Synthesis of a Spacer-Linked Derivative of Heptopyranosyl(α1-3)heptopyranose Expressed in Lipooligosaccharide and Lipopolysaccharide

Glycosylation of penta-O-acetyl heptopyranosyl trichloroacetimidate with the 3-OH acceptor, methyl 2-O-benzyl-4,6-O-benzylidene-7,8-dideoxy-α-D-manno-oct-7-enopyranoside, gave the desired α1-3-linked disaccharide in a 94% yield. The oct-enopyranoside moiety of the disaccharide was converted to the heptoside by oxidative cleavage with osmium tetroxide/NaIO₄ and subsequent reduction with NaBH₄. The resulting α1-3-linked heptose disaccharide was converted to a tricholoroacetaimidate derivative containing a benzoyl group at C-2. This donor was glycosylated with 2-(carbobenzoxyamino)-1-ethanol to give an α spacer-linked disaccharide derivative in a 90% yield. Zemplén deacylation of the derivative and subsequent hydrogenolysis gave a 2-aminoethyl glycoside of heptopyranosyl(α1-3)heptopyranose.     

Synthesis and Antileishmanial Activity of 3-(α-Azolylbenzyl)indoles

The goal of the present study was to evaluate several azolyl-substituted indoles as new antileishmanial agents. Ten 3- (α -azolylbenzyl)indoles have been synthesized using Friedel-Crafts acylation as a key-step. All the target compounds were found to display high levels of activity when tested against Leishmania mexicana promastigotes in vitro. The most active compounds, showing an IC 50 <1 μM, were 5-bromo-1-ethyl-3-[(2,4-dichlorophenyl)(1 H -imidazol-1-yl)methyl]-1 H -indole 15 and its triazole analogue 17. Four representative compounds 15, 17, 22 and, 23 were also tested against intracellular amastigotes of L. mexicana using ketoconazole and meglumine antimoniate as reference compounds, the results of which are discussed.     

Synthesis and biological evaluation of 3-(azolylmethyl)-1H-indoles and 3-(α-azolylbenzyl)-1H-indoles as selective aromatase inhibitors

This present study identifies a number of azolyl-substituted indoles as potent inhibitors of aromatase. In the sub-series of 3-(azolylmethyl)-1H-indoles, four imidazole derivatives and their triazole analogues were tested. Imidazole derivatives 11 and 14 in which the benzyl moiety was substituted by 2-chloro and 4-cyano groups, respectively, were the most active, with IC₅₀ values ranging between 0.054 and 0.050 μM. In the other sub-series, eight 3-(α-azolylbenzyl)-1H-indoles were prepared and tested. Compound 30, the N-ethyl imidazole derivative, proved to be an aromatase inhibitor, showing an IC₅₀ value of 0.052 μM. All target compounds were further evaluated against 17α-hydroxylase/C17,20-lyase to determine their selectivity profile.     

Synthesis of methyl 2-acetamido-2-deoxy-3-O-(β-d-galactopyranosyl)-α-d-galactopyranoside from a corresponding thioglycoside derivative

The title disaccharide glycoside was synthesized by halide ion-promoted glycosidation, using methanol and the disaccharide bromide derived from methyl 2-azido-3-O-(2,3,4,6-tetra-O-benzoyl--d-galactopyranosyl)-4,6-O-benzylidene-2-deoxy-1-thio--d-galactopyranoside. This derivative in turn was prepared by silver triflate-promoted condensation of monosaccharide derivatives.     

Synthesis and moisture absorption and retention activities of a carboxymethyl and a quaternary ammonium derivative of α,α-trehalose

Carboxymethyl α,α-trehalose (CMT) and a quaternary ammonium derivative of α,α-trehalose (QT) were successfully prepared, and their moisture absorption and retention activities were assessed. Results showed that both CMT and QT had better moisture absorption abilities at 43% and 81% relative humidity (RH) than α,α-trehalose. In addition, the two α,α-trehalose derivatives had better moisture retention abilities than α,α-trehalose under three humidity conditions: 81% RH, 43% RH, and under dry conditions. Therefore, carboxymethylation and quaternarization could improve the moisture absorption and retention abilities of α,α-trehalose. CMT and QT showed better moisture absorption ability and moisture retention ability than that of hyaluronan (HA), and could potentially find a use as moisture retention ingredient, for example, in cosmetics.     

Synthesis of 1-(4-Keto-2, 3-O-isopropylidene-α-L-rhamnopyranosyl) uracil

Abstract

Synthesis of 1-(2, 3, 4-tri-0-acetyl-α-L-rhamnopyranosyl) uracil (3), 1-(α-L-rhamnopyranosyl) uracil (4), 1-(2, 3-0-isopropylidene-α-L-rhamnosyl) uracil (5), and 1-(2, 3-0-isopropylidene-4-keto-α-L-rhamnopyranosyl) uracil (6) are reported. Oxidation of (5) to (6) was effected using pyridinium chlorochromate in presence of molecular sieves.     

Stereoselective Synthesis of 1- and 2-O-α-d-Cellotriosyl-3-deoxy-2(R)- and 2(S)-glycerols Related to Rhynchosporoside

The stereoselective synthesis of 1- and 2-O-α-d-cellotriosyl-3-deoxy-2(R)- and 2(S)-glycerols, which determined the structure of rhynchosporoside produced by Rhynchosporium secalis, and their phytotoxicity toward the host plant (Hordeum vulgare) are described in detail.     

Enzymatic Synthesis of 1,4-di-α-d-Glucosyl-l-sorbose and 1-α-Iso-maltosyl-l-sorbose

Several new methylenedioxyphenyl (MDP) ethers were synthesised from sesamol and methoxy substituted sesamols and screened as pyrethrum synergists. In general, the synergistic activity increased with the methoxyl substituents and decreased in the corresponding alkenyl analogs. The synergistic activity of alkyl ethers was found to vary with the alkyl chain, n-propyl ethers showing the maximum. In the case of alkenyl ethers, the activity followed the order γ,γ-dimethyl allyl>β-methallyl > allyl and showed no correlation between R_m and synergistic activity.     

Synthesis and stability assay of 4-methylumbelliferyl (1→3)-β-D-pentaglucoside

The synthesis and stability of 4-methylumbelliferyl (1 → 3)-β-D-pentaglucoside 3 are described. The (1 → 3)-β-D-glucan isolated from the cell walls of Saccharomyces cerevisiae was recovered from the aqueous medium as water-insoluble particles by the spray drying (GS) method. The acid-solubilized (1 → 3)-β-D-oligoglucosides were prepared by partial acid hydrolysis of glucan. The peracetylated (1 → 3)-β-D-pentaglucoside 1 was obtained by isolation of peracetylated (1 → 3)-β-D-oligoglucoside mixture. The peracetylated 4-methylumbelliferyl (1 → 3)-β-D-pentaglucoside 2 was synthesized by treating compound 1 with the 4-methylumbelliferone and a Lewis acid (SnCl₄) catalyst. NaOMe in dry methanol was used for the deacetylation of the blocked derivative, to give the target compound 3 in an overall yield of 35%. Activity assays with β-glucosidase indicated that compound 3 was much more stable than the corresponding pentasaccharide.     

Synthesis of p-trifluoroacetamidophenyl O-α-D-galactopyranosyl-(1→2)-O-α-D-mannopyranosyl-(1→4)-α-L-rhamnopyranoside

The role of exposed tyrosine side-chains in enzyme-catalysed reactions has been studied for porcine-pancreatic alpha-amylase, sweet-potato beta-amylase, and Aspergillus niger glucamylase using N-acetylimidazole as the specific protein reagent. The changes in activity binding affinity (Δk_?1/k₊₁), and kinetic parameters (K_m,k₂) due to acetylation of the phenolic hydroxyl groups have been determined. Acetylation of each enzyme occurred by an “apparent” first-order reaction with a rate constant of 0.72–1.4 x 10^?1min^?1. Acetylation increased the apparent K_m (soluble starch as the substrate) for each enzyme (appreciably for alpha-amylase and glucamylase), whereas k² remained unchanged. Similarly, for each enzyme, the binding affinity for immobilised cyclohexa-amylose decreased appreciably, whereas the catalytic activity was reduced only to a small degree (and remained unchanged for beta-amylase). It is concluded that the tyrosine groups located in the active centre of each enzyme have a substrate-binding function.     

Synthesis of 1,2,3-triazolo-linked octyl (1→6)-α-D-oligomannosides and their evaluation in mycobacterial mannosyltransferase assay

The synthesis of conjugates consisting of two or three mannose units interconnected by a 1,2,3-triazole linker installed by the "click" reaction is reported. These conjugates were evaluated in mycobacterial mannosyltransferase (ManT) assay. Detailed analysis of the reaction products showed that these compounds with triazole linker between sugar moieties were tolerated by the enzyme, which elongated them by one or two sugar units with α-(1→6) linkage. The effectiveness of this transfer was reduced in comparison to that observed for the acceptor analogues containing a glycosidic linkage, but still, this is the first report on such unnatural compounds serving as substrates for mycobacterial ManT. The ability of the studied compounds to function as acceptors for the ManT suggests that the relative distance and spatial orientation of acceptor octyl hydrophobic aglycone (optimal length for the ManT) and free primary C-6 hydroxy group of the nonreducing terminal mannose unit (to which glycosyl residue is transferred by the mycobacterial ManT) are important for ManT activity, but at the same time, their variations are tolerated by the enzyme in a relatively wide range.     

Synthesis of 1-(β-D-Glycopyranosyl)-3-Deazapyrimidines from 2-Hydroxy and 2-Mercaptopyridines

Abstract

The synthesis of new 4- and 5-substituted-3-cyanopyridine nucleosides has been performed by reacting the silylated pyridines and penta-O-acetyl-α -D-glycopyranose in dichloroethane in the presence of SnCl₄. The free nucleosides were tested for their potential activity against HIV and different types of tumor.     

Purification and characterization of a β-1,3-glucomannanase expressed in Pichia pastoris

The glycoside hydrolase β-1,3-glucomannanase is an enzyme that specifically breaks the β-1,3 glycosidic bond of the glucomannan, the main cell wall constituent of some yeasts. In this work, a codon optimized DNA sequence of the MAN5C gene from Penicillium lilacinum ATCC 36010 was expressed in the yeast Pichia pastoris under the control of AOX1 promoter. The recombinant protein plMAN5C was purified from the shake flask culture and the stirred-tank bioreactor culture in yields of 30.0 mg/l and 224.0 mg/l, respectively. The purified protein had a specific activity of 14.6 U/mg at 37 °C, pH 4.5. Biochemical analysis showed that the optimal temperature and pH for plMAN5C were 50 °C and 4.5, respectively. The recombinant plMAN5C was efficient in lysis of the cell wall of the red yeast Rhodosporidium toruloides to form protoplast. Our work provided an effective system for heterogeneous production of β-1,3-glucomannanase, which should facilitate a more convenient application of this enzyme in biotechnology and other related areas.     

Synthesis of a Stereoisomeric Mixture of 3-Hydroxy-α-damascone

The relationships among the spinnability, the rheological properties, the spun fiber strength, and the inhibition of lysinoalanine (LAL) formation with the addition of reducing agents were studied to get safe, edible, fibrous soy protein, having excellent spun fiber strength, when a dope of 20% protein concentration was used as a normal dope. It was found that cysteine and 2-mercaptoethanol were effective in reducing LAL formation and the dopes prepared with the addition of these agents showed almost the same spun fiber strength as that of the normal dope prepared without agents. Especially, cysteine was the most effective agent for inhibiting LAL formation to get fibrous protein for meat analogues. The most suitable concentration for inhibiting LAL formation was 2% cysteine in the total protein. The dopes with the addition of 2-mercaptoethanol and Na₂SO₃ had lower viscoelastic values and their frequency dependence of G' was higher than that of the normal dope. However, the dopes with the addition of other reducing agents (NaHSO₃, glycine, reduced glutathione) had higher viscoelastic values and lower frequency dependence of G'. The viscoelastic values of the dopes with the addition of 2-mercaptoethanol, Na₂SO₃, and that of the normal dope were decreased with the lapse of time, but the dopes prepared by the addition of other agents had constant viscoelastic values.     

Conformation of (1→3)-α-D-Glucan Tribenzoate

The molecular conformation of (1→3)-α-D-glucan tribenzoate (TBG) was studied by X-ray diffraction measurements coupled with a conformational analysis. Although the fiber pattern obtained was of very low crystallinity, the presence of a meridional reflection at the 5th layer line indicated that the TBG molecule took a five-fold helical conformation with a 19.63 A fiber repeat. A conformational analysis on the five-fold helix, which was done by calculating van der Waals’ repulsion energy between non-bonded atoms comprising the TBG chain, suggested that the most preferable energy-based conformation was –5/1, a left-handed five-fold helix.     

Synthesis of methyl α-d-glucopyranosyl-(1–2)-α-d-galactopyranosyl-(1-3)-α-d-glucopyranoside and an acyclic analogue thereof for probing the carbohydrate-binding specificity of bacteriophage ϕX 174

The title trisaccharide was synthesized using methyl 1-thioglycoside building blocks. An acyclic analogue, methyl 3-O-(α-D-glycopyranosyl-oxyethyl)-α-D-glucopyranoside, which has an ethylene bridge in place of the galactosyl residue, was also synthesized.     

Synthesis of 2-(p-trifluoroacetamidophenyl)ethylO-α-l-fucopyranosyl-(1–3)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl) (1–3)-O-β-d-galactopyranosyl-(1–4)-β-d-glucopyranoside,a tetrasaccharide fragment of a tumour-associated glycosphingolipid

The tetrasaccharide 2-(p-trifluoroacetamidophenyl)ethylO-α-l-fucopyranosyl-(1–3)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1–3)-O-β-d-galactopyranosyl-(1–4)-β-d-glucopyranoside was synthesized from thioglycoside intermediates. The key step was a methyl triflate promoted glycosidation of a lactose-derived 3′,4′-diol with a disaccharide thioglycoside to give a β(1–3)-linked tetrasaccharide derivative in 67% yield.     

Synthesis and antitumor activity of β-carboline 3-(substituted-carbohydrazide) derivatives

A series of β-carboline derivatives bearing a substituted-carbohydrazide moiety at C-3 were synthesized and evaluated for their antitumor activity against eight human cancer cell lines. The β-carboline N-(substituted-benzylidene)carbohydrazides showed, in general, a greater antitumor activity than their N-(alkylidene)carbohydrazide analogues. The N(9)-methylation of β-carboline N-(substituted-benzylidene) carbohydrazides resulted in a decrease of antitumor activity. Among compounds tested, the benzylidene-carbohydrazides 3, 4, 11, 13, 16, 21 and 22 were the most active, possessing IC(50) less than 10 μM for six of the eight tumor cell lines assayed. The derivative 4 displayed the most significant activity toward all tested cell lines, with a remarkable cytotoxicity against renal (786-0) cell lines (IC(50)=0.04 μM). Compound 4 was assayed for its in vivo antineoplastic activity in the Ehrlich solid carcinoma assay.     

Synthesis of β-1, 3-Glucan and β-1, 3 and β-1, 4-Mixed Glucan from UDP-α-d-Glucose

A particulate enzyme preparation from Phaseolus aureus (mung bean) seedlings catalyzed the synthesis of a water insoluble β-1,3-glucan from UDP-α-d-glucose (UDPG) at high concentrations (0.4~20 mm) and an alkaline insoluble β-1,3 and β-1,4-mixed glucan from UDPG at a low concentration (8.5 µm).

Furthermore, the two kinds of β-glucan synthetases which were investigated with two reaction systems at high and low concentrations of UDPG had different properties in optimal pH, stability of enzyme activity, and metallic ion requirement.