New saponins from Sechium mexicanum

The chemical study of Sechium mexicanum roots led to the isolation of the two new saponins {3‐O‐β‐D ‐glucopyranosyl (1 → 3)‐β‐D ‐glucopyranosyl‐2β,3β,16α,23‐tetrahydroxyolean‐12‐en‐28‐oic acid 28‐O‐α‐L ‐rhamnopyranosyl‐(1 → 3)‐β‐D ‐xylopyranosyl‐(1 → 4)‐α‐L ‐rhamnopyranosyl‐(1 → 2)‐α‐L ‐arabinopyranoside} (1) and {3‐O‐β‐D ‐glucopyranosyl (1 → 3)‐β‐D ‐glucopyranosyl‐2β,3β,16α,23‐tetrahydroxyolean‐12‐en‐28‐oic acid 28‐O‐α‐L ‐rhamnopyranosyl‐(1 → 3)‐β‐D ‐xylopyranosyl‐(1 → 4)‐[β‐D ‐apiosyl‐(1 → 3)]‐α‐L ‐rhamnopyranosyl‐(1 → 2)‐α‐L ‐arabinopyranoside} (2), together with the known compounds {3‐O‐β‐D ‐glucopyranosyl‐(1 → 3)‐β‐D ‐glucopyranosyl‐2β,3β,6β,16α,23‐pentahydroxyolean‐12‐en‐28‐oic acid 28‐O‐α‐L ‐rhamnopyranosyl‐(1 → 3)‐β‐D ‐xylopyranosyl‐(1 → 4)‐α‐L ‐rhamnopyranosyl‐(1 → 2)‐α‐L ‐arabinopyranoside} (3), tacacosides A₁ (4) and B₃ (5). The structures of saponins 1 and 2 were elucidated using a combination of ¹H and ¹³C 1D‐NMR, COSY, TOCSY, gHMBC and gHSQC 2D‐NMR, and FABMS of the natural compounds and their peracetylated derivates, as well as by chemical degradation. Compounds 1–3 are the first examples of saponins containing polygalacic and 16‐hydroxyprotobasic acids found in the genus Sechium, while 4 and 5, which had been characterized partially by NMR, are now characterized in detail. Copyright © 2009 John Wiley & Sons, Ltd.     

Flavonol Glycosides and Cytotoxic Triterpenoids from Alphitonia Philippinensis

Three new flavonol glycosides, namely, isorhamnetin 3‐O‐(6″‐O‐(Z)‐p‐coumaroyl)‐β‐D ‐glucopyranoside ( 1 ), quercetin 3‐O‐α‐L ‐rhamnopyranosyl(1 → 2)‐α‐L ‐arabinopyranosyl(1 → 2)‐α‐L ‐rhamnopyranoside ( 2 ), and quercetin 3‐O‐α‐L ‐arabinopyranosyl(1 → 2)‐α‐L ‐rhamnopyranoside ( 3 ), were isolated from the stems of Alphitonia philippinensis. Their structures were established by spectral analysis. In addition, NMR data were assigned for ceanothenic acid ( 11 ). Some of the isolated triterpenoids and flavonoid glycosides showed cytotoxicity against human PC‐3 cells and hepatoma HA22T cells, and inhibition of replication on herpes simplex virus type‐1.     

Structural and Kinetic Dissection of the endo‐α‐1,2‐Mannanase Activity of Bacterial GH99 Glycoside Hydrolases from Bacteroides spp.

Glycoside hydrolase family 99 (GH99) was created to categorize sequence‐related glycosidases possessing endo‐α‐mannosidase activity: the cleavage of mannosidic linkages within eukaryotic N‐glycan precursors (Glc_1–3Man₉GlcNAc₂), releasing mono‐, di‐ and triglucosylated‐mannose (Glc_1–3‐1,3‐Man). GH99 family members have recently been implicated in the ability of Bacteroides spp., present within the gut microbiota, to metabolize fungal cell wall α‐mannans, releasing α‐1,3‐mannobiose by hydrolysing αMan‐1,3‐αMan→1,2‐αMan‐1,2‐αMan sequences within branches off the main α‐1,6‐mannan backbone. We report the development of a series of substrates and inhibitors, which we use to kinetically and structurally characterise this novel endo‐α‐1,2‐mannanase activity of bacterial GH99 enzymes from Bacteroides thetaiotaomicron and xylanisolvens. These data reveal an approximate 5 kJ mol^?1 preference for mannose‐configured substrates in the ?2 subsite (relative to glucose), which inspired the development of a new inhibitor, α‐mannopyranosyl‐1,3‐isofagomine (ManIFG), the most potent (bacterial) GH99 inhibitor reported to date. X‐ray structures of ManIFG or a substrate in complex with wild‐type or inactive mutants, respectively, of B. xylanisolvens GH99 reveal the structural basis for binding to D ‐mannose‐ rather than D ‐glucose‐configured substrates.     

Flavonol Glycosides from the Leaves of Embelia Keniensis

Five new flavonol glycosides characterized as syringetin 3‐O‐α‐rhamnoside‐7‐O‐β‐glucoside, syringetin 3‐O‐α‐rhamnoside‐7,4′‐di‐O‐β‐glucoside, quercetin‐7‐O‐β‐galactosyl (1→3)‐β‐galactoside, myricetin 3‐O‐α‐rhamnosyl (1→4)‐β‐galactoside and myricetin 3‐O‐β‐glucosyl (1→2)‐β‐glucoside‐7‐O‐β‐glucosyl‐(1→4)‐α‐rhamnoside have been isolated from a methanolic extract of Embelia keniensis leaves. Known flavonols isolated from the same extract included myricetin, quercetin, kaempferol, myricetin 3‐O‐α‐rhamnoside, myricetin 3‐O‐β‐glucoside, quercetin 3‐O‐α‐rhamnoside, quercetin 3‐O‐β‐glucoside, quercetin 3‐O‐β‐xyloside, isorhamnetin 3‐O‐α‐rhamnoside and myricetin 3‐O‐rutinoside. Their structures were established from extensive spectroscopic and chemical studies and by comparison with authentic samples.     

Four new ursane‐type saponins from Morina nepalensis var. alba

Four new ursane‐type saponins, monepalosides C–F, together with a known saponin, mazusaponin II, were isolated from Morina nepalensis var. alba Hand.‐Mazz. Their structures were determined to be 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[alpha;‐L ‐rhamnopyranosyl‐(1 → 2)]‐α‐L ‐arabinopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside C, 1 ), 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[alpha;‐L ‐rhamnopyranosyl‐(1 → 2)]‐β‐D ‐xylopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside D, 2 ), 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[beta;‐D ‐glucopyranosy‐(1 → 2)]‐α‐L ‐arabinopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside E, 3 ) and 3‐O‐β‐D ‐xylopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranoside (monepaloside F, 4 ) on the basis of chemical and spectroscopic evidence. 2D NMR techniques, including ¹H–¹H COSY, HMQC, 2D HMQC‐TOCSY, HMBC and ROESY, and selective excitation experiments, including SELTOCSY and SELNOESY, were utilized in the structure elucidation and complete assignments of ¹H and ¹³C NMR spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Two new complex triterpenoid saponins from Gledistsia dolavayi Franch.

Two new triterpenoid saponins, gledistside A ( 1 ) and gledistside B ( 2 ), isolated from the fruits of Gledistsia dolavayi Franch., were characterized as the 3,28‐O‐bisdesmoside of echinocystic acid acylated with monoterpene carboxylic acids. On the basis of spectroscopic and chemical evidence, their structures were elucidated as 3‐O‐β‐D ‐xylopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐glucopyranosyl‐28‐O‐β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐xylopyranosyl‐(1→4)‐[β‐D ‐galactopyranosyl‐(1→2)]‐α‐L ‐rhamnopyranosyl‐(1→2)‐{6‐O‐[2,6‐dimethyl‐6(S)‐hydroxy‐2‐trans‐2,7‐octadienoyl]}‐β‐D ‐glucopyranosylechinocystic acid ( 1 ) and 3‐O‐β‐D ‐xylopyranosyl‐(1→2)‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐glucopyranosyl‐28‐O‐β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐xylopyranosyl‐(1→4)‐[β‐D ‐galactopyranosyl‐(1→2)]‐α‐L ‐rhamnopyranosyl‐(1→2)‐{6‐O‐[2‐hydroxymethyl‐6‐methyl‐6(S)‐hydroxy‐2‐trans‐2,7‐octadienoyl]}‐β‐D ‐glucopyranosylechinocystic acid ( 2 ). The complete ¹H and ¹³C assignments of saponins 1 and 2 were achieved on the basis of 2D NMR spectra including HMQC‐TOCSY, TOCSY, ¹H–¹H COSY, HMBC, ROESY and HMQC spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Xanthone O‐Glycosides from the Roots of Pteris Multifida

Two new xanthone glycosides and six known compounds were isolated from the roots of Pteris multifida. Based on spectroscopic and chemical methods, the structures of the new compounds were elucidated as 1‐hydroxy‐4,7‐dimethoxy‐8‐(3‐methyl‐2‐butenyl)‐6‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐[β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐glucopyranosylxanthone ( 1 ), and 1,3‐dihydroxy‐7‐methoxy‐8‐(3‐methyl‐2‐butenyl)‐6‐O‐α‐L‐rhamnopyranosyl‐(1 →2)‐[β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐glucopyranosylxanthone ( 2 ), respectively.     

Structure elucidation and complete NMR spectral assignments of two new oleanane‐type pentacyclic triterpenoid saponins from the husks of Xanthoceras sorbifolia Bunge

Two new saponins were isolated from husks of Xanthoceras sorbifolia Bunge and their structures were elucidated as 3‐O‐[β‐D‐galactopyranosyl(1→2)]‐α‐L‐arabinofuranosyl(1→3)‐β‐D‐methyl glucuronic acid‐21‐O‐(3,4‐diangeloyl)‐α‐L‐rhamnose‐3β, 16α, 21β, 22α, 28β‐pentahydroxyl‐22‐acetoxy‐olean‐12‐ene(1) and 3‐O‐[β‐D‐galactopyranosyl(1→2)]‐α‐L‐arabinofuranosyl(1→3)‐β‐D‐methyl glucuronic acid‐21,22‐O‐diangeloyl‐3β,15α,16α,21β,22α,28β‐hexahydroxyl‐olean‐12‐ene(2) on the basis of 1D and 2D NMR (including ¹H, ¹³C‐NMR, ¹H? ¹H COSY, HSQC, HMBC and DEPT), ESI‐MS spectrometry and chemical methods. Copyright © 2009 John Wiley & Sons, Ltd.     

A New and Practical Procedure for the Preparation of the Glucohexatose Phytoalexin Elicitor

The phytoalexin elicitor β-(1→3)-branched β-( 1→6)-linked glucohexatose has been regio- and stereospecifically synthesized by coupling of the 3, 6-branched gluco-trisaccharide Schmidt reagent 10 with a mixture of multiol 3,6-branched gluco-trisaccharides 13 which consists of free 5,6‘-OH trisaccharide, free 5,2‘ ,6‘-OH trisaccharide, free 5,3‘ ,6‘-OH trisaccharide and so on. The compounds 10 and 13 were prepared from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose , 2, 3, 4, 6-tetra-O-ben-zoyi-a-D-glucopyranosyl trichioroacetimldate, and 2,3,4, 6-tetra-O-acetyl-α-D-glucopyranosyl trichloreacetimidate through regio- and stereoselective manners.     

Detailed Investigation of the Immunodominant Role of O‐Antigen Stoichiometric O‐Acetylation as Revealed by Chemical Synthesis,Immunochemistry, Solution Conformation and STD‐NMR Spectroscopy for Shigella flexneri 3a

Shigella flexneri 3a causes bacillary dysentery. Its O‐antigen has the {2)‐[α‐d ‐Glcp‐(1→3)]‐α‐l ‐Rhap‐(1→2)‐α‐l ‐Rhap‐(1→3)‐[Ac→2]‐α‐l ‐Rhap‐(1→3)‐[Ac→6]_{≈40 %}‐β‐d ‐GlcpNAc‐(1→} ([(E)AB_AcC_AcD]) repeating unit, and the non‐O‐acetylated equivalent defines S. flexneri X. Propyl hepta‐, octa‐, and decasaccharides sharing the (E′)A′B_AcCD(E)A sequence, and their non‐O‐acetylated analogues were synthesized from a fully protected B_AcCD(E)A allyl glycoside. The stepwise introduction of orthogonally protected mono‐ and disaccharide imidate donors was followed by a two‐step deprotection process. Monoclonal antibody binding to twenty‐six S. flexneri types 3a and X di‐ to decasaccharides was studied by an inhibition enzyme‐linked immunosorbent assay (ELISA) and STD‐NMR spectroscopy. Epitope mapping revealed that the 2_C‐acetate dominated the recognition by monoclonal IgG and IgM antibodies and that the B_AcCD segment was essential for binding. The glucosyl side chain contributed to a lesser extent, albeit increasingly with the chain length. Moreover, tr‐NOESY analysis also showed interaction but did not reveal any meaningful conformational change upon antibody binding.     

Structural properties of D‐mannopyranosyl rings containing O‐acetyl side‐chains

The crystal structures of 1,2,3,4,6‐penta‐O‐acetyl‐α‐d ‐mannopyranose, C₁₆H₂₂O₁₁, and 2,3,4,6‐tetra‐O‐acetyl‐α‐d ‐mannopyranosyl‐(1→2)‐3,4,6‐tri‐O‐acetyl‐α‐d ‐mannopyranosyl‐(1→3)‐1,2,4,6‐tetra‐O‐acetyl‐α‐d ‐mannopyranose, C₄₀H₅₄O₂₇, were determined and compared to those of methyl 2,3,4,6‐tetra‐O‐acetyl‐α‐d ‐mannopyranoside, methyl α‐d ‐mannopyranoside and methyl α‐d ‐mannopyranosyl‐(1→2)‐α‐d ‐mannopyranoside to evaluate the effects of O‐acetylation on bond lengths, bond angles and torsion angles. In general, O‐acetylation exerts little effect on the exo‐ and endocyclic C—C and endocyclic C—O bond lengths, but the exocyclic C—O bonds involved in O‐acetylation are lengthened by ～0.02 Å. The conformation of the O‐acetyl side‐chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2°‐alcoholic C atom or bisecting the H—C—H bond angle of a 1°‐alcoholic C atom. Of the two C—O bonds that determine O‐acetyl side‐chain conformation, that involving the alcoholic C atom exhibits greater rotational variability than that involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of O‐acetyl side‐chain conformations in saccharides. Experimental evidence was also obtained to confirm density functional theory (DFT) predictions of C—O and O—H bond‐length behavior in a C—O—H fragment involved in hydrogen bonding.     

Two new acylated flavonoid glycosides from Morina nepalensis var. alba Hand.‐Mazz.

From the whole plant of Morina nepalensis var. alba Hand.‐Mazz., two new acylated flavonoid glycosides ( 1 and 2 ), together with four known flavonoid glycosides ( 3–6 ), were isolated. Their structures were determined to be quercetin 3‐O‐[2″′‐O‐(E)‐caffeoyl]‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐galactopyranoside (monepalin A, 1 ), quercetin 3‐O‐[2″′‐O‐(E)‐caffeoyl]‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐glucopyranoside (monepalin B, 2 ), quercetin 3‐O‐α‐L ‐arabinopyranosyl‐(1→6)‐β‐D ‐galactopyranoside (rumarin, 3 ), quercetin 3‐O‐β‐D ‐galactopyranoside ( 4 ), quercetin 3‐O‐β‐D ‐glucopyranoside ( 5 ) and apigenin 4^′‐O‐β‐D ‐glucopyranoside ( 6 ). Their structures were determined on the basis of chemical and spectroscopic evidence. Complete assignments of the ¹H and ¹³C NMR spectra of all compounds were achieved from the 2D NMR spectra, including H–H COSY, HMQC, HMBC and 2D HMQC‐TOCSY spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of Lacto‐ and Neolacto‐series Ganglioside Analogs Containing N‐Glycolylneuraminic Acid: Probes for Investigation of Specific Receptor Structures Recognized by Influenza A Viruses

Sialic acids are essential components of host‐cell surface receptors for infection of influenza virus. To investigate the specific receptor structures recognized by various influenza A viruses, a series of lacto‐ and neolacto‐series ganglioside analogs containing N‐glycolylneuraminic acid (Neu5Gc) have been synthesized. The pentasaccharide structures of Neu5Gc‐α‐(2→3)/(2→6)‐lactotetraose (IV³⁽⁶⁾Neu5GcLcOse) and Neu5Gc‐α‐(2→3)/(2→6)‐neolactotetraose (IV³⁽⁶⁾Neu5GcnLcOse) were constructed by glycosylation of the suitably protected trisaccharide acceptors (2A and 2B) with the Neu5Gc‐α‐(2→3)/(2→6)‐Gal trichloroacetimidate donors (1 and 21), respectively. Transformation of the 2‐(trimethylsilyl)ethyl group at the reducing end in 4, 11, 23, and 30 into the trichloroacetimidate group gave a series of Neu5Gc‐α‐(2→3)/(2→6)‐lacto‐ and neolactotetraose donors (7, 13, 26, and 33), which were coupled with 2‐(tetradecyl)hexadecanol (8), to give the corresponding glycolipids (9, 14, 27, and 34). Finally, the complete removal of the O‐acyl groups and saponification of the methyl ester group gave the desired ganglioside analogs (10, 15, 28, and 35).     

Synthesis of Cryptococcus neoformans Capsular Polysaccharide Structures. IV. Construction of Thioglycoside Donor Blocks and Their Subsequent Assembly

Di‐ and trisaccharide thioglycoside building blocks, ethyl (2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→2)‐3‐O‐allyl‐4,6‐di‐O‐benzyl‐1‐thio‐α‐d‐mannopyranoside, ethyl (2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→2)‐6‐O‐acetyl‐3‐O‐allyl‐4‐O‐benzyl‐1‐thio‐α‐d‐mannopyranoside and ethyl (2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→4)‐[(2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→2)]‐3‐O‐allyl‐6‐O‐benzyl‐1‐thio‐α‐d‐mannopyranoside, corresponding to repetitive structures in the capsular polysaccharide (CPS) of Cryptococcus neoformans have been synthesised using silver triflate‐promoted couplings between benzobromoxylose and properly protected mannose ethyl thioglycosides. The blocks contain an orthogonal allyl group in the 3‐position of the mannose residue to allow continued formation of the (1→3)‐linked mannan backbone of the CPS. They have benzyl ethers as persistent protecting groups to facilitate access to the acetylated target structures. Assembly of the blocks employing DMTST as promoter in diethyl ether afforded in high yield and complete stereoselectivity penta‐ and hexasaccharide motifs from C. neoformans serotype A–C. The latter were deallylated into new acceptors to allow synthesis of larger CPS‐fragments.     

The achiral tetrapeptide Z‐Aib‐Aib‐Aib‐Gly‐OtBu

The title achiral peptide N‐benzyloxycarbonyl‐α‐aminoisobutyryl‐α‐aminoisobutyryl‐α‐aminoisobutyrylglycine tert‐butyl ester or Z‐Aib‐Aib‐Aib‐Gly‐OtBu (Aib is α‐aminoisobutyric acid, Z is benzyloxycarbonyl, Gly is glycine and OtBu indicates the tert‐butyl ester), C₂₆H₄₀N₄O₇, is partly hydrated (0.075H₂O) and has two different conformations which together constitute the asymmetric unit. Both molecules form incipient 3₁₀‐helices. They differ in the relative orientation of the N‐terminal protection group and at the C‐terminus. There are two 4→1 intramolecular hydrogen bonds.     

Synthesis of benzyl O-(2,3,3'-tri-O-acetyl-β-D-apiofuranosyl)-(1→3)-2,4-di-O-benzoyl-α-D-xylopyranoside and its X-ray structure

The protected apiose-containing disaccharide, benzyl O-(2,3, 3'-tri-O-acetyl-β-D-apiofuranosyl)-( 1→3)-2, 4-di-O-benzoyl-α-D-xylopyranoside, was synthesized and its X-ray structure provided.     

Fluorinated Carbohydrates as Lectin Ligands: Dissecting Glycan–Cyanovirin Interactions by Using 19F NMR Spectroscopy

NMR spectroscopy and isothermal titration calorimetry (ITC) are powerful methods to investigate ligand–protein interactions. Here, we present a versatile and sensitive fluorine NMR spectroscopic approach that exploits the ¹⁹F nucleus of ¹⁹F‐labeled carbohydrates as a sensor to study glycan binding to lectins. Our approach is illustrated with the 11 kDa Cyanovirin‐N, a mannose binding anti‐HIV lectin. Two fluoro‐deoxy sugar derivatives, methyl 2‐deoxy‐2‐fluoro‐α‐D ‐mannopyranosyl‐(1→2)‐α‐D ‐mannopyranoside and methyl 2‐deoxy‐2‐fluoro‐α‐D ‐mannopyranosyl‐(1→2)‐α‐D ‐mannopyranosyl‐(1→2)‐α‐D ‐mannopyranoside were utilized. Binding was studied by ¹⁹F NMR spectroscopy of the ligand and ¹H–¹⁵N HSQC NMR spectroscopy of the protein. The NMR data agree well with those obtained from the equivalent reciprocal and direct ITC titrations. Our study shows that the strategic design of fluorinated ligands and fluorine NMR spectroscopy for ligand screening holds great promise for easy and fast identification of glycan binding, as well as for their use in reporting structural and/or electronic perturbations that ensue upon interaction with a cognate lectin.     

The peptide Z‐Aib‐Aib‐Aib‐L‐Ala‐OtBu

The title peptide, N‐benzyloxycarbonyl‐α‐aminoisobutyryl‐α‐aminoisobutyryl‐α‐aminoisobutyryl‐L‐alanine tert‐butyl ester or Z‐Aib‐Aib‐Aib‐L‐Ala‐OtBu (Aib is α‐aminoisobutyric acid, Z is benzyloxycarbonyl and OtBu indicates the tert‐butyl ester), C₂₇H₄₂N₄O₇, is a left‐handed helix with a right‐handed conformation in the fourth residue, which is the only chiral residue. There are two 4→1 intramolecular hydrogen bonds in the structure. In the lattice, molecules are hydrogen bonded to form columns along the c axis.     

Inositolphosphoglycan Mediators: An Effective Synthesis of the Conserved Linear GPI Anchor Structure*

An effective new preparative synthesis of the conserved linear pseudopentasaccharide structure of the GPI anchors and of the full GPI structure has been carried out that has permitted obtaining both molecules in sufficient quantities as to perform further structural and biologic studies. The synthesis involves a 3+2 block synthesis strategy in which a conveniently protected Man α(1→4) GlcN₃ α(1→6) myo‐Ins building block, previously used in the synthesis of inositolphosphoglycan (IPG) mediators, is glycosylated with a protected Man α(1→2) Man trichloroacetimidate.     

Structure elucidation of new acacic acid‐type saponins from Albizia coriaria

Three new acacic acid derivatives, named coriariosides C, D, and E ( 1–3 ) were isolated from the roots of Albizia coriaria. Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR studies and mass spectrometry as 3‐O‐[β‐D ‐xylopyranosyl‐(1 → 2)‐β‐D ‐fucopyranosyl‐(1 → 6)‐2‐(acetamido)‐2‐deoxy‐β‐D ‐glucopyranosyl]‐21‐O‐{(2E,6S)‐6‐O‐{4‐O‐[(2E,6S)‐2,6‐dimethyl‐ 6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐β‐D ‐quinovopyranosyl}‐2,6‐dimethylocta‐2,7‐dienoyl}acacic acid 28‐O‐β‐D ‐xylopyranosyl‐(1 → 4)‐α‐L ‐rhamnopyranosyl‐(1 → 2)‐β‐D ‐glucopyranosyl ester ( 1 ), 3‐O‐{β‐D ‐fucopyranosyl‐(1 → 6)‐[β‐D ‐glucopyranosyl‐(1 → 2)]‐β‐D ‐glucopyranosyl}‐21‐O‐{(2E,6S)‐6‐O‐{4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl]‐β‐D ‐quinovopyranosyl}‐2,6‐dimethylocta‐2,7‐dienoyl}acacic acid 28‐O‐α‐L ‐rhamno pyranosyl‐(1 → 2)‐β‐D ‐glucopyranosyl ester ( 2 ), and 3‐O‐[β‐D ‐fucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranosyl]‐21‐O‐{(2E,6S)‐6‐O‐{4‐O‐[(2E,6S)‐2,6‐dimethyl‐6‐O‐(β‐D ‐quinovopyranosyl)octa‐2,7‐dienoyl)‐β‐D ‐quinovopyranosyl]octa‐2,7‐dienoyl}acacic acid 28‐O‐β‐D ‐glucopyranosyl ester ( 3 ). Copyright © 2010 John Wiley & Sons, Ltd.