Addition of 1-nitroalkanes to methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside and N6-benzoyl-2′,3′-O-isopropylideneadenosine-5′-aldehyde

Various 1-nitroalkanes reacted with methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside to yield methyl 6-alkyl-6-deoxy-2,3-O-isopropylidene-6-nitro-β-d-ribofuranosides in 64–79% yield. Similarly, nitromethane and 1-nitropentane reacted with N⁶-benzoyl-2′,3′-O-isopropylideneadenosine-5′-aldehyde, to yield the corresponding 9-[6-alkyl-6-deoxy-2,3-O-isopropylidene-6-nitro-α-l-talo(β-d-allo)furanosyl]-N⁶-benzoyladenines in 74 and 44% yield, respectively. The potential utility of this nitroalkane addition for the synthesis of nucleosides having a C-5′C-6′ bond is discussed.     

OLIGOSACCHARIDE STORAGE IN BRAINS FROM PATIENTS WITH FUCOSIDOSIS,GM1-GANGLIOSIDOSIS AND GM2-GANGLIOSIDOSIS (SANDHOFF'S DISEASE)1

Abstract— Analysis of whole autopsy brain from a patient with fucosidosis (α-fucosidase deficiency) revealed minor storage of H-antigen glycolipid [Fuc (α, 1→2) Gal-GlcNAc-Gal-Glc-Ceramide] and a slightly abnormal ganglioside composition in the form of a two-fold elevation of G_M1 and the presence of a fucose-containing glycolipid (a minor component) which co-migrated with G_D1a. The major storage materials in fucosidosis brain were an oligosaccharide (Fuc-Gal-GlcNAc-Man[Fuc-Gal-GlcNAc-Man]-ManGlcNAc) and a disaccharide [Fuc(α, 1→6)-GlcNAc] in the approximate ratio of 5:1. Lesser amounts of a related oligosaccharide (Gal-GlcNAc-Man[Gal-GlcNAc-Man]-Man-GlcNAc) were isolated from the brain of patients with G_M1-gangliosidosis (Types I and II) where the major storage material is known to be G_M1-ganglioside (Gal (β, 1→3)GalNAc(β, 1→4) [NeuNAcf(α, 2→3) Gal(β, 1→4)Glc-Ceramide). Similarly, a related oligosaccharide (GlcNAc-Man [GlcNAc-Man]-Man-GlcNAc) was isolated from the brain of a patient with a total deficiency of N-acetyl-β-d -hexosaminidase (Sandhoff variant of G_M2-gangliosidosis) where the major storage products are known to be G_M2-ganglioside (GalNAc (β 1→4) [NeuNAc (α, 2→3)Gal(β, 1→4)Glc-Ceramine) and its asialo derivative. These studies indicate that glycoproteins containing at least 2 mol of l -fucose per oligosaccharide unit are normally catabolized in human brain. Further, it appears that such glycoproteins are initially catabolized by an endo-N-acetylglucosaminidase to release an oligosaccharide which is then degraded by the sequential action of exo-glycosidases.     

Chemical structures of oligosaccharides in milk of the raccoon (<Emphasis Type="Italic">Procyon lotor</Emphasis>)

In this study on milk saccharides of the raccoon (Procyonidae: Carnivora), free lactose was found to be a minor constituent among a variety of neutral and acidic oligosaccharides, which predominated over lactose. The milk oligosaccharides were isolated from the carbohydrate fractions of each of four samples of raccoon milk and their chemical structures determined by ¹H-NMR and MALDI-TOF mass spectroscopies. The structures of the four neutral milk oligosaccharides were Fuc(α1–2)Gal(β1–4)Glc (2′-fucosyllactose), Fuc(α1–2)Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)Glc (lacto-N-fucopentaose IV), Fuc(α1–2)Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)Glc (fucosyl para lacto-N-neohexaose) and Fuc(α1–2)Gal(β1–4)GlcNAc(β1–3)[Fuc(α1–2)Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (difucosyl lacto-N-neohexaose). No type I oligosaccharides, which contain Gal(β1–3)GlcNAc units, were detected, but type 2 saccharides, which contain Gal(β1–4)GlcNAc units were present. The monosaccharide compositions of two of the acidic oligosaccharides were [Neu5Ac]₁[Hex]₆[HexNAc]₄[deoxy Hex]₂, while those of another two were [Neu5Ac]₁[Hex]₈[HexNAc]₆[deoxy Hex]_3. These acidic oligosaccharides contained α(2–3) or α(2–6) linked Neu5Ac, non reducing α(1–2) linked Fuc, poly N-acetyllactosamine (Gal(β1–4)GlcNAc) and reducing lactose.     

Stereoselective synthesis of spiro and condensed pyrazolines of steroidal α,β-unsaturated ketones and nitrilimines by 1,3-dipolar cycloaddition

Effective syntheses of endo- and exocyclic α,β-unsaturated ketones as CC dipolarophiles were carried out in the 13α-estrone series. The 1,3-dipolar cycloadditions of 15,16α,β-unsaturated ketones of 13α-estrone 3-methyl and 3-benzyl ether with nitrilimines stereoselectively furnished two regioisomers of new condensed pyrazolines in a ratio of 2:1. The main product was the isomer obtained by the attack of the N-terminus of the 1,3-dipole on the carbon atom β to the carbonyl group of the dipolarophile. The nitrilimine cycloadditions to the 16-methylene-17-ketones of 13α-estrone 3-methyl and 3-benzyl ether stereo- and regioselectively furnished spiropyrazolines. The attack of the N-terminus of the dipole occurred on the α-carbon of the α,β-unsaturated ketones. The reactions were performed under both homogeneous and heterogeneous conditions. Silver acetate as a base proved more effective than its triethylamine counterpart. Changes in regio- and stereoselectivities were not observed on variation of the conditions of the cycloaddition reactions. The structures of the new products were determined by NMR (one- and two-dimensional) and MALDI TOF MS techniques, with C₇₀ fullerenes as matrix in the latter case.     

endo/exo Stereoselectivity in DielsAlder Reactions of α,β‐Dialkylated Conjugated Enals to Cyclic 1,3‐Dienes: Intermediates in the Synthesis of (−)‐β‐Santalol and Its Analogs

Highly exo‐selective [4+2] cycloadditions of cyclopenta‐1,3‐diene 2a to α,β‐dialkyl conjugated enals 5 are compared with the analogous endo‐favored Diels? Alder reaction of cyclohexa‐1,3‐diene 7 . The exo‐stereoselectivity is lower in the homologous case of methylcyclopenta‐1,3‐diene 9 . This diastereoselectivity is discussed either in terms of a retro‐homo‐Diels? Alder reaction, associated with thermodynamic control, or with respect to either a competing hetero‐Diels? Alder/Claisen or Cope domino pathway, or retro‐Claisen/retro‐hetero‐Diels? Alder of the endo‐homo‐cycloadducts. These hypothetical mechanisms have been examined by DFT calculations at the MPW1K(CH₂Cl₂)/6‐31+G** level of theory for the AlCl₃‐mediated cycloadditions of 5d to 2a and 7 . Application of Corey's methodology to the γ‐halogeno‐α‐methyl‐substituted dienophiles 5a and 5b allowed an enantioselective preparation of known and useful intermediates for the synthesis of either the naturally occurring (?)‐β‐santalol or its potentially olfactive structural analogs.     

N-Substituted acetamide glycosides from the stems of Ephedra sinica

Five new N-mono-/bis-substituted acetamide glycosides, N-{4-O-[3-O-(4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (1), N-methyl-N-{4-O-[3-O-(4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (2), N-methyl-N-{4-O-[3-O-(6-O-benzoyl-4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (3), N-methyl-N-{4-O-[3-O-(6-O-benzoyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (4), and N-methyl-N-{4-O-[3-O-(6-O-trans-cinnamoyl-4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (5), along with one known acetamide derivative, N-methyl-N-(4-hydroxyphenethyl)-acetamide, the shared aglycone of 2–5, were isolated from the ethanol extract of the stems of Ephedra sinica. The structures of these new compounds were elucidated on the basis of extensive spectroscopic examination, mainly including multiple 1D and 2D NMR and HRESIMS examinations, and qualitative chemical tests. All N,N-bissubstituted acetamide glycosides were found to show the obvious rotamerism, as in the case of the isolated known N-methyl-N-(4-hydroxyphenethyl)-acetamide, under the experimental NMR conditions, with the ratios of integrated intensities between anti- and syn-rotamers always being found to be about 4 to 3.     

Diazomethane-catalysed rearrangement of α-d-glucopyranosyl esters of N-acylamino acids into 2-O-acylaminoacyl-α-d-glucopyranoses

Both anomers of 1-O-[N-(tert-butoxycarbonyl)-L-α-glutamyl]-d-glucopyranose (2) were converted into the unprotected 1-esters, characterised as the trifluoroacetate salts 3α and 3β. On esterification with diazomethane and acetylation, the N-acetylated derivative of 3β and 2β gave the peracetylated 1-O-[5-methyl N-acetyl- and -tert-butoxycarbonyl-L-glutam-1-oyl]-β-d-glucopyranoses (4β and 6β), respectively. Similar treatment of 2α and 3β led to acyl migration, to yield 1,3,4,6-tetra-O-acetyl-2-O-[5-methyl N-(tert-butoxycarbonyl)-L-glutam-1-oyl]-α-d-glucopyranose (7α,64%) with traces of 7β, and a mixture (≈2:1:0.2) of the N-acetyl analogue of 7α (8α), 4α, and 8β, respectively. Treatment of 1-O-[5-methyl N-(tert-butoxycarbonyl)-L-glutam-1-oyl]-α-d-glucopyranose (10) and the corresponding glutam-5-oyl isomer 12 in N,N-dimethylformamide with diazomethane for 1 h resulted in 1 → 2 O-acyl transfer to give, upon acetylation, 7α and the fully acetylated 2-O-[1-methyl N-(tert-butoxy- carbonyl)-L-glutam-5-oyl]-α-d>-glucopyranose in yields of 70 and 90 %, respectively; in the absence of diazomethane, 10 and 12 remained unchanged. Similar experiments with α-d-glucopyranosyl esters of N-acetylglycine, N-acetylalanine, and N-(tert-butoxycarbonyl)phenylalanine yielded the 2-O-acyl derivatives in high yields and with high retention of anomeric configuration. The structures of the rearrangement products were proved both spectroscopically and chemically. The results imply that diazomethane functions as a base in the migration process.     

Synthesis of New 5″-Sulfonylamido Derivatives of 3″-Azido-3″-Deoxythymidine (AZT)

Abstract

A series of 5′-N-methanesulfonyl derivatives of 3′-azido-5′-(alkylamino)-3′,5′-dideoxythymidine was synthesised. The first step of the synthesis involved the reaction of 1-(2,5-dideoxy-5-O-tosyl-β-D-threo-pentofuranosyl)thymine 1 with an appropriate amine to give 1-[5-(alkylamino)-2,5-dideoxy-β-D-threo-pentofuranosyl]thymines 2a-e and 1-(2,5-dideoxy-β-threo-pent-4-enofuranosyl)thymine 3 as a by-product. Compounds 2a-e were treated with an excess of methanesulfonyl chloride to yield intermediates 1-[5-(dimethylamino)-3-O-methanesulfonyl-2,3,5-trideoxy-β-D-threo-pentofuranosyl]-thymine 4a and 1-[5-(N-alkyl-N-methanesulfonyl)-3-O-methanesulfonyl-2,3,5-trideoxy-β-D-threo-penfuranosyl]thymines 4b-e. The reaction of 4a-e with lithium azide in dimethyl-formamide afforded the final compounds 1-[3-azido-5-(N-methyl-N-methanesulfonyl)-2,3,5-trideoxy-β-D-erythro-penofuranosyl]thymine 5a and 1-[3-azido-5-(N-alkyl-N-methanesulfonyl)-2,3,5-trideoxy-β-D-erythro-penofuranosyl]thymines 5b-e. The independent synthesis of 4′,5′-unsaturated product 3 was also described.     

A new hexasaccharide chain isolated from bovine colostrum κ-casein taken at the time of parturition

The carbohydrate units linked to caseinoglycopeptide from colostrum taken 30 min after parturition were released as reduced oligosaccharides by alkaline borohydride treatment, and separated into four acidic oligosacchariditols (a hexa- (11.0%), penta- (38.5%), tetra- (35.5%) and a trisacchariditol (15.0%)). Structural studies showed that the hexasacchariditol was a new structure and had the chemical structure: NeuNAc-α-2-3-Gal-β-1-3-[NeuNAc-α-2-3-Gal-β-1-4-GlcNAc-β-1-6-]-N-acetylgalactosaminitol(GalNAcItol). The other three oligosacchariditols were shown to be NeuNAc-α-2-3-Gal-β-1-3-[Gal-β-1-4-GlcNac- β-1-6-]-GalNAcItol, NeuNAc-α-2-3-Gal-β-1-3-[NeuNAc-α-2-6-]-GalNAcItol and NeuNAc-α-2-3-Gal-β-1-3- GalNAcItol, which were identical with those found previously in colostrum κ-casein taken 6 h after parturition.     

Structural Determination of Monosialyl Trisaccharides Obtained From Caprine Colostrum

Acidic oligosaccharides were separated by dialysis, ion-exchange, preparative paper and gel chromatography from caprine colostrum. Four sialyl trisaccharides were characterized by ¹H-NMR spectrometry as follows: α-N-acetylneuraminyl-(2,6)-β-d-galactopyranosyl-(1,4)-2-N-acetamido-2-deoxy-d-glucopyranose (Neu5Ac α 2-6Gal β 1-4GlcNAc), α-N-acetylneuraminyl-(2,3)-β-d-galactopyranosyl-(1,4)-d-glucopyranose (Neu5Ac α 2-3Gal β-1-4Glc), α-N-acetylneuraminyl-(2,6)-β-d-galactopyranosyl-(1,4)-d-glucopyranose (Neu5Ac α 2-6Gal β 1-4Glc) and α-N-glycolylneuraminyl-(2,6)-β-d-galactopyranosyl-(1,4)-d-glucopyranose (Neu5Gc α 2-6Gal β 1-4Glc).     

Molecular Species of Ceramide and Mono-, Di-, Tri-, and Tetraglycosylceramide in Bran and Endosperm of Rice Grains

Ceramide and mono-, di-, tri-, and tetraglycosylceramide were isolated from the bran and endosperm of rice grains and chemically characterized. The detailed compositions of free ceramide were somewhat different between the bran and endosperm, but those of the ceramide moiety in glycosylceramides were substantially the same. There was a tendency in all the sphingolipid molecules in rice grains for hydroxy acids with C₂₀ to be combined largely with the dihydroxy bases while hydroxy acids with C_24< combined mainly with the trihydroxy bases. Representative molecular species of the sphingolipid classes were concluded to be as follows: for ceramide N-2′-hydroxylignoceroyl-4-hydroxysphinganine, for monoglycosylceramide l-O-β-glucosyl-N-2′-hydroxyarachidoyl-4,8-sphingadienine, for diglycosylceramide 1-O-[β-mannosyl(1→-4)-O-β-glucosyl]- and 1-O-[β-glucosyl(1→4)-O-β-glucosyl]-N-2′-hydroxylignoceroyl-4-hydroxy-8-sphingenine, for triglycosylceramide l-O-[β-mannosyl(1→4)-O-β-mannosyl(l→4)-O-β-glucosyl]- and l-O-[β-glucosyl(l→4)-O-β-mannosyl(1→4)-O-β-glucosyl]-N-2′-hydroxylignoceroyl-4-hydroxy-8-sphingenine, and for tetraglycosylceramide 1-0-[β-mannosyl(l→4)-O-β-mannosyl (1→4)-O-β-mannosyl(1→4)-O-β-glucosyl]- and l-O-[β-glucosyl(1→4)-O-β-mannosyl(l→4)-O-β-mannosyl(1β4)-O-β-glucosyl]-N-2′-hydroxylignoceroyl-4-hydroxy-8-sphingenine.     

Expression of a new disialyllacto structure in the lipopolysaccharide of non-typeable Haemophilus influenzae

The structure of lipopolysaccharide (LPS) expressed by non-typeable Haemophilus influenzae (NTHi) strains 1008 and 1247 has been investigated by mass spectrometry and NMR analyses on O-deacylated LPS and core oligosaccharide material. Both strains express the conserved triheptosyl inner core, [l-α-d-Hepp-(1→2)-[PEtn→6]-l-α-d-Hepp-(1→3)-l-α-d-Hepp-(1→5)-[PPEtn→4]-α-Kdo-(2→6)-Lipid A] with PCho→6)-β-d-Glcp (GlcI) substituting the proximal heptose (HepI) at O-4. Strain 1247 expresses the common structural motifs of H. influenzae; globotetraose [β-d-GalpNAc-(1→3)-α-d-Galp-(1→4)-β-d-Galp-(1→4)-β-d-Glcp-(1→] and its truncated versions globoside [α-d-Galp-(1→4)-β-d-Galp-(1→4)-β-d-Glcp-(1→] and lactose [β-d-Galp-(1→4)-β-d-Glcp-(1→] linked to the terminal heptose of the inner core and GlcI. A genetically distinct NTHi strain, 1008, expresses identical structures to strain 1247 with the exception that it lacks GalNAc. A lpsA mutant of strain 1247 expressed LPS of reduced complexity that facilitated unambiguous structural determination of the oligosaccharide from HepI. By CE-ESI-MS/MS we identified disialylated glycoforms indicating disialyllactose [α-Neu5Ac-(2→8)-α-Neu5Ac-(2→3)-β-d-Gal-(1→4)-β-d-Glcp-(1→] as an extension from GlcI which is a novel finding for NTHi LPS.     

Two new steroidal saponins from Dioscorea panthaica

Two new furostanol saponins, 3-O-[α-l-rhamnopyranosyl-(1→4)-β-d-glucopyranosyl]-26-O-β-d-glucopyranosyl-25(R)-furosta-5,22(23)-dien-3β,20α,26-triol (1), 3-O-[β-d-glucopyranosyl-(1→3)-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl]-26-O-β-d-glucopyranosyl-20(R)-methoxyl-25(R)-furosta-5,22(23)-dien-3β,26-diol (2) were isolated from the Dioscorea panthaica along with five known steroidal saponins (3–7). The structures of the new saponins were determined by detailed analysis of spectral data (including 2D NMR spectroscopy). The inhibitory activities of the saponins against α-glucosidase were investigated, gracillin (4) and 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl]-26-O-β-d-glucopyranosyl-25(R)-furosta-5,20(22)-dien-3β,26-diol (5) were found to exhibit potent activities with IC₅₀ values of 0.11 ± 0.04 mM and 0.09 ± 0.01 mM.     

Forssman hapten N-acetyl-alpha-D-galactosaminidase in rat brain and kidney

—Forssman hapten (N-acetyl-α-galactosaminosyl-N-acetyl-β-galactosaminosyl-α-galactosyl-β-galactosyl-glucosylceramide), prepared from sheep erythrocytes was specifically labelled with tritium at the terminal N-acetyl-α-galactosamine moiety by the galactose oxidase-sodium [³H]borohydride method. Activities to cleave the terminal N-acetyl-α-galactosamine from Forssman hapten were detected in the high-speed supernatant of the frozen-thawed and sonicated crude mitochondrial fraction from adult rat brain and kidney. The optimal pH of the reaction was approximately 4·4. The reaction was linear for at least 1 h for the kidney enzyme and up to 3 h for the brain enzyme. Taurocholate was required for the activity. The optimal concentration was 1·5-2 mg/ml. Several other detergents and bile salts tested could not replace taurocholate. The apparent K_m of the brain and kidney enzymes were 1·0×10^?4M and 3·5×10^?4m , respectively. During development, Forssman hapten-cleaving activities of both brain and kidney gradually declined in specific activity as the animal matured. These changes were similar to those of nonspecific p-nitrophenyl N-acetyl-α-galactosaminidase. Several rat organs examined all showed detectable activities to cleave Forssman hapten.     

Nucleosides and Nucleotides. 139. Stereoselective Synthesis of (2′S)-2′-C-Alkyl-2′-deoxyuridines

Abstract

A synthetic method for (2′S)-2′-C-alkyl-2′-deoxyuridines (9) has been described. Catalytic hydrogenation of 1-[2-C-alkynyl-2-O-methoxalyl-3,5-O-TIPDS-β-D-arabino-pentofuranosyl]uracils (5) gave 1-[2-C-(2-alkyl)-2-O-methoxalyl-3,5-O-TIPDS-β-D-arabino-pentofuranosyl]uracils (4) as a major product, which were then subjected to the radical deoxygenation, affording (2′S)-2′-alkyl-2′-deoxy-3′,5′-O-TIPDS-uridines (7) along with a small amount of their 2′R epimers.

     

Beshornin and beshornoside,steroidal saponins of Beshorneria yuccoides

Two new saponins beshornin and beshornoside have been isolated from the methanolic extract of Beshorneria yuccoides leaves and their structures elucidated. Beshornin is 3-O-[α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl- (1 → 2)-[α-l-rhamnopyranosyl-(1 -+ 4)-P-D-glucopyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d- galactopyranosyl-(25R)-5α-spirostan-3β-ol, whereas beshornoside is 3-O-[α-l-rhamnopyranosyl-(1 → 4)- β-d)-glycopyranosyl-(1 → 2)]-[α-l-rhamnopyranosyl-(1 → 4)-β-d-glucopyranosyl-(1 → 3)]-β-d-glucopyranosyl- (1 → 4)-β-d-galactopyranosyl 26-O-[β-d]-glucopyranosyl-(25R)-5α-furostan-3β,22α,26-triol.     

Cleavage of oligosaccharides by rat kidney sialidase Influence of substrate structure

The specificity of the sialidase activity present in rat kidney cortex (12 000 × g pellet) was studied with various tritiated oligosaccharidic substrates: (i) αNeuAc2 → 3βGall → 4Glc-itol[³H], αNeuAc2 → 6βGall → 4Glc-itol[³H] and αNeuAc2 → 8αNeuAc2 → 3βGall → 4Glc-itol[³H] from bovine colostrum; (ii) α-NeuAc2 → 6βGall → 4βGlcNAc-itol[³H], αNeuAc2 → 3βGal1 → 4βGlcNAcl → 2αManl → 3βMan1 → 4GlcNAc-itol[³H]. αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl α 3(βGall → 4GlcNAcl → 2αManl → 6)βManl → 4GlcNAc-itol [³H]et αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl-3(αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl → 6)βManl 4GlNAc-itol[³H] isolated from the urine of a patient with mucolipidosis I. The enzyme cleaves α2 → 3 and α2 → 8 linkages at a greater rate than the α2 → 6 bonds. Its activity decreases with the length of the oligosaccharidic chain. Substitution of a glucose moiety by Nacetylglucosamine results in diminished activity. The specificity of rat kidney sialidase differs from that reported for other mammalian of viral sialidases.     

Steroidal saponins of Asparagus curillus

Three spirostanol and two furostanol glycosides were isolated from a methanol extract of the roots of Asparagus curillus and characterized as 3-O-[α-l-arabinopyranosyl (1→4)- β-d-glucopyranosyl]-(25S)-5β-spirostan-3β-ol, 3-O-[{α-l-rhamnopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β-d-glucopyranosyl]-(25S)-5β-spirostan- 3β-ol, 3-O-[{β-d-glucopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β- d-glucopyranosyl]-(25S)-5β-spirostan-3β-ol, 3-O-[{β-d-glucopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosyl]- 22α-methoxy-(25S)-5β-furostan-3β, 26-diol and 3-O-[{β-d-glucopyranosyl (1→2)} {α-l-arabinopyranosyl (1→4)}-β-d-glucopyranosyl]-26-O-[β-d-glucopyranosyl]- (25S)-5β-furostan-3β, 22α, 26-triol respectively.     

Plant complex type free N-glycans occur in tomato xylem sap

Free N-glycans (FNGs) are ubiquitous in growing plants. Further, acidic peptide:N-glycanase is believed to be involved in the production of plant complex-type FNGs (PCT-FNGs) during the degradation of dysfunctional glycoproteins. However, the distribution of PCT-FNGs in growing plants has not been analyzed. Here, we report the occurrence of PCT-FNGs in the xylem sap of the stem of the tomato plant.

Abbreviations: RP-HPLC: reversed-phase HPLC; SF-HPLC: size-fractionation HPLC; PA-: pyridylamino; PCT: plant complex type; Hex: hexose; HexNAc: N-acetylhexosamine; Pen: pentose; Deoxyhex: deoxyhexose; Man: D-mannose; GlcNAc: N-acetyl-D-glucosamine; Xyl: D-xylose; Fuc: L-fucose; Le^a: Lewis a (Galβ1-3(Fucα1-4)GlcNAc); PCT: plant complex type; M3FX: Manα1-6(Manα1-3)(Xylβ1-2)Manβ1-4GlcNAcβ1-4(Fucα1-3)GlcNAc-PA; GN2M3FX: GlcNAcβ1-2Manα1-6(GlcNAcβ1-2Manα1-3)(Xylβ1-2)Manβ1-4GlcNAcβ1-4(Fucα1-3)GlcNAc-PA; (Le^a)1GN1M3FX: Galβ1-3(Fucα1-4)GlcNAc1-2 Manα1-6(GlcNAcβ1-2Manα1-3)(Xylβ1-2)Manβ1-4GlcNAcβ1-4(Fucα1-3)GlcNAc-PA or GlcNAc1-2Manα1-6(Galβ1-3(Fucα1-4)GlcNAc1-2Manα1-3)(Xylβ1-2)Manβ1-4GlcNAcβ1-4(Fucα1-3)GlcNAc-PA.     

Functional and structural interaction of (−)-lobeline with human α4β2 and α4β4 nicotinic acetylcholine receptor subtypes

To determine the pharmacologic activity of (−)-lobeline between human (h)α4β2 and hα4β4 nicotinic acetylcholine receptors (AChRs), functional and structural experiments were performed. The Ca²⁺ influx results established that (−)-lobeline neither actives nor enhances the function of the studied AChR subtypes, but competitively inhibits hα4β4 AChRs with potency ∼10-fold higher than that for hα4β2 AChRs. This difference is due to a higher binding affinity for the [³H]cytisine sites at hα4β4 compared to hα4β2 AChRs, which, in turn, can be explained by our molecular dynamics (MD) results: (1) higher stability of (−)-lobeline and its hydrogen bonds within the α4β4 pocket compared to the α4β2 pocket, (2) (−)-lobeline promotes Loop C to cap the binding site at the α4β4 pocket, but forces Loop C to get apart from the α4β2 pocket, precluding the gating process elicited by agonists, and (3) the orientation of (−)-lobeline within the α4β4, but not the α4β2, subpocket, promoted by the t− (or t+) rotameric state of α4-Tyr98, remains unchanged during the whole MD simulation. This study gives a detailed view of the molecular and dynamics events evoked by (−)-lobeline supporting the differential binding affinity and subsequent inhibitory potency between hα4β2 and hα4β4 AChRs, and supports the possibility that the latter subtype is also involved in its activity.