A Novel Glycosidation Promoted by the Combination of Trimethylsilyl Halide and Zinc Triflate.

Higashi, Kunio; Susaki, Hiroshi

doi:10.1248/cpb.40.2019

Cited by 21 publications

(6 citation statements)

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“…We noticed that copper(II) triflate without base was capable of promoting the glycosylation of α‐acetate 1α to give a mixture of α/β‐glycosides, albeit at a low conversion rate (data not shown). Zinc(II) triflate was also tested as a stoichiometric promoter in the glycosylation of n ‐butanol under microwave irradiation. Under the conditions tested, both anomers gave similar results in DCE (81–83 % yield, α/β ratio 2.5–2.3:1; Table , Entries 1 and 2).…”

Section: Resultsmentioning

confidence: 99%

From Chitin to α‐Glycosides of N‐Acetylglucosamine Using Catalytic Copper Triflate in a Heated Sealed‐Vessel Reactor

et al. 2017

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Section: Resultsmentioning

confidence: 99%

From Chitin to α‐Glycosides of N‐Acetylglucosamine Using Catalytic Copper Triflate in a Heated Sealed‐Vessel Reactor

et al. 2017

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“…This protecting group was reported to give rise to a significant increase in donor reactivity in coupling reactions, compared with its N ‐acetyl or N ‐phthaloyl counterparts, while effecting good β selectivity as well 30, 31. The donor was prepared from galactosamine hydrochloride (Scheme ), which was treated32 with trichloroethoxycarbonyl chloride (TrocCl) and NaHCO 3 in water, followed by acetylation with acetic anhydride and pyridine to yield the N ‐Troc compound 10 . Then, for activation of C‐1, a thiophenyl group was introduced33 after reaction with thiophenol and ethereal borontrifluoride in dichloromethane to furnish donor molecule 11 .…”

Section: Resultsmentioning

confidence: 99%

Adhesion Inhibition of F1C‐Fimbriated Escherichia coli and Pseudomonas aeruginosa PAK and PAO by Multivalent Carbohydrate Ligands

et al. 2003

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In order to evaluate their inhibition of bacterial adhesion, the carbohydrate sequences GalNAcbeta1-->4Gal and GalNAcbeta1-->4Galbeta1-->4Glc were synthesized. The disaccharide was conjugated to dendrons based on the 3,5-di-(2-aminoethoxy)-benzoic acid branching unit to yield di- and tetravalent versions of these compounds. A divalent compound was also prepared that had significantly longer spacer arms. Relevant monovalent compounds were prepared for comparison. Their anti-adhesion properties against F1C-fimbriated uropathogenic Escherichia coli were evaluated in an ELISA-type assay by using a recombinant strain and also by using Pseudomonas aeruginosa strains PAO and PAK. Adhesion inhibition was observed in all cases, and multivalency effects of up to one order of magnitude were observed. The combination of spacer and multivalency effects led to a 38-fold increase in the potency of a divalent inhibitor with long spacer arms towards the PAO strain when compared with the free carbohydrate.

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“…We have applied EPR and optical absorption spectroscopy to investigate how complexation with AG, CD and GA can affect the aggregation ability of the xanthophyll carotenoids zeaxanthin, lutein, and astaxanthin, their photostability, and antioxidant activity. Cyclodextrins are the cyclic oligosaccharides derived from starch and are the most developed delivery systems [51]. CDs have a hydrophilic shell and hydrophobic core suitable for the inclusion of lipophilic "guest" molecules of appropriate size.…”

Section: Inclusion Complexes Of Carotenoids With Watersoluble Oligosamentioning

confidence: 99%

Carotenoids: Importance in Daily Life—Insight Gained from EPR and ENDOR

2021

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Carotenoids are indispensable molecules for life. They are present everywhere in plants, algae, bacteria whom they protect against free radicals and oxidative stress. Through the consumption of fruits and vegetables and some carotenoid-containing fish, they are introduced into the human body and, similarly, protect it. There are numerous health benefits associated with the consumption of carotenoids. Carotenoids are antioxidants but at the same time they are prone to oxidation themselves. Electron loss from the carotenoid forms a radical cation. Furthermore, proton loss from a radical cation forms a neutral radical. In this mini-review, we discuss carotenoid radicals studied in our groups by various physicochemical methods, namely the radical cations formed by electron transfer and neutral radicals formed by proton loss from the radical cations. They contain many similar hyperfine couplings due to interactions between the electron spin and numerous protons in the carotenoid. Different EPR and ENDOR methods in combination with DFT calculations have been used to distinguish the two independent carotenoid radical species. DFT predicted larger coupling constants for the neutral radical compared to the radical cation. Previously, INDO calculations miss assigned the large couplings to the radical cation. EPR and ENDOR have aided in elucidating the physisorb, electron and proton transfer processes that occur when carotenoids are adsorbed on solid artificial matrices, and predicted similar reactions in aqueous solution or in plants. After years of study of the physicochemical properties of carotenoid radicals, the different published results start to merge together for a better understanding of carotenoid radical species and their implication in biological systems. Up until 2008, the radical chemistry in artificial systems was elucidated but the correlation between quenching ability and neutral radical formation was an inspiration to look for these radical species in vivo. In addition, the EPR spin-trapping technique has been applied to study inclusion complexes of carotenoids with different delivery systems.

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A Novel Glycosidation Promoted by the Combination of Trimethylsilyl Halide and Zinc Triflate.

Cited by 21 publications

References 0 publications

From Chitin to α‐Glycosides of N‐Acetylglucosamine Using Catalytic Copper Triflate in a Heated Sealed‐Vessel Reactor

From Chitin to α‐Glycosides of N‐Acetylglucosamine Using Catalytic Copper Triflate in a Heated Sealed‐Vessel Reactor

Adhesion Inhibition of F1C‐Fimbriated Escherichia coli and Pseudomonas aeruginosa PAK and PAO by Multivalent Carbohydrate Ligands

Carotenoids: Importance in Daily Life—Insight Gained from EPR and ENDOR

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