[Reactions of 1-(X-benzoyl)-4R-thiosemicarbazide with chloroacetone and omega-bromoacetophenone. IV. 4-phenyl and 4-(p-tolyl)-thiosemicarbazide of o-chlorobenzoic acid]

The reactions of 4-phenyl and 4-(p-tolyl)-thiosemicarbazide of o-chlorobenzoic acid (Ig, h) with chloroacetone and omega-bromoacetophenone were investigated in: methanolic medium (method D); methanolic medium in the presence of anhydrous CH3COONa (method E); methanolic medium in the presence of N(C2H5)3 (method F). In the methods E and F mercaptotriazoles Vg, h were obtained. The properties of compounds II ł-o and III ł-o were determined under the conditions of basic and acidic hydrolysis. The results of UV, IR and NMR spectroscopic measurements were reported.

[Reactions of 1-(X-benzoyl)-4-R-thiosemicarbazide with chloroacetone and omega-bromoacetophenone. V. 4-(o-tolyl)-thiosemicarbazide of of o-chloro- and p-chlorobenzoic acid]

The reactions of 4-(o-tolyl)-thiosemicarbazide of o-chloro- and p-chlorobenzoic acid (Ii, j) with chloroacetone and omega-bromoacetophenone were investigated in: methanolic medium (method D); methanolic medium in the presence of anhydrous CH3COONa (method E); methanolic medium in the presence of N(C2H5)3 (method F). The properties of compounds II p-t and III p-t were determined under the conditions of basic and acidic hydrolysis. The results of UV, IR and NMR spectroscopic measurements were reported.

Studies on the lead-catalyzed synthesis of aldopentoses

The object of this work was to find an efficient means of synthesizing ribose in a manner that could be considered prebiotic. The starting point for synthesis was an aqueous solution of formaldehyde. Heretofore the most frequently used catalyst for this purpose has been calcium hydroxide. Unfortunately this system produces a wide array of products in addition to ribose which constitutes 1% or less of the final product. Attempts were made to find more mild conditions under which the formaldehyde could be reacted. Magnesium hydroxide suspensions were used for this purpose. Formaldehyde does not yield any sugars when incubated in magnesium hydroxide suspensions alone. However, if the magnesium hydroxide suspension was supplemented with doubly charged lead salts and catalytic amounts of any intermediate in the prebiotic pentose pathway, aldopentoses accounted for 30 per cent or more of the final product. The presence of lead in the incubation mixture also accelerated a number of other reactions including the interconversion of the four common aldopentoses, ribose, arabinose, lyxose and xylose.

Anticonvulsant activity of thioureido derivatives of acetophenone semicarbazone

A series of thioureido derivatives of acetophenone semicarbazone were synthesized and evaluated for anticonvulsant activity. Some compounds provided significant protection against maximal electroshock (MES) and subcutaneous pentylenetetrazol (scPTZ) induced seizures. The compound (2e) was the most active compound in the series with a dose of 30 mg kg-1 and ED50 23.5 mg kg-1 and equipotent to phenytoin ED50 23.2 mg kg-1. The toxicity of the compounds was assessed by determination of their approximate TD50 and LD50 values in order to have a better assessment of their pharmacological profile and protective index.

Accuracy of empirical correlations for estimating diffusion coefficients in aqueous organic mixtures

Diffusion coefficients for a homologous series of alkylbenzenes and alkylphenones have been measured by the Aris-Taylor open tube method from 30 to 60 degrees C over a wide range in methanol/water and acetonitrile/water compositions (10-100% by volume of organic). The measurements were compared to estimates derived from five of the most common empirical correlations. The errors for methanolic mixtures by the Wilke-Chang, Scheibel, and Lusis-Ratcliff correlations are usually less than 20%. The Scheibel, Wilke-Chang, and Hayduk-Laudie correlations work better than others for acetonitrile/water mixtures. Overall, the Scheibel correlation shows the smallest errors, and we recommend its use to that of the more widely used Wilke-Chang method for the systems studied here. We have also developed fitting equations for estimating viscosity so that the diffusion coefficients can be easily estimated.

Estimating diffusion coefficients for alkylbenzenes and alkylphenones in aqueous mixtures with acetonitrile and methanol

The accuracy of various empirical approximation methods of estimating the diffusion coefficients of alkylbenzenes and alkylphenones in acetonitrile (ACN)/water and methanol (MeOH)/water solvent systems is reported. Diffusion coefficients for these solutes have been measured over a wide range of solvent compositions and temperatures. A novel empirical modification of the Wilke-Chang method has been developed by correlating measured values with solute and solvent parameters. The correlation, along with the Wilke-Chang and Scheibel correlations, was examined by comparing the computed diffusion coefficients with the measured values. We find that the percent errors of the proposed correlations are no greater than 10% for both ACN/water and MeOH/water systems and that the accuracy of the correlation is 2-3-fold better than those of the other two correlations. We recommend the use of this correlation with the above homologous series of solutes for the evaluation of column performance in reversed-phase liquid chromatography.

Chemical modification of histidine and lysine residues of myotoxic phospholipases A2 isolated from Bothrops asper and Bothrops godmani snake venoms: effects on enzymatic and pharmacological properties

Lysine and histidine residues of two myotoxic phospholipases A2, Bothrops asper myotoxin III and Bothrops godmani myotoxin I, were chemically modified in order to study the effects of these treatments on enzymatic and pharmacological properties. After lysine acetylation the overall basicity of these toxins was lost and their enzymatic activity was significantly reduced, although a residual effect remained, which corresponded to 25% of the activity of native toxins. This treatment abolished both myotoxic and anticoagulant effects, and partially reduced liposome-disrupting activity. Histidine alkylation with p-bromophenacyl bromide affected phospholipase A2, myotoxic and anticoagulant effects in a parallel way. After 24 hr of incubation with the alkylating reagent, these three activities were totally inhibited, in contrast to the liposome-disrupting effect which was only partially affected by this treatment. It is suggested that; (1) catalytic activity plays a role in the pharmacological effects of these myotoxins; (2) lysine residues are relevant for the toxic effects induced by these phospholipases A2; and (3) despite the apparent relevance of enzymatic activity to the pharmacological properties of these toxins, the dissociation observed in lysine acetylation experiments suggests that these myotoxins have a molecular region, different from the catalytic site, which might be also involved in the toxic effects observed.

Matrix performance in matrix-assisted laser desorption/ionization for molecular weight determination in sialyl and non-sialyl oligosaccharide proteins

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry relies on the formation of intact molecular ions to determine molecular weight. In biochemical research, conventional methods of protein analysis at picomol to fentomol sensitivity, such as sodium dodecyl sulphate polyacrylamide gel electrophoresis, have been replaced by this new ionization method. Unfortunately, problems caused by the mass accuracy and low resolution restrict the use of this ionization technique, particularly when a high mass accuracy in a high mass range is required. In this paper it is shown that the appropriate choice of parameters which determine the desorption/ionization of glycoproteins can improve the quality of MALDI mass spectra as well as mass reproducibility and resolution. The study of sample-matrix solution composition, pH and instrumental conditions allow the molecular weight determination of highly glycosylated proteins with a high percentage of sialic acid, e.g. erythropoietin. The glycosylation of this molecule which interferes with the production of multiply charged ions in electrospray ionization does not affect the desorption/ionization in MALDI analysis. We report the best operating conditions used to establish the degree of heterogeneity of erythropoietin.

Hydrogen bond formation as basis for radical scavenging activity: a structure-activity study of C-methylated dihydrochalcones from Myrica gale and structurally related acetophenones

A naturally occurring flavonoid, myrigalone B (2',6' -dihydroxy-4'-methoxy-3',5'-dimethyl-dihydrochal-cone) is an effective antioxidant and scavenger of the diphenylpicrylhydrazyl radical, while the closely related angoletin (2',4'-dihydroxy-6'-methoxy-3',5'-dimethyl-dihydrochalcone) is inactive. From NMR spectra, it appears that myrigalone B has a time-averaged conformation in which the substituted aromatic ring is orthogonal to the carbonyl group, while angoletin is coplanar. By donating a phenolic hydrogen in radical scavenging, myrigalone B will lose its symmetrical structure and may thereby change to a coplanar conformation forming a strong intramolecular hydrogen bond between the remaining phenolic hydrogen and the carbonyl group. The energy gain entailed would then appear to be a driving force for the radical scavenging by myrigalone B. Angoletin, being coplanar, lacks this driving force. To verify this hypothesis, the conformation and radical scavenging activity of a series of phenolic acetophenones were studied. All substances that had an orthogonal conformation and could form intramolecular hydrogen bonds by loss of a phenolic hydrogen were DPPH scavengers, while compounds lacking these properties were inactive. From this, we propose that formation of intramolecular hydrogen bonds may lead to radical scavenging activity.

Danielone, a phytoalexin from papaya fruit

A new phytoalexin was induced and isolated from papaya fruit slices treated with copper salts; its structure was established as 3',5'-dimethoxy-4'-hydroxy-(2-hydroxy)acetophenone. This compound showed high antifungal activity against Colletotrichum gloesporioides, a pathogenic fungus of papaya.

A proposed common spatial pharmacophore and the corresponding active conformations of some peptide leukotriene receptor antagonists

Molecular modeling studies were carried out by a combined use of conformational analysis and 3D-QSAR methods of identify molecular features common to a series of hydroxyacetophenone (HAP) and non-hydroxyacetophenone (non-HAP) peptide leukotriene (pLT) receptor antagonists. In attempts to develop a ligand-binding model for the pLT receptor, the Apex-3D program was used to identify biophoric structural patterns that are common to 13 diverse sets of compounds showing different levels of biological activity. A systematic conformational analysis was carried out to obtain sterically accessible conformations for these flexible compounds. Apex-3D was then utilized to propose common biophoric regions based on the selection of one of several conformations (MOPAC-minimized AM1) from each compound's data set that best fits the biophoric pattern and the resulting superimposition with all the other data-set compounds. Apex-3D identified three common biophoric features important for activity: one as the hydroxyl, acetyl, carbonyl and carboxyl groups, which mimic the acid-binding region of an agonist, the other as the hydrogen-bond donating site, and the third part is represented by a plane in which lipophilic aromatic groups align. The structure-activity relationships were then assessed by using the 3D-QSAR model. A common biophore model is proposed from the Apex-3D analysis which may be useful in designing new pLT antagonists. Molecular volumes and electrostatic potential similarities were also calculated in order to obtain the important structural requirements for the activity.

Complete inhibition of viral breakthrough by combination of MKC-442 with AZT during a long-term culture of HIV-1 infected cells

We have investigated viral breakthrough during a long-term culture of HIV-1-infected cells with the non-nucleoside reverse transcriptase inhibitors (NNRTIs) 6-benzyl-1-ethoxymethyl-5-isopropyluracil (MKC-442), nevirapine and loviride (alpha-APA). When the compounds were examined for their inhibitory effects on HIV-1 (HE strain) replication in MT-4 cells on day 4 after virus infection, the 50% effective concentrations (EC50) of MKC-442, nevirapine and loviride were 9.4, 98 and 21 nM, respectively. After a 48-day culture period, MKC-442, nevirapine and loviride completely inhibited viral breakthrough at concentrations of 1, 5 and 1 microM, respectively. These concentrations were 50-100-fold higher than their EC50 values. When the cells were treated with either MKC-442 (0.04 and 0.2 microM), nevirapine (0.2 and 1 microM) or loviride (0.04 and 0.2 microM) in combination with AZT (0.005 microM), only the combination of 0.2 microM MKC-442 with 0.005 microM AZT could completely inhibit the breakthrough of HIV-1 after a 68-day culture period. Polymerase chain reaction (PCR) analysis revealed that no proviral DNA was detected in the cells treated with this combination. Except for two combinations (0.04 microM MKC-442 + 0.005 microM AZT and 0.04 microM loviride + 0.005 microM AZT), all of the viruses isolated during combination treatments had various amino acid mutations in their reverse transcriptase (RT). These results indicate that the combination treatment with a relatively high dose of MKC-442 and a low dose of AZT may have potential to suppress the emergence of drug resistance during a long-term treatment in vivo and should be further pursued in HIV-1-infected patients.

High-performance liquid chromatographic determination of cytosine-containing compounds by precolumn fluorescence derivatization with phenacyl bromide: application to antiviral nucleosides and nucleotides

A novel precolumn derivatization method for the HPLC determination of cytosine-containing compounds by HPLC is described. Highly fluorescent 2-phenyl-3,N4-ethenocytosine derivatives are produced by a reaction of non-fluorescent cytosine-containing compounds with phenacyl bromide in weakly acidic acetonitrile solution at elevated temperature. The applicability of the method to various biogenic and antiviral compounds is demonstrated. Quantitative determination of cidofovir, a potent antiviral drug currently undergoing evaluation in the clinic for treatment of cytomegalovirus retinitis is also reported. The limit of detection for cidofovir in cynomolgus monkey plasma was 5 ng/ml (ca. 100 fmol on column) with the between-day precision of 16.6, 6.4 and 2.4% for five replicate samples at 20, 160 and 320 ng/ml, respectively. The within-day precision was 15.9, 5.9 and 2.1%, respectively. The method described has broad applicability and may offer significant advantages over existing HPLC methods in antiviral drug development as well as in nucleic acid research.

An acetophenone glycoside from Exacum affine

A new acetophenone glycoside, affinoside, was isolated from the aerial parts of Exacum affine and its structure was determined as 2-O-primeverosylpaenol. The known glucosides, gentiopicroside, 2'-O-E/Z-p-coumaroylloganin and glucopaeonol, were also identified.

Use of 2,6-dihydroxyacetophenone for analysis of fragile peptides, disulphide bonding and small proteins by matrix-assisted laser desorption/ionization

Several peptides were shown to undergo fragmentation during matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to a degree which complicated their analysis using alpha-cyano-4-hydroxycinnamic acid (CHCA) as a matrix, even at threshold laser irradiance. These peptides included synthetic peptides, peptides isolated from viral proteins and a phosphopeptide from beta-casein (residues 33-48). The excessive fragmentation occurred usually as a post-source phenomenon; however, in-source fragmentation was also observed. The combined effects of in-source and post-source fragmentation of one peptide studied led to a failure to observe the protonated molecule of this peptide in reflector mode analysis. The phosphopeptide studied exhibited a high degree of beta-elimination of phosphate. It was demonstrated that the fragility exhibited by these peptides in CHCA, including beta-elimination of phosphate from serine, was not evident with a matrix comprising 2,6-dihydroxyacetophenone (DHAP) and di-ammonium hydrogen citrate (DAHC). The DHAP/DAHC matrix was also adapted for direct analysis of peptides from an acidic reducing milieu containing tris(2-carboxyethyl)phosphine. The molecular weight of equine cytochrome c was determined with a relatively high degree of accuracy (experimental M(r) = 12360.2 +/- 1.4 Da compared to the theoretical M(r) = 12360.09 Da) using DHAP/DAHC as a matrix for reflector mode analysis.

Stereostructure of perimycin A

The gross structure of perimycin A was revised: the position of the keto group was changed from C-13 to C-5. The stereostructure of perimycin A was established based upon NMR studies.

Structure of HIV-1 RT/TIBO R 86183 complex reveals similarity in the binding of diverse nonnucleoside inhibitors

We report the structure of HIV-1 reverse transcriptase (RT) complexed with the nonnucleoside inhibitor TIBO R 86183 at 3.0 A resolution. Comparing this structure with those of complexes of HIV-1 RT/alpha-APA R 95845 and HIV-1 RT/nevirapine provides a basis for understanding the nature of nonnucleoside inhibitor binding, the structure of the binding site and the interactions between the bound inhibitors and surrounding amino acid residues as well as for understanding mechanisms of inhibition by and resistance to nonnucleoside inhibitors. All three inhibitors considered assume a similar butterfly-like shape and bind to HIV-1 RT in a very similar way. Important differences occur in the conformation of amino acid residues that form the binding pocket.

Structure of HIV-1 reverse transcriptase in a complex with the non-nucleoside inhibitor alpha-APA R 95845 at 2.8 A resolution

BACKGROUND

HIV-1 reverse transcriptase (RT) is a multifunctional enzyme that copies the RNA genome of HIV-1 into DNA. It is a heterodimer composed of a 66 kDa (p66) and a 51 kDa (p51) subunit. HIV-1 RT is a crucial target for structure-based drug design, and potent inhibitors have been identified, whose efficacy, however, is limited by drug resistance.

RESULTS

The crystal structure of HIV-1 RT in complex with the non-nucleoside inhibitor alpha-anilinophenyl-acetamide (alpha-APA) R95845 has been determined at 2.8 A resolution. The inhibitor binds in a hydrophobic pocket near the polymerase active site. The pocket contains five aromatic amino acid residues and the interactions of the side chains of these residues with the aromatic rings of non-nucleoside inhibitors appear to be important for inhibitor binding. Most of the amino acid residues where mutations have been correlated with high levels of resistance to non-nucleoside inhibitors of HIV-1 RT are located close to alpha-APA. The overall fold of HIV-1 RT in complex with alpha-APA is similar to that found when in complex with nevirapine, another non-nucleoside inhibitor, but there are significant conformational changes relative to an HIV-1 RT/DNA/Fab complex.

CONCLUSIONS

The non-nucleoside inhibitor-binding pocket has a flexible structure whose mobility may be required for effective polymerization, and may be part of a hinge that permits relative movements of two subdomains of the p66 subunit denoted the 'palm' and 'thumb'. An understanding of the structure of the inhibitor-binding pocket, of the interactions between HIV-1 RT and alpha-APA, and of the locations of mutations that confer resistance to inhibitors provides a basis for structure-based design of chemotherapeutic agents for the treatment of AIDS.

Antispasmodic activity of xanthoxyline derivatives: structure-activity relationships

The antispasmodic activity of several xanthoxyline derivatives against acetylcholine-induced contraction of the guinea pig ileum was evaluated in vitro. The acetophenones with two methoxyl groups, mainly in the 3,4 positions, exhibited potent antispasmodic activity. Modification of the hydroxyl group in xanthoxyline by the introduction of benzoyl, acetyl, or tosyl groups produced inactive compounds, whereas the introduction of benzyl or p-methoxybenzyl groups furnished compounds that were four- to eight-fold more potent than xanthoxyline. In marked contrast, the introduction of a methyl group gave a compound that caused contractant activity. Modification of the carbonyl group of xanthoxyline lead to inactive compounds, whereas the condensation of xanthoxyline with benzaldehydes gave chalkones that were about fivefold more potent than xanthoxyline. The introduction of benzyl and styrene groups, on the basis of the similarity with papaverine, improves the antispasmodic action of the xanthoxyline derivates. Our results suggest that the methoxyl and carbonyl groups are critical structural points for the antispasmodic activity of xanthoxyline derivatives. The hydroxyl group improves antispasmodic activity, but is not fundamental to its manifestation.

Synthesis of ethanone and ethanol derivatives of 2-benzoxazolinone; potent analgesic and antiinflammatory compounds inhibiting prostaglandin E2

Sixteen new ethanone and ethanol derivatives of 6-acyl-2-benzoxazolinones were synthesized and their chemical structures elucidated by IR, 1H-NMR and elemental analysis. Analgesic activities of these compounds were investigated by modified Koster test and constant temperature hot plate test. All the compounds showed higher analgesic activity than aspirin. Therefore the compounds were tested for their antiinflammatory activities using the carrageenan hind-paw edema test. All the compounds that showed high antiinflammatory activity were then further assayed for their ability to inhibit prostaglandin E2 (PGE2) induced paw edema. None of the compounds induced gastric ulceration.

Addition of e-aq and H atoms to hypoxanthine and inosine and the reactions of alpha-hydroxyalkyl radicals with purines. A pulse radiolysis and product analysis study

The reactions of hydrated electrons e-aq with hypoxanthine and inosine were followed using pulse radiolysis methods. In a neutral solution the electron adduct of inosine is immediately protonated at the heteroatoms of the purine ring by water (k >> 2.5 x 10(6)s-1) to give In(N,O-H).. These N,O-protonated intermediates have a single absorption maximum at 300 nm. In basic solution the protonation of the electron adduct of inosine by water leads to other intermediate products with an absorption maximum at 350 nm. These intermediates are believed to be the C-protonated electron adducts of inosine (In(N,O-H).). In (N,O-H). and In(C-H). differ strongly in their ability to reduce p-nitroacetophenone (PNAP). In(N,O-H). are strong reductants and reduce PNAP quantitatively to PNAP.-. Based on the pH dependence of PNAP.- yields, two types of tautomers of In(C-H). could be distinguished. One of the tautomers can reduce PNAP, albeit with slower rate than In(N,O-H)., the other tautomer has no reducing properties. The latter is the one with the higher pKa and therefore thermodynamically more stable. The absorption spectrum of the intermediates produced in the reaction of e-aq with hypoxanthine at neutral pH is very similar to that of In(N,O-H). with a maximum at 300 nm. However, no build-up at 350 nm was observed in basic solution as in the case of the electron adduct of inosine. The reaction of H atoms with inosine produces in basic solution intermediate radicals with the same absorption spectrum as the C-protonated electron adducts of inosine. It is suggested that both the reactions of e-aq and H. with inosine in basic solution produce the same radical, namely the H-adduct of inosine (In(C-H)) with the highest pKa. alpha-Hydroxyalkyl radicals were found to react very slowly with purine bases and nucleosides in neutral to basic solutions. In acidic solution their reactivity increases and a number of rate constants were determined by pulse radiolysis measurements at pH 0.4. The intermediates from the reaction of 2-hydroxy-2-propyl radicals with inosine could be observed pulse spectrometrically in neutral and in basic solutions. In basic solution this reaction leads to intermediates with the same absorption maximum at 350 nm as that of the H-adduct of inosine. Furthermore, the yield of acetone was found to increase strongly in basic pH.(ABSTRACT TRUNCATED AT 400 WORDS)

Secondary metabolites of Penicillium bilaii strain PB-50

A phosphate-solubilizing strain of Penicillium bilaii was tested for the production of gliotoxin and other toxic compounds. The strain was fermented under five different conditions to allow the expression of various metabolites, including gliotoxin. These included Czapek-yeast extract medium under both shaken and still conditions as well as Czapek-yeast extract/malt extract/peptone medium and sucrose/glycerol medium in shake flasks. In addition, culture filtrate from an industrial fermentation of the fungus was examined. No gliotoxin was produced in any of the media. No other expected P. bilaii metabolites were found. Three compounds were identified in all samples: dibutyl phthalate, 1-(4-hydroxy-phenyl)ethanone and 4-hydroxy-3,6-dimethyl-2H-pyran-2-one. The production of other metabolites was dependent on the culture conditions. Two hyalodendrin derivatives were found in some fermentations and two related compounds were tentatively identified. None of the compounds found have been reported as toxic. The identity of the culture was confirmed by comparison with the ex-type culture of P. bilaii.

On the mechanism of action of cytochrome P450: evaluation of hydrogen abstraction in oxygen-dependent alcohol oxidation

The mechanisms of oxidation of primary and secondary benzylic alcohols to the corresponding carbonyl compounds by purified rabbit liver cytochrome P450 forms 2B4 and 2E1 in a reconstituted enzyme system has been examined by linear free energy relationships, intramolecular and steady-state deuterium isotope effects, and the incorporation of an O2-derived oxygen atom or solvent-derived deuterium. The kcat and Km values were found to be relatively insensitive to the presence of electronic perturbations at the para position. The Hammett reaction constants for the oxidation of benzyl alcohols by P450s 2B4 and 2E1 are -0.46 and -0.37, respectively, and with 1-phenylethyl alcohols the corresponding reaction constants are -1.41 and -1.19, respectively. With [1-2H1]benzyl alcohol, P450s 2B4 and 2E1 show similar intramolecular deuterium isotope effects of 2.6 and 2.8, respectively, whereas with [1-2H2]benzyl alcohol under steady-state conditions, the deuterium isotope effects on the catalytic constants are 2.8 and 1.3, respectively. No significant isotope effect on the catalytic constant was noted for either form of P450 with 1-phenylethyl alcohol. In D2O, acetophenone formed by either form of P450 from 1-phenylethyl alcohol does not contain a deuterium atom at the methyl group, whereas under an atmosphere of 18O2 approximately 30% of the labeled oxygen is incorporated into the carbonyl group with either form of the cytochrome. The results are consistent with a mechanism that involves stepwise oxidation of the alcohol to a carbon radical alpha to the alcohol function, followed by oxygen rebound to yield the gem-diol, dehydration of which gives the carbonyl product.(ABSTRACT TRUNCATED AT 250 WORDS)