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.     

Phenolic lipids from related marine algae of the order dictyotales

2-(1′-Oxo-dodeca-5′, 8′, 11′, 14′, 17′(all Z)-pentaenyl)-5-methoxy-1, 3-dihydroxybenzene, 2- (1′-oxo-dodeca-5′, 8′, 11′, 14′, 17′(all Z)-pentaenyl)-1, 3, 5-trihydroxybenzene, 2-(17′-hydroxy-1′-oxo-dodeca-5′, 8′, 11′, 14′(all Z)-tetraenyl)-1, 3, 5-trihydroxybenzene and 2-(1′oxo-hexadecyl)-1, 3, 5-trihydroxybenzene have been isolated from the related brown algae Zonaria farlowii, Z diesingiana and Lobophora papenfussii. The structures of these new metabolites are based on extensive spectral analyses and comparisons with model compounds. The isolation of (+)-7, 8-dimethyltocol, from L. papenfussii, is also reported.     

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.     

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.     

Diastereoisomeric leucoanthocyanidins from the heartwood of acacia melanoxylon

The isolation of two pairs of diastereoisomeric leucoanthocyanidins, namely (2R,3R,4R)-2,3-cis-3,4-cis-3,3′,4,4′,7,8-hexahydroxyflavan or melacacidin, (2R,3R,4S)-2,3-cis-3,4-trans-3,3′,4,4′,7,8-hexahydroxyflavan or isomelacacidin and(2R,3R,4R)-2,3-cis-3,4-cis-4-ethoxy-3,3′,4′,7,8-pentahydroxyflavan or 4-O-ethylmelacacidin, (2R,3R,4S)-2,3-cis-3,4-trans-4-ethoxy-3,3′,4′,7,8-pentahydroxyflavan or 4-O-ethylisomelacacidin is described. 4-O-Ethylmelacacidin is a new compound and all four leucoanthocyanidins are natural constituents of the heartwood of Acacia melanoxylon. Melacacinidin is the name proposed for the anthocyanidin 3,3′,4′,7,8-pentahydroxyflavylium and leucomelacacinidins for the corresponding leucoanthocyanidins. Quinone-methide formation is proposed to account for the difference in reactivity between the diastereoisomers.     

Synthesis and spectra of some octa-O-benzoylaldo-biononitriles

2,3,5,6,2′,3′,4′,6′-Octa-O-benzoyl-cellobiononitrile, -lactobiononitrile, -maltobiononitrile, and 2,3,4,5,2′,3′,4′,6′-octa-O-benzoyl-melibiononitrile were prepared by benzoylation and dehydration of the corresponding disaccharide oximes, and their ¹H- and ¹³C-n.m.r., and e.i.m.s. spectra are described.     

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.     

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].     

The first replacement of a chlorosulphonyloxy group by chlorine at C-2 in methyl α-D-glucopyranoside and sucrose derivatives

Treatment of methyl 3-O-acetyl-4,6-O-benzylidene-α-D-glucopyranoside 2-chlorosulphate (2), 3,4,6,3′,4′,6′-hexa-O-acetylsucrose 2,1′-bis(chlorosulphate), 3,4,6,3′,4′,6′-hexa-O-acetyl-1′-O-benzoylsucrose 2-chlorosulphate, and 3,4,3′,4′-tetra-O-acetyl-6,6′-dichloro-6,6′-dideoxysucrose 2,1′-bis(chlorosulphate) with lithium chloride in hexamethylphosphoric triamide gave the corresponding chlorodeoxy-manno derivatives. Treatment of the 2-chlorosulphate 2 with such nucleophilic reagents as lithium bromide, sodium azide, sodium chloride, and sodium benzoate in hexamethylphosphoric triamide gave the 2-hydroxy compound as a major product. Selective chlorination at C-1′ was achieved when 3,4,6,3′,4′,6′-hexa-O-acetylsucrose was treated with sulphuryl chloride in a mixture of pyridine and chloroform.     

C-methylation of sucrose: synthesis of 6- and 6′-C-methylsucrose

2,3,4,6,1′,3′,4′-Hepta-O-benzylsucrose, obtained by acid-catalysed hydrolysis of the 6′-O-trityl derivative, was oxidised with the Pfitzner-Moffatt reagent and the product was alkylated with methylmagnesium iodide. Removal of the protecting groups then gave a mixture of diastereomers, namely 7-deoxy-β-d-altro and -α-l-galacto-hept-2-ulofuranosyl α-d-glucopyranoside. Application of this reaction sequence to 2,3,4,1′,3′,4′,6′-hepta-O-benzylsucrose afforded β-d-fructo-furanosyl 7-deoxy-dl-glycero-α-d-gluco-heptopyranoside.     

New substituted bibenzyls of Frullania brittoniae subsp. Truncatifolia

The two dihydrostilbenes, Brittonin A and Brittonin B, have been isolated from Frullania brittoniae subsp. truncatifolia (F. F. muscicola). They were identified as 3,4,5,3′,4′,5′-hexamethoxybibenzyl and 3,4,5,3′-tetra- methoxy-4′,5′,-methylenedioxybibenzyl respectively.     

Flavonoids of Chromolaena odorata

A dichloromethane extract of Chromolaena odorata has yielded 2′-hydroxy-3,4,4′,5′,6′-pentamethoxychalcone, 2′,4-dihydroxy-4′,5′,6′-     

An unusual porosin type neolignan from Licaria chrysophylla

The trunk wood of Licaria chrysophylla contains rel-(7S, 8R, 1′S, 5′S)-Δ^8′-3,3′,5′-trimethoxy-4,5-methylenedioxy-1′,4′,5′,6′- tetrahydro-4′-oxo-7.1′,8.0.2′-neolignan (chrysophyllin A), which differs from all other known benzofuranoid neolignans by showing 7.1′ (rather than 8.1′) and 8.0.2′ (rather than 7.0.2′) linkages between the propenylphenol and allylphenol derived moieties.     

Flavonoids from Merrillia caloxylon

Three chalcones and three flavones isolated from the fruit of Merrillia caloxylon (Rutaceae) have been characterised. Two of the flavones and two of the chalcones are related structurally, i.e. 3′,4′,5,7-tetramethoxyflavone with 2′- hydroxy-3,4,4′,6′-tetramethoxychalcone and 3′,4′,5,5′,7-pentamethoxyflavone with 2′,3-dihydroxy-4,4′,6′- trimethoxychalcone. A minor constituent was tentatively characterized as 5-hydroxy-3′,4′,5′,6,7-pentamethoxyflavone and this is accompanied by 2-hydroxy-3,4,4′,5,6′-pentamethoxychalcone and 5-hydroxy-3′,4′,6,7-tetramethoxyfiavone.     

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.     

New coumarins from Coleonema album

Six coumarins have been isolated from the aerial parts of Coleonema album and identified as ulopterol, 7-(3′, 3′-dimethylallyloxy)-coumarin, (R)-(+)-2′,3′-epoxy-suberosin, and the novel coumarins (R)-(+)-7-(2′, 3′-epoxy-3′-methylbutoxy)-coumarin, (R)-(+)-7-(2′,3′-dihydroxy-3′-dihydroxy-3′-methylbutoxy)-coumarin and (R)-(+)-7-methoxy-8-(2′,3′-epoxy-3′-methylbutoxy)-coumarin.     

Selective tritylation and mesitylenesulphonylation of raffinose

Raffinose reacted with 3 molar equivalents of trityl chloride in pyridine to give a complex mixture of products from which 1′,6′,6″-tri-O-tritylraffinose¹ was isolated (20%) after chromatography, and characterised as the crystalline octa-acetate and octabenzoate. The octabenzoate was detritylated in methanolic 1% hydrogen chloride, without significant ester migration, to give the 1′,6′,6″-triol octabenzoate, from which 1′,6′,6″-trisulphonates were obtainable in high yields. Treatment of raffinose with 3 molar equivalents of mesitylenesulphonyl chloride in pyridine gave 1′,6′,6″-tri-O-mesitylenesulphonylraffinose (20%, after chromatography).     

Flavonoids of Gardenia cramerii and G. fosbergii bud exudates

From the bud exudates of Gardenia cramerii and G. fosbergii, two species endemic to Sri Lanka, a new flavonoid with an unusual B-ring oxidation pattern, 5,5′-dihydroxy-6,7,2′,3′-tetramethoxyflavone, was characterized. Two other rare flavonoids, 5,3′,5′-trihydroxy-3,6,7,4′-tetramethoxyflavone and 5-hydroxy-6,7,3′,4′,5′-pentamethoxyflavone were also isolated from both Gardenia species.     

Tetrahydrodiospyrin: a reduced binaphthoquinone from the bark of Diospyros montana

A new reduced dimeric 7-methyljuglone isolated from the fresh bark of D. montana is shown to be 3′,7-dimethyl-5′,6′,7′,8′-tetrahydro-1′,5,5′-trihydroxy [2,2′-binaphthalene]-1,4,8′-trione.     

Novel flavonoids from the stem of Popowia cauliflora

Six flavonoids, five of them novel, have been isolated from the whole stem of Popowia cauliflora and identified as: baicalein trimethyl ether, 5-hydroxy-6,7-dimethoxyflavone, 5,7,8-trimethoxyflavanone, 2′-hydroxy-3′,4′,6′-trimethoxychalcone, 2′,3′,4′,6′-tetramethoxychalcone and 2′,4-dihydroxy-3′,4′,6′-trimethoxychalcone, on the basis of spectral data and simple chemical modifications. The value of ¹³C NMR in assigning the positions of methoxy substituents is briefly discussed.