Site-selective synthesis of acacetin and genkwanin through lipase-catalyzed deacetylation of apigenin 5,7-diacetate and subsequent methylation

Rie Fujita, Susanta Mandal, Kengo Hanaya, Mitsuru Shoji, Shuhei Higashibayashi, Takeshi Sugai

研究成果: Article

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Candida antarctica lipase B-catalyzed deacetylation proceeded with high site-selectivity on the C-4′ acetyl group in apigenin triacetate to give apigenin 5,7-diacetate. Methylation of the liberated hydroxy group with the combination of trimethyloxonium tetrafluoroborate (Meerwein reagent) and 1,8-bis(dimethylamino)naphthalene (proton sponge) in CH2Cl2 proceeded in a quantitative manner to give the product methylated at the C-4′ hydroxy group (acacetin 5,7-diacetate). Even with the same precursor, a different methylation product at the C-7 hydroxy group (genkwanin 4′,5-diacetate) was obtained in 86% yield by applying iodomethane and Cs2CO3 in dimethyl sulfoxide (DMSO). The methylated products were deprotected to form acacetin and genkwanin. We inferred that the latter unexpected methylation was ascribable to the intermolecular migration of an acetyl group from C-7 to C-4′. DFT calculations indicated that the C-7 phenoxide ion was 12.6 kJ/mol more stable than the initially formed C-4′ phenoxide ion.

元の言語English
ページ(範囲)638-648
ページ数11
ジャーナルHeterocycles
99
発行部数1
DOI
出版物ステータスPublished - 2019 1 1

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ASJC Scopus subject areas

  • Analytical Chemistry
  • Pharmacology
  • Organic Chemistry

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