Flavonoid variation in the genus briza

During a survey of 6 Eurasian and 10 South American Briza species for leaf flavonoids, 27 components were found. Twelve of these were identified: tricin 5-glucoside, tricin 7-glucoside, quercetin 3-glucoside, kaempferol 3-glucoside, vitexin, isovitexin, orientin, iso-orientin, and the 4′-O-glucoside of all 4 glycoflavones, 3 of which are reported for the first time. The Eurasian species, with the exception of Briza maxima, are remarkably uniform in their flavonoid pattern, accumulating mainly vitexin and isovitexin; whereas the South American species are characterized by the presence of orientin, iso-orientin and 9 unidentified flavonoids. In Briza media and the South American species, ploidy level is shown to play a large part in flavonoid variation. Examination of 12 diploid and 8 autotetraploid plants of B. media revealed that diploids accumulate vitexin and isovitexin, whereas tetraploids accumulate orientin and iso-orientin, autotetraploidy having apparently upset regulatory genes in the formation of the flavone C-glycosides. Mild alkaline treatment of both isovitexin and iso-orientin was found to give 100% conversion to the corresponding 8-C-glucoside.     

Naphthalene glucoside and other phenolics from the shoot and callus cultures of Drosophyllum lusitanicum

The callus and, for the first time established, shoot cultures of Drosophyllum lusitanicum Link. (Droseraceae) yielded new naphthalene glucoside-5-hydroxy-4-methoxy-2-naphthalenecarboxylic acid 5-O-beta-glucoside (drosophylloside) and 5-hydroxy-4-methoxy-2-naphthalenecarboxylic acid methyl ester besides other phenolics like naphthalenes-5-hydroxy-4-methoxy-2-naphthalenecarboxylic acid (ancistronaphthoic acid B), hydroplumbagin 4-O-glucoside, naphthoquinones-plumbagin and 3-chloroplumbagin, C-glycosylflavones- vitexin, isovitexin, orientin and isoorientin. The pattern of phenolics found supports affinity of Drosophyllum to the families-Droseraceae, Ancistrocladaceae and Dioncophyllaceae.     

Synthesis and glycosidase inhibitory activity of 1-amino-3,6-anhydro-1-deoxy-d-sorbitol derivatives

3,6-Anhydro-1-(aryl or alkylamino)-1-deoxy-d-sorbitol derivatives have been prepared in four steps from isosorbide, a by-product from the starch industry. The inhibitory activities of these new compounds have been evaluated towards 13 glycosidases. A first lead-compound was identified, which inhibited β-N-acetylglucosaminidase from bovine kidney (82% inhibition at 1 mM).     

Flavonoids in the species of Cyrtomium (Dryopteridaceae) and related genera

Flavonoids in 19 Cyrtomium, three Cyrtogonellum and two Phanerophlebia taxa were surveyed. Major flavonoids were flavonol O-glycosides based on kaempferol, quercetin, and sometimes myricetin, and C-glycosylflavones, such as isovitexin, vitexin, isoorientin, orientin and their O-glycosides. The C-methylflavanones, farrerol and cyrtominetin, and their 7-O-glucosides were isolated from Cyrtomium devexiscapulae and Cyrtomium laetevirens. Flavanones have been reported from Cyrtomium falcatum sensu lato. Though C. falcatum sensu lato is divided into four taxa, i.e. C. falcatum subsp. falcatum, C. falcatum subsp. australe, C. falcatum subsp. littorale, and C. devexiscapulae, the occurrence of the flavanones was restricted to C. devexiscapulae, and they did not occur in C. falcatum sensu stricto.     

Intra- and interspecific variations in vacuolar flavonoids among Ficus species from the Budongo Forest,Uganda

Leaves of 14 species of Ficus growing in the Budongo Forest, Uganda, were analysed for vacuolar flavonoids. Three to six accessions were studied for each species to see whether there was intraspecific chemical variation. Thirty-nine phenolic compounds were identified or characterised, including 14 flavonol O-glycosides, six flavone O-glycosides and 15 flavone C-glycosides. In some species the flavonoid glycosides were acylated. Ficus thonningii contained in addition four stilbenes including glycosides. Most of the species could be distinguished from each other on the basis of their flavonoid profiles, apart from Ficus sansibarica and Ficus saussureana, which showed a very strong intraspecific variation. However, on the whole flavonoid profiles were sufficiently distinct to help in future identifications.     

Total synthesis of two isoflavone C-glycosides: genistein and orobol 8-C-beta-D-glucopyranosides

Genistein and orobol 8-C-beta-D-glucopyranosides (1 and 3) were firstly synthesized in overall yields of 39% and 41% from 2,4-di-O-benzylphloroacetophenone (4), as follows: (1) the formation of the chalcone (6, 7) by aldol condensation of the benzyl-protected C-glycosylphloroacetophenone (5), a key intermediate of the total synthesis of 1 and 3 and synthesized by a C-glycosylation method involving the O-->C glycoside rearrangement of 4 in 96% yield; (2) the formation of isoflavones (10, 11 and 12, 13) by the formation of acetals by oxidative rearrangement of the protected chalcones (8 and 9) using Tl(NO3)3, followed by acid-catalyzed cyclization; (3) a final debenzylation by hydrogenolysis.     

Degraded limonoids from Melia azedarach and biogenetic implications

The unique series of C-2'-acylated C-glycosylflavones is extended by the discovery of the C-8-glucosyl derivatives 2'-O-galloylvitexin and 2'-O-galloylorientin and their C-6 analogues 2'-O-galloylisovitexin and 2'-O-galloylisoorientin, representing the first described O-galloyl-C-glycosylflavones. They are accompanied in the aerial parts of Pelargonium reniforme by the known non-galloylated parent analogues vitexin, orientin, isovitexin and isoorientin, as well as several known flavonoid-O-glycosides. The structures of these compounds were established from spectroscopic studies. Differentiation between C-glycosylation at C-6 and C-8 is discussed on the basis of the effects of dynamic rotational isomerism.     

ent-Kaurene diterpenoids from Isodon oresbius

Three new ent-kaurene diterpenoids, oreskaurins A-C (1-3), together with ten known ent-kaurene diterpenoids, enmenin monoacetate (4), effusanin E (5), adenolin B (6), maoecrystal G (7), enmelol (8), trichokaurin (9), sodoponin (10), trichorabdal A (11), nodosin (12), enmein (13), and a flavonoid, vitexin (14), were isolated from Isodon oresbius. Their structures were determined by spectroscopic means. Compound 12 showed inhibitory activity toward K562 cells with IC(50)=1.43 microg/ml.     

Synthesis of 2,3-unsaturated C-glycosides by HClO4-SiO2 catalyzed Ferrier rearrangement of glycals

Alkyl 2,3-unsaturated C-glycopyranosides have been prepared by Ferrier rearrangement of acyl or alkyl protected glycals catalyzed by HClO(4)-SiO(2).     

Isoflavanones and their O-glycosides from Desmodium styracifolium

Two isoflavanones (5,7-dihydroxy-2',3',4'-trimethoxy-isoflavanone and 5,7-dihydroxy-2'-methoxy-3',4'-methylenedioxy-isoflavanone), four isoflavanone O-glycosides (5,7-dihydroxy-2',3',4'-trimethoxy-isoflavanone 7-O-beta-glucopyranoside, 5,7-dihydroxy-2'-methoxy-3',4'-methylenedioxy-isoflavanone 7-O-beta-glucopyranoside, 5,7-dihydroxy-2',4'-dimethoxy-isoflavanone 7-O-beta-glucopyranoside, and 5,7,4'-trihydroxy-2',3'-dimethoxy-isoflavanone 7-O-beta-glucopyranoside), and a coumaronochromone (3,5,7,4'-tetrahydroxy-coumaronochromone), along with 25 known compounds, were isolated from the aerial parts of Desmodium styracifolium. This is for the first time isoflavanone O-glycosides were isolated from a natural source.     

Flavonoid glycosides and isoquinolinone alkaloids from Corydalis bungeana

Two flavonol O-glycosides identified as the 3-O-alpha-arabinopyranosyl(1'-->6')-beta-glucopyranoside 7-O-beta-glucopyranosides of kaempferol and quercetin were isolated from the whole plant of Corydalis bungeana Turcz. together with eight known flavonol O-glycosides. Two isoquinolinone alkaloids were also obtained from the same source, including the new derivative, 6,7-methylenedioxy-2-(6-acetyl-2,3-methylenedioxybenzyl)-1(2H)-isoquinolinone. The structures were determined by spectroscopic methods (NMR and high-resolution MS).     

Synthesis of C-glycopyranosylphloroacetophenone derivatives and their anomerization facilitated by 1,3-diaxial interactions

The reaction of 2,3,4-tri-O-benzyl-6-deoxy-alpha-D-glucopyranosyl fluoride, 2,3,4,6-tetra-O-benzyl-alpha-D-allopyranosyl fluoride, and 2,3,4-tri-O-benzyl-alpha-L-fucopyranosyl fluoride with 2,4-di-O-benzylphloroacetophenone, in the presence of boron trifluoride diethyl etherate, afforded, respectively, the corresponding 3-C-beta-D-glycopyranosylphloroacetophenone derivatives exclusively in anomerically pure form. Alternatively, the reaction of 2,3,4,6-tetra-O-benzyl-alpha-D-gulopyranosyl fluoride with 2,4-di-O-benzylphloroacetophenone afforded both the 3-C-beta-D-gulopyranosylphloroacetophenone derivative (4C(1) conformation) as the major product and the 3-C-alpha-D-gulopyranosylphloroacetophenone derivative (1C(4) conformation) as the minor product under identical conditions. Including the previously prepared C-glycosylphloroacetophenone derivatives that contain 3-C-beta-D-glucosyl, 3-C-beta-D-xylosyl, 3-C-beta-2-deoxy-D-arabino-hexosyl, 3-C-beta-D-galactosyl, 3-C-beta-L-arabinosyl, and 3-C-alpha-L-arabinosyl moieties, the conformation is dictated primarily by the preference of the bulky aromatic aglycon to orient equatorially, due to the strong repulsion of the aglycon. The anomerization is directed secondarily by the presence of 1,3-diaxial interactions in the sugar moiety.     

A "flavone-polysaccharide" redefined as a mixture of 6-methoxyluteolin penta- and hexa-O-glycosides

The incomplete structure proposed in 1972 for a unique "flavone-polysaccharide" compound, MF-1, from the liverwort Monoclea forsteri, has been re-examined. Rather than the proposed 8-methoxyluteolin structure with polysaccharides attached to the 7- and 4'-hydroxyls, MF-1 has been shown to be primarily a mixture of penta- and hexa-O-glycosides of 6-methoxyluteolin, which are accompanied by their luteolin analogues. MS and NMR evidence is marshalled to define the structure of MF-la as 6-methoxyluteolin 7-O-[2-O-alpha-rhamnosyl-3-O-alpha-arabinosyl-beta-glucuronide]-4'-O-[2-O-alpha-rhamnosyl-3-O-beta-xylosyl-beta-glucuronide], and MF-1b as 6-methoxyluteolin 7-O-[2-O-alpha-rhamnosyl-beta-glucuronide]-4'-O-[2-O-alpha-rhamnosyl-3-O-beta-xylosyl-beta-glucuronide]. This report is the first to provide substantive evidence for the existence of flavone penta- and hexa-O-glycosides in nature. The newly defined structure(s) for MF-1 more closely align M. forsteri with the only other species in the order Monocleales, M. gottschei.     

A general route to pendant C-glycosyl 1,2- and 1,3-diamines

Practical and convenient preparations of C-glycosyl 1,2- and 1,3-alkanediamines are described. Two 1,2-ethylenediamine derivatives were synthesized from acetylated allyl alpha-C-glycosyl compounds via dibromination, azidation, carbohydrate deprotection, and azide reduction. Four 1,3-propanediamine derivatives were prepared from acetylated sugar halides via C-glycosylation with sodiomalononitrile, followed by the reduction of the nitrile moieties and the deacetylation of the carbohydrate moiety. These 1,3-propanediamine derivatives have the beta-anomeric configurations. The methods reported here serve as general routes to access carbohydrate-diamine conjugates with C-glycosyl linkages.     

Acetophenone C-glucosides and stilbene O-glucosides in Upuna borneensis

Three acetophenone C-glycosides; 2,4,6-trihydroxyacetophenone 3-C-beta-(2'-O-p-hydroxybenzoyl)-glucopyranoside, 2,4,6-trihydroxyacetophenone 3-C-beta-(2'-O-E-coumaroyl)-glucopyranoside, 2,4,6-trihydroxyacetophenone 3-C-beta-(2'-O-E-cinnamoyl)-glucopyranoside, and two resveratrol O-glycosides; piceid 2'-O-p-hydroxybenzoate and, piceid 2'-O-E-ferulate, together with three known compounds were isolated from the acetone soluble part of stem of Upuna borneensis (Dipterocarpaceae). The structures of isolates were determined by spectral analysis including extensive 2D-NMR spectral analyses.     

Synthesis of a C-galactopyranosyl-linked N-substituted 1,2-ethylenediamine

A straightforward route to a C-galactopyranosyl-linked 1,2-ethylenediamine is described. The five-step synthetic procedure involves: (i) C-allenylation of d-galactopyranose pentaacetate with propargyl trimethylsilane in the presence of a Lewis acid, (ii) iodination of allenyl galactopyranosyl tetraacetate to diiodoallyl galactopyranosyl tetraacetate, (iii) displacement of the allylic iodide with N-Boc-ethylenediamine, (iv) catalytic hydrogenation of vinyl iodide to alkane, (v) deprotection of the acetyl and N-Boc-groups using acid-catalyzed hydrolysis. This method demonstrates a general method to access a new class of carbohydrate-ethylenediamine C-glycosyl chelators.     

Constituents of Pterocarpus marsupium: an ayurvedic crude drug

Five new flavonoid C-glucosides, 6-hydroxy-2-(4-hydroxybenzyl)-benzofuran-7-C-beta-d-glucopyranoside (1), 3-(alpha-methoxy-4-hydroxybenzylidene)-6-hydroxybenzo-2(3H)-furanone-7-C-beta-d-glucopyranoside (2), 2-hydroxy-2-p-hydroxybenzyl-3(2H)-6-hydroxybenzofuranone-7-C-beta-d-glucopyranoside (4), 8-(C-beta-d-glucopyranosyl)-7,3',4'-trihydroxyflavone (5) and 1,2-bis(2,4-dihydroxy,3-C-glucopyranosyl)-ethanedione (6) and two known compounds C-beta-d-glucopyranosyl-2,6-dihydroxyl benzene (7) and sesquiterpene (8), were isolated from an aqueous extract of the heartwood of Pterocarpus marsupium. The structure has been established using spectroscopic data.     

Preparation of 2,6-anhydro-aldose acylhydrazones, -semicarbazones and -oximes from 2,6-anhydro-aldononitriles (glycosyl cyanides)

Reductive transformation of per-O-acylated 2,6-anhydro-aldononitriles (glycopyranosyl cyanides of the D-galacto, D-gluco, D-xylo, and D-arabino configuration) with Raney-nickel-NaH(2)PO(2) in pyridine-AcOH-water solvent mixture in the presence of benzoylhydrazine, ethyl carbazate, and semicarbazide gave the corresponding anhydro-aldose benzoylhydrazones, -ethoxycarbonylhydrazones, and -semicarbazones, respectively. Acid catalyzed transimination of the semicarbazones with thiosemicarbazide, hydroxylamine, and O-benzylhydroxylamine, resulted in the formation of anhydro-aldose thiosemicarbazones, and E/Z mixtures of anhydro-aldose oximes, and O-benzyl-(anhydro-aldose)-oximes, respectively.