- Establishment of Guidelines for the Control of Glycosylation Reactions and Intermediates by Quantitative Assessment of Reactivity
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Stereocontrolled chemical glycosylation remains a major challenge despite vast efforts reported over many decades and so far still mainly relies on trial and error. Now it is shown that the relative reactivity value (RRV) of thioglycosides is an indicator for revealing stereoselectivities according to four types of acceptors. Mechanistic studies show that the reaction is dominated by two distinct intermediates: glycosyl triflates and glycosyl halides from N-halosuccinimide (NXS)/TfOH. The formation of glycosyl halide is highly correlated with the production of α-glycoside. These findings enable glycosylation reactions to be foreseen by using RRVs as an α/β-selectivity indicator and guidelines and rules to be developed for stereocontrolled glycosylation.
- Chang, Chun-Wei,Wu, Chia-Hui,Lin, Mei-Huei,Liao, Pin-Hsuan,Chang, Chun-Chi,Chuang, Hsiao-Han,Lin, Su-Ching,Lam, Sarah,Verma, Ved Prakash,Hsu, Chao-Ping,Wang, Cheng-Chung
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p. 16775 - 16779
(2019/11/03)
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- Stereoselective O-glycosylation reactions using glycosyl donors with diphenylphosphinate and propane-1,3-diyl phosphate leaving groups
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Glycosyl donors having a diphenylphosphinate and a propane-1,3-diyl phosphate leaving group were easily prepared by the addition of the anomeric hydroxyl group of 2,3,4,6-tetra-O-benzyl-α,β-D-glucopyranose to diphenylphosphinic and propane-1,3- diyldioxyphosphoryl chlorides. These glycosyl donors were selectively glycosylated with a number of primary and secondary oxygen nucleophiles in the presence of trimethylsilyl triflate (TMSOTf). The use of 1,3-diyl phosphate resulted in the stereoselective formation of β-O-linked glycosides.
- Vankayalapati, Hariprasad,Singh, Gurdial,Tranoy, Isabelle
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p. 1373 - 1381
(2007/10/03)
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- Stereoselective O-glycosylation reactions employing diphenylphosphinate and propane-1,3-diyl phosphate as anomeric leaving groups
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Glycosidation of tetra-O-benzyl-D-glucose using diphenylphosphinate as the leaving group afforded β-O-linked glycosides as the major products, whilst the use of propane-1,3-diyl phosphate as the leaving group resulted in the exclusive formation of β-O-lin
- Hariprasad, Vankayalapati,Singh, Gurdial,Tranoy, Isabelle
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p. 2129 - 2130
(2007/10/03)
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- An extremely mild and general method for the stereocontrolled construction of 1,2-cis-glycosidic linkages via S-glycopyranosyl phosphorodiamidimidothioates
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A highly stereocontrolled construction of 1,2-cis-glycosidic linkages under extremely mild reaction conditions has been developed by using S-glycopyranosyl N,N,N′,N′-tetramethyl-N-phenylphosphorodiamidimidothioates with a non-participating O-2-benzyl grou
- Hashimoto, Shun-Ichi,Honda, Takeshi,Ikegami, Shiro
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p. 4769 - 4772
(2007/10/02)
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- GLYCOSYLATION USING GLUCOPYRANOSYL FLUORIDES AND SILICON-BASED CATALYSTS. SOLVENT DEPENDECY OF THE STEREOSELECTION
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The title glycosylation method is economical and operationally simple.The steric course is highly influenced by the nature of the reaction media.
- Hashimoto, S.,Hayashi, M.,Noyori, R.
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p. 1379 - 1382
(2007/10/02)
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- Un nouvel agent de glycosylation: l'anhydride trifluoromethanesulfonique. Synthese des α et β O-glycosyl-L-serine, -L-threonine et -L-hydroxyproline
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When 2,3,4,6-tetra-O-benzyl-D-glucopyranose, -D-galactopyranose and 2,3,4-tri-O-benzyl-D-xylopyranose were allowed to react in the cold in dichloromethane or acetonitrile as solvent in the presence of trifluoromethanesulfonic (triflic) anhydride, with methyl or benzyl esters of the N-(benzyloxycarbonyl)-L-serine, -L-threonine, and -L-hydroxyproline, an anomeric mixture of the corresponding O-glycosylaminoacids was obtained (55 to 90percent overall yield), with the α-anomer being predominant.The same experimental procedure was successfully applied to the condensation of the benzyl ester of the N-(benzyloxycarbonyl)-L-hydroxyproline with 2,3,4-tri-O-benzyl-L-arabinopyranose and 2,3,5-tri-O-benzyl-L-arabinofuranose affording the corresponding condensation products with similar yield.Pure α and β anomers were obtained after column chromatography or crystallization with 30 to 65percent yield.Hydrogenolysis of benzyl derivatives afforded the unprotected compounds.Optical rotation, (1)H and (13)C nmr were the main methods used to assess structure and stereochemistry.
- Lacombe, J. M.,Pavia A. A.,Rocheville, J. M.
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p. 473 - 481
(2007/10/02)
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- NOUVELLE METHODE DE SYNTHESE STEREOSELECTIVE DE GLYCOSIDES. SYNTHESE DES α,α-TREHALOSE, ANALOGUES galacto, manno ET AUTRES α-D-GLYCOSIDES
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In the presence of trifluoromethanesulfonic (triflic) anhydride as catalyst and dichloromethane as solvent, in the cold, 2,3,4,6-tetra-O-benzyl-D-glucopyranose, 2,3,4,6-tetra-O-benzyl-D-galactopyranose, and 2,3,4,6-tetra-O-benzyl-D-mannopyranose were converted in almost quantitative yield to a 2:1 mixture of the corresponding α,α-(1->1) and α,β-(1->1) disaccharides.Hence, pure 2,3,4,6,2',3',4',6'-octa-O-benzyl derivatives of α,α-trehalose, and the D-galacto and D-manno analogues were obtained, after column chromatography, in 55-65 percent yield.Hydrogenolysis gave the corresponding free sugars.The pure anomers were obtained in 10-34 percent yield.The potentiality of the method was demonstrated by the synthesis of 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl 2,3:4,5-di-O-isopropylidene-β-D-fructopyranoside in 50 percent yield, and of N-(benzyloxycarbonyl)-3-O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-L-threonine methyl ester in 65 percent yield.
- Pavia, Andre A.,Rocheville, Jean-Michel,Ung, Sak N.
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