Flavonoids from Gutierrezia texana var. texana

Eleven flavonoids, including two new compounds, were isolated from Gutierrezia texana: the structures of the new compounds are 5,7,2′,5′-tetrahydroxy-3,4′-dimethoxyflavone and 5′-acetoxy-5,7,2′-trihydroxy-3,4′-dimethoxyflavone. The nine known compounds are 5,4′,5′-trihydroxy-3,6,7,8-tetramethoxyflavone, 5,7,2′,5′-tetrahydroxy-3,6,4′-trimethoxyflavone, 5,7,3′-trihydroxy-3,4′-dimethoxyflavone, 5,7,3′,4′-tetrahydroxyflavone, 3,5,7,3′,4′- pentahydroxyflavone, 5,7,3′,4′-tetrahydroxy-3-methoxyflavone, 5,6,7,3′,4′,-pentahydroxy-3-methoxyflavone, 5,7,3′,4′-tetrahydroxy-3-methoxyflavone 7-O-glucoside and 3,5,7,3′,4′-pentahydroxyflavanone.     

Synthesis and hybridizing properties of isoDNAs including 3′-O,4′-C-ethyleneoxy-bridged 5-methyluridine derivatives

3′,4′-Ethyleneoxy-bridged 5-methyluridine derivatives with methyl groups in the bridge, (R)-Me-3′,4′-EoNA-T and (S)-Me-3′,4′-EoNA-T, were synthesized, and these two analogs and unsubstituted 3′,4′-EoNA-T were successfully incorporated into a 2′,5′-linked oligonucleotide (isoDNA). Their duplex-forming ability with complementary DNA and complementary RNA, and triplex-forming ability with double-stranded DNA, were evaluated by UV-melting experiments. The results indicated that isoDNAs, including these 3′,4′-EoNA analogs, could hybridize exclusively with complementary RNA. In particular, 3′,4′-EoNA-T and (R)-Me-3′,4′-EoNA-T modifications within isoDNA could stabilize the duplexes with complementary RNA compared with unmodified or 3′,4′-BNA-modified isoDNAs.     

Neolignans from stem bark of ocotea veraguensis

The stem bark of Ocotea veraguensis has yielded nine neolignans of which five appear to be novel. The new neolignans, which were identified on the basis of spectral characteristics, are^* (7S,8R,1′S,2′S,3′R,4′S)-Δ^8′-2′,4′-dihydroxy-3,3′5′-trimethoxy-4,5-methylenedioxy-1′,2′,3′,4′-tetrahydro-7.3′,8.1′-neolignan, (7S,8R,1′S,3′S,4′S)-Δ^8′-4,4'-dihydroxy-3,3′,5′-trimethoxy-1′,2′,3′,4′-tetrahydro-2′-oxo-7.3′,8.1′-neolignan, (7S,8S,1′R)-Δ^8′-3′,5′-dimethoxy-3,4-methylenedioxy-1′,4′-dihydro-4′-oxo-7.0.2′,8.1′-neolignan, (7S,8S,1′R )-Δ^8′-1′-methoxy-3,4-methylenedioxy-1′,6′-dihydro-6′-oxo-7.0.4′,8.3′-neolignan and (7S,8S)-Δ^8′-2′,6′-dimethoxy-3,4-methylenedioxy-7.0.3′,8.4′,1′.0.7′-neolignan.     

Flavonoids from Artemisia ludoviciana var. ludoviciana

Nineteen flavonoids were isolated from Artemisia ludoviciana var. ludoviciana, including a new 2′- hydroxy- 6-methoxyflavone, 5,7,2′,4′-tetrahydroxy-6,5′-dimethoxyflavone. The known compounds include quercetagetin 3,6,3′,4′-tetramethyl ether, eupatilin, 5,7-dihydroxy-3,6,8,4′-tetramethoxyflavone, luteolin 3′,4′-dimethyl ether, jaceosidin, 5,7,4′-trihydroxy-3,6-dimethoxyflavone, tricin, hispidulin, chrysoeriol, kaempferol 3-methyl ether, apigenin, axillarin, eupafolin, selagin and luteolin together with three flavones which were previously isolated for the first time from Artemisia frigida: 5,7,4′-trihydroxy-6, 3′,5′-trimethoxyflavone, 5,7,3′-trihydroxy-6,4′,5′-trimethoxyflavone and 5,7,3′,4′-tetrahydroxy-6,5′- dimethoxyflavone.     

Biosynthesis of the isoflavan isomucronulatol: Origin of the 2′,3′,4′-oxygenation pattern

Feeding experiments with ¹⁴C-labelled isoflavones in seedlings and pods of bladder senna (Colutea arborescens) have demonstrated that 7-hydroxy-4′-methoxyisoflavone (formononetin), 7,3′-dihydroxy-4′-methoxyisoflavone (calycosin), 7,2′,3′-trihydroxy-4′-methoxyisoflavone (koparin) and 7,2′-dihydroxy-3′,4′-dimethoxyisoflavone are excellent precursors of (3R)-isomucronulatol (7,2′-dihydroxy-3′,4′-dimethoxyisoflavan). 7,2′-Dihydroxy- 4′-methoxyisoflavone (2′-hydroxyformononetin) and 7-hydroxy-3′,4′-dimethoxyisoflavone (cladrin) were, however, poor substrates. Thus, the biosynthetic sequence to isomucronulatol from formononetin involves 3′-hydroxylation, 2′-hydroxylation and then 3′-O-methylation, followed presumably by stereospecific reduction of 7,2′-dihydroxy-3′,4′-dimethoxyisoflavone. Treatment of 2′,3′,4′-trimethoxyisoflavones with aluminium chloride in acetonitrile gives modest yields of 2′,3′-dihydroxy derivatives rather than 2′-monohydroxyisoflavones, and thus provides a convenient access to 2′,3′-dihydroxyisoflavones and related pterocarpans.     

Neolignans from mezilaurus itauba

The wood bark of Mezilaurus itauba afforded in addition to seven known neolignans, three new compounds rel-(7R,8R,1′S,3′S)-Δ^5′,8′-5′-methoxy-3,4-methylenedioxy-1′,2′,3′,4′-tetrahydro-2′,4′-dioxo-7.3′,8.1′-neolignan, rel-(7S,8S,1′S, 2′S, 3′R, 4′S)-Δ^8′-2′,4′-dihydroxy-3,4-methylenedioxy-1′,2′,3′,4′,5′,6′-hexahydro-5′-oxo-7.3′,8.1′-neolignan and rel-(7S,8S)-Δ^8′-6′-hydroxy 5′-methoxy-3,4-methylenedioxy-7·O·2′,8.3′-neolignan. The latter compound has been detected previously in Aniba terminalis. The structures were elucidated by spectroscopic methods and comparison with related compounds.     

Polyoxygenated flavones from Ageratum conyzoides

Twelve polyoxygenated flavones have been isolated from Ageratum conyzoides, three of which are new natural flavones, namely ageconyflavones A (5,6,7-trimethoxy-3′,4′-methylenedioxyflavone), B (5,6,7,3′-tetramethoxy-4′-hydroxyflavone) and C (5,6,7,3′,5′-pentamethoxy-4′-hydroxyflavone). The other nine compounds were identified as linderoflavone B, eupalestin, nobiletin, 5′-methoxynobiletin, 5,6,7,5′-tetramethoxy-3′,4′-methylenedioxyflavone, sinensetin, 56,7,3′,4′,5′-hexamethoxyflavone, 5,6,7,8,3′-pentamethoxy-4′-hydroxyflavone and 5,6,7,8,3′,5′-hexamethoxy-4′-hydroxyflavone.     

Six 2′-hydroxyflavonols from Gutierrezia microcephala

Six 2′-hydroxyflavonols were isolated from Gutierrezia microcephala, including four new compounds, 5,7,2′-trihydroxy-3,6,4′,5′-tetramethoxyflavone, 5,7,2′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone, 5,2′-dihydroxy-3,6,7,8,4′,5′-hexamethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,8,5′-trimethxoyflavone and two known compounds, 5,7,2′,5′-tetrahydroxy-3,6,8,4′-tetramethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,6,8,5′-tetramethoxyflavone.     

Lipophilic C-methylflavonoids with no B-ring oxygenation in Metrosideros species (Myrtaceae)

Five unusual C-methylflavonoids lacking B-ring oxygenation (2′,4′-dihydroxy-3′,5′-dimethyl-6′-methoxychalcone, 2′,4′-dihydroxy-3′-methyl-6′-methoxychalcone, 2′,6′-dihydroxy-3′-methyl-4′-methoxychalcone, 2′-hydroxy-3′-methyl-4′,6′-dimethoxychalcone and 5,7-dihydroxy-6,8-dimethylflavanone) were found for the first time in Metrosideros excelsa. The flavanone was the major constituent in leaves, whereas 2′,6′-dihydroxy-3′-methyl-4′-methoxychalcone dominated all other aerial plant parts studied. Other Metrosideros species were investigated for these five flavonoids. C₁₉–C₃₆ aldehydes and C₂₂–C₃₂ alcohols were also identified from the dried seed capsules of M. excelsa.     

Chemistry of toxic range plants. Highly oxygenated flavonol methyl ethers from Gutierrezia microcephala

The perennial American desert shrub, Gutierrezia microcephala, contains 20 flavonol methyl ethers displaying nine different oxygenation patterns. These include 11 new flavonols: 5,7-dihydroxy-3,6,8,3′,4′,5′-hexamethoxyflavone, 5,7,4′-trihydroxy-3,6,8,3′,5′-pentamethoxyflavone, 5,7,3′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone, 5,7,2′,4′-tetrahydroxy-3,6,8,5′-tetramethoxyflavone, 5,7,3′,4′-tetrahydroxy-3,6,8-trimethoxyflavone, 5,7,8,3′,4′-pentahydroxy-3,6-dimethoxyflavone, 3,5,7,3′,4′-pentahydroxy-6,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,6,8-trimethoxyflavone, 5,7,8,4′-tetrahydroxy-3,3′-dimethoxyflavone, 5,7,8,3′,4′-pentahydroxy-3-methoxyflavone and 5,7,8,4′-tetrahydroxy-3-methoxyflavone. In addition, the following known flavonols were isolated: 5,7-dihydroxy-3,8,3′,4′,5′-pentamethoxyflavone, 5,7,4′-trihydroxy-3,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone, 5,7,3′,4′-tetrahydroxy-3,8-dimethoxyflavone, 5,7,4′-trihydroxy-3,6,3′-trimethoxyflavone, 5,7,3′,4′-tetrahydroxy-3-methoxyflavone, 5,4′-dihydroxy-3,6,7,8,3′-pentamethoxyflavone, 5,7,4′-trihydroxy-3,6,8,3′-tetramethoxyflavone and 3,5,7,4′-tetrahydroxy-6,8,3′-trimethoxyflavone.     

Eusiderins and other neolignans from an Aniba species

A previous report disclosed the presence of benzodioxan and bicyclo[3.2.1]octanoid neolignans in the benzene extract of the trunk wood of an Amazonian Aniba (Lauraceae) species. The chloroform extract of the same material contains additionally two new benzodioxan neolignans [rel-(7S,8R)-Δ^8′-7-hydroxy-3,4,5,5′-tetramethoxy-7.0.3′,8.0.4′-neolignan; rel-(7R,8R)-Δ^7′-3,4,5,5′-tetramethoxy-9′-oxo-7.0.3′,8.0.4′-neolignan], two new bicyclo[3.2.1]-octanoid neolignans [(7R,8S,1′S,2′S,3′S,4′R)-Δ^8′-2′,4′-dihydroxy-3,3′-dimethoxy-4,5-methylenedioxy-1′,2′,3′,4′,5′,6′-hexahydro-5′-oxo-7.3′,8.1′-neolignan; (7R,8S,1′R,2′S,3′S)-Δ^8′-2′-hydroxy-3,3′,5′-trimethoxy-4,5-methylenedioxy-1′,2′,3′,4′-tetrahydro-4′-oxo-7.3′,8.1′-neolignan] and a hydrobenzofuranoid neolignan [(7S,8R,1′S,5′S)-Δ^8′-3,3′,5′-tri-methoxy-4,5-methylenedioxy-1′,4′,5′,6′-tetrahydro-4′-oxo-7.0.2′,8.1-neolignan].     

Highly oxygenated flavonoids from Ageratum corymbosum

The investigation of Ageratum corymbosum resulted in the isolation of four new highly oxygenated flavonoids, and their structures established by spectroscopic and degradative evidence as 5,6,7,5′-tetramethoxy-3′,4′-methylenedioxyflavanone; 5,6,7,8,5′-pentamethoxy-3′,4′-methylenedioxyflavanone; 5,6,7,8,2′,4′,5′-heptamethoxy-flavone and 5,2′,4′-trihydroxy-6,7,8,5′-tetramethoxyflavone. The recently reported gardenin A monomethyl ether and 5′-methoxylucidin dimethyl ether (eupalestin) were also isolated.     

Isoflavones from Pterodon apparicioi

The trunk wood of Pterodon apparicioi contains five known compounds: 7-hydroxy-6,4′-dimethoxy-, 7-hydroxy-6-methoxy-3′,4′-methylenedioxy-, 6,7,2′,3′,4′-pentamethoxy-, 6,7,2′,4′,5′-pentamethoxy- and 6,7,2′-trimethoxy-4′,5′-methylenedioxyisoflavone. In addition, there are four new substances, namely 7,3′-dihydroxy-6,4′-dimethoxy-, 7-hydroxy-6,2′,4′,5′-tetramethoxy-, 7,2′-dimethoxy-4′,5′-methylenedioxy- and 7,8,2′-trimethoxy-4′,5′-methylenedioxyisoflavone.     

Flavonoids from Gutierrezia grandis

Thirteen flavonoids, including three new compounds, were isolated from Gutierrezia grandis. The structures of the new compounds were 3,5,7,3′,4′-pentahydroxy-6,8-dimethoxyflavone, 5,7,3′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone and 5,7,3′,5′-tetrahydroxy-3,6,8,4′-tetramethoxyflavone 3′-O-glucoside.     

Two new C-methylated flavonoids from Myrica gale

From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis.     

Octasubstituted flavones from Ageratum houstonianum

Two new highly oxygenated flavones, were isolated from aerial parts of Ageratum houstonianum. Their structures were established as 3′-hydroxy-5,6,7,8,2′,4′,5′-heptamethoxyflavone and 5,3′-dihydroxy-6,7,8,2′,4′,5′-hexamethoxyflavone on the basis of spectral data and chemical degradation. The structure of the latter compound was confirmed by X-ray analysis.     

Conversion of (2Z,4E)-5-(1′,2′-epoxy-2′,6′,6′-trimethylcyclohexyl)-3-methyl-2,4-pentadienoic acid to xanthoxin acid by Cercospora cruenta, a fungus producing (+)-abscisic acid

(±)-(2Z,4E)-5-(1′,2′-epoxy-2′,6′,6′-trimethylcyclohexyl)-3-methyl-2,4-pentadienoic acid was metabolized by Cercospora cruenta, which has the ability to produce (+)-abscisic acid (ABA), to give (±)-(2Z,4E)-xanthoxin acid, (±)-(2Z,4E)-5′-hydroxy-1′,2′-epoxy-1′,2′-dihydro-β-ionylideneacetic acid, (±)-1′,2′-epoxy-1′,2′-dihydro-β-ionone and trace amounts of ABA.     

Induction of porphyrin synthesis in chick embryo liver cell culture by synthetic polychlorobiphenyl isomers

The effects of a series of synthetic di-tetra- and hexachlorobiphenyl isomers and commercial polychlorinated biphenyls on the porphyrin biosynthesis in chick embryo liver cells in culture were examined.It was found that 3,4,3′,4′-tetra- and 3,4,5,3′,4′,5′-hexachlorobiphenyl isomers were the most active inducers, which were approximately 20 times as active as 1,4-dihydro-3,5-dicarbethoxy-2,4,6-trimethylpyridine (DDC) in porphyrin production. 3,5,3′,5′-Tetra- and 2,3,4,2′,3′,4′-hexachlorobiphenyl isomers were moderate inducers, which were approximately 2.0 to 2.5 times as active as DDC. 2,4,6,2′,4′,6′-Hexachlorobiphenyl showed the same activity as DCC. Compounds such as 4,4′-di-, 2,3,2′,3′-, 2,4,2′,4′- and 2,6,2′,6′-tetrachlorobiphenyl were weak inducers and 2,5,2′,5′-tetrachloro- and decachlorobiphenyl isomers were found to be inactive. Kanechlor-400 was the strongest inducer among the commercial polychlorinated biphenyls investigated.The structural requirements for potent porphyrin-inducing activity of chlorobiphenyl isomers were found to be the para and meta substituted structure causing a more highly conjugated and nearly coplanar conformation. It was found that induction caused by some chlorobiphenyls was subject to feed-back repression by end-product heme. In addition, the metabolism of chlorobiphenyls in mice was influenced by the unsubstituted pairs of carbon atoms in the molecule. These results lead us to postulate the following hypothesis, namely, that strong inducers may displace heme directly and incorporate into a hydrophobic pocket of the apo-represor protein, thus causing an induction of δ-aminolevulinic acid synthetase.     

Four flavonoids from Ageratum strictum

Four new flavonoids, three flavanones and one chalcone, were isolated from aerial parts of Ageratum strictum. Their structures were establised as 3′6′-dihydroxy-2′, 4′-dimethoxy- 3, 4-methylenedioxy-chalcone, 6-hydroxy-5,7-dimethoxy-3′,4′-methylenedioxyflavanone, 6-hydroxy- 5,7,3′,4′-tetramethoxyflavanone and 6,4′-dihydroxy-5,7,3′-trimethoxyflavanone on the basis of spectral data and chemical degradation.     

Effective syntheses of 2′,4′-BNANC monomers bearing adenine,guanine, thymine,and 5-methylcytosine,and the properties of oligonucleotides fully modified with 2′,4′-BNANC

We efficiently synthesized 2′-O,4′-C-aminomethylene-bridged nucleic acid (2′,4′-BNA^NC) monomers bearing the four nucleobases, guanine, adenine, thymine, and 5-methylcytosine and incorporated these monomers into oligonucleotides. Initially, we carried out the transglycosylation reaction on several 2′-O-substituted 5-methyluridines to evaluate the effects of 2′-substitutions on this reaction. Under the optimized conditions, purine nucleobases were successfully introduced, and 2′,4′-BNA^NC monomers bearing adenine or guanine were obtained over several steps. In addition, the improved synthesis of the 2′,4′-BNA^NC monomers bearing thymine or 5-methylcytosine was also achieved. The obtained 2′,4′-BNA^NC monomers were subsequently incorporated into oligonucleotides and the duplex-forming abilities of the modified oligonucleotides were investigated. Duplexes containing 2′,4′-BNA^NC monomers in both or either strands were found to possess excellent thermal stabilities.