Synthesis of the mitogenic S-[2,3-bis(palmitoyloxy)propyl]-N-palmitoylpentapeptide from Escherichia coli lipoprotein

The N-terminal pentapeptide of the lipoprotein from the outer membrane of Escherichia coli was obtained by coupling S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-N-palmitoyl-(R)-cysteine to O-tert-butylseryl-O-tert-butyl-seryl-asparaginyl-alanine tert-butyl ester followed by deprotection with trifluoroacetic acid. The tetrapeptide was built up from alanine tert-butyl ester with N-9-fluorenylmethyloxycarbonyl protected amino acids. S-[2,3-Bis(palmitoyloxy)propyl]-N-palmitoylcysteine was obtained from N,N'-dipalmitoylcystine di-tert-butyl ester via reduction to the thiol, and S-alkylation with racemic 3-bromo-1,2-propanediol followed by esterification with palmitic acid in the presence of dicyclohexylcarbodiimide/dimethylaminopyridine and deprotection with trifluoroacetic acid. The compounds were characterized unequivocally by 13C-NMR and mass spectra. The diastereomers of S-[2,3-bis(palmitoyloxy)propyl]-N-palmitoylcysteine tert-butyl ester with opposite configuration at the propyl-C-2 atom could be separated on a silica-gel column.     

DNA targeted platinum complexes: synthesis, cytotoxicity and DNA interactions of cis-dichloroplatinum(II) complexes tethered to phenazine-1-carboxamides

A series of intercalator-tethered platinum(II) complexes PtLCl2 have been prepared, where L are the diamine ligands N-[2-[(aminoethyl)amino]ethyl]-phenazine-1-carboxamide, N-[3-[(2-aminoethyl)amino]propyl]-phenazine-1-carboxamide, N-[4-[(2-aminoethyl)amino]butyl]-phenazine-1-carboxamide and N-[5-[(aminoethyl)amino]pentyl]-phenazine-1-carboxamide. Measurements of the time-course of unwinding of supercoiled pUC19 plasmid DNA by the phenazine complexes PtLCl2 reveal that the presence of the intercalator leads to enhanced rates of DNA platination when compared with the complex Pt(en)Cl2. The platinum(II) complexes where the polymethylene linker chain contains three, four or five carbon atoms are considerably more cytotoxic against murine P388/W than either cisplatin, Pt(en)Cl2, or the metal-free ligands themselves.     

Synthesis of disulfide esters of dialkylaminocarbothioic acid as potent, non-detergent spermicidal agents

S,S'-[disulfanediylbis(dialkylaminopropane-2,1-diyl)]bis- (dialkylaminothiocarbamate) (14-31) were prepared and evaluated for the spermicidal activity and antifungal activity. Dialkyldithiocarbamates (1-5) were reacted with epichlorohydrin to give 1-dialkylaminocarbothioic acid S-[(2,3-epithio)propyl]ester (7-11), these on further reaction with a secondary amine gave S,S'-[disulfanediylbis(dialkylaminopropane-2,1-diyl)]bis- (dialkylaminothiocarbamate) (14-31). Some of these compounds (16, 19-21, 23, 30, 31) were found to be very potent spermicidal agents with marginal antifungal activity. Two compounds (20, 21) were 25 times more active than nonoxynol-9 (N-9), the spermicide currently in the market.     

Comparison of the activities of variant forms of eIF-4D. The requirement for hypusine or deoxyhypusine.

Eukaryotic protein synthesis initiation factor 4D (eIF-4D) (current nomenclature, eIF-5A) contains the unique amino acid hypusine (N epsilon-(4-amino-2-hydroxybutyl)lysine). The first step in hypusine biosynthesis, i.e. the formation of the intermediate, deoxyhypusine (N epsilon-(4-aminobutyl)lysine), was carried out in vitro using spermidine, deoxyhypusine synthase, and ec-eIF-4D(Lys), an eIF-4D precursor prepared by over-expression of human eIF-4D cDNA in Escherichia coli. In a parallel reaction, using N-(3-aminopropyl)cadaverine in place of spermidine, a variant form of eIF-4D containing homodeoxyhypusine (N epsilon-(5-aminopentyl)lysine) was prepared. Evidence that N-(3-aminopropyl)cadaverine can also act as the amine substrate for deoxyhypusine synthase in intact cells was obtained by incubating putrescine- and spermidine-depleted Chinese hamster ovary cells with [3H]cadaverine. In these cells, in which [3H]cadaverine is readily converted to N-(3-aminopropyl) [3H]cadaverine, small amounts of [3H]homodeoxyhypusine and another 3H-labeled compound, presumed to be N epsilon-(5-amino-2-hydroxy[3H]pentyl)lysine, were found. eIF-4D stimulates methionyl-puromycin synthesis, an in vitro model assay for translation initiation. Whereas the unmodified precursor ec-eIF-4D(Lys) appeared inactive, the deoxyhypusine-containing form provided a significant degree of stimulation. The variant form containing homodeoxyhypusine, on the other hand, showed little or no activity. These findings emphasize the importance of hypusine or deoxyhypusine for the biological activity of eIF-4D and demonstrate the influence of both the length and chemical nature of its amino alkyl side chain.     

Vibriobactin, a siderophore from Vibrio cholerae

A novel siderophore (microbial iron transport compound) has been isolated from low iron cultures of Vibrio cholerae. Belonging to the catecholamide family of chelators, it has been shown to contain three residues of 2,3-dihydroxybenzoic acid and two residues of threonine. Both threonine moieties are present in the form of oxazoline rings. Furthermore, the polyamine backbone of the molecule was proved to be not spermidine, but the rare N-(3-aminopropyl)-1,3-diaminopropane, norspermidine. The structure of the new siderophore has been determined to be N-[3-(2,3-dihydroxybenzamido)propyl]-1, 3-bis[2,3-dihydroxyphenyl)-trans-5-methyl-2-oxazoline-4-carboxamido]prop ane. The compound has been given the trivial name vibriobactin. Mutants defective in the synthesis and utilization of vibriobactin were isolated. In an iron-limited environment V. cholerae was found to respond more strongly to vibriobactin, agrobactin, and ferrichrome than to enterobactin.     

cis-Dichloroplatinum(II) complexes tethered to 9-aminoacridine-4-carboxamides: synthesis and action in resistant cell lines in vitro.

A series of intercalator-tethered platinum(II) complexes PtLCl(2) have been prepared where L are the diamine ligands N-[2-[(aminoethyl)amino]ethyl]-9-aminoacridine-4-carboxamide, N-[3-[(2-aminoethyl)amino]propyl]-9-aminoacridine-4-carboxamide, N-[4-[(2-aminoethyl)amino]butyl]-9-aminoacridine-4-carboxamide and N-[5-[(aminoethyl)amino]pentyl]-9-aminoacridine-4-carboxamide and N-[6-[(aminoethyl)amino]hexyl]-9-aminoacridine-4-carboxamide. The activity of the complexes was assessed in the CH-1, CH-1cisR, 41M, 41McisR and SKOV-3 cell lines. The compounds with the shorter linker chain lengths are generally the most active against these cell lines and are much more toxic than Pt(en)C1(2). For example, for the n=2 compound the IC(50) values are 0.017 microM (CH-1), 1.7 microM (41M), 1.4 microM (SKOV-3) and the resistance ratios are 51 (CH-1cisR) and 1.6 (41McisR). For the untethered analogue Pt(en)C1(2) the IC(50) values are 2.5 microM (CH-1), 2.9 microM (41M), 45 microM (SKOV-3) and the resistance ratios are 2.8 (CH-1cisR) and 4.1 (41McisR). The very large differential in IC(50) values between the CH-1 and CH-1cisR pair of cell lines for the 9-aminoacridine-4-carboxamide tethered platinum complexes indicates that repair of platinum-induced DNA damage may be a major determinant of the activity of these compounds.     

A new method of chemical modification of N6-amino group in adenine nucleotides with formaldehyde and a thiol and its application to preparing immobilized ADP and ATP.

Reaction of AMP with formaldehyde and 3-mercaptopropionic acid at pH 11.7 gave a new AMP derivative, N6-[(2-carboxyethyl)thiomethyl]-AMP (I) in 91% yield and reaction at pH 3.1 gave another new derivative, N6,N6-bis[(2-carboxyethyl)thiomethyl]-AMP (II) in 57% yield. The structures were determined by their 13C and 1H nuclear magnetic resonance spectra coupled with those of the simple analogues, N6-[(2-carboxyethyl)thiomethyl]-9-methyladenine (III) and N6,N6-bis[(2-carboxyethyl)thiomethyl]-9-methyladenine (IV) which were synthesized from 9-methyladenine in the same way as for derivatives I and II. ADP and ATP were treated in the same way as AMP to afford the corresponding carboxyl derivatives, N6-[(2-carboxyethyl)thiomethyl]-ADP (V), N6-[(2-carboxyethyl)thiomethyl]-ATP (VI), N6,N6-bis[(2-carboxyethyl)thiomethyl]-ADP (X) and N6,N6-bis[(2-carboxyethyl)thiomethyl]-ATP (XI) in 71%, 75%, 53% and 40% yield, respectively. These compounds were coupled to 1,3-diaminopropane with a water-soluble carbodiimide to give the corresponding amino derivatives, N6-([N-3-aminopropyl)carbamoylethyl]thiomethyl)-ADP (VIII), N6-(N-(3-aminopropyl)carbamoylethyl]thiomethyl)-ATP (IX), N6,N6-bis([N-(3-aminopropyl)carbamoylethyl]thiomethyl)-ADP (XIII), and N6,N6-bis([N-(3-aminopropyl)carbamoylethyl]thiomethyl)-ATP (XIV), which were further bound to CNBr-activated dextran to give new polymer-bound derivatives of ADP and ATP. These free and bo-nd derivatives were tested for their coenzymic activities against several kinases. The activities of the ADP derivatives, V, VIII, X, XIII, dextran-bound VIII, and dextran-bound XIII against acetate kinase were 82%, 81%, 68%, 55%, 35%, and 15%, respectively, relative to ADP and those of the ATP derivatives, VI, IX, XI, XIV, dextran-bound IX, and dextran-bound XIV against hexokinase were 88%, 94%, 60%, 81%, 58%, and 49%, respectively, relative to ATP.     

A Tc-99m-labeled long chain fatty acid derivative for myocardial imaging

C-11- and I-123-labeled long chain fatty acid derivatives have been reported as useful radiopharmaceuticals for the estimation of myocardial fatty acid metabolism. We have reported that Tc-99m-labeled N-[[[(2-mercaptoethyl)amino]carbonyl]methyl]-N-(2-mercaptoethyl)-6-aminohexanoic acid ([(99m)Tc]MAMA-HA), a medium chain fatty acid derivative, is metabolized by beta-oxidation in the liver and that the MAMA ligand is useful for attaching to the omega-position of fatty acid derivatives as a chelating group for Tc-99m. On the basis of these findings, we focused on developing a Tc-99m-labeled long chain fatty acid derivative that reflected fatty acid metabolism in the myocardium. In this study, we synthesized a dodecanoic acid derivative, MAMA-DA, and a hexadecanoic acid derivative, MAMA-HDA, and performed radiolabeling and biodistribution studies. [(99m)Tc]MAMA-DA and [(99m)Tc]MAMA-HDA were prepared using a ligand-exchange reaction. Biodistribution studies were carried out in normal mice and rats. Then, a high initial uptake of Tc-99m was observed, followed by a rapid clearance from the heart. The maximum heart/blood ratio was 3.6 at 2 min postinjection of [(99m)Tc]MAMA-HDA. These kinetics were similar to those with postinjection of p-[(125)I]iodophenylpentadecanoic acid. Metabolite analysis showed [(99m)Tc]MAMA-HDA was metabolized by beta-oxidation in the body. In conclusion, [(99m)Tc]MAMA-HDA is a promising compound as a long chain fatty acid analogue for estimating beta-oxidation of fatty acid in the heart.     

Antimicrobial Poly(methacrylamide) Derivatives Prepared via Aqueous RAFT Polymerization Exhibit Biocidal Efficiency Dependent upon Cation Structure

Antimicrobial peptides (AMPs) show great potential as alternative therapeutic agents to conventional antibiotics as they can selectively bind and eliminate pathogenic bacteria without harming eukaryotic cells. It is of interest to develop synthetic macromolecules that mimic AMPs behavior, but that can be produced more economically at commercial scale. Herein, we describe the use of aqueous reversible addition-fragmentation chain transfer (RAFT) polymerization to prepare primary and tertiary amine-containing polymers with precise molecular weight control and narrow molecular weight distributions. Specifically, N-(3-aminopropyl)methacrylamide (APMA) was statistically copolymerized with N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) or N-[3-(diethylamino)propyl]methacrylamide (DEAPMA) to afford a range of (co)polymer compositions. Analysis of antimicrobial activity against E. coli (Gram-negative) and B. subtilis (Gram-positive) as a function of buffer type, salt concentration, pH, and time indicated that polymers containing large fractions of primary amine were most effective against both strains of bacteria. Under physiological pH and salt conditions, the polymer with the highest primary amine content caused complete inhibition of bacterial growth at low concentrations, while negligible hemolysis was observed over the full range of concentrations tested, indicating exceptional selectivity. The cytotoxicity of select polymers was evaluated against MCF-7 cells.     

A carbene-yielding amino acid for incorporation into peptide photoaffinity reagents

3-[p-[3-(Trifluoromethyl)-3H-diazirin-3-yl]phenyl]alanine has been prepared in 10 steps from p-bromobenzyl alcohol. The alcohol was converted to 3-(alpha-iodo-p-tolyl)-3-(trifluoromethyl)-3H-diazirine, which was used to alkylate N-(diphenylmethylene)glycine ethyl ester. After deprotection the amino acid was obtained with an overall yield of 18%. The D- and L-isomers of 3-[p-[3-(trifluoromethyl)-3H-diazirin-3-yl]phenyl]alanine have also been resolved, and 3-[p-[3-(trifluoromethyl)-3H-diazirin-3-yl]phenyl]alanine labeled with tritium has been prepared. The advantages of using this amino acid as a building block for peptide photoaffinity reagents is discussed.     

Synthesis and reactions of O-acetylated benzyl alpha-glycosides of 6-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-N-acetylmuramoyl-L- alanyl-D-isoglutamine esters: the base-catalysed isoglutamine in equilibrium glutamine rearrangement in peptidoglycan-related structures

Condensation of benzyl 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2- deoxy-3-O-[(R)-1-carboxyethyl]-alpha-D-glucopyranoside (2) and its 4-acetate (4) with L-alanyl-D-isoglutamine benzyl ester via the mixed anhydride method yielded N-(2-O-[benzyl 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D- glucopyranosyl)-2,3-dideoxy-alpha-D-glucopyranosid-3-yl]-(R)-lacto yl)-L- alanyl-D-isoglutamine benzyl ester (5) and its 4-acetate (6), respectively. Condensation by the dicyclohexylcarbodi-imide-N-hydroxysuccinimide method converted 2 into benzyl 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl- 2-deoxy-beta-D-glucopyranosyl)-3-O-[(R)-1-carboxyethyl]-2-deoxy-alpha-D- glucopyranoside 1',4-lactone (7). In the presence of activating agents, 7 underwent aminolysis with the dipeptide ester to give 5. Zemplén O-deacetylation of 5 and 6 led to transesterification and alpha----gamma transamidation of the isoglutaminyl residue to give N-(2-O-[benzyl 2-acetamido-6-O-(2- acetamido-2-deoxy-beta-D-glucopyranosyl)-2,3-dideoxy-alpha-D-glucopyr anosid-3- yl]-(R)-lactoyl)-L-alanyl-D-isoglutamine methyl ester (8) and -glutamine methyl ester (9). Treatment of 6 with MgO-methanol caused deacetylation at the GlcNAc residue to give a mixture of N-(2-O-[benzyl 2-acetamido-6-O-(2-acetamido-2- deoxy-beta-D-glucopyranosyl)-4-O-acetyl-2,3-dideoxy-alpha-D-glucopyra nosid-3- yl]-(R)-lactoyl)-L-alanyl-D-isoglutamine methyl ester (11) and -glutamine methyl ester (12). Benzyl or methyl ester-protection of peptidoglycan-related structures is not compatible with any of the reactions requiring alkaline media. Condensation of 2 with L-alanyl-D-isoglutamine tert-butyl ester gave N-(2-O-[benzyl 2-acetamido- 6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-2,3-d ideoxy- alpha-D-glucopyranosid-3-yl]-(R)-lactoyl-L-alanyl-D-isoglutamine tert-butyl ester (16), deacetylation of which, under Zemplén conditions, proceeded without side-reactions to afford N-(2-O-[benzyl 2-acetamido-6-O-(2-acetamido-2-deoxy-beta-D- glucopyranosyl)-2,3-dideoxy-alpha-D-glucopyranosid-3-yl]-(R)-la cotyl)-L- alanyl-D-isoglutamine tert-butyl ester (17).     

Synthesis of affinity ligands and radioactive probes for isolation and study of myo-inositol 1,4,5-trisphosphate binding proteins

To synthesize an affinity matrix for isolation of D-myo-inositol 1,4,5-trisphosphate binding proteins, racemic 3-cyclohexene-1-carboxaldehyde was oxidized and converted to a mixture of trans-3,4-di-hydroxycyclohexane-1-carboxylic acid methyl ester isomers, which was phosphorylated and separated into (+-)-(1R,3R,4R)- and (+-)-(1R,3S,4S)-trans-3,4-bis[(diphenoxyphosphoryl)oxy]cyclohex an e-1- carboxylic acid methyl esters. Each of these racemic compounds was hydrogenolyzed and reacted with ethylenediamine to give a monoamide, N-(2-aminoethyl)-bis(phosphonyloxy)cyclohexane-1-carboxamide, that was coupled to cyanogen bromide activated Sepharose 4B to provide the desired affinity matrices. The intermediate trans-3,4-bis[(diphenoxyphosphoryl)oxy]cyclohexane-1-carboxylic acid methyl ester was also reduced with lithium borotritide to give the (hydroxy[3H]methyl)cyclohexane derivative, which was phosphorylated and hydrogenolyzed to yield trans-3,4-bis(phosphonyloxy)-1-[(phosphonyloxy)[3H]methyl]cy clohexane, a radiolabeled analogue of inositol 1,4,5-trisphosphate. The carboxamide was also coupled to 4-azidosalicylic acid, and the product was iodinated to provide a 125I-radiolabeled photoactivatable cross-linking derivative of cyclohexanediol bisphosphate.     

Synthesis and evaluation of bifunctional nitrocatechol inhibitors of pig liver catechol-O-methyltransferase

Bifunctional compounds were tested in vitro as potential inhibitors of pig liver catechol-O-methyltransferase (COMT) with respect to the catechol substrate 4-[(3,4-dihydroxyphenyl)azo]benzenesulfonate. The bifunctional compounds were a composite of either two nitrocatechols or one nitrocatechol and one phenol, linked by amide bonds to a spacer unit comprising two to five methylene groups. The unsymmetrical compounds N-[2-(4-hydroxybenzoylamine)ethyl]-3,4-dihydroxy-5-nitrobenzamide], N-[3-(4-hydroxybenzoyl-amine)propyl]-3,4-dihydroxy-5-nitrobenzamide] and N-[5-(4-hydroxybenzoylamine)pentyl]-3,4-dihydroxy-5-nitrobenzamide] demonstrated strong inhibitory action against COMT with K(i) values in the 100 nM range. In comparison, the monofunctional nitrocatechol analogues of these compounds had K(i) values that were significantly higher.     

Biological activities and structure-activity relationship of substitution compounds of N-[2-(3-indolyl)ethyl]succinamic acid and N-[2-(1-naphthyl)ethyl]succinamic acid, derived from a new category of root-promoting substances, N-(phenethyl)succinamic acid analogs

In a previous study, it was demonstrated that N-(phenethyl)succinamic acid (PESA) derivatives form a new category of root-promoting substances which do not exhibit auxin-like activities, such as stem elongation and leaf epinasty (Soejima et al., 2000 [Plant Cell Physiol. 41s: 197]). In this study, N-[2-(3-indolyl)ethyl]succinamic acid (IESA) and N-[2-(1-naphthyl)ethyl]succinamic acid (NESA) were synthesized, and their biological activities were evaluated. In an adzuki root-promoting assay, IESA and NESA exhibited root-promoting activity equivalent to PESA. In adzuki stem elongation assays, elongation activity was not observed in the stem segments soaked in either an IESA or NESA aqueous solution, whereas the stem segments immersed in Indole-3-acetic acid (IAA) or 1-naphthylacetic acid (NAA) aqueous solution were clearly elongated. In an epinastic bending study, IAA and NAA exhibited leaf epinasty, whereas IESA and NESA did not, suggesting that the IESA and NESA derivatives belong to the same category of root-promoting substances as PESA derivatives and are different from auxin-like substances. In addition, eleven kinds of IESA derivatives and nineteen kinds of NESA derivatives were synthesized, and their root-promoting activities were measured. The activities of methyl ester derivatives were approximately three times higher than that of the acid compounds, with exceptions for some compounds. The partition coefficient (P) between 1-octanol and water for each IESA, NESA, and PESA derivative was measured in order to evaluate the hydrophobicity of their molecules and to determine their structure–activity relationship. The results indicate that the root-promoting activity of the acid compounds was significantly correlated with their hydrophobicity, whereas that of ester derivatives was not correlated.     

Synthesis and rearrangements of D-glucosyl esters of aspartic acid linked through the 1- or 4-carboxyl group.

Catalytic hydrogenation of 2,3,4,6-tetra-O-benzyl-1-O-[1-benzyl N-(benzyloxycarbonyl)-L-aspart-4-oyl]-alpha-D-glucopyranose (1alpha) in acetic acid-2-methoxyethanol gave 1-O-(L-beta-aspartyl)alpha-D-glucopyranose (2alpha) contaminated with 2-O-(L-alpha-aspartyl)-D-glucopyranose (8). Evidence that 8 was formed from the 1-oyl isomer of 1alpha, namely 2,3,4,6-tetra-O-benzyl-1-O-[4-benzyl N-(benzyloxycarbonyl)-L-aspart-1-oyl]-alpha-D-glucopyranose (7alpha), via 1 leads to 2 acyl migration, was obtained by submitting the deprotected D-glucosyl ester to successive N-acetylation, esterification, and O-acetylation; the final product was identified as a approximately 4:1 mixture of 2,3,4,6-tetra-O-acetyl-1-O-[1-methyl N-(acetyl)-L-aspart-4-oyl]-alpha-D-glucopyranose (4alpha) and 1,3,4,6-tetra-O-acetyl-2-O-[4-methyl N-(acetyl)-L-aspart-1-oyl]-D-glucopyranose (6) which were also prepared by definitive methods. On the other hand, deprotection of 1beta gave isomerically pure 2beta which was converted into the peracetylated ester derivative 4beta; an explanation for the differences in aglycon isomeric purity of 2alpha and 2beta is given. Hydrogenolysis of 7beta under the above conditions led to intermolecular transesterification with scission of the C-1 ester bond to give 1-(2-methoxyethyl) L-aspartic acid and D-glucose. Catalytic hydrogenation of 7alpha and 7beta, performed in the presence of trifluoroacetic acid, afforded 1-O-(L-alpha-aspartyl)-alpha- and -beta-D-glucopyranoside trifluoroacetate salts (11alpha and 11beta), respectively. The structure of 11beta was established by successive conversion into 2,3,4,6-tetra-O-acetyl-1-O-[4-methyl N-(acetyl)-L-aspart-1-oyl]-beta-D-glucopyranose (5beta) which was also prepared by definitive methods. Analogous treatment of 11alpha gave the N-acetyl derivative 12 which underwent 1 leads to 2 acyl migration during esterification with diazomethane to give the N-acetyl methyl ester derivative 10; acetylation of 10 afforded 6.     

Polyhydroxybenzoates inhibit ascorbic acid activation of mitochondrial glycerol-3-phosphate dehydrogenase: implications for glucose metabolism and insulin secretion

Glycerol-3-phosphate dehydrogenase from pig brain mitochondria was stimulated 2.2-fold by the addition of 50 microm l-ascorbic acid. Enzyme activity, dependent upon the presence of l-ascorbic acid, was inhibited by lauryl gallate, propyl gallate, protocatechuic acid ethyl ester, and salicylhydroxamic acid. Homogeneous pig brain mitochondrial glycerol-3-phosphate dehydrogenase was activated by either 150 microm L-ascorbic acid (56%) or 300 microm iron (Fe(2+) or Fe(3+) (62%)) and 2.6-fold by the addition of both L-ascorbic acid and iron. The addition of L-ascorbic acid and iron resulted in a significant increase of k(cat) from 21.1 to 64.1 s(-1), without significantly increasing the K(m) of L-glycerol-3-phosphate (10.0-14.5 mm). The activation of pure glycerol-3-phosphate dehydrogenase by either L-ascorbic acid or iron or its combination could be totally inhibited by 200 microm propyl gallate. The metabolism of [5-(3)H]glucose and the glucose-stimulated insulin secretion from rat insulinoma cells, INS-1, were effectively inhibited by 500 microm or 1 mm propyl gallate and to a lesser extent by 5 mm aminooxyacetate, a potent malate-aspartate shuttle inhibitor. The combined data support the conclusion that l-ascorbic acid is a physiological activator of mitochondrial glycerol-3-phosphate dehydrogenase, that the enzyme is potently inhibited by agents that specifically inhibit certain classes of di-iron metalloenzymes, and that the enzyme is chiefly responsible for the proximal signal events in INS-1 cell glucose-stimulated insulin release.     

Synthesis and antiplasmodial activity of new N-[3-(4-{3-[(7-chloroquinolin-4-yl)amino]propyl}piperazin-1-yl)propyl]carboxamides

The parallel acylation of N-{3-[4-(3-aminopropyl)piperazin-1-yl]propyl}-7-chloroquinolin-4-amine with polymer-bound carboxylic acids opened straightforward access to novel aminoquinolines with activity against Plasmodium falciparum strains in vitro. Using this amino scaffold prepared in solution and polymer-bound carboxylic, we have synthesized a series of 29 new compounds in good to excellent yield and purity. Biological evaluation included determination of the activity against a chloroquine (CQ) sensitive strain and a CQ resistant mutant. Most of the novel structures presented here displayed activity against both strains in the lower nanomolar range, four compounds showed an at least fourfold increase in the ratio of inhibition of CQ resistant to sensitive strains over CQ itself. These results suggest that this derivatization technique is a useful method to speed up structure-activity relationship studies on aminoquinolines toward improved activity versus CQ resistant strains of P. falciparum in vitro.     

Synthesis of [18F]SU11248, a new potential PET tracer for imaging cancer tyrosine kinase

N-[2-(Diethylamino)ethyl]-5-[(Z)-(5-[18F]fluoro-2-oxo-1,2-dihydro-3H-indol-3-ylidene)methyl]-2,4-dimethyl-1H-pyrrole-3-carboxamide, a new potential positron emission tomography tracer for imaging cancer tyrosine kinase, has been prepared by the nucleophilic substitution of the nitro-precursor N-[2-(diethylamino)ethyl]-5-[(Z)-(5-nitro-2-oxo-1,2-dihydro-3H-indol-3-ylidene)methyl]-2,4-dimethyl-1H-pyrrole-3-carboxamide with K18F/Kryptofix 2.2.2 followed by a simple chromatography methodology combined solid-phase extraction with high-performance liquid chromatography purification procedures in 15-25% radiochemical yields.     

Synthesis and antimicrobial activity of a water-soluble chitosan derivative with a fiber-reactive group

A novel fiber-reactive chitosan derivative was synthesized in two steps from a chitosan of low molecular weight and low degree of acetylation. First, a water-soluble chitosan derivative, N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan chloride (HTCC), was prepared by introducing quaternary ammonium salt groups on the amino groups of chitosan. This derivative was further modified by introducing functional (acrylamidomethyl) groups, which can form covalent bonds with cellulose under alkaline conditions, on the primary alcohol groups (C-6) of the chitosan backbone. The fiber-reactive chitosan derivative, O-acrylamidomethyl-HTCC (NMA-HTCC), showed complete bacterial reduction within 20 min at the concentration of 10ppm, when contacted with Staphylococcus aureus and Escherichia coli (1.5-2.5 x 10(5) colony forming units per milliliter [CFU/mL]).     

A new opine derived from nopaline

Nopaline (N-[4-[(aminoiminomethyl)amino-]-1S-carboxybutyl]-2R-aminopentanedioic acid and isonopaline (N-[4-[(aminoiminomethyl)amino-1S-carboxybutyl]- 2S-aminopentanedioic acid) have been synthesized and separated by crystallization. In addition, a derivative of each of these compounds that forms spontaneously from the parent compounds under the usual crystallization conditions was isolated and characterized. The chemical properties, elemental analysis, 1H-NMR spectrum, and electrophoretic behavior of the derivative from nopaline are consistent with N-[4-[ (aminoiminomethyl)amino]-1S-carboxybutyl]-2-pyrrolidone-5R-carboxylic acid, also called pyronopaline. The presence of pyronopaline in crown gall tumor tissue and the catabolism of it by the bacterium A. tumefaciens establish it as a new opine.