Crystal structure and conformation of 8-(2-hydroxyethylamino) and 8-(pyrrolidin-1-yl) adenosines.

In the course of investigation of 8-alkylamino substituted adenosines, the title compounds were synthesized as potential partial agonists for adenosine receptors. The structure determination of these compounds was carried out with the X-ray crystallography study. Crystals of 8-(2-hydroxyethylamino)adenosine are monoclinic, space group P 2(1); a = 7.0422(2), b = 11.2635(3), c = 8.9215(2) A, beta = 92.261(1) degrees, V = 707.10(3) A3, Z = 2; R-factor is 0.0339. The nucleoside is characterized by the anti conformation; the ribose ring has the C(2')-endo conformation and gauche-gauche form across C(4')-C(5') bond. The molecular structure is stabilized by intramolecular hydrogen bond of N-HO type. Crystals of 8-(pyrrolidin-1-yl)adenosine are monoclinic, space group C 2; a = 19.271(1), b = 7.3572(4), c = 11.0465(7) A, beta = 103.254(2), V = 1524.4(2) degrees A3, Z = 4; R-factor is 0.0498. In this compound, there is syn conformation of the nucleoside; the ribose has the C(2')-endo conformation and gauche -gauche form across C(4')- C(5') bond. The molecular structure is stabilized by intramolecular hydrogen bond of O-HN type. For both compounds, the branching net of intermolecular hydrogen bonds occur in the crystal structures.

Synthesis and antitumour activity of trimethylsilylpropyl substituted benzimidazoles.

The quaternisation of N-substituted benzimidazoles by heating with various alkyl, allyl, propargyl and benzyl chlorides and bromides leads to the formation of benzimidazolinium salts. The interaction of N-monosubstituted benzimidazoles with various salts (CuCl2, ZnCl2, CoCl2, PdCl2 and AgNO3) yielded stable solid complexes. Potential cytotoxic activity of synthesised benzimidazolinium salts and benzimidazole metal complexes was tested in vitro on four monolayer tumour cell lines: MG-22A (mouse hepatoma), HT-1080 (human fibrosarcoma), B16 (mouse melanoma), Neuro 2A (mouse neuroblastoma) and normal mouse fibroblast cells. A preliminary analysis of the structure-activity relationship for the benzimidazole derivatives clearly indicates that the character of substituents in the benzimidazole ring has strong influence on the cytotoxic activity. The insertion of the silicon atom into the N-alkyl chain increases the cytotoxic activity of benzimidazolinium salts significantly, which show a very significant potency in vitro against all studied tumour cell lines, being particularly active in experiments with B16 (mouse melanoma). TD50 for the most active compounds are in the range 0.001-0.008 microg x ml(-1). Cytotoxicity of benzimidazole metal complexes (L2MX2) strongly depends on the metal nature. 1-(3-trimethylsilylpropyl)benzimidazole in dose 1 mg x kg(-1) inhibits carcinoma S-180 tumour growth by 62% (on ICR mice).

Synthesis of silicon and germanium containing heteroaromatic sulfides as cholesterol level lowering and vasodilating agents.

Silicon and germanium containing heteroaromatic sulfides have been prepared using phase transfer catalytic (PTC) system thiol / Si or Ge containing alkyl halide / solid KOH / 18- crown-6 / toluene. The target sulfides were isolated in yields up to 92 %. It has been found that 2-{[dimethyl (beta-triethylgermylethyl)-silylmethyl]thio}-1-methylimidazole and 2-{[dimethyl(beta-triphenylsilylethyl) silyl-methyl]thio}benzothiazole are the most active cholesterol level lowering and vasodilating agents.

Synthesis and biological activity of silyl- and germylsubstituted trifluroacetylfurans.

A series of silyl, germyl and alkyl substituted trifluoroacetylfurans has been synthesized under Friedel-Crafts electrophilic acylation conditions. Biological investigations have demonstrated that germyl derivatives of trifluoroacetylfuran are more toxic than the silicon analogues. 5-Triethylgermyl-2- trifluoroacetylfuran was the most toxic compound (CD(nabla), 11.2 mg kg(-1), i.p. for white mice), 200 times more toxic than the silicon analogue. 5-t-Butyl- and 5-trimethylsilyl-2-trifluroacetylfuran prolong the duration of ethanol anaesthesia by 220 and 140%. 5-Triethylgermyl-2-trifluroacetylfuran exibited high anesthetic activity in hexobarbital test (prolonged the duration by 137%). Some of compounds influenced muscle tone and locomotor coordination parameters. 5-Triethylgermyl-2-trifluomacetylfuran exibited analgesic activity (D(nabla), 0.9 mg k}(-infinity)).

Synthesis and antitumor activity of selected 7-alkylidene substituted cephems.

Selected 7-alkylidene substituted cephems were synthesized and subjected to antitumor assay. The effect of substituents was examined to establish structure-activity relationships. It was found that the intensive intracellular generation of nitric oxide induced by tert-butyl 7-alkylidene cephalosporanate sulfones could be also regarded as an additional cytotoxic factor taking place both in vitro and in vivo experiments.

Cytotoxic Activity of Silyl- and Germyl-Substituted 4,4-Dioxo-3a,6a-Dihydrothieno[2,3-d]isoxazolines-2.

The [2+3] dipolar cycloaddition of nitrile oxides to the double C = C bonds of thiophene-1, 1-dioxides leads to formation of the fused isoxazolines-2 (1, 2). Tumor growth inhibition of these compounds strongly depends on the nature of group IV A element increasing from slightly active tert-butyl derivatives to silicon and germanium containing analogues. The products of benzonitrile oxide cycloaddition have greater cytotoxic effect than the compounds obtained from the cycloaddition reaction of 2, 5-disubstituted thiophene-1, 1-dioxides with acetonitrile oxide. Fused silyl substituted isoxazolines-2 are stronger NO-inducers than their germyl and tert-butyl analogues.

Synthesis, vasodilating, antithrombotic and cardioprotective activity of pyridyl substituted 5-silyl(germyl)isoxazolines-2.

The reactions of [2+3] cycloaddition of pyridylnitrile oxides to vinyl- and allylgermanes proceed regioselectively and afford 5-Ge-substituted isoxazolines-2. We have synthesized 9 new pyridyl substituted 5-Si(Ge)-isoxazolines-2 and investigated their biological activity. The vasodilating, anticoagulant and cardioprotective activities of 5-Si(Ge) substituted isoxazolines-2 have been studied in vitro and in vivo. Substitution of the silicon atom for the germanium one leads to the significant increase in vasodilating, antithrombotic and cardioprotective activity. The insertion of the methylene group between Ge and the isoxazoline ring reduces the vasodilating activity. The most active isoxazoline - 3-(5'-triethylgermyl-3'-isoxazolinyl)pyridine hydrochloride protects the heart from rhythm disturbances and lethality during ischaemia-reperfusion.

Synthesis, structure and biological activity of 6-r(3)si(ge, sn)-substituted 5-fluorouracils.

Direct lithiation of 1-(2-tetrahydrofuryl)-5-fluorouracil (Ftorafur) has been investigated. The treatment of ftorafur with lithium diisopropylamide (LDA)at -70 in ether-hexane, followed by the reaction with various electrophiles afforded the corresponding 6-substituted silicon, germanium and tin derivatives of ftorafur. The results of biological investigation indicate the ability of germanium-modified nucleoside analogues to interfere with transcription and replication processes.

Synthesis and selective vasodilating properties of esters of 2,6-dimethyl-4-(2-difluoromethoxyphenyl)-1,4-dihydro-pyridine-3,5-di- carboxylic acid.

This study presents the synthesis of new 1,4-dihydropyridine (DHP) derivatives which are phenoxy- and alkoxyalkyl esters of 2,6-dimethyl-4-(2-difluoromethoxyphenyl)-1,4-dihydropyridine-3,5-dica rbo xylic acid and reports on the biological activity of the compounds. It was found that the DHP derivatives showed high affinity to the DHP receptor of rat brain membranes and antagonize potently the potassium depolarization-induced vasospasm in a fashion compatible with the assumption of a calcium entry blockade. The higher vasodilating potency of especially compound III for the cerebral vasculature might represent an improved selectivity profile due to specific substitution patterns of the DHP molecule by increasing lipophilicity. Thus, the new DHP derivatives might be useful as therapeutic agents for hypertension and impaired cerebral microcirculation.

3-(2,2,2-Trimethylhydrazinium)propionate (THP)--a novel gamma-butyrobetaine hydroxylase inhibitor with cardioprotective properties.

A protein fraction containing gamma-butyrobetaine hydroxylase (sp.act. 1.54 mU/mg) was isolated from the rat liver by differential precipitation with ammonium sulphate. 3-(2,2,2-Trimethylhydrazinium)propionate (THP), a noncompetitive enzyme inhibitor, when administered orally to rats for 10 days (150 mg/kg) elicited a reduction in myocardial free carnitine and long-chain acyl carnitine content by 63.7 and 74.3%, respectively. This reduction in free carnitine concentration causes a suppression of the free fatty acid oxidation, as measured by the production of 14CO2 and ketone bodies. The inhibition of fatty acid oxidation is particularly manifest when their metabolism is stimulated by feeding a fat-rich diet to the animals or in fasting rats. The inhibition of fatty acid metabolism at the stage of activation (acyl carnitine formation) can account for the cardioprotective effect of THP, which is assessed by its ability to prevent a decrease in ATP level and myocardial energy charge as well as to prevent a rise in creatine phosphokinase and lactic dehydrogenase (myocardium-specific isozyme) activity in rat blood serum in response to isoproterenol and epinephrine. Regulation of the carnitine-dependent fatty acid metabolism in ischaemia is a pathogenetically justified approach to pharmacological treatment of ischaemic myocardium. In its biochemical mechanism, THP significally distinguishes itself from other known inhibitors of fatty acid oxidation.