- Synthesis of 3-deoxyaldulosonic acid esters by one-carbone chain extension of glycal-derived lactone precursors
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A convenient preparative route is described for 3-deoxyaldulosonic acids. Glycal precursors are oxidatively converted into 2-deoxyaldonolactones, which react with 1,3-dithian-2-yl anion to afford 1,3-propanediyl dithioacetals of higher 3-deoxyaldosuloses. Deprotection with mercuric salts in wet or dry alcohols gave high yields of the corresponding alkyl aldulosonates. Preparative reaction conditions were optimized and the anomeric configurations of the ketopyranose products were established by 13C NMR. A convenient preparative route is described for 3-deoxyaldulosonic acids. Glycal precursors are oxidatively converted into 2-deoxyaldonolactones, which react with 1,3-dithian-2-yl anion to afford 1,3-propanediyl dithioacetals of higher 3-deoxyaldosuloses. Deprotection with mercuric salts in wet or dry alcohols gave high yields of the corresponding alkyl aldulosonates. Preparative reaction conditions were optimized and the anomeric configurations of the ketopyranose products were established by13C NMR.
- Horton,Issa,Priebe,Sznaidman
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Read Online
- Two pyran type glycosides from saponaria and dianthus
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2,3-Dihydro 4-O-β-D-glucopyranosyl 3-hydroxy-2-methyl-4H-pyran was isolated from Saponaria officinallis and its relative configuration and conformation determined. A new glycoside, isomeric with the former but having a different configuration at C-4, has been isolated from Dianthus barbatus and D. deltoides.
- Plouvier, Victor,Martin, Marie-Therese,Brouard, Jean-Paul
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Read Online
- Extended RCM-ROM sequences: a novel approach to polyunsaturated trisaccharides
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The first examples of RCM-ROM-RCM-ROM-RCM sequences involving non-strained heterocyclic relays are described. The method can be used for the preparation of polyunsaturated trisaccharides.
- Donnard, Morgan,Tschamber, Théophile,Eustache, Jacques
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Read Online
- Combinatorial synthesis of oligosaccharide library of 2,6-dideoxysugars
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Two combinatorial libraries composed of linear trisaccharides of 2,6- dideoxy-L-sugars have been constructed: All possible regioisomeric trisaccharides with 2-iodo and with 2-deoxy moieties were synthesized by an iodonium ion-catalyzed 'stereoselective-yet-nonregioselective' glycosylation reaction.
- Izumi, Masayuki,Ichikawa, Yoshitaka
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Read Online
- Isolation, Structure, and Total Synthesis of the Marine Macrolide Mangrolide D
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The isolation, characterization, and total synthesis of the macrocyclic polyene mangrolide D is reported. A 16-step total synthesis relies on robust Suzuki and ring-closing metathesis reactions, and an iron-catalyzed hydroazidation of an exomethylene subs
- Gong, Junyu,Li, Wei,Fu, Peng,Macmillan, John,De Brabander, Jef K.
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Read Online
- Silicon-tethered Radical Cyclization and Intramolecular Diels-Alder Strategies are combined to provide a Ready Route to Highly Functionalized Decalins
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Stereoselective addition of carbon branches at C(1) and C(2) of L-rhamnal is achieved via silicon-mediated radical procedures, and the product is readily processed to give a hex-2-enopyranosid-4-ulose whose intramolecular Diels-Alder reaction has been examined.
- Lopez, J. Cristobal,Gomez, Ana M.,Reid-Fraser, Bert
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Read Online
- Synthesis of the α-Linked Digitoxose Trisaccharide Fragment of Kijanimicin: An Unexpected Application of Glycosyl Sulfonates
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Previously, we demonstrated that glycosyl tosylates are effective for the synthesis of β-glycosides of gluco-configured 2-deoxy sugars. Here, we show the same sulfonate system can be used for the selective synthesis of α-glycosides containing the allo-con
- Bennett, Clay S.,Mizia, J. Colin,Syed, Mohammed U.
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supporting information
p. 731 - 735
(2022/01/28)
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- Automated, Multistep Continuous-Flow Synthesis of 2,6-Dideoxy and 3-Amino-2,3,6-trideoxy Monosaccharide Building Blocks
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An automated continuous flow system capable of producing protected deoxy-sugar donors from commercial material is described. Four 2,6-dideoxy and two 3-amino-2,3,6-trideoxy sugars with orthogonal protecting groups were synthesized in 11–32 % overall yields in 74–131.5 minutes of total reaction time. Several of the reactions were able to be concatenated into a continuous process, avoiding the need for chromatographic purification of intermediates. The modular nature of the experimental setup allowed for reaction streams to be split into different lines for the parallel synthesis of multiple donors. Further, the continuous flow processes were fully automated and described through the design of an open-source Python-controlled automation platform.
- Bennett, Clay S.,DeYong, Ashley E.,Florek, John,Nguyen, Tu-Anh,Pohl, Nicola L. B.,Stamper, Gavin,Vasquez, Olivea,Yalamanchili, Subbarao,Zsikla, Alexander
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p. 23171 - 23175
(2021/09/25)
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- Me3SI-promoted chemoselective deacetylation: a general and mild protocol
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A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
- Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
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p. 19310 - 19315
(2021/06/03)
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- Ir(I)-Catalyzed C?H Glycosylation for Synthesis of 2-Indolyl-C-Deoxyglycosides
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The construction of 2-deoxy-C-glycosides has gradually become a hotspot of carbohydrate chemistry in recent years. In this work, we present an efficient, regioselective, stereoselective and widely applicable strategy for the synthesis of 2-indolyl-C-deoxyglycosides via Ir(I)-catalyzed, pyridine-group-directed C?H functionalization. This method exhibits high tolerance for the functional groups of indoles and the protecting groups of carbohydrates. Moreover, this protocol has good stereoselectivity and mainly produces β-configuration products. Gram-scale synthesis and several practical transformations were conducted for further applications. Meantime, we also explored the mechanism of this method and proposed a catalytic cycle. (Figure presented.).
- Yu, Changyue,Liu, Yichu,Xie, Xiong,Hu, Shulei,Zhang, Shurui,Zeng, Mingjie,Zhang, Dan,Wang, Jiang,Liu, Hong
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supporting information
p. 4926 - 4931
(2021/09/09)
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- Modular continuous flow synthesis of orthogonally protected 6-deoxy glucose glycals
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An efficient, modular continuous flow process towards accessing two orthogonally protected glycals is described with the development of reaction conditions for several common protecting group additions in flow, including the addition of benzyl, naphthylme
- Bennett, Clay S.,Nguyen, Tu-Anh V.,Pohl, Nicola L. B.,Yalamanchili, Subbarao
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supporting information
p. 3254 - 3257
(2020/05/14)
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- Deciphering the Biosynthesis of TDP-β- l -oleandrose in Avermectin
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Avermectin (AVM) refers to eight macrolides containing a common l-oleandrosyl disaccharide chain indispensable to their antiparasitic bioactivities. We delineated the biosynthetic pathway of TDP-β-l-oleandrose (1), the sugar donor of AVM, by characterizing AveBVIII, AveBV, and AveBVII as TDP-sugar 3-ketoreductase, 5-epimerase, and 3-O-methyltransferase, respectively. On the basis of this pathway, we successfully reconstituted the biosynthesis of 1 in Escherichia coli. Our work completes the biosynthetic pathway of AVM and lays a solid foundation for further studies.
- Tang, Yue,Wang, Min,Qin, Hua,An, Xiangxiang,Guo, Zhengyan,Zhu, Guoliang,Zhang, Lixin,Chen, Yihua
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p. 3199 - 3206
(2020/11/02)
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- Tuning the Chemoselectivity of Silyl Protected Rhamnals by Temperature and Br?nsted Acidity: Kinetically Controlled 1,2-Addition vs Thermodynamically Controlled Ferrier Rearrangement
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An acidity- and temperature-dependent chemoselective glycosylation of silyl-protected rhamnals with alcohols has been revealed. The reaction undergoes a 1,2-addition pathway with (±)-CSA as the catalyst at rt, affording kinetically controlled 2-deoxyl rhamnosides. In contrast, only thermodynamically controlled 2,3-unsaturated rhamnosides are formed via Ferrier rearrangement when elevating reaction temperature to 85 °C or using CF3SO3H instead. This tunable glycosylation allows facile and practical access to both 2-deoxyl and 2,3-unsaturated rhamnosides with excellent yields and high α-stereoselectivity.
- Wang, Jincai,Deng, Chuqiao,Zhang, Qi,Chai, Yonghai
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p. 1103 - 1107
(2019/02/14)
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- Reagent Controlled Direct Dehydrative Glycosylation with 2-Deoxy Sugars: Construction of the Saquayamycin Z Pentasaccharide
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The first synthesis of the pentasaccharide fragment of the angucycline antibiotic saquayamycin Z is described. By using our sulfonyl chloride mediated reagent controlled dehydrative glycosylation, we are able to assemble the glycosidic linkages with high
- Mizia, J. Colin,Bennett, Clay S.
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supporting information
p. 5922 - 5927
(2019/08/27)
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- Reagent-Controlled Synthesis of the Branched Trisaccharide Fragment of the Antibiotic Saccharomicin B
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A concise synthesis of a branched trisaccharide, α-l-Dig-(1 → 3)-[α-l-Eva-(1 → 4)]-β-d-Fuc, corresponding to saccharomicin B, has been developed via reagent-controlled α-selective glycosylations. Starting from the d-fucose acceptor, l-epi-vancosamine was selectively installed using 2,3-bis(2,3,4-trimethoxyphenyl)cyclopropene-1-thione/oxalyl bromide mediated dehydrative glycosylation. Following deprotection, l-digitoxose was installed using the AgPF6/TTBP thioether-activation method to produce the trisaccharide as a single α-anomer. This highly functionalized trisaccharide can potentially serve as both a donor and an acceptor for the total synthesis of the antibiotic saccharomicin B.
- Soliman, Sameh E.,Bennett, Clay S.
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supporting information
p. 3413 - 3417
(2018/06/11)
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- Stereospecific C-Glycosylation by Mizoroki–Heck Reaction: A Powerful and Easy-to-Set-Up Synthetic Tool to Access α- and β-Aryl-C-Glycosides
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A stereospecific Mizoroki–Heck cross-coupling of differently substituted glycals with haloarenes resulting in the exclusive formation of either α- or β-aryl-C-glycosides depending solely on the configuration at C3 was achieved. The reaction was easy to set up because no specific precautions were required concerning moisture or oxygen, and it proceeded by a chirality transfer from C3 to C1. After optimization of cross-coupling conditions, various prepared glycals (7 examples) and arenes (10 examples) were tested, leading stereospecifically to the corresponding aryl-C-glycosides with a carbonyl group at C3, thus opening up new horizons for the total synthesis of glycosylated natural products.
- Mabit, Thibaud,Siard, Aymeric,Legros, Frédéric,Guillarme, Stéphane,Martel, Arnaud,Lebreton, Jacques,Carreaux, Fran?ois,Dujardin, Gilles,Collet, Sylvain
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supporting information
p. 14069 - 14074
(2018/09/14)
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- 3-Aminodeoxypyranoses in Glycosylation: Diversity-Oriented Synthesis and Assembly in Oligosaccharides
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A concise, diversity-oriented approach for the synthesis of naturally occurring 3-amino- and 3-nitro-2,3,6-trideoxypyranose derivatives and analogues thereof from simple sugars has been developed. In addition, we investigated the synthesis of various 3-aminoglycosyl donors and their application in glycosylation reactions. These studies led to the successful synthesis of a tetrasaccharide containing four different 3-aminosugar components using ortho-alkynylbenzoate donors.
- Zeng, Jing,Sun, Guangfei,Yao, Wang,Zhu, Yangbin,Wang, Ruobin,Cai, Lei,Liu, Ke,Zhang, Qian,Liu, Xue-Wei,Wan, Qian
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p. 5227 - 5231
(2017/04/27)
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- MACROCYCLIC PICOLINAMIDE COMPOUNDS WITH FUNGICIDAL ACTIVITY
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This disclosure relates to macrocyclic picolinamides of Formula (I) and their use as fungicides.
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Paragraph 00117-00118
(2016/08/03)
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- Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes
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Catalytic enantioselective diboration of alkenes is accomplished with readily available carbohydrate-derived catalysts. Mechanistic experiments suggest the intermediacy of 1,2-bonded diboronates.
- Fang, Lichao,Yan, Lu,Haeffner, Fredrik,Morken, James P.
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supporting information
p. 2508 - 2511
(2016/03/12)
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- Callipeltosides A, B and C: Total Syntheses and Structural Confirmation
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Since their isolation almost 20 years ago, the callipeltosides have been of long standing interest to the synthetic community owing to their unique structural features and inherent biological activity. Herein we present our full research effort that has led to the synthesis of these molecules. Key aspects of our final strategy include 1) synthesis of the C1-C9 pyran core (5) using an AuCl3-catalysed cyclisation; 2) formation of C10-C22 vinyl iodide (55) by sequential bidirectional Stille reactions and 3) diastereoselective union of these advanced fragments by means of an alkenylzinc addition (d.r.=91:9 at C9). The common callipeltoside aglycon (4) was completed in a further five steps. Following this, all three sugar fragments were appended to provide the entire callipeltoside family. In addition to this, D-configured callipeltose B was synthesised and appended to the callipeltoside aglycon. The 1H NMR spectrum of this molecule was found to be significantly different to the natural isolate, further supporting our assignment of callipeltoside B (2). Easy as A, B, C: The entire callipeltoside family of natural products have been synthesised in a highly convergent manner. This account details our full research effort and presents further evidence to aid in the stereochemical assignment of the glycosidic linkages present in callipeltosides B and C (see scheme).
- Frost, James R.,Pearson, Colin M.,Snaddon, Thomas N.,Booth, Richard A.,Turner, Richard M.,Gold, Johan,Shaw, David M.,Gaunt, Matthew J.,Ley, Steven V.
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supporting information
p. 13261 - 13277
(2015/09/15)
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- Direct C-H Trifluoromethylation of Glycals by Photoredox Catalysis
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A mild, efficient, and practical transformation for the direct C-H trifluoromethylation of glycals under visible light has been reported for the first time. This reaction employed fac-Ir3+(ppy)3 as the photocatalyst, Umemoto's reagent as the CF3 source, and a household blue LED or sunlight as the light source. Glycals bearing both electron-withdrawing and -donating protective groups performed this reaction smoothly. This visible light-mediated trifluoromethylation reaction was highlighted by the trifluoromethylation of the biologically important Neu2en moiety.
- Wang, Bang,Xiong, De-Cai,Ye, Xin-Shan
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supporting information
p. 5698 - 5701
(2015/12/01)
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- MACROCYCLIC PICOLINAMIDES AS FUNGICIDES
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The disclosure relates to macrocyclic picolinamides of Formula (I) and to the use of these compounds as fungicides.
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Page/Page column
(2014/07/08)
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- A 3,4-trans-fused cyclic protecting group facilitates α-selective catalytic synthesis of 2-deoxyglycosides
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A practical approach has been developed to convert glucals and rhamnals into disaccharides or glycoconjugates with high α-selectivity and yields (77-97 %) using a trans-fused cyclic 3,4-O-disiloxane protecting group and TsOH·H2O (1 mol %) as a catalyst. Control of the anomeric selectivity arises from conformational locking of the intermediate oxacarbenium cation. Glucals outperform rhamnals because the C6 side-chain conformation augments the selectivity.
- Balmond, Edward I.,Benito-Alifonso, David,Coe, Diane M.,Alder, Roger W.,McGarrigle, Eoghan M.,Galan, M. Carmen
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supporting information
p. 8190 - 8194
(2014/08/18)
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- Preparation of C-arylglycals via Suzuki–Miyaura cross-coupling of dihydropyranylphosphates
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The preparation of C-arylglycals has been accomplished by employing the Suzuki–Miyaura cross-coupling reaction of dihydropyranylphosphates with arylboronate esters. The reaction is tolerant of both electron-donating (EDG) and electron-withdrawing (EWG) gr
- Leidy, Michelle R.,Mason Hoffman,Pongdee, Rongson
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supporting information
p. 6889 - 6891
(2019/04/10)
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- N-heterocyclic carbene catalyzed C-glycosylation: A concise approach from stetter reaction
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Described herein is the first example of an organocatalytic approach for acylanion addition to the anomeric carbon of 2-nitroglucal using an N-heterocyclic carbene catalyst. Control over the reaction conditions gives β-selective and nitro-eliminated C-glycosides, providing opportunities to produce new classes of C-glycoside.
- Vedachalam, Seenuvasan,Tan, Shi Min,Teo, Hui Ping,Cai, Shuting,Liu, Xue-Wei
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supporting information; experimental part
p. 174 - 177
(2012/02/16)
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- Convergent total syntheses of callipeltosides A, B, and C
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Going for the hat-trick: The synthesis of the entire callipeltoside family of natural products is described. Key to this synthesis was the coupling of the di-ene-yne and pyran fragments by a diastereoselective alkenylzinc addition allowing rapid access to the common aglycon. Attachment of each relevant L-configured sugar resulted in the first total synthesis of callipeltoside B (see scheme), and the syntheses of callipeltosides A and C.
- Frost, James R.,Pearson, Colin M.,Snaddon, Thomas N.,Booth, Richard A.,Ley, Steven V.
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p. 9366 - 9371
(2012/10/29)
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- Noteworthy observations accompanying synthesis of the apoptolidin disaccharide
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A stereoselective synthesis of the apoptolidin disaccharide is reported. The key chemistry features a new transformation utilizing a highly selective tetramethylalkoxyalanate[v]-directed syn-methylation of a vinylogous ester, isolation of a hydrate of a 2-keto sugar, an eco-friendly radical cleavage of a bromomethyl group, and an efficient preparation of a fluorodisaccharide via the use of XtalFluor-E.
- Srinivasarao, Madduri,Park, Taesik,Chen, Yuzhong,Fuchs, Philip L.
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supporting information; experimental part
p. 5858 - 5860
(2011/07/08)
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- Synthesis study on marmycin A: Preparation of the C3′-desmethyl analogues
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(Chemical Equation Presented) Total synthesis of natural product marmycinAwas studied. An expeditious synthetic strategy for the key fragment 8-amino-3-methylbenz[a]anthraquinone (1) was established with decarboxylative alkylation, Pd(OAc)2-catalyzed cyclization, aromatization, and C - N coupling as the key steps. However, final assembly of marmycin A was hampered by the failure to obtain the carbohydrate fragment 2. Instead, a small library of desmethyl analogues of marmycinAwas prepared in moderate yields by using the InBr3-catalyzed C- and N-glycosidation reaction. The absolute configuration of these compounds was confirmed by comparison of their spectroscopic data with that reported for marmycin A, and by X-ray analysis.
- Ding, Chunyong,Tu, Shanghui,Li, Fuying,Wang, Yuanxiang,Yao, Qizheng,Hu, Wenxiang,Xie, Hua,Meng, Linghua,Zhang, Ao
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scheme or table
p. 6111 - 6119
(2009/12/26)
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- Regio- and stereo-selective synthesis of aryl 2-deoxy-C-glycopyranosides by palladium-catalyzed Heck coupling reactions of glycals and aryl iodides
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The Heck coupling of aryl iodides with pyranoid glycals using a catalytic amount of Pd(OAc)2 to form pyranoid aryl C-glycosides has been achieved. The reaction takes place smoothly in the presence of Ag 2CO3 and Cu(OAc)2 (or DMSO) in acetonitrile. This arylation process, which occurs in a highly regio- and stereo-selective manner, provides a simple, mild, and efficient approach to the synthesis of aryl 2-deoxy-C-glycopyranosides.
- Li, Hou-Hua,Ye, Xin-Shan
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experimental part
p. 3855 - 3861
(2009/10/23)
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- Studies on the synthesis of apoptolidin A. 1. Synthesis of the C(1)-C(11) fragment
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(Chemical Equation Presented) A synthesis of the C(1)-C(11) fragment of apoptolidin A has been accomplished by a convergent route involving the stereoselective glycosidation of 9 and the Suzuki cross-coupling reaction of bromodienoate 7 and the vinylboran
- Handa, Masaki,Scheldt, Karl A.,Bossart, Martin,Zheng, Nan,Roush, William R.
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p. 1031 - 1035
(2008/09/18)
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- On the synthesis of the 2,6-dideoxysugar l-digitoxose
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As deoxysugars are integral components of many natural products, the development of efficient chemical and enzymatic routes to prepare these compounds is of particular interest. Herein, we report a comparison of several synthetic methodologies used to prepare protected derivatives of the 2,6-dideoxysugar l-digitoxose. A novel, stereoselective synthetic route to efficiently access methyl 4-O-tert-butyldimethylsilyl-2,6-dideoxy-3-O-trimethylsilyl-α-l-ribo-hexopyranoside in 35% yield over nine facile steps is described.
- Timmons, Shannon C.,Jakeman, David L.
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p. 2695 - 2704
(2008/03/14)
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- Preparation of an analogue of orbicuside A, an unusual cardiac glycoside
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A steroid containing a multi-linked glycoside, analogous to the bufadienolide orbicuside A, has been prepared. The key steps were (i) the preparation of a 2α-allyloxycarbonyloxy-3β-hydroxy steroid, (ii) a Ferrier reaction between the steroid and a rhamnal derivative, (iii) removal of protecting group and oxidation of the 2-hydroxy group, (iv) dihydroxylation of the pseudoglycal from the sterically more hindered side and finally (v) ring closure by acetal formation under acidic conditions.
- Dixon, John T.,Van Heerden, Fanie R.,Holzapfel, Cedric W.
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p. 393 - 401
(2007/10/03)
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- Synthesis and absolute stereochemistry of roseophilin
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The enantiospecific total synthesis of natural roseophilin has been completed in 7.0% overall yield over 15 steps by means of an asymmetric cyclopentannelation. This establishes the absolute configuration of the natural product as 22R,23R. Cyclopentenone
- Harrington,Tius
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p. 8509 - 8514
(2007/10/03)
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- Stereoselective glycosylations of a family of 6-deoxy-1,2-glycals generated by catalytic alkynol cycloisomerization
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Photolysis of 0.25 equiv of W(CO)6 in the presence of tertiary amines (triethylamine or DABCO) and highly functionalized terminal alkynyl alcohols catalyzes single-step, high-yield cycloisomerization to endocyclic enol ethers. This transformati
- McDonald, Frank E.,Reddy, K. Subba,Diaz, Yolanda
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p. 4304 - 4309
(2007/10/03)
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- Complete regioselectivity in staurosporine chromophore formation
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For the preparation of regioselectively N-substituted indolocarbazole alkaloids two strategies have been employed: 1. the exploitation of different electronic situations at the nitrogen atoms, and 2. the utilization of an orthogonal protecting group strategy that allows regioselective glycoside formation.
- Eils, Stefan,Winterfeldt, Ekkehard
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p. 275 - 281
(2007/10/03)
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- Glycosylation of Branched Amino and Nitro Sugars. 2. Synthesis of the Cororubicin Trisaccharide
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The synthesis of the nitro-sugar-containing trisaccharide found in the antibiotic cororubicin is described. This trisaccharide contains the nitro sugar L-decilonitrose which is attached to two digitoxose residues (a dideoxy sugar) by β-1,4 and α-1,4 linkages. The target trisaccharide synthesized was methyl 2,6-dideoxy-α-L-lyxo-hexopyranosyl-(1-→4)-2,3,6-trideoxy-3-C-methyl- 3-nitro-β-L-ribo-hexopyranosyl-(1-→4)-2,6-dideoxy-α-L-lyxo- hexopyranoside. The principle features of the synthesis are the use of an O-benzylhydroxylamino sugar as the precursor to the nitro sugar decilonitrose and as both the acceptor and donor in glycosyations, a β-selective glycosylation by means of a thioglycoside donor, and novel functional group transformations carried out on the assembled trisaccharide. These include oxidative cleavage of the O-benzylhydroxylamino group to nitro, carried out with dimethyldioxirane in one step. This transformation proved critical in completing the synthesis, which is the first reported of one of the decilonitrose-containing trisaccharides found in antibiotics.
- Noecker, Lincoln,Duarte, Franco,Bolton, Scott A.,McMahon, Wayne G.,Diaz, Maria T.,Giuliano, Robert M.
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p. 6275 - 6282
(2007/10/03)
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- Antibody-oligosaccharide interactions: the synthesis of 2-deoxy-&α-L-rhamnose containing oligosaccharide haptens related to Shigella flexneri variant Y antigen
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A series of di-and trisaccharide glycosides based on the α-L-Rha(1->3)β-D-GlcNAc and α-L-Rha(1->3)α-L-Rha(1->3)β-D-GlcNAc elements have been synthesized to locate the minimal oligosaccharide determinant of the Shigella flexneri O-polysaccharide, which is built from a tetrasaccharide repeating unit, 2) α-L-Rhap(1->2)α-L-Rhap(1->3)α-L-Rhap(1->3)β-D-GlcNAcp(1->n.These compounds are also serve to identify the carbohydrate surface of the Shigella antigen that interacts with a monoclonal antibody, currently the subject of crystallographic studies.Two strategies utilizing suitably protected glycals 1 and 19 were employed to obtain analogs bearing either terminal od glycosylated 2,6-dideoxy-α-L-arabino-hexopyranosyl (2-deoxy-α-L-rhamnopyranosyl) residues.N-Iodosuccinimide activation of the glycals in the presence of selectively protected mono- and disaccharide alcohols afforded 2-deoxy-2-iodo-α-L-rhamnopyranosides and these were ultimately reduced during deprotection stages to afford the desired functionality.Di-O-acetyl L-rhamnal 1 reacted with monosaccharides 2 and 7, and with disaccharide 11, to yield disaccharides 4 and 8, and trisaccharide 12, each bearing a terminal 2-deoxy-α-L-rhamnopyranosyl residue.The selectively protected 3-O-benzoyl-4-O-benzyl-L-rhamnal 19 was synthesized from L-rhamnal and used to prepared trisaccharide 22, which contained an internal 2-deoxy-2-iodo-α-L-rhamnopyranosyl unit.Removal of protecting groups gave the oligosaccharides 6, 10, 14, and 23.Oligosaccharides that contained a 2-deoxy-α-L-rhamnopyranosyl residue showed enhanced inhibitory power: in the case of trisaccharide 23 a 1.8 kcal mol-1 relative increase in free energy of binding compared to a larger pentasaccharide epitope, α-L-Rhap(1->2)α-L-Rhap(1->3)α-L-Rhap(1->3)β-GlcAcp(1->2)α-L-Rhap-1->OMe.These data suggest that the rhamnose O-2 hydroxyl of residue C points toward and has important interactions with bindinbg site amino acids.
- Hanna, H. Rizk,Bundle, David R.
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p. 125 - 134
(2007/10/02)
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- A Simple Procedure for the Synthesis of Carbohydrate Ortholactones
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3,4-Di-O-benzyl-2,6-dideoxy-L-arabino-hexono-1,5-lactone (1b) was synthesized in three steps by starting from di-O-acetyl-L-rhamnal (6).Sequential treatment of 1b or 3,4,6-tri-O-benzyl-2-deoxy-D-arabino-hexono-1,5-lactone (1a) with triethyloxonium tetrafl
- Zagar, Cyrill,Scharf, Hans-Dieter
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p. 447 - 450
(2007/10/02)
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- Alternative syntheses of L-(-)-oleandrose from L-rhamnose. Preparation of glycals
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L-Rhamnal (2) is prepared from L-rhamnose (3) by use of an improved generalized Fischer-Zach reaction. L-Rhamnal (2) is then converted to L-(-)-oleandrose (1) by stannylene mediated selective methylation and effective hydration. Benzyl α-L-oleandrose (12) is prepared by selective methylation and deoxygenation of L-rhamnose (3).
- Bredenkamp,Holzapfel,Toerien
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p. 2459 - 2477
(2007/10/02)
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- Unusual stereoselectivity in sialic acid aldolase-catalyzed aldol condensations: Synthesis of both enantiomers of high-carbon monosaccharides
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An inversion of stereoselectivity in aldol condensations catalyzed by sialic acid aldolase (from Escherichia coli, Shinko American Inc.) was observed when L-mannose, 6-deoxy-L-mannose, L-talose, 2-deoxy-L-glucose, 2-deoxy-L-rhamnose, N-acetyl-L-mannosamin
- Lin, Chun-Hung,Sugai, Takeshi,Halcomb, Randall L.,Ichikawa, Yoshitaka,Wong, Chi-Huey
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p. 10138 - 10145
(2007/10/02)
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- LIMITATIONS IN THE APPLICATION OF ANIONIC OXY-COPE SIGMATROPY TO ELABORATION OF THE FORSKOLIN NUCLEUS
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The functionalized bicyclooctenone 6 has been synthesized in four steps from 2,4,4-trimethyl-2-cyclohexenone.This ketone undergoes 1,2-addition with 6-lithiodihydropyran to deliver alcohols 16 and 17 in a 1:1.8 ratio.The potassium salt of 17 experi
- Paquette, Leo A.,Oplinger, Jeffrey A.
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p. 107 - 124
(2007/10/02)
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- A CONVENIENT, HIGH-YIELD SYNTHESIS OF L-OLEANDROSE AND L-OLEANDRAL
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A short, practical synthesis of L-oleandrose (2,6-dideoxy-3-O-methyl-L-arabino-hexose) from L-arabinose has been achieved.The synthesis is satisfactory for large-scale preparation of oleandrosylating intermediates, and employs dithiolane formation for protection of the aldehyde group during deoxygenation and methylation steps, and Wittig chain-extension to 2-deoxyhexose derivatives.Useful intermediates in the introduction of oleandrose glycosides into natural products, such as the 1,4-dibenzoates and the methyl glycosides, were prepared and characterized.L-Oleandral (1,5-anhydro-2,6-dideoxy-3-O-methyl-L-arabino-hex-1-enitol), another useful intermediate for glycosylation, was prepared from 3,4-di-O-acetyl-L-rhamnal by deacetylation, and regioselective methylation with stannous chloride-diazomethane.
- Tolman, Richard L.,Peterson, Louis H.
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p. 113 - 122
(2007/10/02)
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- Stereoselective C-Glycosidation of Glycals with Organoaluminum Reagents
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A new approach to the stereoselective synthesis of C-glycosides from glycals with various organoaluminum reagents has been demonstrated.
- Maruoka, Keiji,Nonoshita, Katsumasa,Itoh, Takayuki,Yamamoto, Hisashi
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p. 2215 - 2216
(2007/10/02)
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- Syntheses of Selectively Alkylated Enol Ethers in the L-ribo Series
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The reduction of enulose 1a predominantly leads to L-digitoxal (3a), although this method presents a sluggish reaction with moderate yields.In contrast, the preparation from L-digitoxose (4a) in a three-step one-pot procedure represents an advantageous approach.Regioselective 3- or 4-O-alkylations are achieved by phase-transfer catalysis method or via stannylidene intermediates to give monosaccharide precursors of the L-ribo series valuable for further interglycosidic linking.
- Koepper, Sabine,Lundt, Inge,Pedersen, Christian,Thiem, Joachim
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p. 531 - 536
(2007/10/02)
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- Synthesis of N-benzoyl-L-ristosamine and intermediates used in its preparation
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A process for synthesizing N-benzoyl-L-ristosamine is disclosed. Intermediates useful for synthesizing N-benzoyl-L-ristosamine, and processes for preparing such intermediates, are also disclosed.
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