Site-Selective Molecular Transformation: Acylation of Hydroxy Groups and C–H Amination

It is widely recognized that primary hydroxy groups show much higher reactivity than the secondary ones, especially in trialkylsilylation. Actually, DMAP‐catalyzed silylation of unprotected pyranosides gave the 6‐O‐silylate exclusively by silylation of the primary C(6)−OH. On the other hand, catalyst ent‐C1 overcame the general tendency of silylation, and enabled the selective silylation of the secondary C(3)−OH of two β‐glucopyranosides and a β‐galactopyranoside. Although the yields of the silylation are poor at this stage, this is the first example of selective silylation of the secondary hydroxy group in the presence of the free primary C(6)−OH of pyranosides under the catalyst‐controlled conditions.

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Approach Toward Reversal of Chemoselectivity in Catalytic Silylation of Pyranosides

Hisashi

Ueda

Fujimura

et al. 2022

Eur J Org Chem

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Sequential Site-Selective Functionalization: A Strategy for Total Synthesis of Natural Glycosides

Ueda,

Kawabata

2024

Modern Natural Product Synthesis

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Total synthesis of several ellagitannins, strictinin (1), pterocarinin C (2), cercidinin A (3), and tellimagrandin II (19), is described. The key issues for the synthetic strategy rely on the catalyst-controlled site-selective acylation and stereoselective glycosylation with unprotected glucose. Total synthesis of punicafolin (5) with a glucose core in 1C4 (chair) conformation and macaranganin (30) with a glucose core in 5S1 (skew boat) conformation was also accomplished based on a similar unconventional retrosynthetic route. For success in the synthesis of 5 and 30, the flipping behavior of the pyranose ring from the stable 4C1 conformer to the unstable axial-rich 1C4 conformer is the key. Because no protective groups for glucose were employed throughout the synthesis of these natural glycosides, the total synthesis was achieved in extremely short overall steps.

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Spot the difference in reactivity: a comprehensive review of site-selective multicomponent conjugation exploiting multi-azide compounds

Tanimoto,

Tomohiro

2024

Chem. Commun.

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Site-Selective Molecular Transformation: Acylation of Hydroxy Groups and C–H Amination

Cited by 3 publications

References 147 publications

Approach Toward Reversal of Chemoselectivity in Catalytic Silylation of Pyranosides

Approach Toward Reversal of Chemoselectivity in Catalytic Silylation of Pyranosides

Sequential Site-Selective Functionalization: A Strategy for Total Synthesis of Natural Glycosides

Spot the difference in reactivity: a comprehensive review of site-selective multicomponent conjugation exploiting multi-azide compounds

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