Tunable stereoselectivity during sialylation using an N-acetyl-5-N,4-O-oxazolidinone-protected p-toluene 2-thio-sialoside donor with Tf2O/Ph2SO/TTBPy

Wang, Yajuan; Jia, Jia; Gu, Zhen-yuan; Liang, Fenfen; Li, Ri-chen; Huang, Ming-Hao; Xu, Cai-Shuang; Zhang, Jiaxin; Men, Yi; Xing, Guo‐wen

doi:10.1016/j.carres.2011.04.029

Cited by 33 publications

(7 citation statements)

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“…Besides the aforementioned low reactivity of sialyl donor, another difficulty in sialylation is stereochemical control as the naturally existing sialyl linkage is the thermodynamically less favored α linkage[19]. Recently, it was discovered that the installation of an electron withdrawing protective group including TCA and oxazolidinone on the 5- N position significantly enhanced the reaction yield and stereoselectivity[22, 23]. Thus, we investigated three sialyl donors 16 [24], 17 [24] and 18 [25] with their 5- N -acetyl group substituted with more electron withdrawing protective groups.…”

Section: Resultsmentioning

confidence: 99%

Total synthesis of the aminopropyl functionalized ganglioside GM1

2011

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GM1 is a common ganglioside pentasaccharide present on mammalian cell surface. It has been shown to play important roles in cellular communications and initiation of β-amyloid aggregation. In order to synthesize GM1, an efficient synthetic route was developed via a [3+2] strategy. The GM3 trisaccharide acceptor bearing an azido propyl group at the reducing end was prepared using the traditional acetamide protected sialyl thioglycosyl donor, which gave better stereoselectivity than sialyl donors protected with trichloroacetamide or oxazolidinone. The glycosylation of the axial 4-hydroxyl group of GM3 by the disaccharide donor was found to be highly dependent on donor protective groups. Donor bearing the more rigid benzylidene group gave low glycosylation yield. Replacing the benzylidene with acetates led to productive coupling and formation of the fully protected GM1 pentasaccharide. Deprotection of the pentasaccharide produced GM1 functionalized with the amino propyl side chain, which will be a valuable probe for biological studies.

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Section: Resultsmentioning

confidence: 99%

Total synthesis of the aminopropyl functionalized ganglioside GM1

2011

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“…Ph 2 SO (2-3 equiv)/TTBP (0-1 equiv) promotion gave higher selectivity for a-sialylation in dichloromethane, whereas Ph 2 SO (4-5 equiv)/TTBP (0 equiv) or Ph 2 SO (2.0 equiv)/TTBP (2.0 equiv) afforded lower stereoselectivity. [42] Carbonate Carbonate is another kind of useful ring-fused five-membered protecting group in stereoselective glycosylation. It was previously described as promoting b-selective mannosylation and rhamnosylation reactions conducted with glycosyl bromide donors (44,45) by the insoluble silver salt method.…”

Section: Oxazolidinones and Carbonatementioning

confidence: 99%

Preactivation: An Alternative Strategy in Stereoselective Glycosylation and Oligosaccharide Synthesis

Yang

Qin

2013

Asian J Org Chem

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The multifaceted biological importance of carbohydrates has made them very popular targets in modern synthetic chemistry. Great progress has been made in stereoselective glycosylation methods and the construction of complex oligosaccharides. This Focus Review highlights the versatile applications of preactivation strategies in stereoselective glycosylation and oligosaccharide synthesis. Recent advances in synthetic methods, such as 4,6-O-benzylidene-acetal-directed b-mannosylation, the 1,2-cis-glycosylation mediated by a chiral auxiliary, the use of an oxazolidinone or carbonate protecting group, and glycosylation with participating additives, are described. Various examples of sequential glycosylation based on preactivation protocols for efficient oligosaccharide assembly are also summarized. Scheme 4. Mechanism for the 4,6-O-benzylidene-directed formation of a-and b-gluco-and mannopyranosides. CIP = contact ion pairs; SSIP = solvent-separated ion pairs Scheme 5. Fluorinated, deoxy, and deoxyfluoro glycosyl donors.

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“…In the case of α(2,3) sialylations (Table 1), ptoluenethiosialoside 13 (Liang et al, 2009) with an acetyl group attached to the oxazolidinoneprotected nitrogen afforded comparable yields but markedly better selectivities than the previously reported phenylthiosialoside 14 (Crich and Li, O-Sialylation, 2007). Changing the activation method of 13 from NIS/TfOH to diphenylsulfoxide/ trifluoromethanesulfonic anhydride/2,4,6-tri-tert-butylpyridine (Ph2SO/Tf2O/TTBPy) afforded better selectivity (α/β ratio from 6.1:1 to 9.9:1) in α(2,6) sialylation with a 6-OH glucopyranoside acceptor (Wang et al, 2011).…”

Section: Oxazolidinone Protectionmentioning

confidence: 99%

Mini Review: Oxazolidinone and Other Sialic Acid C5 Modifications Over the Past Decade

Salmasan

2016

KIMIKA

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The potential of sialic acids as therapeutic agents has gradually been recognized due to its importance in the proper functioning of living systems, and likewise the virulence of several pathogens. However, synthesis of these compounds often result in poor yields and selectivities because of inherent characteristics associated with their structures. Use of various promoters, solvent systems and introduction of auxiliaries has since improved the outlook of chemical sialylation. Of these, attachment of various groups on C5 has notably resulted in improved α-selectivity. This mini review focuses on C5 structural modification of sialic acids over the past decade, most notably the oxazolidinone group protection.

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Tunable stereoselectivity during sialylation using an N-acetyl-5-N,4-O-oxazolidinone-protected p-toluene 2-thio-sialoside donor with Tf2O/Ph2SO/TTBPy

Cited by 33 publications

References 50 publications

Total synthesis of the aminopropyl functionalized ganglioside GM1

Total synthesis of the aminopropyl functionalized ganglioside GM1

Preactivation: An Alternative Strategy in Stereoselective Glycosylation and Oligosaccharide Synthesis

Mini Review: Oxazolidinone and Other Sialic Acid C5 Modifications Over the Past Decade

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