 1093
(2007/10/03)
-
- Synthesis of new α- and β-gem-difluoromethylene C-glycosides in the galactose and glucose series
-
A synthesis of gem-difluoromethylene C-glycopyranosides was efficiently achieved via a Reformatsky reaction on an aldehyde and subsequent intramolecular cyclization involving either the opening of an epoxide or an oxymercuration.
- Marcotte, Stéphane,D'Hooge, Franc?ois,Ramadas, Sathunuru,Feasson, Christian,Pannecoucke, Xavier,Quirion, Jean-Charles
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p. 5879 - 5882
(2007/10/03)
-
- Further evidence for the gelation ability-structure correlation in sugar-based gelators
-
Eight methyl glycosides of 4,6-O-benzylidene derivatives of the monosaccharides D-glucose, D-mannose, D-allose and D-altrose were synthesized to systematically study the effect of small configurational changes on the ability to gelate organic solvents. Among the β anomers, only the D-mannose glycoside exhibits a strong gelation ability, whereas in the α-series the D-glucose and D-mannose derivatives act as versatile gelators. Also, as a general rule we found that the β anomers possess a higher ability to gelate solvents than the α anomers. The gelation properties are discussed on the basis of SAXS, FTIR, differential scanning calorimetric (DSC) measurements and scanning electron microscopy (SEM) observations. The temperature-dependent SAXS measurements were carried out to elucidate the sol-gel transition temperature. The present study emphasizes that the saccharide family provides, not only valuable information of the structural requirements for the design of new gelators, but also for molecular assembly systems in general.
- Gronwald, Oliver,Sakurai, Kazuo,Luboradzki, Roman,Kimura, Taro,Shinkai, Seiji
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p. 307 - 318
(2007/10/03)
-
- Tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP): A novel catalyst for selective deacetylation
-
Chemo-and stereoselective deacetylation was achieved by the use of a catalytic amount of tris(2,4,6-trimethoxyphenyl)phosphine (TTMPP).
- Yoshimoto, Kazuya,Kawabata, Hirotoshi,Nakamichi, Natsuki,Hayashi, Masahiko
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p. 934 - 935
(2007/10/03)
-
- Sugar-integrated gelators of organic solvents - Their remarkable diversity in gelation ability and aggregate structure
-
Five 1-O-methyl-4,6-O-benzylidene derivatives of the monosaccharides D-glucose, D-galactose, and D-mannose were synthesized. The β-isomer of the D-glucose derivative was sparingly soluble in most organic solvents, whereas the α-isomer of the D-mannose derivative was soluble in many organic solvents. The α-isomer of the D-glucose derivative and the α- and β-isomers of the D-galactose derivative acted as versatile gelators of various organic solvents; this indicates that saccharides are useful as potential templates for the molecular design of chiral gelators. In particular, the two D-galactose-based gelators behaved as "excellent gelators". It is very surprising that a change in the configuration of only one carbon atom results in such a drastic change in the solubility and the gelation properties. The possible relationship between the saccharide structure and the gelation properties is discussed on the basis of FT-IR and 1H NMR spectroscopic data, differential scanning calorimetric (DSC) measurements, scanning electron microscopy (SEM) observations, and computational studies. FT-IR spectroscopy showed that the gelation properties are related to the formation of "moderate" intermolecular hydrogen bonds. The SEM observations showed that the gelators can form various fibrous structures (straight, puckered, and helical). The present study shows that this saccharide family is a potential combinatorial library of organic gelators and more generally, of molecular assembly systems.
- Yoza, Kenji,Amanokura, Natsuki,Ono, Yoshiyuki,Akao, Tetsuyuki,Shinmori, Hideyuki,Takeuchi, Masayuki,Shinkai, Seiji,Reinhoudt, David N.
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p. 2722 - 2729
(2007/10/03)
-
- Synthesis of rhamnogalacturonan I oligosaccharides: Synthesis of a tetrasaccharide intermediate
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A hydroxyl protected tetrasaccharide intermediate, corresponding to a segment of the rhamnogalacturonan I polysaccharide, has been synthesized using the glycosyl imidate technique. This tetrasaccharide is designed to allow for further elongation and branching.
- Rich, Jamie R.,McGavin, Robert S.,Gardner, Rebecca,Reimer, Kerry B.
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- Sugar-integrated gelators of organic fluids: On their versatility as building-blocks and diversity in superstructures
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Three 1-O-methyl-4, 6-O-benzylidene derivatives of monosaccharides (D-glucose, D-galactose and D-mannose) were synthesised: they acted as versatile gelators of various organic fluids, indicating that saccharides are useful as potential building-blocks for
- Yoza, Kenji,Ono, Yoshiyuki,Yoshihara, Kanami,Akao, Tetsuyuki,Shinmori, Hideyuki,Takeuchi, Masayuki,Shinkai, Seiji,Reinhoudt, David N.
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p. 907 - 908
(2007/10/03)
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- The stereocontrolled formation of cyclic vicinal cis-diols via a samarium diiodide pinacol coupling of dialdehydes
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Aliphatic 1,5- and 1,6 dialdehydes with and without α-substituents, as well as derivatives of carbohydrate dialdehydes undergo a pinacol coupling reaction in the presence of SmI2 to give cis-diols as the preponderant products. When α-alkoxy groups are present, the diol has an orientation that is opposite to such groups.
- Chiara, Jose Luis,Cabri, Walter,Hanessian, Stephen
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p. 1125 - 1128
(2007/10/02)
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- Oligosaccharide microanalysis by c.d. spectroscopy. Reference curves for D-mannose derivatives.
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This study completes the spectroscopic basis for a novel oligosaccharide microanalytical method, wherein a derivatization sequence provides monosaccharide subunits bearing two types of exciton-coupling chromophore groups ("bichromophoric") for circular di
- Meyers,Ojika,Wiesler,Nakanishi
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- The Selective Monobenzylidenation of Some Monosaccharides and Their Derivatives with α,α-Dimethoxytoluene
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The treatment of some monosaccharides and their derivatives with α,α-dimethoxytoluene and an acid catalyst in dimethylformamide at about 80 deg C can lead to selective benzylidenation, e.g. methyl α-D-mannopyranoside gives mainly methyl 4,6-O-benzylidene-α-D-mannoside, together with two other minor monobenzylidene derivatives (2,3-) and two minor dibenzylidene derivatives (2,3:4,6-).The treatment of various other pyranoses and pyranosides is also described.As well, a 1H n.m.r. study of the acid transformation of some of the above α-D-mannosides is reported, together with a single-crystal X-ray diffraction structure determination of a novel monobenzylidene derivative, namely methyl (S)-2,3-O-benzylidene-α-D-mannopyranoside.
- Patroni, Joseph J.,Stick, Robert V.,Skelton, Brian W.,White, Allan H.
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- Acetalation studies. Part VI. Concerning the effects of ultrasound on the benzylidenation of some alkyl D-glycopyranosides
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The effects of ultrasound on conventional Freudenberg-type benzylidenation reactions of some alkyl D-glycopyranosides is described.A considerable enhancement in the rates of formation of the expected acetals was observed.The pure products were obtained in good yields.Some of the crude air-dried products were suitable for direct derivatisation.
- Chittenden, Gordon J. F.
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p. 607 - 609
(2007/10/02)
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- An Improvement in the Preparation of Some Carbohydrate Benzylidene Acetals
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Carbohydrate benzylidene and p-methoxybenzylidene acetals are easily prepared by treatment of various sugar derivatives with either benzaldehyde diethyl acetal or p-methoxybenzaldehyde diethyl acetal, respectively, in refluxing chloroform containing camph
- Ferro, Vito,Mocerino, Mauro,Stick, Robert V.,Tilbrook, D. Matthew G.
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p. 813 - 815
(2007/10/02)
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