Studies on the koenigs-knorr reaction

Dejter-Juszynski, Marta; Flowers, Harold M.

doi:10.1016/s0008-6215(00)82857-8

Cited by 61 publications

(34 citation statements)

References 15 publications

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“…1 -6 Presumably the nearby ether oxygen at C-4 is responsible for the selectivity (> 20:1). The examples la and 2a, alongwith previous results, 5 ' 6 confirm that selectivity in triflation of pyranoside diols is not simply a function of the acidity or steric environment of the reacting hydroxyl, nor due any special property of the anomeric center 12. …”

supporting

confidence: 77%

Mono-Triflation of Carbohydrate Diols and Triols

Knapp¹,

Naughton²,

Kukkola³

et al. 1991

Journal of Carbohydrate Chemistry

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supporting

confidence: 77%

Mono-Triflation of Carbohydrate Diols and Triols

Knapp¹,

Naughton²,

Kukkola³

et al. 1991

Journal of Carbohydrate Chemistry

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“…Three derivatives of methyl α‐L‐fucose, methyl 2‐ O ‐methyl‐α‐L‐fucopyranoside ( 5 ), methyl 3‐ O ‐methyl‐α‐L‐fucopyranoside ( 12 ), and methyl 4‐ O ‐methyl‐α‐L‐fucopyranoside ( 13 ) were synthesized each harboring two free hydroxyl groups.…”

Section: Resultsmentioning

confidence: 99%

“…Standard benzylation of compound 3 using benzyl bromide and sodium hydride in DMF afforded methyl 2‐ O ‐benzyl‐3,4‐ O ‐isopropylidene‐α‐L‐fucopyranoside ( 6 ) in 82 % yield after chromatography. Methyl 2‐ O ‐benzyl‐α‐L‐fucopyranoside ( 7 ) was obtained in 97 % yield after chromatography by treatment of 6 with 70 % acetic acid . Monobenzylation of compound 7 under phase‐transfer catalysis using the quaternary ammounium salt tetrabutylammonium hydrogensulfate (TBAHS), benzyl bromide, sodium hydroxide and dichloromethane gave methyl 2,4‐di‐ O ‐benzyl‐α‐L‐fucopyranoside ( 8 ) and methyl 2,3‐di‐ O ‐benzyl‐α‐L‐fucopyranoside ( 9 ) in a 45:55 ratio (89 % overall yield after chromatography).…”

Section: Resultsmentioning

confidence: 99%

“…Methyl 2‐ O ‐benzyl‐α‐L‐fucopyranoside ( 7 ) was obtained in 97 % yield after chromatography by treatment of 6 with 70 % acetic acid . Monobenzylation of compound 7 under phase‐transfer catalysis using the quaternary ammounium salt tetrabutylammonium hydrogensulfate (TBAHS), benzyl bromide, sodium hydroxide and dichloromethane gave methyl 2,4‐di‐ O ‐benzyl‐α‐L‐fucopyranoside ( 8 ) and methyl 2,3‐di‐ O ‐benzyl‐α‐L‐fucopyranoside ( 9 ) in a 45:55 ratio (89 % overall yield after chromatography). Compounds 8 and 9 were treated with methyl iodide and sodium hydride in DMF to introduce a methyl group at the 3‐ or 4‐position, respectively, resulting in formation of methyl 2,4‐di‐ O ‐benzyl‐3‐ O ‐methyl‐α‐L‐fucopyranoside ( 10 ) and methyl 2,3‐di‐ O ‐benzyl‐4‐ O ‐methyl‐α‐L‐fucopyranoside ( 11 ) in 91 % overall yield after chromatography.…”

Section: Resultsmentioning

confidence: 99%

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Chemical Synthesis of L‐Fucose Derivatives for Acceptor Specificity Characterisation of Plant Cell Wall Glycosyltransferases

et al. 2017

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Seven derivatives of L‐fucose: methyl α‐L‐fucopyranoside, methyl 2‐O‐methyl‐α‐L‐fucopyranoside, methyl 3‐O‐methyl‐α‐L‐fucopyranoside, methyl 4‐O‐methyl‐α‐L‐fucopyranoside, α‐L‐fucopyranosyl‐(1→4)‐α/β‐L‐rhamnopyranose, methyl α‐L‐fucopyranosyl‐(1→4)‐α‐L‐rhamnopyranoside and methyl α‐L‐fucopyranosyl‐(1→4)‐β‐L‐rhamnopyranoside, were chemically synthesized and characterized. The derivatives of L‐fucose were designed to mimic the L‐fucose moieties present in the A‐chain of pectic rhamnogalacturonan‐II and used to investigate the regiospecificity of three heterologously expressed xylosyltransferases from Arabidopsis thaliana. The monosaccharide methyl α‐L‐fucopyranoside was the most efficient acceptor, 30 fold more effective than methyl 4‐O‐methyl‐α‐L‐fucopyranoside. O‐methylation in position 2 or 3 abolished acceptor function. The efficiencies of the disaccharides as acceptors were methyl α‐L‐fucopyranosyl‐(1→4)‐β‐L‐rhamnopyranoside > α‐L‐fucopyranosyl‐(1→4)‐α/β‐L‐rhamnopyranose > methyl α‐L‐fucopyranosyl‐(1→4)‐α‐L‐rhamnopyranoside. These findings demonstrate the utility of acceptor derivatives as probes of glycosyltransferase regiospecificity.

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“…As described in our earlier report,4b,13 DEF trisaccharide glycal 6 was obtained from the coupling of disaccharide glycal 4 and fucosyl donor 5 18 using Mukaiyama15-Nicolaou16 conditions, i.e. SnCl 2 /AgClO 4 (Table 1, entry 1).…”

mentioning

confidence: 99%

A Practical Total Synthesis of Globo-H for Use in Anticancer Vaccines

2009

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An improved synthesis of the hexasaccharide MBr1 antigen (globo-H) is reported. Enhanced efficiency in the synthesis was necessary for the scale up production of globo-H, in order to advance globo-H based anticancer vaccines to clinical trials. The key features of the improved synthesis include preactivation-based glycosylations and a revised iodosulfonimidation/ rearrangement.The glycosphingolipid globo-H (1, Figure 1), first isolated by Hakomori and colleagues from the breast cancer cell line MCF-7, 1 is recognized by the monoclonal antibody MBr1. 2 This human breast cancer-associated antigen was found to be distinctively overexpressed on the surfaces of a variety of other epithelial cancer cells such as prostate, ovary, lung, colon, and small cell lung cancers. 3 For this reason, the globo-H antigen has played an important role in our ongoing carbohydrate-based cancer vaccine program. 4 Of particular interest to our laboratory was a recent report, indicating that globo-H and SSEA3 -the pentasaccharide precursor of globo-H -are also overexpressed in breast cancer stem cells. Interestingly, when co-administered with an immunological adjuvant (α-galactosylceramide), a globo-H based vaccine induces antibodies against both globo-H and SSEA3. 5 In the light of the fact that cancer stem cells are often responsible for relapse and metastasis of cancerous tissues,6 it is envisioned that globo-H based therapy might form the basis of an important new direction in cancer treatment. Indeed, the globo-H vaccine, 2, synthesized in our laboratories as a glycoconjugate appended to immunogenic carrier protein, has shown promise as a potential breast and prostate cancer vaccine, in preclinical, and even clinical settings.4a-e More recently, we also disclosed the synthesis and preclinical evaluation of the unimolecular pentavalent vaccine 34f-g, displaying globo-H and other antigens known to be overexpressed on prostate and breast cancer cell surfaces. The thought was to construct a single entity antigen system which reflects the actual degree of carbohydrate heterogeneity associated with most cancers. 7 Nonetheless, the accessibility of such complex carbohydrate antigens remained as an important question. Globo-H isolated from human cancer tissue collections is typically limited to sub-milligram levels, which impedes broader * s-danishefsky@ski.mskcc.org .Supporting Information Available: NMR spectra for 6, 7, 8, 9, and 10. This material is available free of charge via the Internet at http://pubs.acs.org. Figure 2). Although this concise and stereoselective strategy allows rapid access to globo-H, some steps, particularly those leading to DEF donor 7, still require further optimization if we are to secure the globo-H antigen in amounts required for our ongoing clinical trials with globo-H, both in monovalent and multivalent settings. NIH Public AccessIn this regard, we report herein our efforts to seek a much improved synthesis of the DEF donor 7 and ABC accepter 8. As described in our earlier report, 4b,13 DEF trisac...

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Studies on the koenigs-knorr reaction

Cited by 61 publications

References 15 publications

Mono-Triflation of Carbohydrate Diols and Triols

Mono-Triflation of Carbohydrate Diols and Triols

Chemical Synthesis of L‐Fucose Derivatives for Acceptor Specificity Characterisation of Plant Cell Wall Glycosyltransferases

A Practical Total Synthesis of Globo-H for Use in Anticancer Vaccines

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