- Boronic-Acid-Catalyzed Regioselective and 1,2- cis -Stereoselective Glycosylation of Unprotected Sugar Acceptors via SNi-Type Mechanism
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Regio- and 1,2-cis-stereoselective chemical glycosylation of unprotected glycosyl acceptors has been in great demand for the efficient synthesis of natural glycosides. However, simultaneously regulating these selectivities has been a longstanding problem in synthetic organic chemistry. In nature, glycosyl transferases catalyze regioselective 1,2-cis-glycosylations via the SNi mechanism, yet no useful chemical glycosylations based on this mechanism have been developed. In this paper, we report a highly regio- and 1,2-cis-stereoselective SNi-type glycosylation of 1,2-anhydro donors and unprotected sugar acceptors using p-nitrophenylboronic acid (10e) as a catalyst in the presence of water under mild conditions. Highly controlled regio- and 1,2-cis-stereoselectivities were achieved via the combination of boron-mediated carbohydrate recognition and the SNi-type mechanism. Mechanistic studies using the KIEs and DFT calculations were consistent with a highly dissociative concerted SNi mechanism. This glycosylation method was applied successfully to the direct glycosylation of unprotected natural glycosides and the efficient synthesis of a complex oligosaccharide with minimal protecting groups.
- Tanaka, Masamichi,Nakagawa, Akira,Nishi, Nobuya,Iijima, Kiyoko,Sawa, Ryuichi,Takahashi, Daisuke,Toshima, Kazunobu
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- Regioselective and 1,2-cis-α-Stereoselective Glycosylation Utilizing Glycosyl-Acceptor-Derived Boronic Ester Catalyst
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Regioselective and 1,2-cis-α-stereoselective glycosylations using 1α,2α-anhydro glycosyl donors and diol glycosyl acceptors in the presence of a glycosyl-acceptor-derived boronic ester catalyst. The reactions proceed smoothly to give the corresponding 1,2-cis-α-glycosides with high stereo- and regioselectivities in high yields without any further additives under mild reaction conditions. In addition, the present glycosylation method was successfully applied to the synthesis of an isoflavone glycoside.
- Nakagawa, Akira,Tanaka, Masamichi,Hanamura, Shun,Takahashi, Daisuke,Toshima, Kazunobu
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supporting information
p. 10935 - 10939
(2015/09/15)
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- Synthesis of β-maltooligosaccharides of glycitein and daidzein and their anti-oxidant and anti-allergic activities
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The production of β-maltooligosaccharides of glycitein and daidzein using Lactobacillus delbrueckii and cyclodextrin glucanotransferase (CGTase) as biocatalysts was investigated. The cells of L. delbrueckii glucosylated glycitein and daidzein to give their corresponding 4′- and 7-O-β-glucosides. The β-glucosides of glycitein and daidzein were converted into the corresponding β-maltooligosides by CGTase. The 7-O-β- glucosides of glycitein and daidzein and 7-O-β-maltoside of glycitein showed inhibitory effects on IgE antibody production. On the other hand, β-glucosides of glycitein and daidzein exerted 2,2-diphenyl-1- picrylhydrazyl (DPPH) free-radical scavenging activity and supeoxide-radical scavenging activity.
- Shimoda, Kei,Hamada, Hiroki
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experimental part
p. 5153 - 5161
(2011/02/21)
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- Glycosylation of daidzein by the Eucalyptus cell cultures
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The sequential glycosylation of a soybean isoflavone, daidzein, with cultured suspension cells of Eucalyptus perriniana and cyclodextrin glucanotransferase was studied. Daidzein was converted into two glycosylation products, daidzein 7-O-β-d-glucopyranoside (39%) and daidzein 7-O-[6-O-(β-d-glucopyranosyl)]-β-d-glucopyranoside (β-gentiobioside, 6%), by cultured E. perriniana cells. Further glycosylation of daidzein 7-O-β-glucoside with cyclodextrin glucanotransferase gave daidzein 7-O-[4-O-(α-d-glucopyranosyl)]-β-d-glucopyranoside (β-maltoside, 26%), daidzein 7-O-β-maltotrioside (15%), and daidzein 7-O-β-maltotetraoside (7%).
- Shimoda, Kei,Sato, Noriaki,Kobayashi, Tatsunari,Hamada, Hatsuyuki,Hamada, Hiroki
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p. 2303 - 2306
(2008/12/22)
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