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Synthetic Studies of the Flavone Derivatives. VI. The Synthesis of Skullcapflavone I, II and Related Flavones

1979; Pharmaceutical Society of Japan; Volume: 99; Issue: 6 Linguagem: Inglês

10.1248/yakushi1947.99.6_657

1347-5231

Munekazu Iinuma, Shin Matsuura,

Natural product bioactivities and synthesis

5, 2'-Dihydroxy-6, 8-dimethoxyflavone (I), 5, 2'-dihydroxy-7, 8-dimethoxyflavone (II), 5, 2'-dihydroxy-6, 7-dimethoxyflavone (III), and 5, 2'-dihydroxy-6, 7, 8, 6'-tetramethoxyflavone (IV) were prepared in order to confirm the proposed structures for skullcapflavone I and II isolated from the roots of Scutellaria baicalensis GEORGI. The structure of IV was identified with that of skullcapflavone II, but the spectral properties of skullcapflavone I were different from those of I or III, being coincident with those of II. Therefore the structure of skullcapflavone I should be corrected to II. The generalization of cyclization of 2'-benzyloxy-dibenzoylmethanes, which are the precursors of 2'-hydroxyflavones, in the presence of conc. H2SO4, was also considered.