Reaktionen der glucuronsäure : 7. Mitt. Oxidationen an d-glucofuranosidurono-6,3-lactonen

Methyl α-D- (1) and methyl β-D-glucofuranosidurono-6,3-lactone (5) were oxidized at C-2 or C-5, 1,2-O-isopropylidene-α-D- (10) and 1,2-O-cyclohexylidene-α-D-glucofuranurono-6,3-lactone (11) at C-5 by various methods to the corresponding D-arabino- or D-xylo-hexulofuranosiduronolactones. In contrast to the starting materials 5, 10, and 11, the 5-uloses 15, 17, and 18 do not exhibit reducing power in alkaline Cu²⁺ solutions. Methyl 5-O-benzyl-α-D- and methyl 5-O-benzyl-β-D-arabino-2-hexulofuranosidurono-6,3-lactone reduce Benedict solution at room temperature.     

Stereoselective entry into the d-GalNAc series starting from the d-Gal one: a new access to N-acetyl-d-galactosamine and derivatives thereof

A new stereoselective preparation of N-aceyl-d-galactosamine (1b) starting from the known p-methoxyphenyl 3,4-O-isopropylidene-6-O-(1-methoxy-1-methylethyl)-β-d-galactopyranoside (10) is described using a simple strategy based on (a) epimerization at C-2 of 10 via oxidation-reduction to give the talo derivative 11, (b) amination with configurational inversion at C-2 of 11 via a S_N2-type reaction on its 2-imidazylate, (c) anomeric deprotection of the p-methoxyphenyl β-d-galactosamine glycoside 14, (d) complete deprotection. Applying the same protocol to 2,3:5,6:3′,4′-tri-O-isopropylidene-6′-O-(1-methoxy-1-methylethyl)-lactose dimethyl acetal (4), directly obtained through acetonation of lactose, the disaccharide β-d-GalNAcp-(1→4)-d-Glcp (1a) was obtained with complete stereoselectivity in good (40%) overall yield from lactose.     

1,4-Dioxane-2,5-dione-type monomers derived from l-ascorbic and d-isoascorbic acids. Synthesis and polymerisation

l-Ascorbic and d-isoascorbic acids have been used as the starting materials for the preparation of (3R,4′S)-3-(2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)-1,4-dioxane-2,5-dione (IPTA), (3R and S, 4′S,6R)-3-methyl-6-(2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)-1,4-dioxane-2,5-dione (IPTP) and (3R,4′R)-3-(2′,2′-dimethyl-1′,3′-dioxolan-4′-yl)-1,4-dioxane-2,5-dione (IPEA), three novel 1,4-dioxane-2,5-dione-type monomers. Ring-opening homopolymerisation and copolymerisation of the IPTA monomer, derived from l-ascorbic acid, with d,l-lactide have been performed. The polymers were characterised by elemental microanalysis, as well as IR and ¹H and ¹³C NMR spectroscopies. GPC was used to estimate product molecular weights, and thermal studies (DSC and TGA) revealed that all the polymers were amorphous, being stable up to 250 °C under nitrogen.     

Stereosensitive formation and interconversion of sulfur-bridged cobalt(III)-mercury(II) polynuclear complexes with d- and/or l-penicillaminates

The reaction of trans(N)-[Co(d-pen)₂]⁻ (pen = penicillaminate) with HgCl₂ or HgBr₂ in the molar ratios of 1:1 gave the sulfur-bridged heterodinuclear complex, [HgX(OH₂){Co(d-pen)₂}] (X = Cl (1a) or Br (1b)). A similar reaction in the ratio of 2:1 produced the trinuclear complex, [Hg{Co(d-pen)₂}₂] (1c). The enantiomers of 1a and 1c, [HgCl(OH₂){Co(l-pen)₂}] (1a′) and [Hg{Co(l-pen)₂}₂] (1c′), were also obtained by using trans(N)-[Co(l-pen)₂]⁻ instead of trans(N)-[Co(d-pen)₂]⁻. Further, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 1:1 resulted in the formation of [HgCl(OH₂){Co(d-pen)(l-pen)}] (2a). During the formations of the above six complexes, 1a, 1b, 1c, 1a′, 1c′, and 2a, the octahedral Co(III) units retain their configurations. On the other hand, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 2:1 gave not [Hg{Co(d-pen)(l-pen}₂] but [Hg{Co(d-pen)₂}{Co(l-pen)₂}] (2c), accompanied by the ligand-exchange on the terminal Co(III) units. The X-ray crystal structural analyses show that the central Hg(II) atom in 1c takes a considerably distorted tetrahedral geometry, whereas that in 2c is of an ideal tetrahedron. The interconversion between the complexes is also examined. The electronic absorption, CD, and NMR spectral behavior of the complexes is discussed in relation to the crystal structures of 1c and 2c.     

Toward the synthesis of fine chemicals from lactose: preparation of d-xylo and l-lyxo-aldohexos-5-ulose derivatives

The transformation of (5R)-2,6-di-O-benzyl-5-C-methoxy-β-d-galactopyranosyl-(1→4)-2,3:5,6-di-O-isopropylidene-aldehydo-d-glucose dimethyl acetal (8) into partially protected derivatives of d-xylo- and l-lyxo-aldohexos-5-ulose has been reported, applying appropriate epimerisation methods to its 3′-O- and 4′-O-protected alcoholic derivatives.     

Studies in the sphingolipids series,XXXII : Synthesis and resolution into optical antipodes of C20-phytosphingosine

C₂₀-Phytosphingosine, D(+)-ribo-2-amino-1, 3, 4-trihydroxyeicosane (8a), is synthesized through the following intermediates: 2-Methoxyoctadecanoic acid chloride (1)→Ethyl 2-methoxyoctadecanoylacetoacetate (2)→Ethyl (2-p-nitrophenylhydrazono)-2,3-dioxo-4-methoxyeicosanoate (3)→Ethyl 2-acetamido-3-oxo-4-methoxyeicosanoate (4)→Ethyl 2-acetamido-3-hydroxy-4-methoxyeicosanoate (5)→2-Acetamido-3-hydroxy-4-methoxyeicosanoic acid (6), 2-Amino-3-hydroxyeicosanoic acid 1,4-lactone hydrobromide (7a, b)→DL-ribo (8a) and DL-xylo(?)-2-amino-1,3,4-trihydroxyeicosane (8b). The resolution of the racemic base (8a) has been effected through its salts with D-tartaric acid.     

Homochiral metal-organic coordination networks from l-typtophan

Three homochiral metal-organic coordination networks [Co₂(l-Trp)₂(Py)₆] · Py · (ClO₄)₂ (1), [Ni(l-Trp)(Py)₃] · H₂O · ClO₄ (2) and [Co₂(l-Trp)(INT)₂(H₂O)₂(ClO₄)] (3), all containing natural amino acid l-HTrp (l-typtophan), were hydrothermally synthesized and structurally characterized. The compounds 1 and 2 crystallize in the orthorhombic space group C222₁, with a = 10.731(2) Å, b = 19.709(4) Å, c = 27.365(6) Å and Z = 4 for 1 and a = 10.710(10) Å, b = 20.088(18) Å, c = 27.63(3) Å and Z = 8 for 2, respectively. The compound 3 has the monoclinic space group P2₁, with a = 8.1934(14) Å, b = 13.209(2) Å, c = 12.464(2) Å, β = 104.107(3)° and Z = 2. Both 1 and 2 consist of 1D helical chains. Compound 3 is composed of 2D networks, which further assemble into a 3D supramolecular structure via weak interlayer interactions. The optically pure amino acid l-HTrp plays an important role leading to homochiral structures reported here.     

Synthesis and antitumor activity of new d-seco and d-homo androstane derivatives

Starting from 3β-hydroxy-17-oxo-16,17-secoandrost-5-ene-16-nitrile (1), the new 16,17-secoandrostane derivatives 4-9 were synthesized. On the other hand, 3β-hydroxy-17-oxa-d-homoandrost-5-ene-16-one (10) yielded the new d-homo derivatives 12, 13 and 15. In vitro antiproliferative activity of selected compounds against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER−, MDA-MB-231, prostate cancer AR−, PC-3, and normal fetal lung fibroblasts, MRC-5) was evaluated. Compounds 3 and 12 showed strong antiproliferative activity against PC-3 cells, the IC₅₀ values being 2 μM and 0.55 μM, respectively. Compounds 6 (10 μM) and 14 (9 μM) showed moderate activity against MDA-MB-231 cells. The synthesized compounds 1-3, 5-8, 10 and 12-15 were not toxic to normal fetal lung fibroblasts cells, MRC-5.     

Synthesis of new N-substituted 3,4,5-trihydroxypiperidin-2-ones from d-ribono-1,4-lactone

d-Ribono-1,4-lactone was treated with ethylamine in DMF to afford N-ethyl-d-ribonamide 8a in quantitative yield. Using this reaction procedure, N-butyl, N-hexyl, N-dodecyl, N-benzyl, N-(3-methyl-pyridinyl)-, N-(2-hydroxy-ethyl)-, and N-(2-cyano-ethyl)-d-ribonamides 8b-h were obtained in quantitative yield. Bromination of the amides 8a-e with acetyl bromide in dioxane followed by acetylation gave 2,3,4-tri-O-acetyl-5-bromo-5-deoxy-N-ethyl, N-butyl, N-hexyl, N-dodecyl, and N-benzyl-d-ribonamides 9a-e in 40-54% yields. To obtain 2,3,4-tri-O-acetyl-5-bromo-5-deoxy-N-(3-methyl-pyridinyl)-, N-(2-hydroxy-ethyl)-, and N-(2-cyano-ethyl)-9f-h, the bromination is necessary before the amidation reaction. Treatment of the bromoamides 9a-h with NaH in DMF followed by methanolysis affords N-alkyl-d-ribono-1,5-lactams 12a-h in quantitative yield.     

Structural requirements of (E)-6-benzylidene-4a-methyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one derivatives as novel melanogenesis inhibitors

Chalcone type compound 1a ((E)-6′-benzylidene-4a′-methyl-4′,4a′,7′,8′-tetrahydro-3′H-spiro[[1,3]dithiolane-2,2′-naphthalen]-5′(6′H)-one) was discovered as an potent inhibitor in melanogenesis. To define its structure-activity relationship, a series of analogs 1b-n, dithiolane truncated 2a-b and ring A removed 3a-e were prepared and evaluated. The electron donating substitution on the phenyl ring (ring C) rather than an electron withdrawing group and dithiolane motif of 1 are needed for the activity enhancement. The scaffold containing both rings A and B associated with α,β-unsaturated system connected to phenyl of 1 was essential for antimelanogenesis.     

5a-Carba-glycopyranoside primers: potential building blocks for biocombinatorial synthesis of glycosphingolipid analogues

Three ether-linked alkyl 5a-carba-glycopyranosides 1b,d, and 5b, and 5a′-carba-lactoside 7b were examined as potent primers in mouse B16 melanoma cells for their feasibility as building blocks for oligosaccharide biosynthesis. Uptake by B16 cells was first observed for all carba-glycoside primers, and, especially, the 5a-carba-sugar analogues of N-acetyl-β-d-glucosaminide 1b and β-d-glucoside 1d were shown to produce two-to-four-fold larger amounts of glycosylated products than the corresponding true sugar primers 1a and 1c. The carba glycoside uptake by cells resulted in β-galactosylation and subsequent sialylation of the incorporated galactose residues, giving rise to glycosylated products 3b and 3d having similar glycan structures as the ganglioside GM3. According to efficient uptake in cells, in addition to stability of the ether-linked pseudo-reducing ends of the oligosaccharides that formed, the carba glycoside primers have been demonstrated to be versatile building blocks for these biocombinatorial syntheses of glycolipid oligosaccharide mimetics. On the other hand, uptake for 5a-carba-galactopyranoside residue was found to be decreased by one-third for dodecyl 5a-carba-β-d-galactopyranoside 5b. Observation of similar levels for 5a′-carba-β-lactoside 7b under both cellular and cell-free conditions suggested that enzymes are likely to recognize the pyranose oxygen atom.     

Sulphated polysaccharides of the grateloupiaceae family : Part VII. Investigation of the acetolysis products of a partially desulphated sample of the polysaccharide of pachymenia carnosa

Investigation of the acetolysis products of a partially desulphated sample of the polysaccharide isolated from Pachymenia carnosa led to the isolation and characterization of the following oligosaccharides: 3-O-α-D-galactopyranosyl-D-galactose (1), 4-O-β-D-galactopyranosyl-D-galactose (2), 3-O-(2-O-methyl-α-D-galactopyranosyl)-D-galactose (3), a 4-O-galactopyranosyl-2-O-methylgalactose (4), 3-O-α-D-galactopyranosyl-6-O-methyl-D-galactose (5), 4-O-β-D-galactopyranosyl-2-O-methyl-D-galactose (6), 2-O-methyl-4-O-(6-O-methyl-β-D-galactopyranosyl)-D-galactose (14), O-β-D-galactopyranosyl-(1→4)-O-α-D-galactopyranosyl-(1→3)-D-galactose (8), O-α-D-galactopyranosyl-(1→3)-O-β-D-galactopyranosyl-(1→4)-D-galactose (9), O-β-D-galactopyranosyl-(1→4)-O-α-(2-O-methyl-D-galactopyranosyl)-(1→3)-D-galactose (11), O-α-(2-O-methyl-D-galactopyranosyl)-(1→3)-O-β-D-galactopyranosyl-(1→4)-D-galactose (12), O-α-D-galactopyranosyl-(1→3)-O-β-D-galactopyranosyl-(1→4)-2-O-methyl-D-galactose (13), O-α-(2-O-methyl-D-galactopyranosyl)-(1→3)-O-β-D-galactopyranosyl-(1→4)-2-O-methyl-D-galactose (16), and O-β-D-galactopyranosyl-(1→4)-O-α-D-galactopyranosyl-(1→3)-O-β-D-galactopyranosyl-(1→4)-D-galactose (10). In addition, evidence was obtained for the presence of 4-O-(6-O-methyl-β-D-galactopyranosyl)-D-galactose (7) and O-β-D-galactopyranosyl-(1→4)-O-α-D-galactopyranosyl-(1→3)-6-O-methyl-D-galactose (15).     

Fluorinated carbohydrates : Part XIII. 2-deoxy-2-fluoro-D-galactose

Reaction of trifluoro(fluoroxy)methane at ca. −80° with 3,4,6-tri-O-acetyl-D-galactal affords trifluoromethyl 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-α-D-galactopyranoside (2, 39%), 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-α-D-galactopyranosyl fluoride (3, 37%), trifluoromethyl 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-α-D-talopyranoside (4, 3%), and 3,4,6-tri-O-acetyl-2-deoxy-2-fluor-α-D-talopyranosyl fluoride (5, 2%). The structures of compounds 2–5 have been established by n.m.r. spectroscopy. Acid hydrolysis of 2 or 3 allords 2-deoxy-2-fluoro-D-galactose.     

Enantiopure dihalocyclopropyl alcohols and esters by lipase catalyzed kinetic resolution

Four halogenated cyclopropane derivatives with a side chain containing a primary (1 and 2) or secondary (3 and 4) alcohol moiety were subject to kinetic resolution catalyzed by lipases. Two of them containing secondary alcohol groups gave excellent results with Candida antarctica lipase B with E-values around 1000. Two enantiopure alcohols and two enantiopure butanoates are described: (1S,1′S)-1-(2′,2′-dichloro-3′,3′-dimethylcyclopropyl) ethanol (3), the corresponding (1R,1′R)-butanoate (3b) and (1S,1′S)-1-(1′-methyl-2′,2′-dibromocyclopropyl) ethanol (4) and the corresponding (1R,1′R)-butanoate (4b).     

Ruthenium(II) carbonyl chloride complexes containing pyridine-functionalised bidentate N-heterocyclic carbenes: Synthesis, structures, and impact of the carbene ligands on catalytic activities

A series of new ruthenium(II) carbonyl chloride complexes with pyridine-functionalised N-heterocyclic carbenes [Ru(Py-NHC)(CO)₂Cl₂], [Py-NHC = 3-methyl-1-(2-pyridyl)imidazol-2-ylidene, 1 (1a and 1b); 3-methyl-1-(2-picoyl)imidazol-2-ylidene, 2 (2a and 2b); 3-methyl-1-(2-pyridyl)benzimidazolin-2-ylidene, 3 (3b); 3-methyl-1-(2-picoyl)benzimidazolin-2-ylidene, 4 (4a and 4b); 1-methyl-4-(2-pyridyl)-1,2,4-triazoline-5-ylidene, 5 (5a and 5b)] have been prepared by transmetallation from the corresponding silver carbene complexes and characterized by NMR, IR spectroscopy and elemental analysis. In these complexes with bidentate Py-NHC ligands, one CO ligand is trans to the Py ligand. In 1a, 2a, 4a, and 5a, the NHC ligand is trans to the other CO ligand, thus leaving the two Cl⁻ ligands trans to each other. In 1b, 2b, 3b, 4b, and 5b, the NHC ligands are trans to one Cl⁻ ligand, and the two Cl⁻ ligands are cis to each other. The structures for 1b, 2b, 3b and 4b have been determined by single-crystal X-ray diffraction. These complexes are efficient catalysts in the transfer hydrogenation of acetophenone and their catalytic activities are found to be influenced by electronic effect of the N-heterocyclic carbene ligands.     

New ternary copper(II) complexes of l-alanine and heterocyclic bases: DNA binding and oxidative DNA cleavage activity

Four new ternary copper(II) complexes of α-amino acid having polypyridyl bases of general formulation [Cu(l-ala)(B)(H₂O)](X) (1-4), where l-ala is l-alanine, B is an N,N-donor heterocyclic base, viz. 2,2′-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2) and 5,6-phenanthroline dione (dione, 3), dipyrido[3,2:2′,3′-f]quinoxaline (dpq, 4), and X = / are synthesized, characterized by various spectroscopic and X-ray crystallographic methods. The complexes show a distorted square-pyramidal (4 + 1) CuN₃O₂ coordination geometry. The one-electron paramagnetic complexes (1-4) display a low energy d-d band near 600 nm in aqueous medium and show a quasi-reversible cyclic voltammetric response due to one-electron Cu(II)/Cu(I) reduction near −100 mV (versus SCE) in DMF-0.1 M TBAP. Binding interactions of the complexes with calf thymus DNA (CT-DNA) were investigated by UV-Vis absorption titration, ethidium bromide displacement assay, viscometric titration experiment and DNA melting studies. All the complexes barring the complexes 1 and 3 are avid binder to the CT-DNA in the DNA minor groove giving an order: 4 > 2 ? 1, 3. The complexes 2 and 4 show appreciable chemical nuclease activity in the presence of 3-mercaptopropionic acid (MPA) as a reducing agent. Hydroxyl radical was investigated to be the DNA cleavage active species. Control experiments in the presence of distamycin-A show primarily minor groove-binding propensity for the complexes 2 and 4 to the DNA.     

Perfluoroalkylated derivatives of 6-deoxy-6-ethylamino-d-galactose, 1-deoxy-1-methylamino-d-glucitol, and 1-amino-1-deoxy-d-glucitol: syntheses, hemocompatibility, and effect on perfluorocarbon emulsion

N-Polyfluoroalkyl derivatives of 6-deoxy-6-ethylamino-1,2;3,4-di-O-isopropylidene-α-d-galactopyranose (8-10), 1-deoxy-1-methylamino-d-glucitol (13-15), and 1-amino-1-deoxy-d-glucitol (16-18), all possessing perfluoroalkyl segment, were prepared using nucleophilic epoxide ring opening of 2-[(perfluoroalkyl)methyl]oxiranes 1-3. Co-emulsifying properties and hemolytic activity of the new perfluoroalkylated amphiphiles were tested. Both types of the polyol derivatives 8-10 and 13-18 generally displayed good to excellent co-emulsifying properties on testing on perfluorodecalin/Pluronic F-68 microemulsions. Mono-perfluoroalkylated compounds 8-10 and 13-15 displayed high hemolysis, whereas acyclic bis-perfluoroalkylated compounds 16-18 were non-hemolytic even for short perfluorobutyl segment (16). The properties were generally improving with increasing perfluoroalkyl chain length.     

Synthesis and characterisation of pyrazolic palladium compounds containing alcohol functionality:: rotation around the Pd-N bond

The ligands 1-hydroxymethylpyrazole (hl¹), 1-(2-hydroxyethyl)pyrazole (hl²) and 1-(3-hydroxypropyl)pyrazole (hl³) react with [PdCl₂(CH₃CN)₂] to give trans-[PdCl₂(hl)₂] compounds. Due to a hindered rotation around the Pd-bond, these compounds present two different conformations in solution: anti and syn. The conformation presented depends on the relative disposition of the hydroxyalkylic chains of the two pyrazolic ligands. The present study was carried out on the basis of NMR experiments. The present paper reports the crystal structure of trans-[PdCl₂(hl²)₂]. The synthesis and characterisation of compounds [Pd(hl)₄](BF₄)₂ (hl = hl¹, hl² and hl³) starting from [Pd(CH₃CN)₄](BF₄)₂ and the corresponding chlorocomplexes trans-[PdCl₂(hl)₂] are also described.     

Multivalent human blood group ABH and Lewis glycotopes are key recognition factors for a lFuc>Man binding lectin from phytopathogenic Ralstonia solanacearum

Ralstonia solanacearum lectin (RSL), that might be involved in phytopathogenicity, has been defined as lFuc?Man specific. However, the effects of polyvalency of glycotopes and mammalian structural units on binding have not been established. In this study, recognition factors of RSL were comprehensively examined with natural multivalent glycotopes and monomeric ligands using enzyme linked lectin-sorbent and inhibition assays. Among the glycans tested, RSL reacted strongly with multivalent blood group A_h (GalNAcα1–3[Fucα1–2]Gal) and H (Fucα1–2Gal) active glycotopes, followed by B_h (Galα1–3[Fucα1–2]Gal), Le^a (Galβ1–3[Fucα1–4]GlcNAc) and Le^b (Fucα1–2Galβ1–3[Fucα1–4]GlcNAc) active glycotopes. But weak or negligible binding was observed for blood group precursors having Galβ1–3/4GlcNAcβ1- (I_β/II_β) residues or Galβ1–3GalNAcα1- (T_α), GalNAcα1-Ser/Thr (Tn) bearing glycoproteins. These results indicate that the density and degree of exposure of multivalent ligands of α1–2 linked lFuc to Gal at the non-reducing end is the most critical factor for binding. An inhibition study with monomeric ligands revealed that the combining site of RSL should be of a groove type to fit trisaccharide binding with highest complementarity to blood group H trisaccharide (H_L; Fucα1–2Galβ1–4Glc). The outstandingly broad RSL saccharide-binding profile might be related to the unusually wide spectrum of plants that suffer from R. solanacearum pathogenicity and provide ideas for protective antiadhesion strategies.     

Discovery of novel ureas and thioureas of 3-decladinosyl-3-hydroxy 15-membered azalides active against efflux-mediated resistant Streptococcus pneumoniae

A series of novel ureas and thioureas of 3-decladinosyl-3-hydroxy 15-membered azalides, were discovered, structurally characterized and biologically evaluated. They have shown good antibacterial activity against selected Gram-positive and Gram-negative bacterial strains. These include N″ substituted 9a-(N′-carbamoyl-γ-aminopropyl)- (6a,c), 9a-(N′-thiocarbamoyl-γ-aminopropyl)- (7a,e), 9a-[N′-(β-cyanoethyl)-N′-(carbamoyl-γ-aminopropyl)]- (9a-c, 9g) 9a-[N′-(β-cyanoethyl)-N′-(thiocarbamoyl-γ-aminopropyl)]-derivatives (10d-f) of 5-O-desosaminyl-9-deoxo-9-dihydro-9a-aza-9a-homoerythronolide A (3).Among the synthesized compounds thiourea 7a and urea 9b have shown substantially improved activity comparable to azithromycin (1) and significantly better activity than the 3-decladinosyl-azithromycin (2) and the parent 3-cladinosyl analogues against efflux-mediated resistant S. pneumoniae.