The reactions of organosulfur transfer reagents with Fe2(CO)9 and the synthesis of the Fe2(CO)6 derivative of α-lipoic acid

Treatment of Fe₂(CO)₉ with sulfur-transfer reagents of the types ImideSSImide and RSSImide where H-imide = phthalimide, succinimide, benzimidazole, morpholine and piperazine, and R  CH₂Ph and CMe₃ leads to cleavage of both the sulfursulfur bond and the sulfurnitrogen bond to give Fe₃(CO)₉S₂ in varying yields, some Fe₂(CO)₆S₂ plus low yields of the appropriate dimers of the type Fe₂(CO)₆(SR)(SR′), where R = R′ = phthal imido, CH₂Ph, CMe₃ and R = CH₂Ph, CMe₃, R′ = phthalimido. The naturally occurring cyclic disulfide D,L-α-lipoic acid, its methyl ester and amide react with Fe₂(CO)₉ to give Fe₂(CO)₆ derivatives wherein the sulfursufur bond has been broken.     

Stereoselective synthesis of chaulmoogric acid and related fatty acid from 2-(±)-cyclopentenecarboxylic acid by Bacillus subtilis (ATCC 7059)

2-(±)-Cyclopentenecarboxylic acid added to the culture medium is incorporated into two new fatty acids by the growing cells of Bacillus subtilis (ATCC 7059). The new fatty acids, amounting to 24% of the total cellular fatty acids, are identified as hydrocarpic [11-(2′-cyclopentenyl)-hendecanoic] and chaulmoogric [13-(2′-cyclopentenyl)-tridecanoic] by gas-liquid chromatography and mass spectrometry. These C₁₆ and C₁₈ fatty acids are optically active, levorotatory, with the specific rotation of ?50.4° as mixture, thus the optical purity of approximately 80%. This indicates that the optical rotation of these bacterial fatty acids are opposite with that of the fatty acids from plant oils.     

In vivo anticoccidial activity of berberine [18, 5,6-dihydro-9,10-dimethoxybenzo(g)-1,3-benzodioxolo(5,6-a) quinolizinium] – An isoquinoline alkaloid present in the root bark of Berberis lycium

Coccidiosis, caused by various Eimeria species, is a major parasitic disease in chicken. However the increasing resistance of these parasites to currently used anticoccidial drugs has stimulated the search for new methods of control. As part of this effort we investigated the root bark of Berberis lycium (barberry) as a potential source of compounds with anticoccidial activity. In the present study anticoccidial activity of different solvent extracts of the root bark of B. lycium and berberine was evaluated in vivo using broiler chicken. Results of the study demonstrated equipotent efficacy of pure berberine in comparison to that of standard drug amprolium on the basis of reduction in coccidian oocyst output, body weight gain of chicken and feed conversion ratio. Among the extracts crude methanolic extract showed highest anticoccidial activity tested at 300 mg/kg body weight which could be due to the presence of alcohol-soluble active ingredients in root bark of B. lycium. Toxicological studies revealed that B. lycium extracts as well as berberine were not lethal up to dosage of 2000 mg/kg body weight. LD⁵⁰ was not determined as mortalities were not recorded in any of the five groups of chicken. From the present study it can be concluded that root bark of B. lycium has the immense potential to contribute to the control of coccidian parasites of chicken. Our results corroborate the use of berberine for treatment of severe diarrhoea, amoebiasis and intestinal infections and could justify its use in folk medicine for treatment of haemorrhagic dysentery.     

Why is a specific amino acid sequence of F glycoprotein required for the membrane fusion reaction between envelope of HVJ (Sendai virus) and target cell membranes?

Since homology among the fusogenic sequences of the F glycoprotein of paramyxoviruses is high compared with other hydrophobic sequences such as transmembrane sequences and signal peptides, specific binding of this segment to some membrane component was suspected. Thus, temperature-dependent binding of cholesterol to F protein was found. A virus inhibitory peptide (Z-D-Phe-L-Phe-Gly) was found to bind to virus particles also temperature dependently. These dependency are very similar to that of the fusion reaction. Binding of cholesterol and the peptide to the fusogenic sequence of F protein was suggested based on construction of molecular models. Importance of these bindings for understanding the fusion mechanism is discussed.     

Biotransformation of oleic acid into (E)-10-hydroxy-8-octadecenoic acid and (E)-7,10-dihydroxy-8-octadecenoic acid by Pseudomonas sp. 42A2 in an immobilized system

Oleic acid was transformed into 10-hydroxy-8E-octadecenoic acid and 7,10-dihydroxy-8E-octadecenoic acid using Pseudomonas sp. 42A2 NCIMB 40045 in different immobilised supports. Celite R633 gave highest conversions in 48 h: the cellular yield (Y _p/x) g products g^–1 of cellular protein in the immobilised culture was 5 compared with the free-cell culture Y _p/x of 3.8. Conversion of oleic acid in the immobilised cell culture was 50% of the carbon source supplied.     

Structural and functional interaction of (±)-2-(N-tert-butylamino)-3′-iodo-4′-azidopropiophenone,a photoreactive bupropion derivative,with nicotinic acetylcholine receptors

The pharmacological properties of (±)-2-(N-tert-butylamino)-3′-iodo-4′-azidopropiophenone [(±)-SADU-3-72], a photoreactive analog of bupropion (BP), were characterized at different muscle nicotinic acetylcholine receptors (AChRs) by functional and structural approaches. Ca²⁺ influx results indicate that (±)-SADU-3-72 is 17- and 6-fold more potent than BP in inhibiting human (h) embryonic (hα1β1γδ) and adult (hα1β1εδ) muscle AChRs, respectively. (±)-SADU-3-72 binds with high affinity to the [³H]TCP site within the resting or desensitized Torpedo AChR ion channel, whereas BP has higher affinity for desensitized AChRs. Molecular docking results indicate that both SADU-3-72 enantiomers interact with the valine (position 13′) and serine (position 6′) rings. However, an additional domain, between the outer (position 20′) and valine rings, is observed in Torpedo AChR ion channels. Our results indicate that the azido group of (±)-SADU-3-72 may enhance its interaction with polar groups and the formation of hydrogen bonds at AChRs, thus supporting the observed higher potency and affinity of (±)-SADU-3-72 compared to BP. Collectively our results are consistent with a model where BP/SADU-3-72 and TCP bind to overlapping sites within the lumen of muscle AChR ion channels. Based on these results, we believe that (±)-SADU-3-72 is a promising photoprobe for mapping the BP binding site, especially within the resting AChR ion channel.     

Synthesis of the Fully Protected Phosphoramidite of the Benzene-DNA Adduct,N 2-(4-Hydroxyphenyl)-2′-Deoxyguanosine and Incorporation of the Later into DNA Oligomers

N²- (4-Hydroxyphenyl)-2 ′-deoxyguanosine-5 ′-O-DMT-3 ′-phosphoramidite has been synthesized and used to incorporate the N²-(4-hydroxyphenyl)-2 ′-dG (N²-4-HOPh-dG) into DNA, using solid-state synthesis technology. The key step to obtaining the xenonucleoside is a palladium (Xantphos-chelated) catalyzed N²-arylation (Buchwald-Hartwig reaction) of a fully protected 2 ′-deoxyguanosine derivative by 4-isobutyryloxybromobenzene. The reaction proceeded in good yield and the adduct was converted to the required 5 ′-O-DMT-3 ′-O-phosphoramidite by standard methods. The latter was used to synthesize oligodeoxynucleotides in which the N²-4-HOPh-dG adduct was incorporated site-specifically. The oligomers were purified by reverse-phase HPLC. Enzymatic hydrolysis and HPLC analysis confirmed the presence of this adduct in the oligomers.     

Synthesis of 1,3,4,6-tetra-O-acetyl-2-[3-alkyl-(aryl)-thioreido]-2-deoxy-α-d-glucopyranoses and their transformation into 2-alkyl(aryl)amino-(1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-thiazolines

1,3,4,6-Tetra-O-acetyl-2-deoxy-2-isothiocyanato-α-d-glucopyranose, produced from 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-α-d-glucopyranose hydrochloride, thiophosgene, and calcium carbonate, was condensed with alkyl- and aryl-amines in ether to afford the crystalline 1,3,4,6-tetra-O-acetyl-2-[3-alkyl(aryl)-thioureido]-2-deoxy-α-d-glucopyranoses (2). Compounds 2 and the β anomers 3 were converted in high yield into 2-alkyl(aryl)amino-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-thiazoline hydrobromides (4) by hydrogen bromide-promoted cyclisation. The O-deacetylated thiazoline hydrobromide 5 was also isolated and converted into 2-[N-(4-methoxyphenyl)acetamido]-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-glucopyrano)[2,1-d]-2-thiazoline (8). Conformational studies of 4 and 8 were made by ¹H-n.m.r. spectroscopy.     

Effect of 2-Amino Substitution on the Antiviral Effects of 5-Ethyl-2′-Deoxyuridine and (E)-5-(2-bromovinyl)-2′-Deoxyuridine and Their Incorporation into DNA

Abstract

The 2-amino derivatives of 5-ethyl-2′-deoxyuridine (EDU) and (E)-5-(2-bromovinyl)-2′-deoxyuridine (BVDU) have been synthesized and evaluated for anti-herpesvirus activity. They were at least 1000-fold less effective against herpes simplex virus replication than the parent compounds EDU and BVDU. The 5′-triphosphates of the 2-amino substituted EDU, BVDU and thymidine derivatives were also synthesized and examined on their substrate/inhibitor properties against different DNA polymerases. None of the compounds proved markedly inhibitory to HSV-1 DNA polymerase or cellular DNA polymerase a. Nor were they incorporated into the growing DNA chain.     

(±)-Octahydro-2-methy 1-trans-5 (1H)-isoquinolone methiodide: A probe that reveals a partial map of the nicotinic receptor's recognition site

A new, semirigid, nicotinic agonist ( ± )-octahydro-2-methyl-trans-5 (1H)-isoquinolone methiodide was synthesized. The disposition of this agonist's nitrogen and carbonyl group conforms well to the prevailing notion of a pharmacophore for the nicotinic receptor. Comparing its structure and electrostatic potential surfaces, we predicted that its activity would be similar to that of carbamylcholine at the frog neuromuscular junction. Instead, the potency of the isoquinolone was only 0.015 times as potent as (+) carbamylcholine. We conclude, after eliminating other possibilities, that the vicinity of the carbonyl group of an agonist must be planar to fit a confined space within the receptor's recognition site. The isoquinolone is a weak agonist because its methylene group β to the carbonyl intrudes on this space.     

Design,synthesis and in vitro evaluation of (R)-4-(2-(tert-butylamino)-1-hydroxyethyl)-2-(hydroxymethyl)phenyl hydrogen phenylboronate: A novel salbutamol derivative with high intrinsic efficacy on the β2 adrenoceptor

We tested a set of boron containing arylethanolamine derivatives on the human and guinea pig β₂ adrenoceptor (β₂AR) 3-D structures by docking methodology. The compound with the highest affinity based on docking analysis, (R)-4-(2-(tert-butylamino)-1-hydroxyethyl)-2-(hydroxymethyl)phenyl hydrogen phenylboronate (boronterol) was synthesized, characterized and tested in guinea pig tracheal rings at basal tone and with histamine-induced contractions. Boronterol was at least eightfold more potent than salbutamol as a smooth muscle relaxant drug (judged by the EC₅₀ values) and showed a similar maximal relaxant effect as isoproterenol. ICI118,551 showed competitive antagonism on the relaxing effect of boronterol. These results suggest the β₂AR agonist action of boronterol.     

Efficient RNA-targeting by the introduction of aromatic stacking in the duplex major groove via 5-(1-phenyl-1,2,3-triazol-4-yl)-2′-deoxyuridines

Three pyrimidine nucleosides with differently substituted phenyltriazoles attached to the 5-position were prepared by Cu(I)-assisted azide–alkyne cycloadditions (CuAAC) and incorporated into oligonucleotides. Efficient π–π-stacking between two or more phenyltriazoles in the major groove was found to increase the thermal stability of a DNA:RNA duplex significantly. The best stacking, and most stable duplex, was obtained by a sulfonamide substituted derivative.     

Molecular insight into amyloid oligomer destabilizing mechanism of flavonoid derivative 2-(4′ benzyloxyphenyl)-3-hydroxy-chromen-4-one through docking and molecular dynamics simulations

Aggregation of amyloid peptide (Aβ) has been shown to be directly related to progression of Alzheimer’s disease (AD). Aβ is neurotoxic and its deposition and aggregation ultimately lead to cell death. In our previous work, we reported flavonoid derivative (compound 1) showing promising result in transgenic AD model of Drosophila. Compound 1 showed prevention of Aβ-induced neurotoxicity and neuroprotective efficacy in Drosophila system. However, mechanism of action of compound 1 and its effect on the amyloid is not known. We therefore performed molecular docking and atomistic, explicit-solvent molecular dynamics simulations to investigate the process of Aβ interaction, inhibition, and destabilizing mechanism. Results showed different preferred binding sites of compound 1 and good affinity toward the target. Through the course of 35 ns molecular dynamics simulation, conformations_5 of compound 1 intercalates into the hydrophobic core near the salt bridge and showed major structural changes as compared to other conformations. Compound 1 showed interference with the salt bridge and thus reducing the inter strand hydrogen bound network. This minimizes the side chain interaction between the chains A–B leading to disorder in oligomer. Contact map analysis of amino acid residues between chains A and B also showed lesser interaction with adjacent amino acids in the presence of compound 1 (conformations_5). The study provides an insight into how compound 1 interferes and disorders the Aβ peptide. These findings will further help to design better inhibitors for aggregation of the amyloid oligomer.     

2-(Benzothiazol-2-yl)-phenyl-β-d-galactopyranoside derivatives as fluorescent pigment dyeing substrates and their application for the assay of β-d-galactosidase activities

2-(Benzothiazol-2-yl)-phenyl-β-d-galactopyranoside derivatives were synthesized as novel artificial fluorescent pigment dyeing substrates for β-d-galactosidase. The substrates, which exhibited non-fluorescence or weak fluorescence in solution phase, were smoothly hydrolyzed by β-d-galactosidase from Aspergillus oryzae and yielded a water-insoluble strong fluorescent pigment. The difference of fluorescent intensity exhibited a linear relationship with the amount of enzyme.     

Flow cytometric monitoring of multidrug drug resistance protein 1 (MRP1/ABCC1) -mediated transport of 2′,7′-bis-(3-carboxypropyl)-5-(and-6)- carboxyfluorescein (BCPCF) into human erythrocyte membrane inside-out vesicles

The presence of human multidrug resistance protein 1 (MRP1/ABCC1) in the human erythrocyte membrane is well established. In the present study, flow cytometric monitoring is introduced to identify MRP1 as the main transporter of 2′,7′-bis-(3-carboxypropyl)-5-(and-6)-carboxyfluorescein (BCPCF) in the erythrocyte membrane and to facilitate inhibition and kinetic studies of MRP1-mediated transport. The ATP-dependent transport of BCPCF into human erythrocyte inside-out vesicles and, for comparison, into MRP1-expressing Sf9 cell membrane inside-out vesicles were studied. The MRP1-specific monoclonal antibody, QCRL-3 and the MRP1 inhibitor, MK-571 strongly decreased the uptake of BCPCF into both erythrocyte and MRP1-expressing Sf9 cell membrane inside-out vesicles. The inhibition profiles of cyclosporin A, verapamil, benzbromarone, and probenecid in erythrocyte membrane vesicles were typical for MRP1-mediated transport. Furthermore, kinetic constants K_m and V_max of BCPCF transport into erythrocyte membrane inside-out vesicles were determined in the absence and in the presence of selected inhibitors (MK-571, cyclosporin A, benzbromarone and verapamil). The presented results identified MRP1 as the major transporter of BCPCF in the human erythrocyte membrane and showed for the first time that the active transport of fluorescent substrate into inside-out vesicles can be monitored by flow cytometry.     

Identification of the initial binding sites of αs2-casein f(183-207) and effect on bacterial membranes and cell morphology

The aim of this work was to identify the initial binding sites to the bacterial membranes of the antimicrobial peptide α_s2-casein f(183-207) and also to acquire further insight into membrane permeabilization of this peptide. Furthermore, cell morphology was studied by transmission electron microscopy. In all the experiments, bovine LFcin was employed as a comparison. Results showed that initial binding sites of α_s2-casein f(183-207) peptide were lipoteichoic acid in Gram-positive bacteria and lipopolysaccharide in Gram-negative. The peptide was able to permeabilize the outer and inner membranes. Moreover, the α_s2-casein peptide f(183-207) generated pores in the outer membrane of Gram-negative bacteria and in the cell wall of Gram-positive bacteria. In the Gram-negative bacteria, f(183-207) originated cytoplasm condensation, and in the Gram-positive bacteria the cytoplasmic content leaked into the extracellular medium. Furthermore, the experiments of inner and outer membrane permeabilization performed with LFcin-B showed that this peptide also has the ability to permeabilize both the inner and outer membranes.     

CD and NMR assignment of the anomeric configuration of 4-(5-deoxy-α,β-l-arabinofuranosyl)-2-phenyl-2H-1,2,3-triazole C-nucleoside analogs

Acid-catalyzed dehydrative cyclization of 5-deoxy-l-manno-pentitol-1-yl)-2-heptulose bisphenylhydrazone and subsequent reflux with copper sulfate gave an anomeric mixture of 4-(5-deoxy-α,β-l-arabinofuranosyl)-2-phenyl-2H-1,2,3-triazole C-nucleoside analogs. The mixture was separated by chromatography, and the anomeric compositions configurations of the components were determined by CD, NMR, mass spectroscopy, and acylation.     

Isolation,stereochemical study,and racemization of (±)-pratenone A,the first naturally occurring 3-(1-naphthyl)-2-benzofuran-1(3H)-one polyketide from a marine-derived actinobacterium

(±)-Pratenone A ( 1 ), the first representative of natural 3-(1-naphthyl)-2-benzofuran-1(3H)-one polyketides, was isolated from a marine-derived Streptomyces pratensis strain KCB-132 together with three other new analogues ( 2−4 ). Its structure was assigned by spectroscopic analysis, and the absolute configurations of the two enantiomers separated by high-performance liquid chromatography were determined by single-crystal X-ray diffraction and electronic circular dichroism calculations. The solvent-induced racemization of 1 and a proposed biogenetic pathway to 1−4 from the co-isolated angucyclinone precursor, as well as their biological activity, are also discussed.     

Structure–activity relationship and interaction studies of new SIRT1 inhibitors with the scaffold of 3-(furan-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole

SIRT1 is a NAD⁺-dependent deacetylase. It deacetylates a broad range of substrates and is involved in multiple diseases such as type 2 diabetes and cancer. Here we discovered a new class of SIRT1 inhibitors with the scaffold of 3-(furan-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole. The inhibitors up-regulate acetyl p53 level in human breast cells MCF-7. The docking simulations indicated that the scaffold and the R-substituents of the inhibitors bind in the C and D pocket of SIRT1, respectively, which was supported by the structure–activity relationship and SIRT1 mutagenesis studies. We propose that binding of the inhibitors repels the entering of the nicotinamide moiety of NAD⁺ to the C pocket, prevents its transformation to the productive conformation and therefore inhibits the deacetylation catalyzed by SIRT1.