132351-62-3Relevant articles and documents
Site-selective synthesis of acacetin and genkwanin through lipase-catalyzed deacetylation of apigenin 5,7-diacetate and subsequent methylation
Fujita, Rie,Hanaya, Kengo,Higashibayashi, Shuhei,Mandal, Susanta,Shoji, Mitsuru,Sugai, Takeshi
, p. 638 - 648 (2019/07/31)
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.
3,5,7,3',5'-PENTAHYDROXYFLAVAN AND 3α-METHOXYFRIEDELAN FROM HUMBOLDTIA LAURIFOLIA
Samaraweera, Upasiri,Sotheeswaran, Subramaniam,Sultanbawa, M. Uvais S.
, p. 565 - 568 (2007/10/02)
The leaf, bark and timber extractives of Humboldtia laurifolia were investigated and the following compounds have been isolated: O-acetyloleanolic aldehyde, a sitosteryl ester, lupeol, sitosterol, a fatty acid, 5,7,4'-trihydroxyflavone (apigenin), (2R,3R)-3,5,7,3',5'-pentahydroxyflavan and 3α-methoxyfriedelan.The latter two compounds are new natural products.Key Word - Humboldtia laurifolia; Leguminosae; O-acetyloleanolic aldehyde; lupeol; 5,7,4'-trihydroxyflavone; (2R,3R)-3,5,7,3',5'-pentahydroxyflavan; 3α-methoxyfriedelan.