Derivatives of methanopterin, a coenzyme involved in methanogenesis

Degradational studies of methanopterin, a coenzyme involved in methanogenesis, are reported. The results of these studies are in full accordance with the proposed structure of methanopterin as N-[1'-(2'-amino-4'-hydroxy-7' -methyl-6'-pteridinyl)ethyl]-4-[2', 3', 4', 5'-tetrahydroxypent-1'-yl(5'-1' )O-alpha-ribofuranosyl-5'-phosphoric acid] aniline in which the phosphate group is esterified with alpha-hydroxyglutaric acid. Acid hydrolysis of methanopterin cleaved the 5'----1' glycosidic bond and yielded a 'hydrolytic product' which was identified as N-[1'-(2'-amino-4'-hydroxy-7' -methyl-6'-pteridinyl)ethyl]-4-[2', 3', 4', 5'-tetrahydroxypent-1'-yl]aniline. Alkaline permanganate oxidation of methanopterin yielded 7-methylpterin-6-carboxylic acid. Catalytic (or enzymatic) hydrogenation of methanopterin gave a mixture of 6-ethyl-7-methyl-7,8-dihydropterin, 6-ethyl-7-methylpterin and a third compound, named methaniline which was identified as 4-[2', 3', 4', 5'-tetrahydroxypent-1'-yl(5'----1')O-alpha -ribofuranosyl-5'-phosphoric acid]aniline, in which the phosphate group is esterified with alpha-hydroxyglutaric acid. Methanosarcina barkeri contains a closely related coenzyme called sarcinapterin, which was identified as a L-glutamyl derivative of methanopterin, where the glutamate moiety is attached to the alpha-carboxylic acid group of the alpha-hydroxyglutaric acid moiety of methanopterin via an amide linkage.     

Structural characterization of tatiopterin, a novel pterin isolated from Methanogenium tationis

Cofactor extracts of Methanogenium tationis were screened for the presence of pterin-derivatives. Methanopterin, sarcinapterin and 7-methylpterin were absent, while 2-amino-4-hydroxy-pteridine and another blue fluorescent compound with a pterin spectrum were detected. The latter pterin was purified by ion exchange and reversed-phase column chromatography. The structure of this compound was elucidated by combining spectrophotometry, amino acid analysis and 1H-NMR spectroscopy. The pterin, which we named tatiopterin, was identified as an aspartyl derivative of sarcinapterin with a 7-proton instead of a 7-methyl group in the pterin moiety. The IUPAC name is: N-[-1'-(2'-amino-4'-hydroxy-7'-proton-6'-pteridinyl)ethyl]-4- [2',3',4',5'-tetrahydroxypent-1'-yl(5'----1')O-alpha- ribofuranosyl-5'-phosphoric acid]aniline, in which the phosphate group is esterified with alpha-hydroxyglutarylglutamylaspartic acid.     

Novel synthesis of cholesterol analogs: condensation of pregnenolone with dihydropyran or dihydrofuran.

Pregnenolone 3-(2'-tetrahydropyranyl) ether (1) was condensed with 3,4-[2H]dihydropyran to mainly give (20R)-[6'-(3',4'-[2'H]dihydropyranyl)]-pregn-5-ene-3 beta,20-diol 3-(2'-tetrahydropyranyl) ether (20R-3), according to nuclear magnetic resonance (NMR). Cold, dilute HCl in ethanol removed the tetrahydropyranyl group at C-3 and also opened the dihydropyranyl ring at the C-20 position of 20R-3 to give (20R)-27-norcholest-5-en-22-one-3 beta,20,26-triol (20R-5). Analogous results were obtained by condensing pregnenolone 3-acetate with 3,4-[2H]dihydropyran to provide (20R)-[6'-(3',4'-[2'H]dihydropyranyl)]-pregn-5-ene-3 beta,20-diol 3-acetate (20R-4). Acid-catalyzed opening of the dihydropyranyl ring at C-20 in 20R-4 yielded 20R-7, which, on acetylation followed by crystallization, provided (20R)-27-norcholest-5-en-22-one-3 beta,20,26-triol 3,26-diacetate (20R-8), identical to the diacetate made from 20R-5. Varying the reaction sequence beginning with 20(R,S)-4 gave an 84:16 ratio of 20R to 20S in a mixture of 20(R,S)-8, according to NMR analysis. Crystallization of the mixture from methanol provided pure 20R-8. Condensing 2,3-dihydrofuran and 1 for producing (20R)-[5'-(2',3'-dihydrofuranyl)]-pregn-5-ene-3 beta,20-diol 3-(2'-tetrahydropyranyl) ether (6) gave instead (20R)-26,27-bisnorcholest-5-en-22-one-3 beta,20,25-triol 3-(2'-tetrahydropyranyl) ether (20R-9) by partial hydrolysis during workup. Treating 20R-9 briefly with dilute HCl produced (20R)-26,27-bisnorcholest-5-en-22-one-3 beta,20,25-triol (20R-10).(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis of 3-[4'-(p-chlorophenyl)-thiazol-2'-yl]-2-[(substituted azetidinone/thiazolidinone)-aminomethyl]-6-bromoquinazolin-4-ones as anti-inflammatory agent

N-Chloroacetyl-5-bromoanthranilic acid (1), 3-[4'-(p-chlorophenyl)-thiazol-2'-yl]-2-chloromethyl-6-bromoquinazolin-4-one (2), 3-[4'-(p-chlorophenyl)-thiazol-2'-yl]-2-hydrazinomethyl-6-bromoquinazolin-4-one (3), 3-[4'-(p-chlorophenyl)-thiazol-2'-yl]-2-substitutedbenzylidene aminomethyl-6-bromoquinazolin-4-ones (4-11), 2-[(4'-oxo-3'-chloro-2'-phenylazetidin-1'-yl)aminomethyl]-3-[4'-(p-chlorophenyl)thiazol-2'-yl]-6-bromoquinazolin-4-ones (12-19) and 2-(4'-oxo-2'-phenyl-thiazolidin-3'-yl-aminomethyl)- 3-[4'-(p-chlorophenyl)-thiazol-2'-yl]-6-bromoquinazolin-4-ones (20-27) have been synthesized. All the compounds have been screened for their anti-inflammatory and analgesic activities at the dose of 50mg/kg po. Compound 21 showed maximum anti-inflammatory (38.35%) and analgesic (37.36%) activities. Compound 21 was also tested for ulcerogenic activity and the UD(50) value was found to be 195.6mg/kg po. The structure of all compounds has been evaluated by elemental analysis (C, H, N) and spectral analysis (IR, (1)H NMR and mass spectrometry).     

Microwave induced synthesis and antibacterial activity of cephalosporin derivatives using solid support

Reaction of 7-amino-3-[5'-methyl-1',3',4'-thiadiazol-2'-ylthiomethyl]cephalo-sporanic acid with heterocyclic amines using basic alumina under microwave irradiation (MWI) afforded new cephalosporin analogs in shorter reaction time with improved yield as compared to conventional heating. All the synthesised compounds were tested for their in vitro antibacterial activity, using cefotaxime and cephalothin as reference drugs. All compounds showed significant in vitro antibacterial activity against E. herbicola, P. vulgaries, and Z. mobilis.     

Diprenylated chalcones and other constituents from the twigs of Dorstenia barteri var. subtriangularis

The twigs of Dorstenia barteri var. subtriangularis yielded three diprenylated chalcones: (-)-3-(3,3-dimethylallyl)-5'-(2-hydroxy-3-methylbut-3-enyl)-4,2',4'-trihydroxychalcone, (+)-3-(3,3-dimethylallyl)-4',5'-[2'-(1-hydroxy-1-methylethyl)-dihydrofurano]-4,2'-dihydroxychalcone and 3,4-(6",6"-dimethyldihydropyrano)-4',5'-[2',-(1-hydroxy-1-methylethyl)-dihydrofurano]-2'-hydroxychalcone for which the names bartericins A, B and C, respectively, are proposed. Stipulin, beta-sitosterol and its 3-beta-D-glucopyranosyl derivative were also isolated. The structures of these secondary metabolites were determined on the basis of spectroscopic analysis, especially, NMR spectra in conjunction with 2D experiments, COSY, HMQC and HMBC. The structural relationship of bartericins B and C was further established by the chemical cyclization of one to the other.     

Inhibitory effect on NO production of phenolic compounds from Myristica fragrans

Three new phenolics: ((7S)-8'-(benzo[3',4']dioxol-1'-yl)-7-hydroxypropyl)benzene-2,4-diol (1), ((7S)-8'-(4'-hydroxy-3'-methoxyphenyl)-7-hydroxypropyl)benzene-2,4-diol (2) and ((8R,8'S)-7-(4-hydroxy-3-methoxyphenyl)-8'-methylbutan-8-yl)-3'-methoxybenzene-4',5'-diol (3), along with four known compounds (4-7) were isolated from the seeds of Myristica fragrans. Their chemical structures were established mainly by 1D and 2D NMR techniques and mass spectrometry. Their anti-inflammatory activity was evaluated against LPS-induced NO production in macrophage RAW264.7 cells.     

Complete conformational family of 2',3'-didehydro-2',3'-dideoxyguanosine: quantum chemical and electron density topological study

Comprehensive conformational analysis of the biologically active nucleoside 2',3'-didehydro-2',3'-dideoxyaguanosine (d4G) has been performed at the MP2/6-311++G(d,p)//DFT B3LYP/6-31G(d,p) level of theory. The energetic, geometrical and polar characteristics of twenty d4G conformers as well as their conformational equilibrium were investigated. The electron density topological analysis allowed us to establish that the d4G molecule is stabilized by nine types of intramolecular interactions: O5'H...N3, O5'H...C8, C8H...O5', C2'H...N3, C5'H1...N3, C5'H2...N3, C8H...H1C5', C8H...H2'C5' and N2H1...O5'. The obtained results of conformational analysis permit us to think that d4G may be a terminator of the DNA chain synthesis in the 5'-3' direction. Thus it can be inferred that d4G competes with canonical 2'-deoxyaguanosine in binding an active site of the corresponding enzyme.     

Synthesis and biological evaluation of phosphonated dihydroisoxazole nucleosides

Phosphonated isoxazolinyl nucleosides have been prepared via 1,3-dipolar cycloaddition reaction of nitrile oxides with corresponding vinyl or allyl nucleobases for antiviral studies. The cytotoxicity, the anti-HSV activity and the RT-inhibitory activity of the obtained compounds were evaluated and compared with those of AZT and diethyl{(1'SR,4'RS)-1'-[[(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)]-3'-methyl-2'-oxa-3'-azacyclopent-4'-yl]}methylphosphonate, a saturated phosphonated dihydroisoxazole nucleoside analogue.     

Synthesis and structure determination of some sugar amino acids related to alanine and 6-deoxymannojirimycin.

(5'R)-5'-Methyl-5'-[methyl (4S)-2,3-O-isopropylidene-beta-L-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione was synthesised starting from methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosid-5-ulose applying the Bucherer-Bergs reaction. Its 5'-R configuration was confirmed by X-ray crystallography. Corresponding alpha-amino acid-methyl (5R)-5-amino-5-C-carboxy-5,6-dideoxy-alpha-D-lyxo-hexofuranoside (alternative name: 2-[methyl (4S)-2,3-O-isopropylidene-beta-L-erythrofuranosid-4-C-yl]-D-alanine) was obtained from the above hydantoin by acid hydrolysis of the isopropylidene group followed by basic hydrolysis of the hydantoin ring. Total deprotection afforded 5-C-carboxy-6-deoxymannojirimycin. Analogously, methyl (5S)-5-amino-5-C-carboxy-5,6-dideoxy-alpha-L-lyxo-hexofuranoside and 5-C-carboxy-6-deoxy-L-mannojirimycin were prepared from the corresponding (5'S)-5'-methyl-5'-[methyl (4R)-2,3-O-isopropylidene-beta-D-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione starting from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexofuranosid-5-ulose.     

Conformational capacity of 2',3'-didehydro-2',3'-dideoxyadenosine as a key to understanding its biological activity: results of quantum chemical modelling

Comprehensive conformational analysis of the biologically active nucleoside 2',3'-didehydro-2',3'-dideoxyadenosine (d4A) has been performed at the MP2/6-311++G(d,p)//DFT B3LYP/6-31G(d,p) level of theory. The energetic, geometrical and polar characteristics of twenty one d4A conformers as well as their conformational equilibrium were investigated. The electron density topological analysis allowed us to establish that the d4A molecule is stabilized by eight types of intramolecular interactions: O5'H...N3, O5'H...C8, C8H...O5', C2'H...N3, C5'H1...N3, C5'H2...N3 Ta C8H...H1/2C5'. The obtained results of conformational analysis lead us to think that d4A may be a terminator of the DNA chain sythesis in the 5'-3' direction. Thus it can be inferred that d4A competes with canonical 2'-deoxyadenosine in binding an active site of the corresponding enzyme.     

Conjugates of steroids and anti-cancer agents. III. The synthesis of estrynamine and certain derivatives

Propargyl amine was protected by condensing it with 2,5-hexane-dione to give 2,5-dimethyl-N-(2'-propyn-1'-yl)pyrrole (2). The latter was converted to the corresponding Grignard reagent with ethylmagnesium bromide, and then condensed with estrone tetrahydropyranyl ether to give 17 alpha-[3'-(2',5'-dimethyl-1'-pyrryl)-1'-propyn-1'-yl)-1,3 ,5( 10)- estratriene-3,17 beta-diol 3-tetrahydropyranyl ether (3), in 85% yield. Acetic acid and methanol cleaved the tetrahydropyranyl ether group, and hydroxylamine and sodium bicarbonate cleaved the pyrrole ring to give 17 alpha-(3'-amino-1'-propyn-1'-yl)-1,3,5(10)-estratriene-3,17 beta-diol (1), estrynamine. Several derivatives and analogs of 1 were also synthesized. Estrynamine binds to estrogen receptor with an RBA of 0.0045 (estradiol = 1.0). Several of the compounds, including estrynamine, are weak estrogens (stimulation of prolactin synthesis).     

Geranyl chalcone derivatives with antifungal and radical scavenging properties from the leaves of Artocarpus nobilis

Antifungal activity guided fractionation of the n-butanol extract from the methanol extract of the leaves of Artocarpus nobilis furnished 2',4',4-trihydroxy-3'-geranylchalcone (1), 2 ',4',4-trihydroxy-3'-[6-hydroxy-3,7-dimethyl-2(E),7-octadienyl]chalcone (2), 2',4',4-trihydroxy-3'-[2-hydroxy-7-methyl-3-methylene-6-octaenyl]chalcone (3), 2',3,4,4'-tetrahydroxy-3'-geranylchalcone (4), 2',3,4,4'-tetrahydroxy-3'-[6-hydroxy-3,7-dimethyl-2(E),7-octadienyl]chalcone (5). The chalcones 3 and 5 are new natural products whereas 1 and 2 are reported first time from the family Moraceae. All these compounds showed good fungicidal activity against Cladosporium cladosporioides and high radical scavenging activity towards the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical in TLC bio-autography method.     

Xanthones from the bark of Garcinia merguensis

The bark of Garcinia merguensis yielded 10 xanthones, merguenone, 1,5-dihydroxy-6'-methyl-6'-(4-methyl-3-pentenyl)-pyrano(2',3':3,2)-xanthone, subelliptenone H, 8-deoxygartanin, rheediaxanthone A, morusignin G, 6-deoxyjacareubin, 1,3,5-trihydroxy-4,8-di(3-methylbut-2-enyl)-xanthone, rheediachromenoxanthone and 6-deoxyisojacareubin. The structure of merguenone was determined using spectroscopic techniques, mainly 1D and 2D NMR spectroscopy.     

Elucidation of the structure of methanopterin, a coenzyme from Methanobacterium thermoautotrophicum, using two-dimensional nuclear-magnetic-resonance techniques

Methanopterin is a coenzyme involved in methanogenesis. From 2 kg wet cells of Methanobacterium thermoautotrophicum about 35 mumol methanopterin were isolated. The structure of this compound was elucidated by various two-dimensional nuclear-magnetic-resonance techniques. Methanopterin was identified as N-[1'-(2"-amino-4"-hydroxy-7" - methyl-6"- pteridinyl) ethyl]-4-[2',3',4',5'- tetrahydroxypent-1'- yl (5' leads to 1") O-alpha-ribofuranosyl-5"-phosphoric acid] aniline, in which the phosphate group is esterified with alpha-hydroxyglutaric acid. The molecular formula of the sodium salt of methanopterin at pH 7.0 is C30H38O16N6PNa3 X chiH2O (chi is about 4). The anhydrous sodium salt of methanopterin has a molecular mass of 838.60 Da and the molar absorption coefficient at 342 nm is 7.4 mM-1 cm-1 at pH 7.0.     

Role of 5-HT1B/D receptors in canine gastric accommodation: effect of sumatriptan and 5-HT1B/D receptor antagonists

The 5-HT1B/D receptor agonist sumatriptan has been proposed to treat dyspeptic symptoms, because it facilitates gastric accommodation. It is unknown whether stimulation of 5-HT1B/D receptors is involved. Thus, in four conscious dogs, we compared the effects of sumatriptan alone or combined with N-[4-methoxy-3-(4-methyl-1-piperazinyl) phenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)-[1,1-biphenyl]-4-carboxamide hydrocloride (GR-127935), N-[3-[3 (dimethylamino)-ethoxy]-4-methoxyphenyl]-2'-[methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)]-[1,1-biphenyl]-4-carboxamide hydrocloride (SB-216641 hydrochloride), or 3-[4-(4-chloro-phenyl)piperazin-1-yl]-1,1-diphenyl-2-propanol hydrochloride (BRL-15572 hydrochloride) (respectively, nonselective 5-HT1B/D, selective 5-HT1B, and selective 5-HT1D receptor antagonists) on gastric accommodation to isobaric distensions performed with a barostat. An exponential and a linear model were used to fit the pressure-volume relationship. An exponential equation fitted the data better than a linear equation. Sumatriptan (800 nmol/kg iv) induced an immediate gastric relaxation (Deltavolume: 112 +/- 44 ml, P < 0.05). After sumatriptan, the pressure-volume curve was shifted toward significantly higher volumes. This effect was fully reversed by GR-127935 or SB-216641 but not by BRL-15572. In conclusion, 5-HT1B receptors seem to play an important role in modulating gastric accommodation to a distending stimulus. An exponential model for pressure-volume curves fits well with the concept of gastric adaptive relaxation.     

Microbial transformation of xanthohumol

Microbial transformation of xanthohumol using the culture broth of Pichia membranifaciens afforded three metabolites, (E)-2"-(2"'-hydroxyisopropyl)-dihydrofurano[2",3":4',3']-2', 4-dihydroxy-6'-methoxychalcone, (2S)-2"-(2"'-hydroxyisopropyl)-dihydrofurano[2",3":7,8]-4'-hydroxy-5-methoxyflavanone and (E)-2"-(2"'-hydroxyisopropyl)-dihydrofurano[2",3":2',3']-4'-hydroxy-5-methoxychalcone.     

Synthesis of amide-linked [(3')CH2CO-NH(5')] nucleoside analogues of small oligonucleotides

We report syntheses of new amide-linked (di-penta)nucleoside analogues of antisense oligonucleotide components. Solution-phase coupling of 3'-(carboxymethyl)-3'-deoxy- and 5'-amino-5'-deoxynucleoside derivatives provides amide dimers. Activated [3'-(carboxymethyl)-3'-deoxy] units with a 5'-azido-5'-deoxy function provide "masked" 5'-amino-5'-deoxy residues for chain extension, and a 5'-O-DMT-protected unit provides the 5'-terminus for attachment to a phosphodiester linkage.