N-acetylmuramyl-L-alanyl-D-isoglutamine glycosides. Effect of glycoside center configuration and aglycone nature on biological activity

Hexyl, octyl, and cyclohexyl beta-glycosides and heptyl and cyclohexyl alpha-glycosides of muramyl dipeptide (MDP) were synthesized. Tests in vitro and in vivo revealed lower immunostimulating activities of MDP alpha-glycosides in comparison with the corresponding beta-glycosides and MDP itself. In the case of alkyl beta-glycosides, differences in hydrocarbon chain lengths (C4-C8) and in aglycone (aliphatic chain and aliphatic or aromatic ring) exerted no substantial effect on the immunostimulating activity.     

Dialkylmethyl beta-glycosides of N-acetylmuramyl-L-alanyl-D-isoglutamine: synthesis and infection protective and cytotoxic activities

Symmetric secondary linear alcohols were proposed as aglycones for the synthesis of lipophilic beta-glycosides of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP). Pentadecan-8-ol, nonadecan-10-ol, and tricosan-12-ol were glycosylated by the oxazoline method. Based on the corresponding glucosaminides, alkyl beta-glycosides of 4,6-O-isopropylidene-N-acetylmuramic acid were synthesized and coupled with the dipeptide. Deprotection of isopropylidene groups by acidic hydrolysis and catalytic hydrogenolysis of benzyl esters resulted in the target muramyldipeptide glycosides. Nonadecan-10-yl and tricosan-12-yl [beta]-MDPs at doses 2 microg/mice most effectively stimulated antibacterial resistance in mice against Staphylococcus aureus. In contrast to the previously synthesized undecan-6-yl beta-MDP, pentadecan-8-yl, nonadecan-10-yl, and tricosan-12-yl beta-MDPs demonstrated direct cytotoxicity toward tumor cells E-562 and blood mononuclear cells.     

Synthesis of N-acetylglucosamine beta-aryl glycosides catalyzed by crown ethers]

Glycosylation of phenols of various structure with alpha-D-glucosaminyl chloride peracetate in a solid phase-liquid system catalyzed by crown compounds was studied. The highest yields of aryl beta-glycosides were observed at room temperature in acetonitrile using anhydrous potassium carbonate as a base. The optimum phenol-glycosyl donor-base-crown ether ratio was 1:1:1:0.2.     

Syntheses of <Emphasis Type="Italic">N</Emphasis>-vanillyl-nonanamide glycosides using amyloglucosidase from <Emphasis Type="Italic">Rhizopus</Emphasis> and β-glucosidase from sweet almond

Enzymatic syntheses of N-vanillyl-nonanamide, 1, glycosides with D-glucose, 2, D-galactose, 3, D-mannose, 4, D-ribose, 5, maltose, 6, and lactose, 7, were carried out using amyloglucosidase from Rhizopus and beta-glucosidase from sweet almond. The latter catalysed the syntheses of N-vanillyl-nonanamide glycosides (8-13) and exclusively yielded beta-glycosides with carbohydrates 2, 3, 4, 6 and 7, while amyloglucosidase yielded C1-alpha- and beta-glycosides and 6-O-aryl derivatives (8, 9, 11 and 12).     

Synthesis of N-Acetylmuramyl-L-Alanyl-D-Isoglutamine Aryl β-Glycosides

Synthesis of N-acetylmuramyl-L-alanyl-D-isoglutamine phenyl and (2-naphthyl) -glycosides, novel muramyl dipeptide derivatives with phenolic aglycons, was reported. The starting N-acetylglucosamine aryl glycosides were obtained by glycosylation of phenols with peracetylated -glucosaminyl chloride under the conditions of phase-transfer catalysis and used for the synthesis of 4,6-O-isopropylidene-N-acetylmyramic acid aryl -glycosides. Condensation of these derivatives with a dipeptide and subsequent deprotection resulted in the intended glycopeptides.     

A new glycosidation method through nitrite displacement on substituted nitrobenzenes

Benzyl, benzoyl, and acetyl protected 1-OH and 1-SH glycoses in the glucose, glucosamine, galactose, mannose, and lactose series react with nitrobenzenes activated by one or two electron withdrawing substituents like nitro and cyano to afford the corresponding aryl glycosides in 50-100% yield. The S(N)Ar displacement of nitrite by 1-OH glycoses is reversible and gives predominantly the alpha-glycosides, whereas 1-SH glycoses do not anomerize and afford the beta-glycosides. Thus, the prepared dicyanophenyl gycosides are useful building blocks for the preparation of phthalocyanine-glycoconjugates via template synthesis.     

Preparation of oligomeric beta-glycosides from cellulose and hemicellulosic polysaccharides via the glycosyl transferase activity of a trichoderma reesei cellulase

Oligoglycosyl (allyl, 2,3-dihydroxypropyl, ethyl, 2-hydroxyethyl, and methyl) beta-glycosides were generated by endo -transglycosylation reactions catalyzed by commercially available Trichoderma reesei cellulase. A polymeric donor substrate (xyloglucan or cellulose) was incubated with the enzyme in an aqueous solution containing 20% of the acceptor alcohol (allyl alcohol, glycerol, ethanol, ethylene glycol, and methanol, respectively). The products of these reactions included oligomeric alkyl beta-glycosides and reducing oligosaccharides. The high yield of alkyl beta-glycosides may be explained by the resistance of the xyloglucan beta-glycosides to cellulase-mediated hydrolysis. The resistance of the oligoxyloglucan beta-glycosides to endo glucanase catalyzed hydrolysis supports the hypothesis that productive binding of the glycan substrate depends on its interaction with enzyme subsites on both sides of the cleavage point, leading to distortion of the ring geometry of the residue whose glycosidic bond is cleaved. Oligoxyloglucan beta-glycosides were purified by a combination of gel-permeation and reversed-phase HPLC and were structurally characterized by MS and NMR spectroscopy. These results demonstrate that novel oligosaccharide beta-glycosides can be efficiently produced by enzyme-catalyzed fragmentation/transglycosylation reactions starting with a polysaccharide donor substrate. This class of reactions may represent a convenient source of beta-glycosides to be used as synthons for the rapid synthesis of complex glycans.     

Syntheses of the 3- and 4-thio analogues of 4-nitrophenyl 2-acetamido-2-deoxy-beta-D-gluco- and galactopyranoside

The syntheses of 4-nitrophenyl beta-glycosides of the 3-thio and 4-thio analogues of the two principal 2-acetamido-2-deoxy-hexoses found in living systems, GlcNAc and GalNAc, are described. While synthesis of the 4-thio analogues could be achieved via nucleophilic displacements of sulfonate derivatives with thioacetate, problems with neighbouring group acetamido participation necessitated the use of sulfamidate intermediates for the 3-thio analogues. These 3- and 4-thio analogues are employed in the chemo-enzymatic synthesis of thio-oligosaccharide analogues of structures present in glycosaminoglycans, glycoproteins and glycolipids.     

Interaction of tyrosyl aryl dipeptides with S. aureus tyrosyl tRNA synthetase: inhibition and crystal structure of a complex.

Tyrosyl aryl dipeptide inhibitors of S. aureus tyrosyl tRNA synthetase have been identified with IC50 values down to 0.5 microM. A crystal structure of the enzyme complexed to one of the inhibitors shows occupancy of the tyrosyl binding pocket coupled with inhibitor interactions to key catalytic residues.     

Effect of silybin and its glycosides on the expression of cytochromes P450 1A2 and 3A4 in primary cultures of human hepatocytes

Four beta-glycosides of flavonoligan silybin, i.e. silybin beta-galactoside, silybin beta-glucoside, silybin beta-maltoside, silybin beta-lactoside were synthesized in order to improve silybin water solubility and bioavailability (Kren et al., J Chem Soc, Perkin Trans 1, 2467-2474, 1997). The presented paper deals with the effect of silybin and its synthetic beta-glycosides on the expression of two major cytochrome P450 isoforms, CYP1A2 and CYP3A4. Primary cultures of human hepatocytes were the model of choice. mRNAs were analyzed using Northern blot and P-radiolabelled probes. CYP protein content was determined by immunoblotting using specific antibodies. Silybin and its beta-glycosides do not induce expression of CYP1A2 and CYP3A4. Tested compounds did not affect inducible expression of CYP1A2 and CYP3A4 by dioxin and rifampicin, respectively, as evaluated at the level of mRNAs and proteins. Silybin and its beta-glycosides do not interfere with the expression of CYP1A2 and CYP3A4, are not likely to produce drug-drug interactions in terms of the inducibility of two important cytochromes P450.     

Practical synthesis of the 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucosides of Fmoc-serine and Fmoc-threonine and their benzyl esters

Mercuric bromide-promoted glycosylation of Fmoc-Ser-OBn and Fmoc-Thr-OBn with 2-acetamido-2-deoxy-3,4,6-tri-O-acetyl-alpha-D-glucopyranosyl chloride in refluxing 1,2-dichloroethane gave the corresponding beta-glycosides in good yields (64 and 62%, respectively). Direct coupling of the commercially available Fmoc-Ser-OH and Fmoc-Thr-OH carboxylic acids under similar conditions gave the corresponding beta-glycosides, possessing free carboxyl groups, in moderate yields (50 and 40%, respectively).     

Identification of aryl dihydrouracil derivatives as palm initiation site inhibitors of HCV NS5B polymerase

Aryl dihydrouracil derivatives were identified from high throughput screening as potent inhibitors of HCV NS5B polymerase. The aryl dihydrouracil derivatives were shown to be non-competitive with respect to template RNA and elongation nucleotide substrates. They demonstrated genotype 1 specific activity towards HCV NS5B polymerases. Structure activity relationships and genotype specific activities of aryl dihydrouracil derivatives suggested that they bind to the palm initiation nucleotide pocket, a hypothesis which was confirmed by studies with polymerases containing mutations in various inhibitor binding sites. Therefore, aryl dihydrouracil derivatives represent a novel class of palm initiation site inhibitors of HCV NS5B polymerase.     

Design and synthesis of cholecystokinin-4 dipeptide analogues with anxiolytic and anxiogenic activities

A new series of dipeptide analogues of the general formula Ph(CH2)nCO-NH(CH2)mCO-Trp-NH2 (n = 1, 3-5; m = 1-3) was designed based on the structure of the endogenous tetrapeptide cholecystokinin-4 (CCK-4) and the topochemical Shemyakin-Ovchinnikov-Ivanov principle. The L-tryptophan derivatives exhibited anxiolytic properties and the D-tryptophan derivatives, anxiogenic properties. The dipeptide Ph(CH2)5CO-Gly-L-Trp-NH2 (GB-115) with the activity in rats of 0.05-0.2 mg/kg after oral and intraperitoneal administration was chosen for further studies as a promising anxiolytic agent.     

Inhibitors and Dipeptide Substrates for a Microsomal Tyrosylsulfotransferase from rat Brain

Abstract

The sulfotransferase associated with a microsomal fraction from rat brain was previously shown to transfer sulfate groups from 3′-phosphoadenosine 5′-phosphosulfate (PAPS) to peptides derived from the chole cystokinin (CCK) molecule. Three tyrosine-containing dipeptide derivatives, i.e., Cbz-Glu-Tyr, Cbz-Gly-Tyr and Ac-Phe-Tyr are shown here to accept the [³⁵S] sulfate group from [³⁵S] PAPS under the action of this sulfotransferase. The sulfotransferase activity evaluated with either any of these dipeptide derivatives or CCK-8 as acceptors is similarly inhibited by a series of compounds, i.e., lipophilic polycyclic compounds like fluphenazine, tyrosine derivatives like Boc-O-benzyl-tyrosine and phenolsulfotransferase inhibitors like 4,4-di-isothiocyano 2′,2′-disulfonic acid stilbene.     

the synthesis of diporphyrin systems on the basis of tetraphenylporphyrin derivatives bridged with peptide spacers

Diporphyrin systems based on tetraphenylporphyrin derivatives bridged with dipeptide or tripeptide spacers containing Gly and Phe residues were synthesized, and their physicochemical properties were studied.     

Synthesis and fungitoxicity of some pyrimidine derivatives

A series of 12 pyrimidine derivatives were prepared and testedin vitro against growth, sporulation and nucleic acid content ofFusarium oxysporum f. sp.lycopersici andHelminthosporium oryzae. Introduction of a thiazole ring together with two aryl groups into 2-aminopyrimidine brought about drastic toxicity for both fungi. Pyrimidine derivatives with aryl groups alone were less toxic. Nitro groups were found to enhance the toxicity of the pyrimidine derivatives especially when substituted in the ortho-position of the aryl groups. Inhibition of nucleic acid synthesis of both fungi was attributed mainly to the presence of the thiazole ring.     

Inhibitors and dipeptide substrates for a microsomal tyrosylsulfotransferase from rat brain

The sulfotransferase associated with a microsomal fraction from rat brain was previously shown to transfer sulfate groups from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to peptides derived from the cholecystokinin (CCK) molecule. Three tyrosine-containing dipeptide derivatives, i.e., Cbz-Glu-Tyr, Cbz-Gly-Tyr and Ac-Phe-Tyr are shown here to accept the [35S] sulfate group from [35S] PAPS under the action of this sulfotransferase. The sulfotransferase activity evaluated with either any of these dipeptide derivatives or CCK-8 as acceptors is similarly inhibited by a series of compounds, i.e., lipophilic polycyclic compounds like fluphenazine, tyrosine derivatives like Boc-O-benzyl-tyrosine and phenolsulfotransferase inhibitors like 4,4-di-isothiocyano 2',2'-disulfonic acid stilbene.     

Synthesis and characterization of a series of novel glutamic gamma-15N-anilide dipeptides.

The preparation of a series of novel Cbz-Gln-Gly dipeptide derivatives is reported, wherein the gamma-carboxamide groups of the glutamine side chains have been modified to gamma-15N-anilides which are substituted in the para position with -NO2, -Cl, -H, -CH3, -OCH3, and -N(CH3)2. Characterization of the free anilines (p(kappa)a values and 15N NMR chemical shifts) and corresponding gamma-anilides (15N NMR chemical shifts and FTIR wavenumbers) is also reported. Correlation of these physicochemical data to Hammett substituent parameters ((sigma)para) is discussed. These novel dipeptide derivatives should prove to be generally useful for structure-function enzymology studies of gamma-glutamyl transferring enzymes.     

Application of Plasmid to ATP Production by E. coli

A variety of immunomodulators were synthesized by combining biologically active derivatives of 1-thio-muramoyl dipeptide with 4-O-phosphono-d-glucosamine derivatives related to bacterial lipid A, and using the (succinoylamino)undecanoyl group as a spacer. Their immunoadjuvant activities in guinea-pigs were examined.     

Two synthetic antigens related to Streptococcus pneumoniae type 3 capsular polysaccharide

The synthesis of the allyl beta-glycosides (8 and 20, respectively) of beta-D-GlcpA-(1----4)-D-Glcp and beta-D-Glcp-(1----3)-D-GlcpA (overlapping disaccharide fragments A and B) in the linear chain of the capsular polysaccharide (S3) from Streptococcus pneumoniae type 3 is described. Oxidation of allyl 2,3,6,2',3',4'-hexa-O-acetyl-beta-cellobioside with chromic acid and saponification of the product gave 8. The synthesis of 20 involved glycosylation of methyl 5-O-acetyl-1,2-O-isopropylidene-alpha-D-glucofuranuronate or its 3-O-trityl derivative and subsequent furanose----pyranose transformation. The derivatives 8 and 20 were each copolymerised with acrylamide. In serological tests (enzyme immunoassay and passive hemagglutination), the resulting antigens exhibited the specificity of S3. It was concluded that fragment A was a much stronger immunodeterminant than fragment B.