Epimerization, transacylation and bromination of dihydroquercetin acetates; synthesis of 8-bromodihydroquercetin

• Authors: Eberhard Kiehlmann , Monica Szczepina
• Languages of publication: EN

Abstracts

EN

Dihydroquercetin (dhq) and its 3-acetate react with acetic anhydride in the absence of a base catalyst to yield mixtures of partially acetylated products. Three new esters were characterized by NMR spectroscopy as dhq 3,7,3′-triacetate, 3,7,4′-triacetate and 5,7,3′,4′-tetraacetate. At its melting point neat dhq 3,7,3′,4′-tetraacetate is partially converted to dhq 3,3′,4′-triacetate and dhq pentaacetate by intermolecular acetyl transfer. Dhq 7,3′,4′-triacetate yields exclusively dhq 3′,4′-di- and 3,7,3′,4′-tetraacetate under these conditions. The acetylation/deacetylation reactions are accompanied by partial epimerization: 3 new acetates with 2,3-cis stereochemistry (dhq 3-, 3,7,3′,4′-tetra- and penta-) were identified. Dhq and its 3,7,3′,4′-tetraacetate undergo regiospecific dibromination at C-6 and C-8 with excess N-bromosuccinimide in polar solvents, and 6,8-dibromo-dhq can be regioselectively debrominated to 8-bromo-dhq with sodium sulfite.

Keywords

EN

Dihydroflavonol acetylation; Cis-2,3-dihydroflavonols; 6,8-dibromoflavanonols; Taxifolin; Intermolecular acetyl transfer

• Publisher: De Gruyter Open
• Journal: Open Chemistry
• Year: 2011
• Volume: 9
• Issue: 3
• Pages: 492-498

Dates

published

1 - 6 - 2011

online

22 - 3 - 2011

Contributors

author

Eberhard Kiehlmann

• Simon Fraser University

author

Monica Szczepina

• Simon Fraser University

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Identifiers

DOI

10.2478/s11532-011-0032-8