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A variety of polyphenols have been isolated from plants, and their biological activities have been examined. Sudachitin (5,7,4′-trihydroxy-6,8,3′-trimethoxyflavone) is a polymethoxyflavone that is isolated from the peel of Citrus sudachi. Although we previously reported that sudachitin possesses an anti-inflammatory activity, its other biological activities are not yet understood. In this study, we report a novel biological activity of sudachitin, which selectively induced apoptosis in human keratinocyte HaCaT cells. Another polymethoxyflavone, nobiletin (5,6,7,8,3′,4′-hexamethoxyflavone), promoted autophagy but not apoptosis in HaCaT cells. On the other hand, 3′-demethoxysudachitin (5,7,4′-trihydroxy-6,8-dimethoxyflavone) failed to induce apoptosis and autophagy. These results show that three polymethoxyflavones have different effects on apoptosis and autophagy in HaCaT cells. Understanding the structure and biological activity of polymethoxyflavones may lead to the discovery of potential candidates for cancer drug development without significant toxic side effects. Abbreviations: ROS: reactive oxygen species; DMSO: dimethyl sulfoxide; MTT: 3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; PARP: poly(ADP-ribose) polymerase; PI: propidium iodide; MAPK: mitogen-activated protein kinase.

マイクロ波照射によるメタノール中ユコウ搾汁乾燥果皮から生理活性機能性物質タンゲレチンとノビレチンが迅速・効率よく分離され，ヘスペリジン以外にこれら2種の化合物の存在が始めて明らかにされた．マイクロ波の2.5～5分間の照射によるユコウ乾燥果皮中のポリメトキシフラボンの抽出は，通常加熱抽出法に比べて極めて短い時間で効率よく分離され優れていることが分かった．これらの結果からマイクロ波抽出法は，柑橘類搾汁残渣（果皮）からの有用成分の効率的抽出法として応用できる可能性があり，再利用に有効であることを示唆している．

The charge-transfer reaction of tetraarylbutatriene 1 with tetracyanoethene (TCNE) in dichloromethane at room temperature was studied and we found a novel addition reaction. A red crystalline material 2 was isolated as an intermediate product which is converted slowly into dihydronaphthalene derivative 3 in dichloromethane but rapidly in protic solvent. The structure of the compounds was determined by X-ray crystallography. The detailed structure and the plausible reaction mechanism have also been discussed.

The oxidative rearrangement of 3′‐iodotetraalkoxychalcone with [hydroxyl(tosyloxy)iodo]benzene, followed by cyclization of the resultant acetal gave 6‐iodotrialkoxyisoflavone. The coupling reaction of the isoflavone with 2‐methyl‐3‐butyn‐2‐ol gave 6‐alkynylisoflavone, whose hydrogenation gave wighteone hydrate. Wighteone was synthesized by dehydration of wighteone hydrate.

Under an oxygen atmosphere, the E and Z isomer ratio of N-methoxy-4-methoxyphenyl-4'-methylphenylmethanimine (one of the title compounds; initially, ⌈E⌉/⌈Z⌉ = 1/1) reached to 4/96 upon irradiation (> 360 nm) of 9, 10-dicyanoanthracene (DCA) as a photosensitizer in acetonitrile. Key intermediate is presumed to be a putative distonic radical cation which is a unique one having a spatially separate radical and ionic centers on the molecular framework. The whole scenario of the reaction was supported by molecular orbital calculations. An excited singlet state of DCA generated by light absorption was quenched by oxime ethers to give the DCA anion radical and radical cations of E- and Z-oxime ethers. Then the subsequent single electron transfer from the DCA anion radical to molecular oxygen generates superoxide anion radical, which reacted with distonic radical cations of E- and Z-oxime ethers bya ⌈supra + antara⌉ manner. Geometry selection occurs at a stage of just making a new bond between nitrogen and oxygen terminals in the ensuing peroxyaminy1-1,4-diradical. The final oxime ether is afforded by releasing molecular oxygen without successful single bond formation. Instead, ring closure to azadioxetane gives rise to formation of byproducts, benzophenones and methyl nitrite, by decomposion of it in a metathesis fashion.

Fulleropyrrolidines have been very welcomed in a community of a fullerene science. But sometimes the synthesis ends up with disappointing yields of the products. In order to overcome the problem and to explore more environmentally benign method for synthesizing fullerene derivatives having various attachment on the surface of the fullerenes, a solid-phase synthesis is examined. We found that the dipolar cycloaddition of an azomethine ylide, i.e., 2-phenyl-N-benzylideneglycine methyl ester, supported on a Wang resin, proceeded feasibly with C 60 and the objective fulleropyrrolidines were afforded in good yields (>75%). The method is expected to be utilized with wide range of application and it is therefore able to provide a compound library of modified fullerenes which is hard to obtain by other methods employed so far.

One-way geometrical isomerization around a C=C bond of 1,1-diary1-2-t-butylethene is achieved upon photoirradiation of cyanoaromatics as a light-absorbing sensitizer. In the thermochemical view, there is no difference between both E and Z isomers of the ethene. Key intermediate is a putative distonic radical cation which is a unique one having a spatially separate radical and ionic centers on the molecular framework. Generation of such an intermediate is due to the presence of a π-donating substituent on an aromatic ring and a bulky t-butyl group. Molecular oxygen interacts as superoxide with the C=C bond of the radical cation in a [supra + antara] manner to give a decomposition product, i.e. a benzophenone derivative and pivalaldehyde, via a dioxetane and competitively, one geometrical isomer of the ethene is afforded by splitting oxygen before making two bonds with the ethene radical cation and superoxide.

Isoflavones are synthesized in one-pot manner by action of a hypervalent iodine (III) reagent, ⌊hydroxy(tosyloxy)iodo⌋benzene (HTIB, Koser's reagent) on 2'-benzoyloxychalcones in MeOH. A combined usage of iodobenzene diacetate (IBD)—p-toluenesulfonic acid (TsOH) is also effective for the same purpose. As an extension of those monomeric reagents, polymer-supported IBD (PSIBD, poly ⌊4-(diacetoxy)iodo⌋styrene) with TsOH works also well with merit of easy separation of isoflavones from the reaction mixture, no liberation of PhI, and reuse of the reagent.

Isoflavones are synthesized in an one-pot reaction by treating the hypervalent iodine(III) reagent, [hydroxy(tosyloxy)iodo]benzene (HTIB, Koser's reagent) with 2'-benzoyloxychalcones in McOH. A combined use of (diacetoxyiodo)benzene (DIB)/p-toluenesulfonic acid (TsOH) is also effective for the same purpose. As an extension of these monomeric reagents, polymer-supported DIB {PSDIB, poly[4-(diacetoxy)iodo]styrene} with TsOH works also well. The merits of the latter are the ease of separation of isoflavones from the reaction mixture, no liberation of Phi, and reuse of the reagent.

4′,5,7-Trihydroxy- or 8-alkyl-4′,5,7-trihydroxycoumaronochromones were synthesized by oxidative cyclization of the corresponding 2′-hydroxyisoflavones with o -chloranil under mild conditions. By contrast, alkoxycoumaronochromones were synthesized by oxidative cyclization of the corresponding 2′-hydroxyisoflavones with DDQ.

Under an oxygen atmosphere, the E and Z isomer ratio of N -methoxy-4-methoxyphenyl-4′-methylphenylmethanimine (initially, [ E ]/[ Z ]=1/1) reached 4/96 upon irradiation (>360 nm) of 9,10-dicyanoanthracene (DCA) as a photosensitizer in acetonitrile.

Photosensitized oxygenation of extremely stable P-ylides, dimethyl fluorenylidenetributyl-and triphenylphosphoranylidenesuccinate, afforded dimethyl fluorenylideneoxalacetate in good yield, when 9-fluorenone was employed as a photosensitizer.

The palladium-catalyzed coupling reaction of 2′,4′,5,7-tetrakis(benzyloxy)-5′-iodoisoflavone (12), synthesized from the 5-iodochalcone 9, with 2-methyl-3-butyn-2-ol gave the corresponding 5′-(3-hydroxy-3-methyl-1-butynyl)isoflavone 13. The catalytic hydrogenation of 13 gave 2′,4′,5,7-tetrahydroxy-5′-(3-hydroxy-3-methylbutyl)isoflavone (2). Dehydration of the benzoate 14 of 2 afforded a mixture of 5′-(3-methyl-2-butenyl)isoflavone 15 and the isomer 5′-(3-methyl-3-butenyl)isoflavone 16. The separation of 15 was accomplished by a treatment of the mixture (15 and 16) with mercury(II) nitrate. Hydrolysis of 15 afforded 2′,4′,5,7-tetrahydroxy-5′-prenylisoflavone (allolicoisoflavone A) (1). In a similar manner, 2′,4′,5,7-tetrahydroxy-8-prenylisoflavone (2,3-dehydrokievitone) (3) and 2′,4′,5,7-tetrahydroxy-8-(3-hydroxy-3-methylbutyl)isoflavone (2,3-dehydrokievitone hydrate) (4) were synthesized from the corresponding 8-iodoisoflavone 22. The tetramethyl ether 5 of 3 was also prepared from the 8-iodotetramethoxyis...

The 13 C NMR spectra of polyhydroxyflavones were systematically examined by using about 70 examples which have a 4-methoxyphenyl B-ring, such as 5,6,7-, 5,7,8 and 5,6,8-trioxygenated and 5,6,7,8-tetraoxygenated flavones and flavonols, and the following results were obtained. In the 13 C NMR spectra of flavones, the signals at the 2-, 3- and 4-positions in the C-ring were hardly affected by the substituents on the A-ring except for those at the 5-position and shifted regularly by introduction of a methoxy or hydroxy group at the 3-position. The signals at the 5- to 10-positions in the A-ring were greatly affected by the substituents and oxygenated patterns on the A-ring and exhibited the respective characteristic pattern reflecting the A-ring substituents without the effects of the substituents on the B- and C-rings. The substituent effects on the A-ring were estimated from the spectral data. Consequently, it is found that the structures of polyhydroxyflavones can be correctly defined by their 13 C NMR spectral assignment. Additionally, we examined the structures of some natural flavones previously reported.

2', 4'-Bis(benzyloxy)-3', 6'-dimethoxychalcones (5), which were obtained from the dibenzyl ether of 2, 4-dihydroxy-3, 6-dimethoxyacetophenone (3), were oxidatively rearranged with thallium (III) nitrate in methanol and the resultant products were converted into 7-hydroxy-5, 8-dimethoxyisoflavones (8) by hydrogenolysis, followed by cyclization. The isoflavones were quantitatively demethylated to 5, 7-dihydroxy-8-methoxyisoflavones (2) via their acetates. The isomeric 5, 7-dihydroxy-6-methoxyisoflavones (1) were also synthesized from the chalcones, obtained from 2, 3-dimethoxy- (16) or 2-isopropoxy-3-methoxy-4, 6-bis(benzyloxy)acetophenones (21), by a similar method. On the other hand, the isoflavones with two hydroxy groups at the 2'- and 4'-positions were easily synthesized by the following method. Treatment of the rearranged product from 2, 2', 4, 4'-tetrakis(bezyloxy)-3', 6'-dimethoxychalcone (5f) with hydrochloric acid (HCl) in acetic acid afforded 2', 4', 7-tris(benzyloxy)-5, 8-dimethoxyisoflavone (10f). The 5-methoxy group in the isoflavone was quantitatively cleaved to give the corresponding 5-hydroxyisoflavone (11f), which was isomerized to 2', 4', 7-tris(benzyloxy)-5-hydroxy-6-methoxyisoflavone (25f) in the presence of anhydrous potassium carbonate. Hydrogenolysis of the two 5-hydroxyisoflavones proceeded smoothly to give 2', 4', 5, 7-tetrahydroxy-8-(2f) and 6-methoxyisoflavones(1f), respectively. The 13C-NMR spectra of these isoflavones supported the proposed structures of polyhydroxyisoflavones. The proposed structures of two natural isoflavones were revised.

Methylenetriphenylphosphoranes having two phenyl groups tied together with ethano or etheno bridge were prepared by conventional ways in order to suppress delocalization of an ylide-carbanion by deforming geometrical arrangement of phenyl groups from that of the diarylmethylene derivative and hence to elevate reactivities of diarylmethylenephosphoranes. These P-ylides were, however, still unreactive with usual aldehydes and ketones. The reasons are deliberated by molecular orbital calculations and the 31P-NMR data. The HOMO orbitals of ethano-bridged and etheno-bridged diarylmethylenephosphoranes are located on a monoarylcarbanion and a carbanion, respectively. Although these tendencies are auspicious to enhance the Wittig reactivity of them, the electron densities of the ylidic carbons are still insufficient, 31P-NMR chemical shifts of the ylides revealed that the objective P-ylides do not have a large extent of the ylide-contribution in the ylide-yllene resonance. Meanwhile, they reacted readil...

Upon irradiation (>340 nm) of a benzene solution of diazofluorene with di- p -tolyl- or di- p -anisyl disulfide, the corresponding 9,9′-bis(arylmercapto)bifluorenyl was afforded in moderate to good yield accompanied by formation of 9,9′-bis(arylmercapto)fluorene. The major reaction pathway is considered to be a disulfur ylide formation followed by two times of successive Stevens rearrangement or by concerted electron redistribution via [2,3]sigmatropic rearrangement.

An air and moisture stable P-ylide, dimethyl fluorenylidenetributylphosphoranylidene-succinate acts as a new type of dehydrating agent for synthesizing acid anhydride, ester, and amide. The ylide is most suitable for inducing these reactions in analogous P-ylides. The reaction is considered to be caused by internal reductive and oxidative nature of the P-ylide.

In the demethylation of 6-hydroxy-3, 4', 7-trimethoxy-5-tosyloxyflavone (1) with anhydrous aluminum bromide (AlBr3) or anhydrous aluminum chloride-sodium iodide (AlCl3-NaI) in acetonitrile, the elimination of the 5-tosyloxy group proceeded after demethylation to give 8-bromo-3, 6, 7-trihydroxy-4'-methoxyflavone (6) or 3, 6, 7-trihydroxy-4'-methoxyflavone (5) as a main product. The demethylation of 6-hydroxy-4', 7-dimethoxy-5-tosyloxyflavone (2) with AlCl3-NaI also afforded 6, 7-dihydroxy-4'-methoxyflavone (12), but that with AlBr3 afforded 8-bromo-5, 6, 7-trihydroxy-4'-methoxyflavone (13) as a main product. The demethylation of 1 with anhydrous aluminum chloride (AlCl3) was accompanied by migration of the tosyl group to give a mixture of 3, 6-dihydroxy-7, 4'-dimethoxy-5-tosyloxyflavone (3) and 5-hydroxy-3, 4', 7-trimethoxy-6-tosyloxyflavone (9), but that of 2 proceeded after the cleavage of the 5-tosyloxy group to give a mixture of 5, 6-dihydroxy-7, 4'-dimethoxy- (14) and 5, 6, 7-trihydroxy-4'-methoxyflavones (15) other than the corresponding 6-tosyloxyflavone (16). In the demethylation of the acetates of 1 and 2 with AlCl3, the cleavage of the 5-tosyloxy group proceeded prior to the demethylation to afford the corresponding 5, 6, 7-trihydroxyflavones (8 and 15), although the demethylation of the former acetate was accompanied by formation of 3, 5, 7-trihydroxy-4'-methoxy-6-tosyloxyflavone (10). Mechanisms are proposed for these reactions.

The demethylation of 3, 4-dioxygenated 6-methoxy-2-isopropoxyacetophenones was studied and it was found that 4-benzyloxy-6-hydroxy-3-methoxy-2-isopropoxyacetophenone was easily obtained from 4-benzyloxy-3, 6-dimethoxy-2-isopropoxyacetophenone by selective demethylation with anhydrous aluminum bromide-sodium iodide in acetonitrile. The acetophenone was converted into 7-benzyloxy-3-hydroxy-6-methoxy-5-isopropoxyflavones by cyclization followed by oxidation with dimethyldioxirane. The isopropoxy group in the flavones was selectively cleaved with anhydrous aluminum chloride via the corresponding tosylates to give 7-benzyloxy-3, 5-dihydroxy-6-methoxyflavones, which were converted into the desired 3, 5, 7-trihydroxy-6-methoxyflavones by hydrogenolysis. The process was suitable as a general method for synthesizing 3, 5, 7-trihydroxy-6-methoxyflavones and five flavones were synthesized. We also examined the 13C-NMR spectra of twelve kinds of 3, 5, 6, 7-tetraoxygenated 4'-methoxyflavones and revised the proposed structure of a natural flavone.

Although some polymethoxyflavones possess several important biological properties, including neuroprotective, anticancer, and anti-inflammatory ones, sudachitin, a polymethoxyflavone from Citrus sudachi, has been little studied. In this study, we found that sudachitin inhibited nitric oxide production by suppressing the expression of inducible nitric oxide synthase in lipopolysaccharide-stimulated macrophages, indicating that sudachitin has an anti-inflammatory effect.

The palladium-catalyzed coupling reaction of 2′,4′,5,7-tetrakis(benzyloxy)-8-iodoisoflavone with 2-methyl-3-butyn-2-ol gave the corresponding 8-(3-hydroxy-3-methylbutynyl)isoflavone 8. Dehydration of the benzoate obtained from 8 in two steps gave a mixture of 8-prenylisoflavone 10 and its regioisomer [8-(3-methyl-3-butenyl)isoflavone]. Treatment of the mixture with aq. Hg(NO3)2 allowed the isolation of 10, which was hydrolyzed to give 2,3-dehydrokievitone. Similarly, 2,3-dehydrokievitone tetramethyl ether was also synthesized from 8-iodo-2′,4′,5,7-tetramethoxyisoflavone.

The palladium-catalyzed coupling reaction of 4′,6′-bis(benzyloxy)-3′-iodo-2′-tosyloxyacetophenone with 2-methyl-3-butyn-2-ol gave 4′,6′-bis(benzyloxy)-3′-(3-hydroxy-3-methylbutynyl)-2′-tosyloxyacetophenone (7). Dehydration of the benzoate obtained via two steps from 7 gave the 3′-prenylacetophenone, which was converted into 4′,6′-dihydroxy-3′-prenyl-2′-tosyloxyacetophenone (12). Respective geranylation and prenylation of 12, followed by hydrolysis gave 4′-geranyloxy- and 4′-prenyloxy-2′,6′-dihydroxy-3′-prenylacetophenone (1 and 2). The structures of natural prenylacetophenones proposed as 2′-alkenyloxy isomers were revised as 1 and 2, respectively.

The palladium-catalyzed coupling reaction of 4′,6′-bis(benzyloxy)-3′-iodo-2′-methoxyacetophenone with 2-methyl-3-butyn-2-ol gave 4′,6′-bis(benzyloxy)-3′-(3-hydroxy-3-methylbutynyl)-2′-methoxyacetophenone (5). Demethylation and bromination of the benzoate obtained from 5 with BBr3 gave 4′,6′-bis(benzoyloxy)-3′-(3-bromo-3-methylbutyl)-2′-hydroxyacetophenone (8). O-Prenylation of 8 with prenyl bromide, followed by hydrolysis of the resultant compound gave 4′,6′-dihydroxy-2′-prenyloxy-3′-prenylacetophenone. In a similar manner, 4′,6′-dihydroxy-2′-geranyloxy-3′-prenylacetophenone also was prepared from 8 and geranyl bromide.

The palladium-catalyzed coupling reaction of 2′,4′,5,7-tetrakis(benzyloxy)-8-iodoisoflavone with 2-methyl-3-butyn-2-ol gave the corresponding 8-(3-hydroxy-3-methylbutynyl)isoflavone 8. Dehydration of the benzoate obtained from 8 in two steps gave a mixture of 8-prenylisoflavone 10 and its regioisomer [8-(3-methyl-3-butenyl)isoflavone]. Treatment of the mixture with aq. Hg(NO3)2 allowed the isolation of 10, which was hydrolyzed to give 2,3-dehydrokievitone. Similarly, 2,3-dehydrokievitone tetramethyl ether was also synthesized from 8-iodo-2′,4′,5,7-tetramethoxyisoflavone.

The palladium-catalyzed coupling reaction of 4′,6′-bis(benzyloxy)-3′-iodo-2′-tosyloxyacetophenone with 2-methyl-3-butyn-2-ol gave 4′,6′-bis(benzyloxy)-3′-(3-hydroxy-3-methylbutynyl)-2′-tosyloxyacetophenone (7). Dehydration of the benzoate obtained via two steps from 7 gave the 3′-prenylacetophenone, which was converted into 4′,6′-dihydroxy-3′-prenyl-2′-tosyloxyacetophenone (12). Respective geranylation and prenylation of 12, followed by hydrolysis gave 4′-geranyloxy- and 4′-prenyloxy-2′,6′-dihydroxy-3′-prenylacetophenone (1 and 2). The structures of natural prenylacetophenones proposed as 2′-alkenyloxy isomers were revised as 1 and 2, respectively.

Electrolytic reduction of 2-(1-bromo-1-methylethyl)benzofurans in acetonitrile affords the corresponding 2,2-dimethylchromenes in good yields even in the absence of a proton donor and comprises the cleavage of a carbon–bromine bond followed by ring expansion.

Catalytic hydrogenation and the subsequent dehydration of 8-(3-hydroxy-3-methylbutynyl)isoflavone 12, which was synthesized by the palladium-catalyzed coupling reaction of 4′,5,7-tris(benzyloxy)-8-iodoisoflavone 11 with 2-methyl-3-butyn-2-ol, gave a mixture of 8-prenylisoflavone 16 and the isomer [5-acetoxy-8-(3-methyl-3-butenyl)isoflavone] 17, and after the separation of 16 was accomplished by treatment of the mixture with Hg(NO3)2, hydrolysis of 16 afforded 4′,5,7-trihydroxy-8-prenylisoflavone (lupiwighteone) 1.

4′,5,7-Trihydroxy- or 8-alkyl-4′,5,7-trihydroxycoumaronochromones were synthesized by oxidative cyclization of the corresponding 2′-hydroxyisoflavones with o -chloranil under mild conditions. By contrast, alkoxycoumaronochromones were synthesized by oxidative cyclization of the corresponding 2′-hydroxyisoflavones with DDQ.

Several diarylmethylenephosphoranes themselves, act as triplet sensitizers to give singlet oxygenation products, i.e., benzophenones and triphenylphosphine oxide, efficiently upon photoirradiation.

Thermolysis of 3,3-diphenyl-2-t-butyloxaziridine gave benzophenone oxime and isobutylene via the C–O bond fission followed by the intramolecular synchronous hydrogen migration from the t-butyl group without the intervention of the corresponding nitrone.

Microwave-assisted oxidative rearrangement of 3′-iodotetraalkoxychalcones with hypervalent iodine such as [hydroxy(tosyloxy)iodo]benzene or [bis(trifluoroacetoxy)iodo]benzene, followed by microwave-mediated hydrolysis and in situ cyclization of the resultant acetals gave 6-iodotrialkoxyisoflavones. Pd(0)-catalyzed coupling reaction of the 6-iodoisoflavones with 2-methyl-3-butyn-2-ol under microwave irradiation gave 6-alkynylisoflavones, whose hydrogenation gave the respective hydrates of wighteone, lupisoflavone and derrubone. Wighteone ( 1a ), lupisoflavone ( 1b ) and derrubone ( 1c ) were obtained by dehydration of their respective hydrates under microwave irradiation.

The palladium-catalyzed coupling reaction of 6-iodoisoflavone, prepared from 3'-iodoacetophenone derivative, with 2-methyl-3-butyn-2-ol gave 6-alkynylisoflavone derivative, which was hydrogenated to give 6-alkylhydroxyisoflavone (luteone hydrate) (2). Dehydration of 2 gave 2',4',5,7-tetrahydroxy-6-prenylisoflavone (luteone) (1). Wighteone hydrate (3) was also synthesized from 6-iodotris(benzyloxy)isoflavone in a similar manner. 6-Alkyl-4'5,7-trihydroxy-coumaronochromone (4) was synthesized by oxidative cyclization of 2 with o-chloranil.

The palladium-catalyzed coupling reaction of 6-iodoisoflavone, prepared from 3′-iodoacetophenone derivative, with 2-methyl-3-butyn-2-ol gave the 6-alkynylisoflavone derivative, which was hydrogenated to give the 6-alkylhydroxyisoflavone (luteone hydrate) 2. Dehydration of 2 gave 2′,4′,5,7-tetrahydroxy-6-prenylisoflavone (luteone).

Under an oxygen atmosphere, the E and Z isomer ratio of N -methoxy-4-methoxyphenyl-4′-methylphenylmethanimine (initially, [ E ]/[ Z ]=1/1) reached 4/96 upon irradiation (>360 nm) of 9,10-dicyanoanthracene (DCA) as a photosensitizer in acetonitrile.

The palladium-catalyzed coupling reaction of 6-iodoisoflavone, prepared from 3′-iodoacetophenone derivative, with 2-methyl-3-butyn-2-ol gave the 6-alkynylisoflavone derivative, which was hydrogenated to give the 6-alkylhydroxyisoflavone (luteone hydrate) 2. Dehydration of 2 gave 2′,4′,5,7-tetrahydroxy-6-prenylisoflavone (luteone).

Microwave-assisted Friedel-Crafts acetylation of polymethoxybenzenes with acetic anhydride in the presence of In(CF 3 SO 3 ) 3 under solvent-free conditions was achieved rapidly to give polymethoxyacetophenones in high yields. Microwave-assisted benzoylation of 2'-hydroxypolymethoxyacetophenones with polymethoxybenzoyl chlorides, followed by the rearrangement of the resulting benzoates and the final formation of natural polymethoxyflavones was achieved rapidly and efficiently. The polymethoxyflavones showed inhibitory effects on melanogenesis in human melanoma cells.

Catalytic hydrogenation and the subsequent dehydration of 8-(3-hydroxy-3-methylbutynyl)isoflavone 12, which was synthesized by the palladium-catalyzed coupling reaction of 4′,5,7-tris(benzyloxy)-8-iodoisoflavone 11 with 2-methyl-3-butyn-2-ol, gave a mixture of 8-prenylisoflavone 16 and the isomer [5-acetoxy-8-(3-methyl-3-butenyl)isoflavone] 17, and after the separation of 16 was accomplished by treatment of the mixture with Hg(NO3)2, hydrolysis of 16 afforded 4′,5,7-trihydroxy-8-prenylisoflavone (lupiwighteone) 1.

The microwave-assisted methylation of 2,5-dihydroxy-1,3-dimethoxybenzene with (CH 3 O) 2 SO 2 for 5 min gave easily 1,2,3,5-tetramethoxybenzene, which was converted into pentamethoxybenzene. The microwave-assisted Friedel-Crafts acylation of pentamethoxybenzene in the presence of In(CF 3 SO 3 ) 3 gave pentamethoxyacetophenone for 15 min under solvent-free conditions in high yield. The microwave-assisted cyclization reaction of the diketones, which were synthesized from the acetophenone via three steps under microwave irradiation, gave the desired polymethoxyflavones for 1.5-3 min in high yields. The polymethoxyflavones showed inhibitory effects on melanogenesis in a human melanoma.