Synthesis and antibacterial activity of new carbapenems containing isoxazole moiety

The synthesis and biological activity of a series of new 1beta-methylcarbapenems 1a-g containing 5'-isoxazolopyrrolidin-3'-ylthio derivatives as C-2 side chain are described. Most compounds exhibited potent and well-balanced antibacterial activity as well as high stability to DHP-I comparable to that of meropenem. 1e and 1c showed the best combination of antibacterial activity and stability to DHP-I, respectively.     

Synthesis and biological evaluation of novel 1 beta-methylcarbapenems with isothiazoloethenyl side chains

The synthesis of novel 1 beta-methylcarbapenems 1a,b bearing isothiazoloethenyl moieties at C-5 position of pyrrolidine ring and their biological evaluation are described. Both compounds showed potent and well-balanced antibacterial activity as well as high stability to DHP-I. Especially, 5-isothiazole derivative 1a exhibited excellent DHP-I stability and advanced pharmacokinetics profiles, compared to 5-isoxazole derivative 2, imipenem, and meropenem.     

Synthesis and biological activity of 1β-methyl-2-[5′-isoxazoloethenylpyrrolidin-3′-ylthio]carbapenems

A new series of 1β-methylcarbapenems 1a–i bearing isoxazoloethenyl groups on the pyrrolidine ring has been prepared and evaluated for in vitro antibacterial activity and stability to DHP-I. Most compounds showed excellent antibacterial activity and high stability to DHP-I superior to that of meropenem. Of these new carbapenems, 1a,b,h exhibited the best combination of antibacterial activity and DHP-I stability.     

Photoaffinity labelling of the 2-oxoglutarate binding site of prolyl 4-hydroxylase with 5-azidopyridine-2-carboxylic acid

The synthesis of the photoaffinity label 5-azidopyridine-2-carboxylic acid is described. The 2-oxoglutarate analogue photoaffinity label is a competitive inhibitor with respect to 2-oxoglutarate with a Ki value of 9 X 10(-3) M. Upon ultraviolet irradiation, 5-azidopyridine-2-carboxylic acid inactivated prolyl 4-hydroxylase irreversibly by up to 50%. The extent of inactivation depended on the 5-azidopyridine-2-carboxylic acid concentration and the irradiation time. Inactivation was prevented in the presence of an excess of 2-oxoglutarate. It is concluded that the 5-azidopyridine-2-carboxylic acid became covalently bound to the alpha subunit of prolyl 4-hydroxylase, as the alpha subunit of the photoaffinity labelled enzyme had a decreased electrophoretic mobility in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate.     

Synthesis and biological activity of 1beta-methyl-2-[5'-isoxazoloethenylpyrrolidin-3'-ylthio]carbapenems

A new series of 1beta-methylcarbapenems 1a-i bearing isoxazoloethenyl groups on the pyrrolidine ring has been prepared and evaluated for in vitro antibacterial activity and stability to DHP-I. Most compounds showed excellent antibacterial activity and high stability to DHP-I superior to that of meropenem. Of these new carbapenems, 1a,b,h exhibited the best combination of antibacterial activity and DHP-I stability.     

Purification and Properties of Cystathionine [gamma]-Synthase from Wheat (Triticum aestivum L.)

Cysthathionine [gamma]-synthase (CS), an enzyme involved in methionine biosynthesis, was purified from an acetone powder prepared from wheat (Triticum aestivum L.). After several chromatographic steps and radiolabeling of the partially purified enzyme with sodium cyanoboro[3H]hydride, a single polypeptide with a molecular weight of 34,500 was isolated by sodium dodecyl sulfate-high performance electrophoresis chromatography. Since the molecular weight of the native enzyme was 155,000, CS apparently consists of four identical subunits. The pyridoxal 5[prime]-phosphate-dependent forward reaction has a pH optimum of 7.5 and follows a hybrid ping-pong mechanism with Km values of 3.6 mM and 0.5 mM for L-homoserine phosphate and L-cysteine, respectively. L-Cysteine methyl ester, thioglycolate methyl ester, and sodium sulfide were also utilized as thiol substrates. The latter observation suggests that CS and phosphohomoserine sulfhydrase might be a single enzyme. CS does not seem to be a regulatory enzyme but was irreversibly inhibited by DL-propargylglycine (Ki = 45 [mu]M, Kinact = 0.16 min-1). Furthermore, the homoserine phosphate analogs 4-(phosphonomethyl)-pyridine-2-carboxylic acid, Z-3-(2-phosphonoethen-1-yl)pyridine-2-carboxylic acid, and DL-E-2-amino-5-phosphono-3-pentenoic acid acted as reversible competitive inhibitors with Ki values of 45, 40, and 1.1 [mu]M, respectively.     

Isolation and characterization of a 3-chlorobenzoate degrading pseudomonad

A pseudomonad has been isolated from sewage, which can utilize 3-chlorobenzoic acid as a sole carbon source. In cells grown on benzoate the enzymes of the -ketoadipic acid pathway are present. Considerable enzymic activities for chlorinated substrates were found in benzoate grown cells only for the oxygenation of 3-chlorobenzoate and the dehydrogenation of 3- and 5-chloro-3,5-cyclohexadiene-1,2-diol-1-carboxylic acid. 3-Chlorobenzoate grown cells show additional high activities for the turnover of 3- and 4-chlorocatechols and chloromuconic acids.Abbreviations Used DHB (-)-3,5-cyclohexadiene-1,2-diol-1-carboxylic acid (derived from the trivial name, dihydrodihydroxybenzoate) - 3- and 5-Cl-DHB correspondingly 3- and 5-chloro-3,5-cyclohexadiene-1,2-diol-1-carboxylic acid     

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.     

棕色扁海绵中的吡咯生物碱

从中国南海棕色扁海绵Phakellia fusca Schimidt的乙醇浸提物中,分离得到3个吡咯生物碱,结合理化性质,波谱分析,文献检索,确定其结构分别为4,5-二溴-1H-吡咯-2-甲酸甲酯(1)、4,5-二溴-3-氰-1H-吡咯-2-甲酸甲酯(2)、4,5-二溴-1H-吡咯-2-甲酰氨(3)。其中化合物(2)未见文献报道。     

Synthesis and biological evaluation of (R)-N-(diarylmethylthio/sulfinyl)ethyl/propyl-piperidine-3-carboxylic acid hydrochlorides as novel GABA uptake inhibitors

A series of new (R)-1-(2-diarylmethylthio/sulfinyl)ethyl-piperidine-3-carboxylic acid hydrochlorides 5a-d/6a-d and (R)-1-(3-diarylmethylthio)propyl-piperidine-3-carboxylic acid hydrochlorides 5'a-d were synthesized and evaluated as gamma-aminobutyric acid uptake inhibitors through cultured cell lines expressing mouse GAT1. Biological screening results demonstrated that the compounds 6a-d with diarylmethylsulfinyl ethyl side chain show more potent GAT1 inhibitory activities than 5a-d/5'a-d with diarylmethylthio ethyl/propyl moieties. Some of them, such as 6a, exhibited excellent inhibitions of [(3)H]-GABA uptake in cultured cells, which is 496-fold higher than (R)-nipecotic acid and 11.5 times less than tiagabine. The synthesis and structure-activity relationships are discussed.     

Biological activity of novel N-substituted amides of endo-3-(3-methylthio-1,2,4-triazol-5-yl)bicyclo[2.2.1]hept-5-ene-2-carboxylic acid and N-substituted amides of 1-(5-methylthio-1,2,4-triazol-3-yl)cyclohexane-2-carboxylic acids

N-Substituted amides of endo-3-(3-methylthio-1,2,4-triazol-5-yl)bicyclo[2.2.1]hept-5-ene-2-carboxylic acid and 1-(5-methylthio-1,2,4-triazol-3-yl)cyclohexane-2-carboxylic acid were prepared by the condensation reaction of endo-S-methyl-N1-(bicyclo[2.2.1]hept-5-ene-2,3-dicarbonyl)isothiosemicarbazide and S-methyl-N1-(cyclohexane-2,3-dicarbonyl)isothiosemicarbazide with primary amines. The synthesized compounds were screened for their microbiological and pharmacological activities.     

Design, synthesis, and structural analysis of inhibitors of influenza neuraminidase containing a 2,3-disubstituted tetrahydrofuran-5-carboxylic acid core

(+/-)-(2R,3R,5R)-[2-(1'-S-acetamido-3'-methyl)butyl-3-methoxycarbonyl]tetrahydrofuran-5-carboxylic acid (9) and (+/-)-(2R,3R,5R)-[2-(1'-S-acetamido-3'-methyl)butyl-3-(4'-imidazolyl)]tetrahydrofuran 5-carboxylic acid (14) were synthesized as inhibitors of influenza neuraminidase (NA). Both compounds 9 and 14 inhibit influenza NA A with an IC(50) of about 0.5 microM and NA B with an IC(50) of 1.0 microM.     

Synthesis and thrombolytic activity of pseudopeptides related to fibrinogen fragment

Two kinds of linkers consisting of 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, ARPAK, GRPAK and QRPAK were synthesized. The thrombolytic activities in vivo indicated that the coupling position of 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in the peptides effected on the potencies significantly. When the C-terminal of the peptides was amidated by 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, the thrombolytic potency of the peptides was enhanced or kept. When the N-terminal of the peptides was acylated by 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, however, the thrombolytic effect of the peptides was banished. The expected specific beta II'-turn conformation and the stability to trypsin in the pseudopeptides with 3-(S)-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in its C-terminal may be responsible for the enhanced thrombolytic potency.     

Amino acid-azetidine chimeras: synthesis of enantiopure 3-substituted azetidine-2-carboxylic acids.

Azetidine-2-carboxylic acid (Aze) analogs possessing various heteroatomic side chains at the 3-position have been synthesized by modification of 1-9-(9-phenylfluorenyl) (PhF)-3-allyl-Aze tert-butyl ester (2S,3S)-1. 3-Allyl-Aze 1 was synthesized by regioselective allylation of alpha-tert-butyl beta-methyl N-(PhF)aspartate 13, followed by selective omega-carboxylate reduction, tosylation, and intramolecular N-alkylation. Removal of the PhF group and olefin reduction by hydrogenation followed by Fmoc protection produced nor-leucine-Aze chimera 2. Regioselective olefin hydroboration of (2S,3S)-1 produced primary alcohol 23, which was protected as a silyl ether, hydrogenated and N-protected to give 1-Fmoc-3-hydroxypropyl-Aze 26. Enantiopure (2S,3S)-3-(3-azidopropyl)-1-Fmoc-azetidine-2-carboxylic acid tert-butyl ester 3 was prepared as a Lys-Aze chimera by activation of 3-hydroxypropyl-Aze 26 as a methanesulfonate and displacement with sodium azide. Moreover, orthogonally protected azetidine dicarboxylic acid 4 was synthesized as an alpha-aminoadipate-Aze chimera by oxidation of alcohol 26. These orthogonally protected amino acid-Aze chimeras are designed to serve as tools for studying the influence of conformation on peptide activity.     

1-(5-Carboxyindol-1-yl)propan-2-ones as inhibitors of human cytosolic phospholipase A2α: Synthesis and properties of bioisosteric benzimidazole,benzotriazole and indazole analogues

The indole ring systems of the cytosolic phospholipase A₂α (cPLA₂α) inhibitor 1-[3-(4-octylphenoxy)-2-oxopropyl]indole-5-carboxylic acid (2) and the isomeric 6-carboxylic acid (3) were replaced by benzimidazole, benzotriazole and indazole scaffolds, respectively. The effect of the structural variations on cPLA₂α inhibitory potency, metabolic stability and solubility was studied. The lead 2 and the indazole-5-carboxylic acid 28 were the metabolically most stable compounds in an assay with rat liver microsomes, while the benzimidazole-5-carboxylic acid derivative 13 possessed the best water solubility (22 μg/mL at pH 7.4). The indazole-5-carboxylic acid 28 revealed the highest cPLA₂α inhibitory potency of the compounds in this series. With an IC₅₀-value of 0.005 μM it was about sevenfold more active than the lead 2.     

A new method for the preparation of delta 1-pyrroline 5-carboxylic acid and proline.

Hydroxylysine was oxidized with sodium metaperiodate and the major product characterized as Δ¹-pyrroline 5-carboxylic acid by the visible spectrum of its o-aminobenzaldehyde complex and by its reduction to proline by subsequent treatment with sodium borohydride. The reduction product was positively identified as proline by proton nuclear magnetic resonance spectroscopy and mass spectral analysis. The pH dependence for the preparation of Δ¹-pyrroline 5-carboxylic acid was determined by a study of the yields of proline obtained by variation of the pH values of the oxidative step. These observations support the hypothesis of intramolecular cyclization of α-aminoglutaric γ-semialdehyde as the second step in the reaction mechanism.     

Dicationic dithiocarbamate carbapenems with anti-MRSA activity.

A new class of 1 beta-methylcarbapenems bearing a doubly quaternarized 1,4-diazabicyclooctane (DABCO) substituted dithiocarbamate moiety at the C-2 side chain was prepared, and the biological profiles of the compounds, including in vitro and in vivo anti-MRSA activity and DHP-I susceptibility, were evaluated to identify a carbapenem derivative that was superior to BO-3482 (1). As a result, we discovered a 1 beta-methyl-2-[4-(4-carbamoylmethyl-1,4-diazabicyclo[2,2,2]octanediium-1-yl)methyl-1,2,3,6-tetrahydropyridinylthiocarbonylthio]carbapenem, 14a showing greater than 2-fold better anti-MRSA activity in a mouse infection model and 3-fold better DHP-I susceptibility as compared with BO-3482 (1).     

Synthesis and biological evaluation of pyridin-2-one nucleosides

The synthesis of 1-(beta-D-ribofuranosyl)pyridin-2-one-3-carboxylic acid and the 3-carboxamide as well as a short series of 3N-carboxamides, prepared by TPTU/HOBt coupling of primary amines with 1-(beta-D-ribofuranosyl)pyridin-2-one-3-carboxylic acid, and their evaluation as anti-infective agents is described.     

Novel ring cleavage products in the biotransformation of biphenyl by the yeast Trichosporon mucoides

The yeast Trichosporon mucoides, grown on either glucose or phenol, was able to transform biphenyl into a variety of mono-, di-, and trihydroxylated derivatives hydroxylated on one or both aromatic rings. While some of these products accumulated in the supernatant as dead end products, the ortho-substituted dihydroxylated biphenyls were substrates for further oxidation and ring fission. These ring fission products were identified by high-performance liquid chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance analyses as phenyl derivatives of hydroxymuconic acids and the corresponding pyrones. Seven novel products out of eight resulted from the oxidation and ring fission of 3,4-dihydroxybiphenyl. Using this compound as a substrate, 2-hydroxy-4-phenylmuconic acid, (5-oxo-3-phenyl-2,5-dihydrofuran-2-yl)acetic acid, and 3-phenyl-2-pyrone-6-carboxylic acid were identified. Ring cleavage of 3,4,4'-trihydroxybiphenyl resulted in the formation of [5-oxo-3-(4'-hydroxyphenyl)-2,5-dihydrofuran-2-yl]acetic acid, 4-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid, and 3-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid. 2,3,4-trihydroxybiphenyl was oxidized to 2-hydroxy-5-phenylmuconic acid, and 4-phenyl-2-pyrone-6-carboxylic acid was the transformation product of 3,4,5-trihydroxybiphenyl. All these ring fission products were considerably less toxic than the hydroxylated derivatives.     

Photodegradation of Fleroxacin Injection: Different Products with Different Concentration Levels

Photodegradation of fleroxacin is investigated in different injections and solutions. After UV irradiation, fleroxacin was degraded to afford two major products in large-volume injection (specification, 200 mg:100 ml), while degraded to afford another major product in small-volume injection (specification, 200 mg:2 ml). The photodegradation products were detected and isolated by reversed-phase HPLC. Based on the spectral data (FT-IR, MSⁿ, TOF-MS, ¹H/¹³C, DEPT, and 2D NMR), the structures of these products were: 8-fluoro-9-(4-methyl-piperazin-1-yl)-6-oxo-2,3-dihydro-6H-1-oxa-3a-aza-phenalene-5-carboxylic acid (impurity-I); 6-fluoro-1-(2-fluoro-ethyl)-7-(2-methylamino-ethylamino)-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (impurity-II); and 6,8-difluoro-1-(2-fluoro-ethyl)-7-(2-methylamino-ethylamino)-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (impurity-III), respectively. Different photodegradation pathways of fleroxacin were proposed, which led to the different stability characteristics of fleroxacin in the injections. The fluorine atom at C8 is more photolabile in dilute injection, so defluorination and cyclization reactions are prone to take place, whereas photo irradiation only cause ring-opening oxidation reaction of piperazine side chain in concentrated injection.