Structure-based design,synthesis, and evaluation of imidazo[1,2-b]pyridazine and imidazo[1,2-a]pyridine derivatives as novel dual c-Met and VEGFR2 kinase inhibitors

To identify compounds with potent antitumor efficacy for various human cancers, we aimed to synthesize compounds that could inhibit c-mesenchymal epithelial transition factor (c-Met) and vascular endothelial growth factor receptor 2 (VEGFR2) kinases. We designed para-substituted inhibitors by using co-crystal structural information from c-Met and VEGFR2 in complex with known inhibitors. This led to the identification of compounds 3a and 3b, which were capable of suppressing both c-Met and VEGFR2 kinase activities. Further optimization resulted in pyrazolone and pyridone derivatives, which could form intramolecular hydrogen bonds to enforce a rigid conformation, thereby producing potent inhibition. One compound of particular note was the imidazo[1,2-a]pyridine derivative (26) bearing a 6-methylpyridone ring, which strongly inhibited both c-Met and VEGFR2 enzyme activities (IC₅₀ = 1.9, 2.2 nM), as well as proliferation of c-Met-addicted MKN45 cells and VEGF-stimulated human umbilical vein endothelial cells (IC₅₀ = 5.0, 1.8 nM). Compound 26 exhibited dose-dependent antitumor efficacy in vivo in MKN45 (treated/control ratio [T/C] = 4%, po, 5 mg/kg, once-daily) and COLO205 (T/C = 13%, po, 15 mg/kg, once-daily) mouse xenograft models.     

Relationship between the expression of Rab family GTPases and neuropeptide hormones in the brain of Bombyx mori

Rab proteins are small GTPases that play essential roles in vesicle transport. In this study, we examined the expression of Rab proteins and neuropeptide hormones in the brain of the silkworm, Bombyx mori. We produced antibodies against B. mori Rab1 and Rab14 in rabbits. Immunoblotting of samples of brain tissue from B. mori revealed a single band for each antibody. Rab1 and Rab14 immunohistochemical labeling in the brain of B. mori was restricted to neurons of the pars intercerebralis and dorsolateral protocerebrum. Rab1, Rab7 and Rab14 co-localized with bombyxin. Rab1 and Rab7 co-localized with eclosion hormone. Rab1 co-localized with prothoracicotropic hormone. These results suggest that Rab1, Rab7 and Rab14 may be involved in neuropeptide transport in the brain of B. mori. This is the first report on the specificity of Rab proteins for the secretion of different neuropeptides in insects.     

Syntheses and Biological Activities of 1-O-Glucopyranosyl Fatty Acid Esters

1-O-Palmitoyl-d-glucopyranose was prepared by the selective 1-O-acylation of 4,6-O-benzylideneglucose followed by hydrogenolysis of the protecting group. 1-O-Oleoyl-d-glucopyranose was synthesized from the corresponding benzylidene derivative by selective hydrolysis in acetic acid. This procedure constitutes a useful method for the synthesis of 1-O-acyl-d-glucopyranoses containing unsaturated carboxylic acids. However, 4,6-O-benzylidene-l-O-linolenoyl-d-glucopyranose was converted to 3-O-linolenoyl-d-glucopyranose by the acidic hydrolysis due to acyl migration.

Synthesized glucosyl esters were inactive in the bean second-internode bioassay. However, it was found that 3-O-linolenoyl-d-glucopyranose had a promoting activity on germination of pollen and growth of pollen tube.     

Extracellular Production of l-Lysine α-Oxidase in Wheat Bran Culture of a Strain of Trichoderma viride

A mold strain Y244-2 capable of producing l-lysine α-oxidase, a new enzyme catalyzing the α-oxidative deamination of l-lysine, was identified as Trichoderma viride. Among strains belonging to the genus Trichoderma tested, only Trichoderma viride Y244-2 produced the enzyme in wheat bran culture. The maximum enzyme production by the mold grown on wheat bran was observed after 10 and 14 days incubation with and without NaN0₃, respectively. Addition of NaN0₃, NH₄N0₃, adenine, purine nucleosides, l-histidine, glycine or l-glutamine to wheat bran stimulated the production of the enzyme. In the liquid culture, the enzyme was produced extracellulary under the aerobic conditions, although the production was much lower than that in the wheat bran culture.     

Chemical Synthesis and Characterization of α-N-Octanoyl and Other α-N-Acyl Colistin Nonapeptide Derivatives

Eight α-N-acyl colistin nonapeptide derivatives including three aliphatic, four aromatic and one alicyclic derivatives were synthesized by the reaction of colistin nonapeptide with corresponding acid chlorides. This acylation reaction was carried out under the condition kept restrictedly at pH 5,0 in order to introduce an acyl group only to α-amino group but not to γ-amino group existing in a colistin nonapeptide molecule. Synthetic method and several physico-chemical natures of these acyl colistin nonapeptide derivatives are given in this paper.

All of the acylated derivatives thus synthesized exhibited characteristic antimicrobial activities. Antimicrobial spectra were substantially based upon a gram-negative type and not so much altered by chemical structures of acyl groups which were considerably differentiated from each other such as cyclic or chain form. Thus, more possible response of carbon size than its structure to the antimicrobial effectiveness was inferred. In spite of almost no toxicity and feeble antimicrobial activity of colistin nonapeptide itself, these acylated colistin nonapeptide derivatives showed a toxicity against mice at a dose of 16.9~70 mg/kg in LD₅₀, which, however, was inferior to the toxicity of colistin sulfate, possibly correspondent to their much weaker antimicrobial activities, as a whole. Hence, it seems likely that acyl part of these acylated colistin nonapeptide derivatives including that of colistin is seriously responsible for the biological activities.     

Acid-Catalyzed Stereoselective Cyclization of Germacrene D

A monohalomethane-producing enzyme, S-adenosyl-L-methionine-dependent halide ion methyltransferase (EC 2.1.1.-) was purified from the marine microalga Pavlova pinguis by two anion exchange, hydroxyapatite and gel filtration chromatographies. The methyltransferase was a monomeric molecule having a molecular weight of 29,000. The enzyme had an isoelectric point at 5.3, and was optimally active at pH 8.0. The K_m for iodide and SAM were 12 mM and 12 μM, respectively, which were measured using a partially purified enzyme. Various metal ions had no significant effect on methyl iodide production, suggesting that the enzyme does not require metal ions. The enzyme reaction strictly depended on SAM as a methyl donor, and the enzyme catalyzed methylation of the I^-,Br^-, and Cl^- to corresponding monohalomethanes and of bisulfide to methyl mercaptan.     

Continuous ATP Regeneration Using Immobilized Yeast Cells

Arthrobacter simplex was screened as an α-keto-δ-guanidinovalerate (ketoarginine) assimilating organism. A characteristic feature was its growth on ketoarginine as a carbon source; it began to grow after an extremely long lag. Its growth was stimulated by addition of 0.02% yeast extract to the medium.

The results indicated the transamination of arginine-α-ketoglutarate (α-KGA) and the hydrolyzing reaction of ketoarginine into α-keto-δ-aminovalerate and urea. Two intermediates, ketoarginine and α-keto-δ-aminovalerate, were isolated and identified by various procedures. Coupling of the two reactions was demonstrated in cell-free extracts of arginine-grown cells; ketoarginine formed from arginine by transamination with α-KGA was hydrolyzed directly to α-keto-δ-aminovalerate and urea. The metabolic routes of arginine in microorganisms were discussed.     

Effects of Chemical Agents on Radiation Inactivation of Streptomyces Protease in Aqueous System

Inactivation of crystalline enzyme, Streptomyces protease G, by γ-ray irradiation in an aqueous system has been investigated. It is indicated that inactivation of the enzyme is attributable mainly to the indirect action of radiation. The inactivation curve is exponential and the G-value for enzyme inactivation is calculated as 0.1 at an enzyme concentration of 1×10^?5m, which is not influenced by varying pH. Effects of various other solutes on radiation inactivation have been also studied. Halogen ions, especially iodine ion, and nitrite ion are most protective among various inorganic anions examined, and alkali metal and alkali earth metal cations are ineffective. Among various organic compounds examined, sulfur-containg compounds and unsaturated compounds are generally effective for protection of enzyme activity against radiation damages. The protective effect of benzene is enhanced by the substitution of electron donating groups. Chloroform and chloral are found to act as a synergist for irradiation inactivation.     

Modification of Combined Effect of Radiation and Sodium Chloride on Microorganisms by Chemical Agents during Irradiation

Effects of various chemical agents on the synergistic action of NaCl to the radiation inactivation of bacteria and yeast were studied. The remarkable modification of the radiation lethal effect by some reagents is considered to be a strong evidence for an indirect nature of NaCl synergistic action during irradiation. Most of these modification effects were restricted to the actions during irradiation, supporting the free radical hypothesis in which the short-life active species formed by radiation were considered to attack bacterial cells. Furthermore, pre-irradiation effects under various conditions suggest that the enhancement of radiation lethal effect by NaCl may involve the intracellular events.