Saponins from Albizzia lucida

Three main saponins were isolated from the seeds of Albizzia lucida. Their structures were established by spectral analyses and chemical and enzymatic transformations as 3-O-[β- -xylopyranosyl(1→2)-α- -arabinopyranosyl (1→6)] [β- -glucopyranosyl (1→2)] β- -glucopyranosyl echinocystic acid; 3-O-[α- -arabinopyranosyl (1→6)][β- -glucopyranosyl (1→2)]-β- -glucopyranosyl echinocystic acid and 3-O-[β- -xylopyranosyl (1→2)-β- -fucopyranosyl (1→6)-2-acetamido-2-deoxy-β- -glucopyranosyl echinocystic acid, characterized as its methyl ester.     

Cycloartane triterpene glycosides from Astragalus trigonus

Three new cycloartane glycosides, trigonoside I, II and III, and the known astragalosides I and II were isolated from the roots of Astragalus trigonus. The structures of the new glycosides were totally elucidated by high field (600 MHz) NMR analyses as cycloastragenol-6-O-β-xylopyranoside, cycloastragenol-3-O-[-l-arabinopyranosyl(1 → 2)-β-d-xylopyranosyl]-6-O-β- d-xylopyranoside and cycloastragenol-3-O-[-l-arabinopyranosyl(1 → 2)-β-d-(3-O-acetyl)-xylopyranosyl]-6-O-β-d-xylopyranoside.     

A triterpenoid and its saponin from Phytolacca esculenta.

A new triterpenoid, esculentagenin, and its glycoside, esculentoside M, were isolated from the roots of Phytolacca esculenta and characterized as 11-oxo-3-O-methyloleanata-12-en-2β,3β,23-trihydroxy-28-oic acid and 3-O-[β - -glucopyranosyl (1→4)-β- -Xylopyranosyl]-28-O-β- -glucopyranosyl-11-oxo-30-methyloleanate-12-en-2β,3β,23-trihydroxy-28-oic acid by spectral and chemical evidence.     

A spirostane hexaglycoside from Agave cantala fruits.

A new steroidal glycoside, agaveside D, isolated from the fruits of Agave cantata was characterized as 3β-{- -rhamnopyranosyl-(1→2), β- -glycopyranosyl-(1→3)-β- -glucopyranosyl[β- -xylopyransoyl-(1→4)-- -rhamnopyranosyl-(1→2)]-β- -glucopyranosyl}-25R-5- spirostane on the basis of chemical degradation and spectrometry.     

Structure of the serine-containing capsular poly-saccharide K40 antigen from Escherichia coli O8:K40:H9

The structure of the K40 antigenic capsular polysaccharide (K40 antigen) of E. coli O8:K40:H9 was elucidated by determination of the composition, ¹H- and ¹³C-n.m.r. spectroscopy, periodate oxidation and Smith degradation, and methylation analysis. The K40 polysaccharide consists of [(O-β- -glucopyranosyluronic acid)-(1→4)-O-(2-acetamido-2-deoxy-- -glucopyranosyl)-(1→6)-O-(2-acetamido-2-deoxy-- -glucopyranosyl)-(1→4)] repeating units. All of the glucuronic acid residues are substituted amidically with -serine.     

Synthesis of the tetrasaccharide repeating-unit of the lipopolysaccharide isolated from pseudomonas maltophilia

The title tetrasacharide having the structure 3-O-Me-β- -Xylp-(1→4)-- -Rhap-(1→4)-- -Rhap-(1→2)- -Rhap was obtained by reaction of the -acetobromo derivative of 4-O-(3-O-methyl-β- -xylopyranosyl)- -rhamnopyranose and benzyl 3,4-di-O-benzyl-2-O-(2,3-O-isopropylidene-- -rhamnopyranosyl)-- -rhamnopyranoside, followed by removal of the protecting groups. The synthesised compounds were characterised on the basis of n.m.r. data.     

Triterpenoidal saponins from Dumasia Truncata

Extraction of the aerial parts of Dumasia truncata Sieb et Zucc. afforded two new triterpenoidal saponins, together with four known ones. The structures of the new compounds were elucidated by spectral analysis as 3-O--l-rhamnopyranosyl-(1 → 3)-β-d-glucuronopyranosy-28-O-β-d-glucopyransoyl hederagenin and 3-O-β-d-xylopyranosyl-(1 → 2)-[-l-rhamnopyranosyl(1 → 3)]-β-d-glucuronopyranosyl oleanic acid.     

Leucasin, a triterpene saponin from Leucas nutans.

A new saponin, leucasin, has been isolated from Leucas nutans and characterized on the basis of chemical investigation and spectroscopic studies as 3-O-[β- -glucopyranosyl(1→2)β- -glucopyranosyl]2,3β-dihydroxylup-20(29)-ene. Lupeol palmitate, sitosterol and stigmasterol were also isolated.     

Streptococcus pneumoniae type XIV polysaccharide: synthesis of a repeating branched tetrasaccharide with dioxa-type spacer-arms

β-Glycosides of 2-acetamido-2-deoxy- -glucopyranose were synthesized, using either 7-methoxycarbonyl-3,6-dioxa-1-heptanol or 8-azido-3,6-dioxa-1-octanol. Selective β-lactosylation of 7-methoxycarbonyl-3,6-dioxaheptyl 2-acetamido-3-O-benzyl-2-deoxy-β- -glucopyranoside with hepta-O-acetyl-lactosyl-trichloroacetimidate, followed by β-galactosylation of the secondary hydroxyl group with O-(2,3,4,6-tetra-O-acetyl-- -galactopyranosyl)trichloroacetimidate, catalytic hydrogenolysis, and O-deacetylation, gave 7-methoxycarbonyl-3,6-dioxaheptyl 2-acetamido-2-deoxy-4-O-β- -galactopyranosyl-6-O-(4-O-β- -galactopyranosyl-β- -glucopyranosyl)β- -glucopyranoside. Selective β-lactosylation of 8-azido-3,6-dioxaocytl 2-acetamido-3-O-benzyl-2-deoxy-β- -glucopyranoside with hepta-O-acetyl-lactosyl bromide in the presence of silver triflate, followed by condensation with 2,3,4,6-tetra-O-acetyl-- -galactopyranosyl bromide in the presence of silver triflate, catalytic hdyrogenolysis, and O-deacetylation, gave 8-azido-3,6-dioxaoctyl 2-acetamido-2-deoxy-4-O-β- -galactopyranosyl-6-O-(4-O-β- -galactopyranosyl-β- -glucopyranosyl)-β- glucopyranoside.     

Six new C21 steroidal glycosides from Asclepias curassavica L

Six new C₂₁ steroidal glycosides, named curassavosides A–F (3–8), were obtained from the aerial parts of Asclepias curassavica (Asclepiadaceae), along with two known oxypregnanes, 12-O-benzoyldeacylmetaplexigenin (1) and 12-O-benzoylsarcostin (2). By spectroscopic methods, the structures of the six new compounds were determined as 12-O-benzoyldeacylmetaplexigenin 3-O-β-d-oleandropyranosyl-(1 → 4)-β-d-digitoxopyranoside (3), 12-O-benzoylsarcostin 3-O-β-d-oleandropyranosyl-(1 → 4)-β-d-digitoxopyranoside (4), sarcostin 3-O-β-d-oleandropyranosyl-(1 → 4)-β-d-canaropyranosyl-(1 → 4)-β-d-oleandropyranosyl-(1 → 4)-β-d-digitoxopyranoside (5), sarcostin 3-O-β-d-oleandropyranosyl-(1 → 4)-β-d-canaropyranosyl-(1 → 4)-β-d-canaropyranosyl-(1 → 4)-β-d-digitoxopyranoside (6), 12-O-benzoyldeacylmetaplexigenin 3-O-β-d-glucopyranosyl-(1 → 4)-β-d-oleandropyranosyl-(1 → 4)-β-d-canaropyranosyl-(1 → 4)-β-d-oleandropyranosyl-(1 → 4)-β-d-digitoxopyranoside (7), and 12-O-benzoylsarcostin 3-O-β-d-glucopyranosyl-(1 → 4)-β-d-oleandropyranosyl-(1 → 4)-β-d-canaropyranosyl-(1 → 4)-β-d-oleandropyranosyl-(1 → 4)-β-d-digitoxopyranoside (8), respectively. All compounds (1–8) were tested for in vitro cytotoxicity; only compound 3 showed weak inhibitory activity against Raji and AGZY cell lines.     

Synthesis of part of the antigenic repeating-unit of streptococcus pneumoniae type II

Condensation of methyl 4-O-acetyl-3-O-(2,3,4-tri-O-acetyl-α- -rhamnopyranosyl)-α- -rhamnopyranoside with 2,3,4,6-tetra-O-benzyl-α- -glucopyranosyl chloride gave a mixture of methyl O-[2,3,4,6-tetra-O-benzyl-α- (4) and -β- -glucopyranosyl]-(1→2)-O-[(2,3,4-tri-O-acetyl-α- -rhamnopyranosyl)-(1→3)]-4-O-acetyl-α- -rhamnopyranoside (9) in 43:7 proportion in 63% yield. After chromatographic separation, removal of the benzyl and acetyl groups gave methyl O-α- -glucopyranosyl-(1→2)-[O-α- -rhamnopyranosyl-(1→3)]-α- -rhamnopyranoside and the β anomer. Removal of benzyl groups of 4 was followed by tritylation, acetylation, and detritylation of the α- -glucopyranosyl group, and finally condensation with benzyl (2,3,4-tri-O-benzyl- -glucopyranosyl chloride)uronate gave a mixture of two tetrasaccharides (15 and 16), containing the α- and β- -glucopyranosyluronic acid groups in the ratio 81:19, and an overall yield of 71%. After chromatographic separation, alkaline hydrolysis and hydrogenation of 15 gave methyl O-α- -glucopyranosyluronic acid-(1→6)-O-α- -glucopyranosyl-(1→2)-[O-α- -rhamnopyranosyl-(1→3)]-α- -rhamnopyranoside. The β- anomer was obtained by similar treatment of 16. 6-O-α- -glucopyranosyluronic acid-α,β- -glucopyranose was synthesized as a model compound.     

Chalconoid and stilbenoid glycosides from Guibourtia tessmanii

Phytochemical studies on the stem bark of Guibourtia tessmanii yielded a dihydrochalcone glucoside, 2′,4-dihydroxy-4′-methoxy-6′-O-β-glucopyranoside dihydrochalcone and a new stilbene glycoside, 3,5-dimethoxy-4′-O-(β-rhamnopyranosyl-(1→6)-β- glucopyranoside) stilbene besides the known pterostilbene. Their structures were established on the basis of one and two dimensional NMR spectroscopic techniques, FABMS and chemical evidence.     

Chiral macrocyclic compounds from lactose derivatives

The reaction of benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-isopropylidene-β-lactoside with 1,11-ditosyloxy-3,6,9-trioxaundecane gave benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-isopropylidene-3,2′-O--(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (2, 47%). Acid hydrolysis of 2 and condensation of the product with 1,14-ditosyloxy-3,6,9,12-tetra-oxatetradecane afforded benzyl 2,6,6′-tri-O-benzyl-3′,4′-O-(3,6,9,12-tetraoxa-tetradecane-1,14-diyl)-3,2′-O-(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (29%). Similarly, the reaction of benzyl 2,6,2′,4′,6′-penta-O-benzyl-β-lactoside with Ts[OCH₂CH₂]₄OTs gave benzyl 2,6,2′,4′,6′-penta-O-benzyl-3,3′-O-(3,6,9-trioxaundecane-1,11-diyl)-β-lactoside (78%). ¹H-N.m.r. spectroscopy has been used to study the formation of host-guest complexes with some of these macrocyclic compounds and benzyl ammonium thiocyanate.     

The structures of six urinary oligosaccharides that are characteristic for a patient with morquio syndrome type b

Morquio syndrome type B is an inherited, lysosomal storage disease characterised by a marked deficiency in acid β-d-galactosidase, while the 2-acetamido-2-deoxy-β-d-galactose 6-sulphate sulphatase activity is normal. Urinary oligosaccharides were studied in order to evaluate the effect of the diminished β-d-galactosidase activity on the catabolism of glycoconjugates and to compare their structures with those excreted by patients with GM₁-gangliosidosis. The following oligosaccharides were isolated: β-d-Galp-(1→4)-β-d-GlcpNAc-(1→2)-α-d-Manp-(1→6)-β-d-Manp-(1→4)- d-GlcpNAc (1), β-d-Galp-(1→4)-β-d-GlcpNAc-(1→2)-α-d-Manp-(1→6)-[α-d-Manp- (1→3)]-β-d-Manp-(1→4)-d-GlcpNAc (2a), β-d-Galp-(1→4)-β-d-GlcpNAc-(1→2)- α-d-Manp-(1→3)-[α-d-Manp-(1→6)]-β-d-Manp-(1→4)-d-GlcpNAc (2b), β-d-Galp- (1→4)-β-d-GlcpNAc-(1→2)-α-d-Manp-(1→3)-[β-d-Galp-(1→4)-β-d-GlcpNAc-(1→ 2)-α-d-Manp-(1→6)]-β-d-Manp-(1→4)-d-GlcpNAc (3), β-d-Galp-(1→4)-β-d-Glcp- NAc-(1→2)-α-d-Manp-(1→3)-{β-d-Galp-(1→4)-β-d-GlcpNAc-(1→2)-[β-d-Galp- (1→4)-β-d-GlcpNAc-(1→6)]-α-d-Manp-(1→6)}-β-d-Manp-(1→4)-d-GlcpNAc (4), β-d-Galp-(1→4)-β-d-GlcpNAc-(1→2)-α-d-Manp-(1→3)-[β-d-GlcpNAc-(1→4)]-[β- d-Galp-(1→4)-β-d-GlcpNAc-(1→2)-α-d-Manp-(1→6)]-β-d-Manp-(1→4)-d-Glcp- NAc (5). Significant differences between Morquio syndrome type B and GM₁-gangliosidosis have been observed, with regard to the excretion rate and the specific structures of urinary oligosaccharides. Compounds 2a, 2b, and 5 are novel members of the series of oligosaccharides isolated from the urine of patients with inherited, lysosomal storage diseases.     

Synthesis of a series of ganglioside GM3 analogs containing a deoxy-N-acetylneuraminic acid residue.

Ganglioside GM₃ analogs containing 4-, 7-, 8-, and 9-deoxy-N-acetylneuraminic acids in the place of N-acetylneuraminic acid (Neu5Ac) have been synthesized. Glycosylation of 2-(trimethylsilyl)ethyl O-(6-O-benzoyl-β- - galactopyranosyl)-(1 → 4)-2,6-di-O-benzoyl-β- -glucopyranoside with the methyl 2-thioglycoside derivatives of the respective deoxy-N-acetylneuraminic acids, using dimethyl(methylthio)sulfonium triflate as a promoter, gave the four required 2-(trimethylsilyl)ethyl -sialosyl-(2 → 3b)-β-lactosides. These were converted via O-acetylation, selective removal of the 2-(trimethylsilyl)ethyl group, and subsequent imidate formation, into the corresponding -sialosyl-(2 → 3b)--lactose trichloroacetimidates 15, 17, 19, and 21. Glycosylation of (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol with 15, 17, 19, and 21 in the presence of boron trifluoride etherate afforded the expected β glycosides, which were transformed in good yields, via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and de-esterification, into the target compounds.     

Biotransformation of paeonol by Panax ginseng root and cell cultures

Panax ginseng root and cell cultures were shown to biotransform paeonol (1) into its 2-O-β-d-glucopyranoside (2). P. ginseng root cultures were also able to biotransform paeonol (1) into its 2-O-β-d-xylopyranoside (3), 2-O-β-d-glucopyranosyl(1 → 6)-β-d-glucopyranoside (4) and 2-O-β-d-xylopyranosyl(1 → 6)-β-d-glucopyranoside (5), and its demethylated derivate, 2′,4′-dihydroxyacetophenone (6). Compounds 3 and 4 are new glycosides. It is the first example that the administrated compound was converted into its xylopyranoside by plant biotransformation.     

Cordiachromes from Auxemma oncocalyx

Further cordiachromes, rel-10,11β-epoxy-11-ethoxy-8-hydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10aβ-octahydro-1,4-anthracendione, 6-formyl-2-methoxy-9-methyl-7,8-dihydro-1,4-phenanthrendione, rel-8,11;9,11-diepoxy-1,4-dihydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10,10aβ-octahydro-10-anthracenone, rel-9,11-epoxy-1,4,8-trihydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10,10aβ-octahydro-10-anthracenone, rel-2″-methoxy-7″-methyl-1″,4″-naphtalendione-(6″→5)-tetrahydropyran-(2-eq→O→2ax)-tetrahydropyran-(5′→6)- 2-methoxy-7-methyl-1,4-naphthalendione, together with the known, allantoin, sitosterol and 3β-O-d-glucopyranosylsitosterol, have been isolated from Auxemma oncocalyx. Their structures were determined from spectral data, including 2D NMR experiments.     

Structure elucidation of the core octasaccharide from Citrobacter PCM 1487 with the aid of 500-MHz, two-dimensional phase-sensitive correlated, relayed-coherence transfer, double-quantum, triple-quantum filtered, and N.O.E. H-n.m.r. spectra

The main features of the primary structure of the octasaccharide, - -Glcp-(1→2)-- -Glcp-(1→2)-[- -GalpNAc- (1→3)]-- -Galp-(1→3)-- -Glcp-(1→3)-[- -Hepp-(1→7)]-- -Hepp-(1→3)-- -Hep, have been determined in the ab initio manner by ¹H-n.m.r. spectroscopy without resorting to biochemical methods of analysis. Several nontypical interresidue n.O.e. values point to a preferred solution conformation of the molecule.     

Catalytic properties of the endoxylanase I from Thermoascus aurantiacus

Endo-β-1,4-xylanase I previously purified from Thermoascus aurantiacus solid state culture was further characterized. The enzyme had a molecular weight of 33 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and 31 kDa by gel filtration. Thin layer chromatography (TLC) analysis showed that endoxylanase liberates aldotetrauronic acid MeGlcA-1,2-Xylβ-1,4-Xylβ-1,4-Xyl as the shortest acidic fragment from glucuronoxylan and an isomeric xylotriose (Xyl₃) of the structure Xylβ1-3Xylβ1-4Xyl from rhodymenan. The enzyme performed ideally on O-acetyl-4-O-methylglucuronoxylan, liberating large amounts of short acetylated and non-acetylated fragments. Also, the enzyme was capable to hydrolyse arabinoxylan to arabinose (Arab), xylose (Xyl) and xylobiose (Xyl₂). The enzyme degraded pNPX (4-nitrophenyl β- -xylopyranoside) by a complex reaction pathway that involved both hydrolysis and glycosyl transfer reactions. The enzyme tolerates the replacement of β-xylopyranosyl units in several artificial substrates by β-glucopyranosyl, - -arabinopyranosyl and - -arabinofuranosyl units and was active on pNPC (4-nitrophenyl β- -cellobioside), pNP-Arap (4-nitrophenyl - -arabinopyranoside) and pNPAraf (4-nitrophenyl - -arabinofuranoside). The enzyme also hydrolysed the 4-methylumbelliferyl glycosides of β- -xylobiose and β- -xylotriose at the agluconic linkage. The results suggested that the xylanase I from T. aurantiacus has catalytic properties similar to those belonging to family 10.     

Pustulan and branched β-galactofuranan from the phytopathogenic fungus Guignardia citricarpa, excreted from media containing glucose and sucrose

Guignardia citricarpa is a phytopathogenic fungus and the causal agent of citrus black spot. Incubation in a semi-defined media resulted in formation of exopolysaccharides [EPS(s)]. A medium containing glucose gave rise to a (1→6)-linked β-glucan (200 kD), pustulan, which was characterized by NMR and methylation analysis. A sucrose-containing medium provided a homogalactan (376 kD) and methylation analysis showed nonreducing end- (20%), 6-O- (53%) and 5,6-di-O-substituted Galf units (27%). An HMQC spectrum of the homogalactan showed C-1/H-1 signals at δ 108.2/4.820, 108.3/4.820 and 107.1/5.079, corresponding to three types of β- -Galf units. A DEPT analysis showed inverted signals (CH₂) at δ 67.8 and 67.2, corresponding to 6-O-substituted β- -Galf units, whereas a C-5 signal at δ 77.0 suggests 5-O-substitution, confirming a novel structure for a β-galactofuranan.