ABSTRACT
Amyloid is a term for extracellular protein fibril deposits that have characteristic tinctorial and structural properties. Heparan sulphate, or the heparan sulphate proteoglycan perlecan, has been identified in all amyloids and implicated in the earliest stages of inflammation-associated (AA) amyloid induction. Heparan sulphate interacts with the AA amyloid precursor and the beta-peptide of Alzheimer's amyloid, imparting characteristic secondary and tertiary amyloid structural features. These observations suggest that molecules that interfere with this interaction may prevent or arrest amyloidogenesis. We synthesized low-molecular-weight (135-1,000) anionic sulphonate or sulphate compounds. When administered orally, these compounds substantially reduced murine splenic AA amyloid progression. They also interfered with heparan sulphate-stimulated beta-peptide fibril aggregation in vitro.
Subject(s)
Alkanesulfonates/therapeutic use , Amyloidosis/drug therapy , Serum Amyloid A Protein/drug effects , Sulfates/therapeutic use , Acute Disease , Alkanesulfonates/chemical synthesis , Alkanesulfonates/toxicity , Alzheimer Disease/drug therapy , Amyloidosis/chemically induced , Animals , Anions , Chronic Disease , Glycols/chemical synthesis , Glycols/therapeutic use , Glycols/toxicity , Heparitin Sulfate/pharmacology , Mice , Polyvinyls/chemistry , Polyvinyls/therapeutic use , Polyvinyls/toxicity , Serum Amyloid A Protein/analysis , Serum Amyloid A Protein/metabolism , Serum Amyloid A Protein/ultrastructure , Spleen/pathology , Sulfates/chemical synthesis , Sulfates/toxicityABSTRACT
AIMS/HYPOTHESIS: Islet amyloid in type 2 diabetes contributes to loss of beta cell mass and function. Since islets are susceptible to oxidative stress-induced toxicity, we sought to determine whether islet amyloid formation is associated with induction of oxidative stress. METHODS: Human islet amyloid polypeptide transgenic and non-transgenic mouse islets were cultured for 48 or 144 h with or without the antioxidant N-acetyl-L: -cysteine (NAC) or the amyloid inhibitor Congo Red. Amyloid deposition, reactive oxygen species (ROS) production, beta cell apoptosis, and insulin secretion, content and mRNA were measured. RESULTS: After 48 h, amyloid deposition was associated with increased ROS levels and increased beta cell apoptosis, but no change in insulin secretion, content or mRNA levels. Antioxidant treatment prevented the rise in ROS, but did not prevent amyloid formation or beta cell apoptosis. In contrast, inhibition of amyloid formation prevented the induction of oxidative stress and beta cell apoptosis. After 144 h, amyloid deposition was further increased and was associated with increased ROS levels, increased beta cell apoptosis and decreased insulin content. At this time-point, antioxidant treatment and inhibition of amyloid formation were effective in reducing ROS levels, amyloid formation and beta cell apoptosis. Inhibition of amyloid formation also increased insulin content. CONCLUSIONS/INTERPRETATION: Islet amyloid formation induces oxidative stress, which in the short term does not mediate beta cell apoptosis, but in the longer term may feed back to further exacerbate amyloid formation and contribute to beta cell apoptosis.
Subject(s)
Amyloid/biosynthesis , Apoptosis/physiology , Insulin-Secreting Cells/cytology , Insulin-Secreting Cells/physiology , Oxidative Stress/physiology , Amyloid/genetics , Amyloid/physiology , Animals , Diabetes Mellitus, Type 2/physiopathology , Humans , Insulin/genetics , Insulin/metabolism , Insulin Secretion , Insulin-Secreting Cells/metabolism , Islet Amyloid Polypeptide , Mice , Mice, Transgenic , RNA, Messenger/genetics , Reactive Oxygen Species/metabolismABSTRACT
Fibroblast apoptosis plays a crucial role in normal and pathological scar formation and therefore we studied whether the putative apoptosis-inducing factor curcumin affects fibroblast apoptosis and may function as a novel therapeutic. We show that 25-microM curcumin causes fibroblast apoptosis and that this could be inhibited by co-administration of antioxidants N-acetyl-l-cysteine (NAC), biliverdin or bilirubin, suggesting that reactive oxygen species (ROS) are involved. This is supported by our observation that 25-microM curcumin caused the generation of ROS, which could be completely blocked by addition of NAC or bilirubin. Since biliverdin and bilirubin are downstream products of heme degradation by heme oxygenase (HO), it has been suggested that HO-activity protects against curcumin-induced apoptosis. Interestingly, exposure to curcumin maximally induced HO-1 protein and HO-activity at 10-15 microM, whereas, at a concentration of >20-microM curcumin HO-1-expression and HO-activity was negligible. NAC-mediated inhibition of 25-microM curcumin-induced apoptosis was demonstrated to act in part via restored HO-1-induction, since the rescuing effect of NAC could be reduced by inhibiting HO-activity. Moreover pre-induction of HO-1 using 5-microM curcumin protected fibroblasts against 25-microM curcumin-induced apoptosis. On a functional level, fibroblast-mediated collagen gel contraction, an in vitro wound contraction model, was completely prevented by 25-microM curcumin, while this could be reversed by co-incubation with NAC, an effect that was also partially HO-mediated. In conclusion, curcumin treatment in high doses (>25 microM) may provide a novel way to modulate pathological scar formation through the induction of fibroblast apoptosis, while antioxidants, HO-activity and its effector molecules act as a possible fine-tuning regulator.
Subject(s)
Apoptosis/drug effects , Cicatrix/enzymology , Curcumin/pharmacology , Fibroblasts/cytology , Fibroblasts/enzymology , Heme Oxygenase (Decyclizing)/metabolism , Wound Healing/drug effects , Acetylcysteine/pharmacology , Antioxidants/pharmacology , Bilirubin/pharmacology , Collagen/metabolism , Dermis/cytology , Dose-Response Relationship, Drug , Fibroblasts/drug effects , Gels , Glutathione/pharmacology , Humans , Reactive Oxygen Species/metabolismABSTRACT
An improved, convenient synthesis of 3-deoxy-D-xylo-hexose (3-deoxy-D-galactose) has been developed, and the chemical synthesis of a novel monosaccharide derivative, methyl (methyl 4-chloro-4-deoxy-beta-D-galactopyranosid)uronate (compound 10), is described. Using primary hepatocytes in culture, each was used to explore its effect on glycosaminoglycan (GAG) synthesis. In the absence of analogues hepatocytes synthesize primarily (92-95%) heparan sulphate. At 1 mM, 3-deoxy-D-galactose had little observable effect on either liver cell GAG or protein synthesis. At 10 mM and 20 mM, 3-deoxy-D-galactose reduced [3H]glucosamine and 35SO4 incorporation into hepatocyte cellular GAGs to, respectively, 75% and 60% of the control cells. This inhibition of GAG synthesis occurred without any effect on hepatocyte protein synthesis, indicating that 3-deoxy-D-galactose's effect on GAG synthesis is not mediated through an inhibition of proteoglycan core protein synthesis. Furthermore, GAGs in the presence of 20 mM of the analogue were significantly reduced in size, 17 kDa vs. 66 kDa in untreated cells. These results reflect either impaired cellular GAG chain elongation, and/or altered GAG chain degradation. Compound 10 exhibited a concentration-dependent inhibition of both hepatocyte cellular GAG and protein synthesis. At concentrations of 5, 10 and 20 mM, compound 10 inhibited GAG and protein synthesis by 20, 65 and 90%, respectively. Exogenous uridine was able to restore partially the inhibition of protein synthesis, but was unable to reverse the effect of compound 10 on GAG synthesis. These results show that part of the effect of compound 10 on GAG synthesis is not mediated by an inhibition of proteoglycan core protein synthesis. GAGs in the presence of compound 10 are half as large as those in the absence of this compound (33 and 66 kDa, respectively). These results again may reflect either impaired cellular GAG chain elongation and/or altered GAG chain degradation. Potential metabolic routes for each analogue's effect are presented.
Subject(s)
Galactose/analogs & derivatives , Galactosides/pharmacology , Glycosaminoglycans/biosynthesis , Hexuronic Acids/pharmacology , Liver/metabolism , Animals , Cells, Cultured , Female , Galactose/chemical synthesis , Galactose/pharmacology , Galactosides/chemical synthesis , Glycosaminoglycans/chemistry , Hexuronic Acids/chemical synthesis , Liver/cytology , Liver/drug effects , Mice , Molecular Weight , Protein Biosynthesis , Uridine/pharmacologyABSTRACT
A novel carbohydrate, 4-deoxy-L-threo-pentose (4-deoxyxylose), was synthesized by way of reductive dechlorination of a chlorodeoxy sugar. This carbohydrate, an analogue of xylose which is required for the initiation of glycosaminoglycan (GAG) synthesis, was used to explore the function of GAG side chains in neurite outgrowth on a laminin substrate. 4-Deoxyxylose inhibited the incorporation of 35SO4 into the GAGs of neuronal and astrocytic proteoglycans, with no effect being seen on the incorporation of [3H]glucosamine into proteoglycan. Direct analysis of the heparan sulphate fraction from such cells using nitrous acid digestion confirmed that the GAGs were undersulphated. No inhibition of either 35SO4 or [3H]glucosamine incorporation was observed in primary mouse hepatocytes exposed to 4-deoxyxylose. 4-Deoxyxylose produced a direct dose-dependent inhibition of neurite outgrowth by sensory neurons, and medium conditioned by neurons or astrocytes in the presence of 4-deoxyxylose displayed less laminin-complexed neurite-promoting activity than medium conditioned in its absence. These data suggest that 4-deoxyxylose inhibits neurite outgrowth by altering the sulphation of the GAGs of heparan sulphate proteoglycans.
Subject(s)
Neurons/drug effects , Proteoglycans/biosynthesis , Xylose/analogs & derivatives , Animals , Animals, Newborn , Astrocytes/drug effects , Glycosaminoglycans/biosynthesis , Liver/drug effects , Liver/metabolism , Neurons/metabolism , Rats , Xylose/chemical synthesis , Xylose/pharmacologyABSTRACT
Nine pyrimidine nucleoside analogues, in which the group attached at N-1 is a six-membered ring containing two heteroatoms, have been synthesized using the Vorbrüggen and Bennua (Vorbrüggen, H.; Bennua, B. Tetrahedron Lett. 1978, 1339) coupling procedure. These are 1-(1,4-oxathian-3-yl)-5-fluorouracil (8), 1-(4-oxo-1,4-oxathian-3-yl)-5-fluorouracil (two stereoisomers 9 and 10, resolved by silica gel column chromatography, 1-(1,4-oxathian-3-yl)-5-fluorouracil (11), 1-(1,4-oxathian-2-yl)-5-fluorouracil (12), 1-(1,4-dithin-2-yl)-5-flourouracil (15), 1-(1,4-dithian-2-yl)uracil (16), 1-(1,4-dithian-2-yl)thymine (17), and 1-(1,4-dioxan-2-yl)-5-fluorouracil (20). All of the analogous were tested for cell-growth inhibition using mouse and human tumor cell lines. The ID50 values of all of the analogues are greater than 10(-4) M, except in the case of 11 using the L1210 cell line. The most active analogues found are compounds 11 and 17, which were found to be 100 and 200 times less active, respectively, than 5-fluorouracil in the human erythroleukemia cell line, K-562.
Subject(s)
Antineoplastic Agents/chemical synthesis , Pyrimidine Nucleosides/chemical synthesis , Animals , Cells, Cultured , Chemical Phenomena , Chemistry , Fluorouracil/pharmacology , Heterocyclic Compounds/chemical synthesis , Heterocyclic Compounds/pharmacology , Humans , Mice , Neoplasms, Experimental/drug therapy , Pyrimidine Nucleosides/pharmacologyABSTRACT
The bound carbohydrates of noncataractous , decapsulated, human lenses have been examined. The hexoses and hexosamines of the water-soluble, water-insoluble nonmembrane, and membrane fractions of lenses from six age groups were determined by gas-liquid chromatography. The plasma membrane contains 60-70% of all bound carbohydrates, including glucose, galactose, mannose, fucose, glucosamine, and galactosamine. These also occur in the water-insoluble nonmembrane fraction, suggesting that the latter contains glycoproteins. The water-soluble fraction contains glucose, galactose, and mannose.
Subject(s)
Carbohydrates/analysis , Lens, Crystalline/analysis , Adolescent , Adult , Aged , Child , Chromatography, Gas , Humans , Middle AgedABSTRACT
1-(5-Deoxy-beta-D-arabino-hexofuranosyl)cytosine (4'-homoara-C) (11), a higher homolog of the antileukemic agent ara-C (1-beta-D-arabinofuranosylcytosine), was prepared by two independent routes. The first one involved the inversion of configuration at C-2' of the D-ribo epimer (1-(5-deoxy-beta-D-ribo-hexofuranosyl)cytosine, 4'-homocytidine) by the diphenylcarbonate technique; the 5-deoxy-D-ribo-hexofuranosyl moiety of 4'-homocytidine was obtained by way of an anti-Markovnikov addition of iodine trifluoroacetate to the double bond of 5,6-dideoxy-1, 2-O-isopropylidene-3-O-p-tolylsulfonyl-alpha-D-ribo-hex-5-enofu ranose and reduction of the resulting iodide(s). In the second approach, 5-deoxy-1,2-O-isopropylidene-3-O-p-tolylsulfonyl-beta-D-xylo-he xofuranose was acetolyzed and condensed with 4-acetyl-N-bis(trimethylsilyl)cytosine, and alkaline treatment gave 11 by way of a 2',3'-anhydro intermediate. The structure of 11, in particular the configuration at C-2', was confirmed by its 1H- and 13C-n.m.r. spectra.
Subject(s)
Cytarabine/analogs & derivatives , Cytarabine/chemical synthesis , Magnetic Resonance SpectroscopyABSTRACT
4-Deoxy-4-fluoro analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-galactose were synthesized and evaluated as inhibitors of hepatic glycosaminoglycan biosynthesis. 2-Acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-fluoro-D-glucopyranose (16) exhibited a reduction of [3H]GlcN and [35S]SO4 incorporation into hepatocyte cellular glycosaminoglycans to 12 and 18%, respectively, of the control cells, at 1.0 mM. Similarly, 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-fluoro-D-galactopyranose (31) exhibited a reduction of [3H]GlcN and [35S]SO4 incorporation to 1 and 9%, respectively, of the control cells, at 1.0 mM. Unlike 16, 31 exhibited a reduction of [14C]Leu incorporation into cellular protein to 57% of control cells, at 1.0 mM.
Subject(s)
Acetylglucosamine/chemical synthesis , Galactose/chemical synthesis , Glycosaminoglycans/biosynthesis , Acetylgalactosamine/analogs & derivatives , Acetylglucosamine/analogs & derivatives , Acetylglucosamine/chemistry , Acetylglucosamine/pharmacology , Animals , Cells, Cultured , Female , Galactose/analogs & derivatives , Galactose/pharmacology , Hepatocytes/drug effects , Hepatocytes/metabolism , Magnetic Resonance Spectroscopy , Mice , Molecular Structure , Protein BiosynthesisABSTRACT
The coupling of 2,3,6,2',3',4',6-hepta-O-acetyl-alpha-lactosyl bromide with 1,4-di-O-benzyl-D-threitol using mercury(II) cyanide as a promoter, with subsequent deprotection of one or both of the benzyl groups, further glycosylation, and deacetylation afforded the title compounds. This class of compound is useful in the assessment of binding properties of D-galactopyranose to human and rabbit hepatocytes.
Subject(s)
Lactose/analogs & derivatives , Acetylation , Carbohydrate Sequence , Glycosylation , Lactose/chemical synthesis , Molecular Sequence DataABSTRACT
The N-(1-deoxy-D-mannitol-1-yl) and N-(1-deoxy-D-glucitol-1-yl) derivatives of L-valine, L-alanine, L-threonine, and L-leucine were prepared by reductive amination of D-mannose and D-glucose with the appropriate amino acids, in the presence of sodium cyanoborohydride. N epsilon-(1-Deoxy-D-mannitol-1-yl)- and N epsilon-(1-deoxy-D-glucitol-1-yl)-L-lysine were prepared by similar reactions of hexoses with N alpha-tert-butoxycarbonyl and N alpha-benzyloxycarbonyl-L-lysine, followed by removal of the protecting groups. The structures were confirmed by 1H-n.m.r. spectroscopy, which showed that each compound was completely free of its C-2 epimer. The synthetic compounds may be used as reference compounds for the identification of N-(1-deoxyhexitol-1-yl)amino acids formed when N-(1-deoxy-D-fructose-1-yl) groups of nonenzymically glycosylated proteins, of the hemoglobin A1c type, are reduced with sodium borohydride, and the protein is subjected to acid-catalyzed hydrolysis.
Subject(s)
Amino Acids/chemical synthesis , Glycoproteins/chemical synthesis , Sugar Alcohols/chemical synthesis , Carbon Radioisotopes , Indicators and Reagents , Magnetic Resonance Spectroscopy , Optical Rotation , TritiumABSTRACT
4-Deoxy analogues of 2-acetamido-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-xylose were synthesized and evaluated as inhibitors of glycoconjugate biosynthesis. Methyl 2-acetamido-2,4-dideoxy-beta-D-xylo-hexopyranoside (11) showed a reduction in [3H]GlcN and [14C]Leu incorporation into hepatocyte cellular glycoconjugates by 89 and 88%, of the control cells, respectively, at 20 mM, whereas the free sugars, 2-acetamido-2,4-dideoxy-alpha,beta-D-xylo-hexopyranoses (15), showed a reduction of [3H]GlcN and [14C]Leu incorporation by 75 and 64%, respectively, at 20 mM. The acetylated analogues of 11 and 15, namely methyl 2-acetamido-3,6-di-O-acetyl-2,4-dideoxy-beta-D-xylo-hexopyranoside and 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-alpha,beta-D-xylo-hexopyra noses, showed a greater inhibition of [3H]GlcN and [14C]Leu incorporation at 1 mM compared with their non-acetylated counterparts, but were toxic to hepatocytes at concentrations of 10 and 20 mM. Corresponding derivatives of 2-acetamido-2,4-dideoxy-L-threo-pentopyranose showed no biological effect up to 20 mM, suggesting that the C-6 substituent is important for the biological activity.
Subject(s)
Deoxy Sugars/chemical synthesis , Glycoconjugates/biosynthesis , Acetylglucosamine/analogs & derivatives , Animals , Carbohydrate Conformation , Cells, Cultured , Deoxy Sugars/pharmacology , Leucine/metabolism , Liver/drug effects , Liver/metabolism , Magnetic Resonance Spectroscopy , Mice , Xylose/analogs & derivativesABSTRACT
The binding affinities of a series of D-galactose-terminated glycerol glycosides and oligosaccharides for the asialoglycoprotein receptor isolated from rabbit liver were determined in vitro using a radioreceptor-inhibition assay with 125I-asialoorosomucoid. The relative affinities of the synthetic ligands increased with the number of exposed D-galactose termini. Of the compounds examined, 1,2,3-tri-O-beta-lactosylglycerol associated with the greatest affinity (estimated Kd = 7.97 x 10(-5) M). Examination of the affinities of the synthetic series indicated that both the number and propinquity of the D-galactose termini influenced the strength of the binding interactions.
Subject(s)
Galactose , Ligands , Liver/metabolism , Oligosaccharides/chemistry , Oligosaccharides/metabolism , Receptors, Cell Surface/metabolism , Animals , Asialoglycoprotein Receptor , Asialoglycoproteins/metabolism , Binding, Competitive , Carbohydrate Conformation , Carbohydrate Sequence , Iodine Radioisotopes , Kinetics , Molecular Sequence Data , Oligosaccharides/pharmacology , Orosomucoid/analogs & derivatives , Orosomucoid/metabolism , Rabbits , Receptors, Cell Surface/drug effects , Receptors, Cell Surface/isolation & purificationABSTRACT
A synthesis of L-dendroketose (5) has been achieved by microbiological oxidation by Acetobacter suboxydans of the branched-chain alditol 2-C-(hydroxy-methyl)-D-erythro-pentitol (4). Treatment of the oxidation product with acetone, copper(II) sulfate, and sulfuric acid afforded the two di-O-isopropylidene-L-dendro-ketose derivatives 6 and 7. Assignment of configuration at the branching carbon atom (C-4) and at the anomeric center in 6 and 7 was made on the basis of the carbon-13 magnetic resonance spectra of these derivatives.
Subject(s)
Acetobacter/metabolism , Monosaccharides/biosynthesis , Sugar Alcohols/metabolism , Magnetic Resonance Spectroscopy , Optical RotationABSTRACT
Under conditions of desorption-chemical ionization or fast-atom-bombardment mass-spectrometry, the azido groups in some carbohydrate derivatives and other substances undergo apparent reduction to amino groups. Experimental evidence is provided to corroborate the reduction, and possible explanations are proposed for the phenomenon.
Subject(s)
Azides/chemistry , Glycosides/chemistry , Ammonia/analysis , Carbohydrate Conformation , Carbohydrate Sequence , Molecular Sequence Data , Spectrometry, Mass, Fast Atom Bombardment/methodsABSTRACT
The reaction of 2,3,6,2',3',4',6'-hepta-O-acetyl-alpha-lactosyl bromide (5) and 1,3-di-O-benzylglycerol in the presence of mercury(II) cyanide in benzene-nitromethane afforded 1,3-di-O-benzyl-2-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)glyc erol (70%), which was converted into 2-O-beta-lactosylglycerol. 1,2-Di-O-beta-lactosyl-(R,S)-glycerols were obtained by way of the coupling of 5 to either 1-O-benzyl-(R,S)-glycerol or 1-O-benzyl-2-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)-(R,S)-gl ycerols. The most efficient route to 1,2, 3-tri-O-beta-lactosylglycerol (17) involved treatment of 2-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)glycerol with 3 mol. equiv. of 5 followed by removal of the blocking groups, to give 17 (47%).
Subject(s)
Glycerol/chemistry , Lactose/chemistry , Carbohydrate Sequence , Molecular Sequence Data , Receptors, Cell Surface/metabolismABSTRACT
1,2,3,2',3',4',6'-Hepta-O-acetyl-beta-lactose (4) was coupled with 2,3,6,2',3',4',6'-hepta-O-acetyl-alpha-lactosyl bromide (7) in the presence of Hg(CN)2 to afford 1,2,3,2',3',4',6'-hepta-O-acetyl-6-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-b eta- lactosyl)-beta-lactose (11) which, upon O-deacetylation, gave 6-O-beta-lactosyl-alpha,beta-lactoses (64% from 4). In contrast, the reaction of 7 with benzyl 2,3,2',3',4',6'-hexa-O-acetyl-beta-lactoside in the presence of Hg(CN)2 produced 3,6,2',3',4',6'-hexa-O-acetyl-1,2-O- (2,3,2',3',4',6'-hexa-O-acetyl-1-O-benzyl-beta-lactos-6-yl orthoacetyl)-alpha-lactose (63%) and 3,6,2',3',4',6'-hexa-O-acetyl-1,2-O-(1- cyanoethylidene)-alpha-lactose (27%). The glycosidation of 4 using 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide in the presence of Hg(CN)2 afforded, after deprotection, 4,6-di-O-beta-D-galactopyranosyl-alpha,beta-D-glucoses (66%). The reaction of 11 with 1,2-di-O-benzyl-(R,S)-glycerols and trimethylsilyl trifluoromethanesulfonate yielded, after deprotection, 1-O-(6-O-beta-lactosyl-beta-lactosyl)-(R,S)-glycerols (18%). Under the same coupling conditions 11 reacted with 2-O-benzylglycerol to form 3-O-acetyl-2-O-benzyl-1-O-[2',3',4',6'-hexa-O-acetyl-6-O-(2,3,6,2',3',4' ,6'- hepta-O-acetyl-beta-lactosyl)-beta-lactosyl]-(R,S)-glycerols (16%).
Subject(s)
Glycerides/chemistry , Lactose/chemistry , Lipopolysaccharides/chemistry , Asialoglycoprotein Receptor , Diglycerides/chemistry , Glycosides/chemistry , Magnetic Resonance Spectroscopy , Molecular Sequence Data , Receptors, Immunologic/metabolism , Triglycerides/chemistryABSTRACT
The reaction of 2,3,6,2',3',4',6'-hepta-O-acetyl-alpha-lactosyl bromide (4) and benzyl 3,4-di-O-benzyl-alpha-D-mannopyranoside (3) in the presence of mercury(II) cyanide in benzene-nitromethane produced benzyl 3,4-di-O-benzyl-2,6-bis-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lact osy l)-alph a D-mannopyranoside (5) and benzyl 3,4-di-O-benzyl-6-O-(2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)-alp ha-D- mannopyranoside (6), as part of a complex mixture. Column chromatography, followed by acetylation of the fraction containing 5 and 6, gave a sample of 5 and benzyl 2-O-acetyl-3,4-di-O-benzyl-6-O (2,3,6,2',3',4',6'-hepta-O-acetyl-beta-lactosyl)-alpha-D-mannopyranoside (7) in approximately 35% and 17% yields (based on 4), respectively. Deprotection of 5 and 7 afforded the target compounds, namely 2,6-di-O-beta-lactosyl-alpha,beta-D-mannopyranoses and 6-O-beta-lactosyl-alpha,beta-D-mannopyranoses, respectively. If the coupling of 4 with 3 were performed in the presence of silver trifluoromethanesulfonate and 2,4,6-trimethylpyridine, only a mixture of 3,6,2',3',4',6'-hexa-O-acetyl- alpha-lactose-1,2-[( 3,6,2',3',4',6'-hexa-O-acetyl-alpha-lactose 1,2-(benzyl 3,4-di-O-benzyl-alpha-D-mannopyranosid-6-yl orthoacetyl)-2-yl]orthoacetate) and 3,6,2',3',4',6'-hexa-O-acetyl-alpha-lactose 1,2-(benzyl 3,4-di-O-benzyl-alpha-D-mannopyranosid-6-yl orthoacetate) was obtained. The orthoacetates were characterized by n.m.r. spectroscopy. The two target materials are useful in the assessment of the binding properties of galactose-terminated ligands to the asialoglycoprotein receptor of normal rabbit and human hepatocytes.