- Triflic Imide-Catalyzed Glycosylation of Disarmed Glycosyl ortho-Isopropenylphenylacetates and ortho-Isopropenylbenzyl Thioglycosides
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Glycosylation reaction involving the coupling of a glycosyl donor with a glycosyl acceptor is one of the cornerstones of chemical preparation of pure glycans and glycoconjugates of biological relevance. Catalytic glycosylation of glycosyl ester donors and thioglycosides is an attractive but underexplored topic in carbohydrate chemistry. Herein, triflic imide (Tf2NH)-catalyzed glycosylation of various O-, S-, and C-nucleophiles has been achieved using disarmed glycosyl ortho-isopropenylphenylacetates (GIPPAs) and ortho-isopropenylbenzyl thioglycosides as glycosylating agents. The reactions proceed under mild conditions to give the desired glycosides in good-to-excellent yields. Of particular note, the comparable reactivity for the α-isomers and the β-ones of GIPPAs is observed. The mechanistic investigation demonstrates that the isopropenyl group is essential for the reaction and its preferential protonation triggers the reaction. This work provides another member to the arsenals of glycosyl ester and thioglycoside donors suitable for acid-catalyzed glycosylation to create various glycosidic bonds.
- Li, Dongwei,Li, Ming,Li, Tiantian,Ni, Jingxuan,Qiao, Zhi,Sun, Yao,Wang, Peng
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- NIS/TMSOTf-Promoted Glycosidation of Glycosyl ortho-Hexynylbenzoates for Versatile Synthesis of O-Glycosides and Nucleosides
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Glycosidation plays a pivotal role in the synthesis of O-glycosides and nucleosides that mediate a diverse range of biological processes. However, efficient glycosidation approach for the synthesis of both O-glycosides and nucleosides remains challenging in terms of glycosidation yields, mild reaction conditions, readily available glycosyl donors, and cheap promoters. Here, we report a versatile N-iodosuccinimide/trimethylsilyl triflate (NIS/TMSOTf)-promoted glycosidation approach with glycosyl ortho-hexynylbenzoates as donors for the highly efficient synthesis of O-glycosides and nucleosides. The glycosidation approach highlights the merits of mild reaction conditions, cheap promoters, extremely wide substrate scope, and good to excellent yields. Notably, the glycosidation approach performs very well in the construction of a series of challenging O- and N-glycosidic linkages. The glycosidation approach is then applied to the efficient synthesis of oligosaccharides via the one-pot strategy and the stepwise strategy. On the basis of the isolation and characterization of the departure species derived from the leaving group, a plausible mechanism of NIS/TMSOTf-promoted glycosidation of glycosyl ortho-hexynylbenzoates is proposed.
- Liu, Rongkun,Hua, Qingting,Lou, Qixin,Wang, Jiazhe,Li, Xiaona,Ma, Zhi,Yang, You
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p. 4763 - 4778
(2021/04/06)
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- Isoquinoline-1-Carboxylate as a Traceless Leaving Group for Chelation-Assisted Glycosylation under Mild and Neutral Reaction Conditions
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Glycosyl isoquinoline-1-carboxylate was developed as a novel benchtop stable and readily available glycosyl donor. The glycosylation reaction was promoted by the inexpensive Cu(OTf)2 salt under mild reaction conditions. The copper isoquinoline-1-carboxylate salt was precipitated from the solution and thus rendered a traceless leaving group. Surprisingly, the proton from the acceptor was absorbed by the precipitated metal complex and the reaction mixture remained at neutral pH. The copper-promoted glycosylation was also proven to be completely orthogonal to the gold-promoted glycosylation, and an iterative synthesis of oligosaccharides from benchtop stable anomeric ester building blocks becomes possible under mild reaction conditions.
- Wang, Hao-Yuan,Simmons, Christopher J.,Blaszczyk, Stephanie A.,Balzer, Paul G.,Luo, Renshi,Duan, Xiyan,Tang, Weiping
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p. 15698 - 15702
(2017/11/13)
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- Photoinduced C-S Bond Cleavage of Thioglycosides and Glycosylation
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A glycosyl coupling reaction via photoinduced direct activation of thioglycosides and subsequent O-glycosylation in the absence of photosensitizer was developed for the first time. This reaction underwent a selectively homolytic cleavage of a C-S bond to generate a glycosyl radical, which was oxidized to an oxacarbenium ion by Cu(OTf)2, and a sequential O-glycosylation. A wide range of glycosides were synthesized in moderate to excellent yield using sugars, amino acids, or cholesterol as the acceptors.
- Mao, Run-Ze,Guo, Fan,Xiong, De-Cai,Li, Qin,Duan, Jinyou,Ye, Xin-Shan
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supporting information
p. 5606 - 5609
(2015/12/01)
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- Facile synthesis of unusual glycosyl carbamates and amino acid glycosides from propargyl 1,2-orthoesters as glycosyl donors
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Propargyl 1,2-O-orthoesters are exploited for the synthesis of 1,2-trans O-glycosides of protected amino acids. N-Fmoc- and N-Cbz protected serine/threonine - benzyl/methyl esters reacted well with glucosyl-, galactosyl-, mannosyl- and lactosyl- derived propargyl 1,2-orthoesters affording respective 1,2-trans glycosides in good yields under AuBr3/4 A MS Powder/CH2Cl2/rt. t-Boc serine derivative gave serine 1,2-orthoester and glycosyl carbamate. Optimized conditions enabled preparation of new glycosyl carbamates from N-Boc protected amines in a single step using gold catalysts and propargyl 1,2-orthoesters in excellent yields.
- Shaikh, Ashif Y.,Sureshkumar, Gopalsamy,Pati, Debasish,Gupta, Sayam Sen,Hotha, Srinivas
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supporting information; experimental part
p. 5951 - 5959
(2011/10/09)
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