Novel Glycosidation Method Using 2,6-Anhydro-2-thio Sugars for Stereocontrolled Synthesis of 2,6-Dideoxy-.alpha.- and -.beta.-glycosides

Toshima, Kazunobu; Mukaiyama, Satsuki; Nozaki, Yuko; Inokuchi, Hatsuki; Nakata, Masaya; Tatsuta, Kuniaki

doi:10.1021/ja00099a022

Cited by 38 publications

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“…With this consideration in mind, we chose an EDB group. The glycosylation reaction using the EDB-bridged glucosyl fluoride 8 afforded the corresponding glucosides with a selectivity even at room temperature [supplementary material sections 2 and 19 to 24 (SM-2, - [19][20][21][22][23][24]]. The reaction proceeded through the corresponding oxocarbenium ion intermediate, as similar a selectivities were observed with 8-a and 8-b (SM-15, -16).…”

mentioning

confidence: 92%

Conformationally supple glucose monomers enable synthesis of the smallest cyclodextrins

Ikuta

Hirata

Wakamori

et al. 2019

Science

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Cyclodextrins (CDs) are cyclic oligomers of α-1,4-d-glucopyranoside and are known mainly as hexamers to octamers. The central cavities of CDs can retain small molecules, enabling diverse applications. The smallest members, CD3 and CD4, have ring sizes too small to permit the most stable conformations of glucopyranose and have not been accessible synthetically. In this study, we present methods to chemically synthesize both CD3 and CD4. The main factor in the successful synthesis is the creation of a glucopyranose ring conformationally counterbalanced between equatorial- and axial-rich forms. This suppleness is imparted by a bridge between O-3 and O-6 of glucose, which enables the generation of desirable, albeit deformed, conformers when synthesizing the cyclic trimer and tetramer.

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mentioning

confidence: 92%

Conformationally supple glucose monomers enable synthesis of the smallest cyclodextrins

Ikuta

Hirata

Wakamori

et al. 2019

Science

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“…For example, the highly stereoselective glycosylation of the thiabicyclic acetal 86 (Scheme 25) [95] can be explained by a Felkin-Anhlike anti-attack onto the bicyclic oxocarbenium ion 89, not ring-opening of a highly strained tricyclic episulfonium ion 90. This analysis appears to be applicable for systems with substituents other than sulfur: Díaz, Castillón, and coworkers explained the reactions of 2-phenylselenenyl glycosyl donors as the result of a conformational bias of an oxocarbenium ion and stereoelectronically controlled addition to it.…”

Section: Comparisons Between Substituted Oxocarbenium Ions and Ketonesmentioning

confidence: 99%

Nucleophilic Substitution Reactions of 2‐Phenylthio‐Substituted Carbohydrate Acetals and Related Systems: Episulfonium Ions vs. Oxocarbenium Ions as Reactive Intermediates

2008

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A powerful approach for controlling the stereochemistry of glycosylation reactions involves using a directing group at an adjacent carbon to influence the stereochemistry of nucleophilic attack. The use of substituents such as I, PhS, and PhSe has proven to be especially valuable because it enables the preparation of 2‐deoxysugars after reductive removal of the directing group. The mechanisms of these reactions are generally considered to involve nucleophilic opening of bridged onium ions and to proceed with inversion. Onium ions, however, equilibrate with open cations, and these open forms can be favored when the cation is highly stabilized. Although the selectivities of reactions of carbohydrate‐derived cations are consistent with the intermediacy of onium ions, the reactions of acyclic cations are not. Instead, consideration of the preferred conformations of the oxocarbenium ions and stereoelectronically favored additions to these intermediates provides a predictive model to explain the diastereoselectivities observed in reactions of oxocarbenium ions bearing proximal heteroatoms.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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“…[80][81][82][83][84][85][86] Both glycosylations of the 2,6-anhydro-2thio sugars possessing a phenylthio group 142 with NBS and 2,6-anhydro-2-thio fluoride 143 with several Lewis acids provided 2,6-anhydro-2-thio-a-glycoside a-145 in high yields with a nearly complete selectivity. [80][81][82][83][84][85][86] Both glycosylations of the 2,6-anhydro-2thio sugars possessing a phenylthio group 142 with NBS and 2,6-anhydro-2-thio fluoride 143 with several Lewis acids provided 2,6-anhydro-2-thio-a-glycoside a-145 in high yields with a nearly complete selectivity.…”

Section: Indirect Synthetic Methodsmentioning

confidence: 99%

Stereoselective Formation of 2‐Deoxyglycosidic Bonds in Biologically Active Natural Products

Takahashi

Toshima

2013

Stereoselective Synthesis of Drugs and Natural Products

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Novel Glycosidation Method Using 2,6-Anhydro-2-thio Sugars for Stereocontrolled Synthesis of 2,6-Dideoxy-.alpha.- and -.beta.-glycosides

Cited by 38 publications

References 0 publications

Conformationally supple glucose monomers enable synthesis of the smallest cyclodextrins

Conformationally supple glucose monomers enable synthesis of the smallest cyclodextrins

Nucleophilic Substitution Reactions of 2‐Phenylthio‐Substituted Carbohydrate Acetals and Related Systems: Episulfonium Ions vs. Oxocarbenium Ions as Reactive Intermediates

Stereoselective Formation of 2‐Deoxyglycosidic Bonds in Biologically Active Natural Products

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