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The structures of four new flavone derivatives, kuwanon A, B, C and oxydihydromorusin, which were isolated from the root bark of the cultivated mulberry tree (a variety of Morus alba L.), were shown to be I, II, III and IV, respectively.

Kanzakiflavone-1 and-2, isolates from Iris unguicularis, and their position isomers were synthesized to confirm the structures of the isolates. The differences among these flavones are discussed on the basis of spectral data.

In addition to mulberrofuran D, a new 2-arylbenzofuran derivative, six flavone derivatives, morusin, oxydihydromorusin, cyclomorusin, kuwanon C, G and H, were isolated from extracts of root bark of MORUS AUSTRALIS P OIR. The structure of mulberrofuran D was shown to be 5 on the basis of spectral and chemical data. Mulberrofuran D is the first example of a geranylated and prenylated 2-arylbenzofuran derivative found in nature.

The13C NMR of a number of 3- and 5-hydroxyflavones and of 3- and 5-methoxyflavones have been studied for the first time and all the signals have been assigned. A comparison of the chemical shifts of the13C nuclei with the acidity and basicity parameters of the compounds investigated and with the results of calculations of π-charge density has been made. It has been shown that the chemical shifts of the individual signals in the13C NMR spectra are qualitatively connected with estimates of the reactivities of the compounds studied.

Three flavone derivatives, TT-a (1), TT-b (2) and TT-c (3), were isolated from Thalictrum thunbergii DC. Compound 1 was characterized as apigenin 7, 4'-bis-O-β-D-allopyranoside, and 2 and 3 were found to be acetyl derivatives of TT-a (1).

A new 2-arylbenzofuran derivative, mulberrofuran H and two isoprenylated flavones, kuwanons S and T, were isolated from the ethyl acetate extract of the root bark of cultivated mulberry tree (Japanese name "Roso, "a cultivated variety of Morus lhou KOIDZ.). The structures of mulberrofuran H and kuwanons S and T were shown to be 1, 2, and 3, respectively, on the basis of spectral evidence. Mulberrofuran H can be regarded biogenetically as a variation of a Diels-Alder type adduct of a chalcone derivative and a dehydroprenyl-2-arylbenzofuran derivative.

Die Synthese und die β-sympatholytischen Eigenschaften einiger Flavon-Derivate mit einer am Ring B befindlichen propranololartigen, basischen Seitenkette wird beschrieben. β-Adrenergic Blocking Agents of the Flavone Group The preparation and the β-adrenergic blocking activity of some flavone derivatives bearing the basic chain of the propranolol type on the ring B are described.

The structures of four new flavone derivatives, kuwanon A, B, C and oxydihydromorusin were isolated from the benzene extract of the root bark of the cultivated mulberry tree (a variety of Morus alba L.), and were shown to be I, II, III and IV, respectively, on the basis of spectroscopic and chemical evidences. Photooxidative cyclization did not occur with I but with II leading to the formation of a hydroperoxide possessing a dihydrooxepin ring. III was cyclized on photooxidation as II and was converted to morusin (V) by treating with DDQ. On hydration with methanolic hydrochloric acid, V was converted to IV.

An essential attribute of good chromatographic methods is the achievement of optimal resolution of the components of interest in a reasonable time. The resolution of pairs of incompletely separated peaks in each sample is evaluated by the Purnell equation (R.E. Kaiser and E. Oelrich, Optimization in HLPC, Huthig, Heidelberg, 1981). The resolution of nitroaromatics and flavone derivatives has been optimized by three different methods and the results compared. An empirical function, obtained in a factorial design, relates resolution to several factors, such as eluent composition and system temperature. A general time constraint of 16 min is introduced.

The correlation between the structure and fluorescence intensity of flavone derivatives and their beryllium chelates was investigated. The ligands of type I, II in Chart 1 and their beryllium chelates did not produce fluorescence, while the ligands of type III, IV fluoresced by themselves and formed fluorescent chelates with beryllium ion. The ligands of type V which were non-fluorescent ligands formed fluorescent beryllium chelates.

Die Bestimmung der Redoxpotentiale mittels diskontinuierlicher Titration ergab, das Flavon mit freier 3-Hydroxylgruppe ein wesentlich niedrigeres Redoxpotential besitzen als Verbindungen, bei denen dies OH-Gruppe verathert oder glykosidisch gebunden ist oder fehlt; bei der letztgenannten Substanzgruppe liegt das Potential positiver als des des Brenzcatechins. Der Einflus von Hydroxyl- und Methoxylgruppen in 5- und 7-Stellung auf das Redoxpotential ist nur gering. Die bei der Oxydation gebildeten Chinone sind instabil und polymerisieren, so das die Potentiale der Reaktionslosungen nicht konstant sind. Die Potentialanderung in der Zeiteinheit ist bei den Flavonolen deutlich kleiner als bei den Flavonderivaten ohne freie 3-OH-Gruppe. The redox potentials of flavones with a free hydroxyl group at the 3-position have been determined by discontinuous titration to be significantly lower than those of flavones with an etherized, glycosidic linked or missing 3-hydroxyl group. Flavones and the flavonol derivatives without a free OH-group at the 3-position showed more positive potentials than catechol. Hydroxyl and methoxy groups at the 5-and 7-position have only a small influence on the redox potentials. Since the quinones formed by oxidation are unstable and polymerize easily, the potentials of the reaction solutions are not constant. The rate of change in potential is much smaller in the case of flavonols than of flavone derivatives without a free 3-hydroxyl group.

By using the method of Allan-Robinson’s flavone synthesis, the condensation of 3,ω-dimethoxy-2,1,6-trihydroxyacetophenone with 3,4-dibenzyloxybenzoic anhydride gave a mixture of 3,6- and 3,8-dimethoxy-3′,4′-dibenzyloxy-5,7-dihydroxyflavone (X and XI). The catalytic debenzylation of the above flavones then gave axillarin (I) and 3,8-dimethoxy-5,7,3′,4′-tetra-hydroxyflavone (IV) respectively. Axillarin 7-O-methyl ether(III) was prepared by the partial methylation of X, followed by catalytic debenzylation.

The partial benzylation of 3-methoxy-2,4,6-trihydroxyacetophenone gave a mixture of 2,4-dibenzyloxy-6-hydroxy- and 4,6-dibenzyloxy-2-hydroxy-3-methoxyacetophenone. The latter was esterified with 4-benzyloxy-3-methoxybenzoyl chloride, and the resulting ester was converted into 8,3′-dimethoxy-5,7,4′-tribenzyloxyflavone via the corresponding diketone. The catalytic debenzylation of the flavone gave 8,3′-dimethoxy-5,7,4′-trihydroxyflavone. Its diethyl ether was also prepared from 3,6-dimethoxy-4-ethoxy-2-hydroxyacetophenone by an unambiguous method.

For the purpose of preparing 7-flavonylmethyl carbamate derivatives, syntheses of a series of 7-substituted flavones were attempted by use of 7-hydroxyflavone as a starting material.The following 7-substituted flavones have been prepared, namely, 7-haloflavones, 7-cyanoflavone, flavone-7-carboxylic acid and related derivatives, 7-hydroxymethyl-flavone, and 7-flavonylmethyl carbamate derivatives.In the case of the synthesis of 7-hydroxymethylflavone, the reduction of the ester group in flavone derivatives was studied and it was found that ethyl-7-flavonoxyacetate was converted into 7- (hydroxyethoxy) -flavone in good yield at low temperature with lithiumaluminum hydride.Some β (7-flavonoxy) ethyl carbamate derivatives have also been prepared.

The Hoesch reaction of iretol with methoxyacetonitrile yielded 2,4,6-trihydroxy-3,ω-dimethoxyacetophenone. According to the Allan-Robinson flavone synthesis with O-benzylvanillic anhydride, the acetophenone afforded 4′-benzyloxy-5,7-dihydroxy-3,3′,6-trimethoxyflavone. The catalytic debenzylation of the flavone gave jaceidin, 4′,5,7-trihydroxy-3,3′,6-trimethoxyflavone, which had previously been isolated from Centaurea species. Its triethyl ether was prepared from 3,5-diethoxy-4-methoxyphenol via the corresponding acetophenone, followed by the abovementioned flavone synthesis with O-ethylvanillic anhydride. The ultraviolet spectra of these flavones will also be reported.

The acid-catalyzed isomerization of 4-benzyloxy-2′-hydroxy-3,4′,5′,6′-tetramethoxychalcone gave 4′-benzyloxy-3′,5,6,7-tetramethoxyflavanone, which was then converted by oxidation to 4′-benzyloxy-3-hydroxy-3′,5,6,7-tetramethoxyflavone. This, after debenzylation to 3,4′-dihydroxy-3′,5,6,7-tetramethoxyflavone, was partially demethylated with aluminum chloride or aniline hydrochloride to give 3,4′,5-trihydroxy-3′,6,7-trimethoxyflavone (I) (mp 213–214°C), the structure proposed previously for the chrysosplenetin (mp 177–178°C) isolated from Chrysosplenium japonicum Makino. However, the synthetic flavone was found to be different from natural chrysosplenetin by a mixed melting point determination and by a comparison of the spectra. Finally, the structures of chrysosplenetin and chrysosplenin were established by the spectroscopic studies to be 4′,5-dihydroxy-3,3′,6,7-tetramethoxyflavone (XIII) and its 4′-glucoside (XIV) respectively. The revised structure for chrysosplenetin has been fully confirmed by direct co...

2,4-Dibenzyloxy-6-hydroxy-3-methoxyacetophenone was esterified with 3,4-disubstituted benzoyl chlorides, and the resulting esters were converted into 7-benzyloxy-5-hydroxy-6-methoxyflavone derivatives via the corresponding diketones. The catalytic hydrogenolysis of the benzyloxyflavones gave the desired 5,7-dihydroxy-6-methoxyflavones. Ethyl ethers of these flavones were also prepared from 2,4-diethoxy-3-methoxy-6-hydroxyacetophenone by an unambiguous method. 6,3′-Dimethoxy-5,7,4′-trihydroxyflavone, desmethoxycentaureidin (6,4′-dimethoxy-5,7,3′-trihydroxyflavone), and 6-methoxyluteolin (6-methoxy-5,7,3′,4′-tetrahydroxyflavone) were thus prepared.

From the roots of BROSIMOPSIS OBLONGIFOLIA three new flavone derivatives, named brosimone G ( 3), H ( 4), and I ( 5) together with the known albanin A ( 1) and E ( 2), were isolated. Antimicrobial activity of the compounds is also reported.

5, 3', 4'-Trihydroxy-6, 7-dimethoxyflavone and 5, 4'-dihydroxy-6, 7, 3'-trimethoxyflavone were synthesized and identified with cirsiliol and cirsilineol obtained from Cirsium lineare SCH. BIP.

A new natural flavone (5-hydroxy-7,8,3′,4′-tetramethoxyflavone, I) has been isolated from bergamott oil. A flavone previously isolated from Ammi visnaga has been identified as rhamnazin. Evidence for a weak spin coupling between ring and OMe protons in flavone derivatives is given.