Masao Tsukayama

13C NMR spectral assignment of the A-ring of polyoxygenated flavones

Abstract 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.

DEHYDRATION INDUCED BY INTRAMOLECULAR REDOX CHARACTER OF A STABLE ALLYLIDENETRIBUTYLPHOSPHORANE

Abstract 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.

Three flavone glycosides from citrus sudachi

Abstract Three flavone glycosides, sudachiins B, C and D, were isolated from the green peel of Citrus sudachi . On the basis of UV, 1 H NMR and 13 C NMR spectral data sudachiins B and C were identified as sudachiin A 6″- (3-hydroxy-3-methyl)glutarateand 7- O -β-D-glucosyl sudachitin 6″-(3-hydroxy-3-methyl)glutarate, respectively. Sudachiin D was found to be a unique glycoside in which sudachiin A and 7- O -β-D-glucosylsudachitin were esterified at their 6″-positions with 3-hydroxy-3-methylglutaric acid.

Curious oxygen effect on photosensitized electron-transfer reactions of benzophenone oxime O-methyl ethers: one-way photoisomerization of an iminic double bond

Abstract 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.

Sudachitin, a polymethoxyflavone from Citrus sudachi, suppresses lipopolysaccharide-induced inflammatory responses in mouse macrophage-like RAW264 cells.

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.

3,5-Dihydroxy-7,8-dimethoxyflavones and revised structures for some natural flavones

Abstract Seven 3,5-dihydroxy-7,8-dimethoxyflavones were synthesized from the corresponding 3,5,7,8-tetramethoxyflavones using selective demethylation and protection of 3- or 5- methoxy group, and their properties were clarified by the UV and 1 H NMR spectral data. The structures of the four natural flavones were revised as follows: the three flavones, isolated from Heteromma simplicifolium , are 5,7-dihydroxy-3,8,3′,4′-tetramethoxyflavone, 5,7-dihydroxy-3,8,3′,4′,5′-pentamethoxyflavone, and 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone, respectively; the flavone glycoside, isolated from Rudbeckia bicolor , is proposed to be 3,5,4′-trihydroxy-6,7-dimethoxyflavone 3-rhamnoside.

CHARGE-TRANSFER REACTION OF BUTATRIENE: FORMATION OF DIHYDRONAPHTHALENE DERIVATIVE

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.

Regioselective Synthesis of 6‐Prenylpolyhydroxyisoflavone (Wighteone) and Wighteone Hydrate with Hypervalent Iodine

Abstract 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.

Diinsertion of fluorenylidene into a sulfur-sulfur bond of diaryl disulfides

Abstract 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.

Regioselective prenylation of phenols by palladium catalyst: syntheses of prenylphenols and chromans

The palladium-catalyzed coupling reaction of iodophenols (1) with 2methyl-3-butyn-2-ol gave alkynylpbenols (2). Catalytic hydrogenation of 2 over Raney nickel and the subsequent dehydration of the resultant alkylphenols (3) gave regioselectively the desired prenylphenols (4). Dehydration of alkylphenols (3f-h) gave chromans (7)