Orcein and Litmus

Orcein was separated into 14 dyes by partition chromatography. Their constitutions were determined mainly by spectroscopy and led to formulae that are derived from 7-amino-2-phenoxazone, 7-hydroxy-2-phenoxazone, and 7-amino-2-phenoxazime, and that were confirmed by syntheses. The major constituent of litmus is assembled polymerically from 7-hydroxy-2-phenoxazone chromophores. The mechanism of formation is elucidated.     

Hydroxylated 2-amino-3H-phenoxazin-3-one derivatives as products of 2-hydroxy-1,4-benzoxazin-3-one (HBOA) biotransformation by Chaetosphaeria sp., an endophytic fungus from Aphelandra tetragona

The biotransformation of the phytoanticipin HBOA and its major degradation metabolites 2-hydroxy-N-(2-hydroxyphenyl)acetamide (7) and N-(2-hydroxyphenyl)acetamide (8) by Chaetosphaeria sp., an endophytic fungus isolated from Aphelandra tetragona, was studied. Three new metabolites could be identified as 2-amino-7-hydroxy-3H-phenoxazin-3-one (12), 2-acetylamino-7-hydroxy-3H-phenoxazin-3-one (13) and 7-hydroxy-2-(2-hydroxyacetyl)-amino-3H-phenoxazin-3-one (14). Structure elucidation of 12 and 13 was performed by MS, 1H, 13C NMR and 2D NMR techniques and confirmed by chemical transformation.     

Electrochemical and electron spin resonance studies of actinomycin D and other phenoxazones

Electrochemical studies on actinomycin D (1) and two analogs, 2-amino-3-phenoxazone (2) and 1,2,4-trichloro-7-nitrophenoxazone (3) were analyzed by polarography and ESR spectroscopy. The polarograms of the three compounds in acetonitrile all show two reduction waves. ESR experiments confirm that the first reduction wave corresponds to a one-electron transfer process which produces a phenoxazone free radical anion and the second wave corresponds to a subsequent one-electron transfer producing a diamagnetic dianion. Substitution with electron-withdrawing groups such as NO2 (at C-7) and chloro (at C-1, C-2 and C-4)3 facilitated the reduction of the phenoxazone ring system to a free radical (i.e., half-wave potentials; 1, -0.815 V; 2, -0.920 V; 3, -0.135 V). It was found, by computer simulation of the ESR spectra, that the spin density in the electrochemically generated free radicals from 1, 2 and 3 was preferentially located in the benzenoid ring and at the N-10 nitrogen. For radicals obtained from 1 and 2, only a small residual spin density could be detected in the quinoid ring. Since 1 can be metabolized to a free radical in cells, these free radical forms of 1 and its analogs may represent reactive forms of the phenoxazone nucleus.     

Inhibition of Excitatory Amino Acid-Stimulated Phosphoinositide Hydrolysis in the Neonatal Rat Hippocampus by 2-Amino-3-Phosphonopropionate

The effects of excitatory amino acid agonists and alpha-amino-omega-phosphonocarboxylic acid antagonists on phosphoinositide hydrolysis in hippocampal slices of the 7-day neonatal rat were examined. Significant stimulation of [3H]inositol monophosphate formation was observed with ibotenate, quisqualate, L-glutamate, L-aspartate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, L-homocysteate, and kainate. N-Methyl-D-aspartate had no effect. Of these agonists, ibotenate and quisqualate were the most potent and efficacious. Stimulations by ibotenate and quisqualate were partially inhibited by L-2-amino-4-phosphonobutyrate (10(-3) M), but this antagonist had no effect on L-glutamate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, or kainate. At 10(-3) M, D,L-2-amino-3-phosphonopropionate completely inhibited ibotenate and quisqualate stimulations, partially inhibited L-glutamate stimulation, and had no effect on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-, kainate-, or carbachol-induced [3H]inositol monophosphate formation. Concentration-effect experiments showed D,L-2-amino-3-phosphonopropionate to be five times more potent as an antagonist of ibotenate-stimulated phosphoinositide hydrolysis than L-2-amino-4-phosphonobutyrate. Thus in the neonatal rat hippocampus, like in the adult rat brain, D,L-2-amino-3-phosphonopropionate is a selective and relatively potent inhibitor of excitatory amino acid-stimulated phosphoinositide hydrolysis. Because this glutamate receptor is uniquely sensitive to D,L-2-amino-3-phosphonopropionate, these studies provide further pharmacological evidence for the existence of a novel excitatory amino acid receptor subtype that is coupled to phosphoinositide hydrolysis in brain.     

Synthesis and evaluation of 2-amino-6-fluoro-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine mono- and diesters as potential prodrugs of penciclovir

2-Amino-6-fluoro-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine (7), and its mono- and diesters 8-15 were prepared and evaluated for their potential as prodrugs of penciclovir. Treatment of 2-amino-6-chloro-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine (5) with trimethylamine in THF followed by a reaction of the resulting trimethylammonium chloride salt 6 with KF in DMF afforded 2-amino-6-fluoro-9-(4-hydroxy-3-hydroxymethylbut-1-yl)purine (7) in 80% yield. Esterification of 7 with an appropriate acid anhydride [Ac2O, (EtCO)2O, (n-PrCO)2O, or (i-PrCO)2O] in DMF in the presence of a catalytic amount of DMAP produced the mono-esters 8-11 in 42-45% yields and diesters 12-15 in 87-99% yields. Of the prodrugs tested in rats, the monoisobutyrate 11 was the most efficiently absorbed and metabolized to 7, showing the mean maximum total concentration of penciclovir (5.5 microg/mL) and 7 (10.8 microg/mL) in the blood was much higher than the mean maximum concentration of penciclovir (11.5 microg/mL) from famciclovir. However, the mean concentrations of penciclovir from 11 were lower than those from famciclovir because of the limited conversion of a major metabolite 7 to penciclovir by adenosine deaminase.     

Isolation of two new natural pteridines from photosynthetic bacteria, Rhodopseudomonas sphaeroides

Two new natural pteridines have been isolated from the cultured medium of Rhodopseudomonas sphaeroides GM-1. The compounds are tentatively identified as 2-amino-4-hydroxy-6-hydroxy-6-(1,2, 3,4-tetrahydroxybutyl)pteridine and 2-amino-4-hydroxy-6-(3-hydroxy-4-phosphonoxy-1-butenyl)pteridine by degradative experiments and by electrophoretic and paper chromatographic comparison with authentic materials.     

The Synthesis of 2-Amino 7-Substituted Purines

Abstract

The putative antiviral agent, (S)-2-amino-7-(2,3-dihydroxy-propyl) purine (1b), and its achiral analogue, 2-amino-7-(2-hydroxyethyl) purine (2), were synthesized by a procedure involving alkylation at N7 of guanosine followed by deribosylation and deoxygenation. Evidence for the stereochemical integrity of the former preparation was obtained from the X-ray diffraction structure of the novel tricyclic compound, (S)-6H, 7H, 8H-2-amino-7-hydroxy-[1,4] oxazepino [1,2,3-d, elpurine (17, obtained by a similar synthetic sequence. Compound (1a), a regioisomer of the known antiviral agent, (S)-9-(2,3-dihydroxypropyl) adenine ((S)-DHPA), was tested and found to be inactive in tissue culture against herpes virus type-2, rotavirus, poliovirus, and parainfluenza virus.     

Characterisation of Na+-Independent L-[3H]Glutamate Binding Sites in Human Temporal Cortex

The binding of L-[3H]glutamate to membranes from human temporal cortex was studied in the absence of Na+, Ca2+, and Cl- ions. Pharmacological characterisation revealed that approximately 35% of specific binding at 50 nM L-[3H]glutamate was sensitive to a combination of kainate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid. The remaining approximately 65% of specific binding was to a single population of sites with a KD of 844 nM and a Bmax of 0.92 pmol/mg protein. The pharmacological characteristics were consistent with an interaction at the N-methyl-D-aspartate subclass of excitatory amino acid receptor. The inclusion of Cl- ions revealed additional glutamate binding; this was sensitive to quisqualate and DL-2-amino-4-phosphonobutyrate, but not to kainate, DL-2-amino-7-phosphonoheptanoate, or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid.     

Two carboxy- and two hydroxymethyl-substituted aristololactams from Aristolochia argentina

Four new aristololactams have been isolated from Aristolochia argentina. The evidence indicates them to be 10-amino-3-hydroxymethyl-2,4-dimethoxyphenanthrene-1-carboxylic acid lactam, 10-amino-3-hydroxymethyl-2,4,6-trimethoxyphenanthrene-1-carboxylic acid lactam, 10-amino-2-hydroxy-4-methoxyphenanthrene-1,3-dicarboxylic acid lactam and 10-amino-2-hydroxy-4,6-dimethoxyphenanthrene-1,3-dicarboxylic acid lactam.     

Microbial transformation of 2-amino-4-methyl-3-nitropyridine

Biotransformation of the highly substituted pyridine derivative 2-amino-4-methyl-3-nitropyridine by Cunninghamella elegans ATCC 26269 yielded three products each with a molecular weight of 169?Da which were identified as 2-amino-5-hydroxy-4-methyl-3-nitropyridine, 2-amino-4-hydroxymethyl-3-nitropyridine, and 2-amino-4-methyl-3-nitropyridine-1-oxide. Biotransformation by Streptomyces antibioticus ATCC 14890 gave two different products each with a molecular weight of 169?Da; one was acid labile and converted to the other stable product under acidic conditions. The structure of the stable product was established as 2-amino-4-methyl-3-nitro-6(1H)-pyridinone, and that of the less stable product was assigned as its tautomer 2-amino-6-hydroxy-4-methyl-3-nitropyridine. Four of the five biotransformation products are new compounds. Several strains of Aspergillus also converted the same substrate to the lactam 2-amino-4-methyl-3-nitro-6(1H)-pyridinone. Microbial hydroxylation by C. elegans was found to be inhibited by sulfate ion. In order to improve the yield and productivity of the 5-hydroxylation reaction by C. elegans, critical process parameters were determined and Design of Experiments (DOE) analyses were performed. Biotransformation by C. elegans was scaled up to 15-l fermentors providing 2-amino-5-hydroxy-4-methyl-3-nitropyridine at ca. 13?% yield in multi-gram levels. A simple isolation process not requiring chromatography was developed to provide purified 2-amino-5-hydroxy-4-methyl-3-nitropyridine of excellent quality.     

Isolation and characterization of degradation impurities in epirubicin hydrochloride injection

The degradation of epirubicin hydrochloride aqueous formulation has been investigated during stability study. Some unknown degradation impurities were detected and out of these, three were characterized. These degradation impurities were isolated, enriched and were subjected to mass and NMR spectral studies. Based on the spectral data these were characterized as epirubicin dimer (impurity-1), 4-(4-amino-5-hydroxy-6-methyl-tetrahydro-pyran-2-yloxy)-2,5,12-trihydroxy-7-methoxy-6,11-dioxo-1,2,3,4,6,11-hexahydro-naphthacene-2-carboxylic acid hydroxymethyl ester (impurity-3) and 4-(4-amino-5-hydroxy-6-methyl-tetrahydro-pyran-2-yloxy)-2,5,12-trihydroxy-7-methoxy-6,11-dioxo-1,2,3,4,6,11-hexahydro-naphthacene-2-carboxylic acid (impurity-4). Structure elucidations of these degradation impurities are discussed in detail. Out of these degradation impurities, epirubicin dimer (impurity-1) has been previously identified while the other two impurity-3 and impurity-4 were previously unreported.     

Toussaintines A-E: antimicrobial indolidinoids, a cinnamoylhydrobenzofuranoid and a cinnamoylcyclohexenoid from Toussaintia orientalis leaves

Toussaintine A (N-cinnamoyl-5,6-dehydro-4-hydroxyindolidin-2,7-dione), toussaintine B (N-cinnamoyl-5,6-dehydro-4,7-dihydroxyindolidin-2-one), toussaintine C (N-cinnamoyl-5,6-dehydro-4-hydroxyindolidin-7-one), toussaintine D (N-cinnamoyl-2-amino-4-hydroxy-7-oxo-2,3,8,9-tetrahydrobenzofuran) and toussaintine E (N-cinnamoyl-1-acetoxymethyl-2-amino-1-hydroxycyclox-5-en-4-one) were isolated as antibacterial and antifungal constituents of the leaves of Toussaintia orientalis Verdc. (Annonaceae) and their structures established from analysis of spectroscopic data. The compounds belong to a series of variously cyclized aminocinnamoyl tetraketide derivatives, showing the importance of rarely occurring Annonaceae species as sources of structurally diverse natural products.     

Origin of the ribityl side-chain of riboflavin from the ribose moiety of guanosine triphosphate in Pichia guilliermondii yeast.

In wild-type cells and some riboflavin-deficient mutants of P. guilliermondii GTP is transformed to the ribitylated intermediates 2,5-diamino-6-hydroxy-4-ribitylaminopyrimidine and 5-amino-2,6-dihydroxy-4-ribitylaminopyrimidine of the riboflavin biosynthetic path. We were able to show that these compounds were formed in vitro as well as in permeabilized cells by reactions including a reductive conversion of the product of GTP cyclohydrolase II action upon GTP. In order to analyse the pyrimidine derivates, 6,7-dimethyl-8-ribitylpterin and 6,7-dimethyl-8-ribityllumazine were synthesized by reaction of pyrimidines with diacetyl. The formation of ribitylated pyrimidines was shown to be strictly dependent on the presence of NADPH2. The data obtained indicate that the reductive step is catalyzed by a 2,5-diamino-6-hydroxy-4-ribosylaminopyrimidine-reductase. 6,7-Dimethyl-8-ribitylpterin and 6,7-dimethyl-8-ribityllumazine isolated from the incubation mixtures have been identified by chromatography and by their ultraviolet and fluorescence spectra.     

Lipopolysaccharides from Pseudomonas maltophilia: composition of the lipopolysaccharide and structure of the side-chain polysaccharide from strain N.C.I.B. 9204

Lipopolysaccharide was extracted from defatted cell-walls of Pseudomonas maltophilia N.C.I.B. 9204. The major fatty acid components were 9-methyldecanoic acid, 2-hydroxy-9-methyldecanoic acid, 3-hydroxy-9-methyldecanoic acid, 3-hydroxy-dodecanoic acid, and 3-hydroxy-11-methyldodecanoic acid. Monosaccharide components of the phosphorylated core-oligosaccharide were D-glucose, D-mannose, D-galacturonic acid, 2-amino-2-deoxyglucose, and a 3-deoxyoctulosonic acid. The putative O-specific polysaccharide was composed mainly of 2-amino-2-deoxy-D-glucose, D-arabinose, and 6-deoxy-L-talose, but also contained an O-acetyl group and small proportions of rhamnose and 6-deoxy-3-O-methyltalose. Degradative and n.m.r. (1H and 13C) studies showed that the polymer had a branched trisaccharide repeating-unit with the following structure; the O-acetyl group was tentatively assigned to C-2 of the 6-deoxytalopyranosyl residue. (Formula: see text).     

Nature of riboflavin precursors in Pichia guilliermondi yeasts]

Thirty-nine riboflavin-deficient mutants have been isolated from three yeast strains of Pichia guilliermondii (ATSS 9058, VKM Y-1256, VKM Y-1257) and F5-121 mutant which is capable of production of large amounts of riboflavin in the presence of iron in the medium. All mutants were divided into five groups according to the nature of precursors accumulated in the medium and growth reaction in media with 6,7-dimethyl-8-ribityllumasine and diacetyl. The mutants of the first group did not accumulate specific precursors of riboflavin either in the cells or in the medium. The mutants of the second, third and fourth groups accumulated, after the incubation with diacetyl, 2-amino-4-hydroxy-6,7-dimethylpteridine, 2-amino-4-hydroxy-6,7-dimethyl-8-ribitylpteridine and 6,7-dimethyl-8-ribityllumasine; therefore, they synthesized the following precursors of riboflavin: 2,4,5-triamino-6-hydroxy-pyrimidine, 2,5-diamino-6-hydroxy-4-ribitylaminopyrimidine and 2,6-dihydroxy-5-amino-4-ribitylaminopyrimidine. The mutants of the fifth group accumulated 6,7-dimethyl-8-ribityllumasine in the medium and lacked riboflavin synthetase activity, as was confirmed by enzymatic studies.     

Pteridines produced by Methylococcus capsulatus. Isolation and identification of a neopterin 2′:3′-phosphate

Three pteridines have been isolated from the methane- or methanol-oxidizing bacterium Methylococcus capsulatus. Two of these are known compounds, 2-amino-6-carboxy-4-hydroxypteridine and 2-amino-4-hydroxy-6-methylpteridine. The third is shown by degradative and synthetic experiments to be l-threo-neopterin 2':3'-phosphate. Labelling experiments show that both the pteridine moiety and phosphate residue are derived from a single GTP molecule. The possible metabolic significance of these compounds in methanol oxidation is discussed.     

广东土牛膝的化学成分

广东土牛膝为菊科泽兰属植物华泽兰（Eupatorium chinense）的干燥根。从其甲醇提取物中共分离得到11个化合物,其中eupatorinA（1）为一新化合物,经波谱学方法鉴定为（threo）-3-O-acetyl-1-（4-hydroxy-3-methoxyphenyl）-2-[4-（3-hydroxy-1-（E）-propenyl）-2,6-dimethoxyphenoxy]propyl-β-D-glucopy-ranoside。已知化合物分别鉴定为（threo）-3-hydroxy-1-（4-hydroxy-3-methoxyphenyl）-2-[4-（3-hydroxy-1-（E）-propenyl）-2,6-dimethoxyphenox-y]-propyl-β-D-glucopyranoside（2）,ardisiacrispinA（3）,ardisiac-rispinB（4）,euparone（5）,3-（2,3-dihydroxy-isopen-tyl）-4-hydroxyacetophenone（6）,12,13-di-hydroxy-euparin（7）,gymnastone（8）,N-（2′-hydroxy-tetracosanosyl）-2-amino-1,3,4-trihydroxy-octa-dec-8-（E）-ene（9）,stigmasterol（10）和stigmasterol-3-O-β-D-glucopyranoside（11）。化合物2-4为首次从菊科植物,5-8为首次从泽兰属植物中分离得到。     

Enzymatic synthesis of 2-amino- 3-hydroxy-1,6-hexanedicar☐ylic acid using serinehydroxymethyltransferase

The scale up of earlier work from these laboratories using the enzyme serinehydroxymethyltransferase has resulted in the use of this enzyme for the synthesis of 2-amino-3-hydroxy-1,6-hexanedicar☐ylic acid (7) on a preparative scale. This compound, which has been barely described in the literature, is potentially useful for the synthesis of carbocyclic β-lactams and carbocyclic nucleosides.     

Characterization of mutationally altered dihydropteroate synthase and its ability to form a sulfonamide-containing dihydrofolate analog.

Among spontaneous mutants of Escherichia coli selected for resistance against sulfonamides, thermosensitive strains were found. These were shown to possess a changed dihydropteroate synthase (EC 2.5.1.15), which had a substantially higher Km value for its normal substrate, p-aminobenzoic acid, and an about 150-fold higher Km for sulfonamides. The mutationally changed dihydropteroate synthase was found to be thermosensitive by in vitro assays. The thermosensitivity was used as an enzyme marker to demonstrate the complex formation between 2-amino-4-hydroxy-6-pyrophosphorylmethyl pteridine and sulfonamides by partially purified dihydropteroate synthase. The formation of folate from 2-amino-4-hydroxy-6-pyrophosphorylmethyl pteridine and p-aminobenzoylglutamic acid by dihydropteroate synthase was found to be very sensitive to inhibition by sulfonamides and very inefficient with the mutationally changed enzyme.     

Chemical modification of the sugar part of methyl acarviosin: synthesis and inhibitory activities of nine analogues.

Nine analogues of methyl acarviosin (1), the core structure of acarbose and its homologues, the 6-hydroxy-(2), 6-azido-(3), 6-amino- (4), 6-acetamido-(5), 6-methoxy-(6), 6-hydroxy-2-O-methyl-(8), and 6-hydroxy-3-O-methyl derivatives (9), including the 5-methoxycarbonyl analogue (7) and 3,6-anhydro derivative (10) of 2, were synthesized by chemical modification of the sugar part of 2 derived by condensation of methyl 3,4-anhydro-alpha-D-galactopyranoside (17) and 4,7:5,6-di-O-isopropylidenevalienamine (26) or by direct coupling between 26 and the 6-substituted methyl 3,4-anhydro-alpha-D-galactopyranoside derivatives. Compounds 2 and 8 show notable inhibitory activity against yeast alpha-D-glucosidase almost comparable to that of 1. Introduction of a polar substituent at C-6 of 1 decreases the inhibitory activity. Interestingly, inversion of the conformation of the sugar part of 1 by introduction of the 3,6-anhydro bridge elicits almost no effect on the inhibitory activity.