Growth inhibition and induction of cellular differentiation of human myeloid leukemia cells in culture by carbamoyl congeners of ribavirin

A series of 1,2,3-triazole (2), pyrazole (3 and 5), and pyrrole (4) ribonucleosides with two adjacent carbamoyl groups have been synthesized and evaluated for cell growth inhibition and induction of cellular differentiation of HL-60 cells in culture. Glycosylation of the TMS derivatives of dimethyl 1,2,3-triazole-4,5-dicarboxylate (6) and diethyl pyrazole-3,4-dicarboxylate (7) with 1-O-acetyl-2,3,5-tri-O-benzoyl-D- ribofuranose (8) in the presence of TMS triflate gave predominantly the beta-nucleosides 9 and 14, respectively. Ammonolysis of 9 and 14 furnished 2-beta-D-ribofuranosyl-1,2,3-triazole-4,5-dicarboxamide (2) and 1-beta-D-ribofuranosylpyrazole-3,4-dicarboxamide (3), respectively. Stereoselective ring annulation of 1-deoxy-1-hydrazinyl-2,3-O-isopropylidene-D- ribose (16) with tetracyanoethylene (15) gave 5-amino-1-(2,3-O-isopropylidene-beta-D-ribofuranosyl)pyrazole-3,4- dicarbonitrile (17). Deisopropylidenation of 17, followed by oxidative hydrolysis of the reaction product (18), gave the 5-amino derivative of 3 (5). Stereospecific glycosylation of the sodium salt of preformed diethyl pyrrole-3,4-dicarboxylate (22) with 1-chloro-2,3-O-isopropylidene-5-O-(tert-butyldimethylsilyl)-alpha-D- ribofuranose (23) was accomplished to furnish blocked nucleoside 24, which on ammonolysis and deisopropylidenation gave 1-beta-D-ribofuranosylpyrrole-3,4-dicarboxamide (4). The structures of 2 and 3 were assigned by single-crystal X-ray diffraction studies, which showed extensive inter- and intramolecular hydrogen bonding. Nucleosides 2-5 are devoid of significant cytotoxic properties against L1210 and WI-L2 leukemia cells in culture. However, these compounds were found to be inducers of cellular differentiation of HL-60 cells in the range of 30-60 microM and were comparable to ribavirin in this regard.     

Estrogen receptor stereochemistry: ligand binding orientation and influence on biological activity

Racemic (Rac) 4'- and 5-deoxyindenestrol A (4'-DIA and 5-DIA), monohydroxyl analogs of the diethylstilbestrol (DES) oxidative metabolite indenestrol A (IA), were synthesized, and their enantiomers were resolved and isolated. Each compound was then tested for estrogen receptor (ER) binding affinity, uterotropic activity, and nuclear ER levels, to further define the stereochemical preference of the ER and to structually evaluate the function of each IA hydroxyl group for binding and biological activity. Competitive binding to cytosolic ER determined the relative binding affinity of racemic mixtures of 4'- and 5-DIA as 1.3 and 3.7, respectively, compared with that of DES, 286. The ER exhibited a binding preference for the S-enantiomer of both compounds, with relative binding affinities of 4'-DIA-R, 0.2; 4'-DIA-S, 1.8; 5-DIA-R, 0.9; and 5-DIA S, 5.6. 4'-DIA-Rac produced 3 times the in vivo stimulation of 5-DIA-Rac in the uterotropic bioassay (with mouse uterine doubling doses of 302.4 and 800 micrograms/kg, respectively). Nuclear ER levels measured 1 hr after in vivo treatment with either 160 micrograms/kg 4'-DIA or 80 micrograms/kg 5-DIA showed a maximum binding level of 2 (4'-DIA) and 1.5 (5-DIA) times saline control, with these doses producing levels nearly equal to that caused by a 10 micrograms/kg dose of IA. Metabolic studies were carried out by treating mice with [3H]4'- and [3H]5-DIA-Rac, to determine the differential binding affinity and biological stimulation of 4'-DIA and 5-DIA. The in vivo metabolism of the [3H]DIA compounds showed formation of [3H]IA-Rac in urine extracts, as analyzed by chiral high performance liquid chromatography. Furthermore, in vitro incubation of unlabeled 4'- and 5-DIA-Rac with mouse liver microsomes showed stereospecific metabolism, with IA-S primarily formed from 4'-DIA-Rac and IA-R from 5-DIA-Rac. Metabolism of 4'-DIA-Rac to the more active IA S-enantiomer and of 5-DIA-Rac to the less active IA R-enantiomer contributes to the different biological activities, because the ER exhibits a chiral preference for these compounds. The higher binding affinity of 5-DIA indicates that the phenyl ring hydroxyl group is required for high affinity binding; however, both hydroxyl groups are needed for subsequent biological activity. These data further suggest that the ER demonstrates stereochemical ligand binding and that IA binds in an orientation relative to 17 beta-estradiol in which the IA phenyl ring corresponds to the estradiol A-ring.     

Disposition of flurbiprofen in man: influence of stereochemistry and age

1. The stereoselective metabolism and pharmacokinetics of the enantiomers of flurbiprofen were investigated following the oral administration of the racemic drug (100 mg) to four young and four elderly healthy volunteers (two males and two females per group). 2. The stereochemical composition of the drug and the 4'-hydroxy- metabolite in serum and the drug, 4'-hydroxy- and 3'-hydroxy-4'-methoxy- metabolites, both free and conjugated, in urine were determined by a direct chromatographic method of enantiomeric analysis. 3. Modest enantioselectivity in clearance (CL S/R: young, 0.86; elderly, 0.88) was largely responsible for the apparent elimination half-life of (S)-flurbiprofen being significantly greater (p<0.01) than that of the R-enantiomer in both age groups (young, S: 5.2 +/- 0.7 versus R: 4.5 +/- 0.6 h; elderly, S: 9.6 +/- 1.2 versus R: 7.1 +/- 1.0 h). The serum concentrations of 4'-hydroxyflurbiprofen were five- to 20-fold lower than those of the corresponding drug enantiomers, stereoselective disposition being evident in the significantly greater (p<0.05) apparent half-lives of the S- compared with the R-enantiomer in both groups (young, S: 10.6 +/- 2.4 versus R: 6.7 +/- 1.1 h; elderly, S: 13.7 +/- 1.7 versus R: 10.2 +/- 1.2 h). 4. Some 60 and 72% of the dose was excreted in 24-h urine in elderly and young volunteers, respectively, a significantly greater (p<0.05) proportion of which was of the R-configuration in both age groups (S/R: young, 0.87; elderly, 0.81). The major urinary excretion products were flurbiprofen and 4'-hydroxyflurbiprofen, and their acyl-conjugates in both groups. 5. Age-associated differences in the pharmacokinetics of flurbiprofen occurred in a non-stereoselective manner and were primarily as a consequence of a significant approximately 40% decrease (p<0.01) in clearance of both enantiomers in the elderly due to reduced metabolic activity. Consequently, the elderly had greater exposure to both enantiomers, as reflected by the AUCs(0-inf) being significantly higher (p<0.05), by 60%, in this age group compared with the young. 6. The findings suggest that age-related alterations in the disposition of flurbiprofen could have significant implications for the use of the drug in the elderly.     

Disposition of flurbiprofen in man: influence of stereochemistry and age

1. The stereoselective metabolism and pharmacokinetics of the enantiomers of flurbiprofen were investigated following the oral administration of the racemic drug (100?mg) to four young and four elderly healthy volunteers (two males and two females per group).

2. The stereochemical composition of the drug and the 4′-hydroxy- metabolite in serum and the drug, 4′-hydroxy- and 3′-hydroxy-4′-methoxy- metabolites, both free and conjugated, in urine were determined by a direct chromatographic method of enantiomeric analysis.

3. Modest enantioselectivity in clearance (CL S/R: young, 0.86; elderly, 0.88) was largely responsible for the apparent elimination half-life of (S)-flurbiprofen being significantly greater (?p<0.01) than that of the R-enantiomer in both age groups (young, S: 5.2 ± 0.7 versus R: 4.5 ± 0.6?h; elderly, S: 9.6 ± 1.2 versus R: 7.1 ± 1.0?h). The serum concentrations of 4′-hydroxyflurbiprofen were five- to 20-fold lower than those of the corresponding drug enantiomers, stereoselective disposition being evident in the significantly greater (?p<0.05) apparent half-lives of the S- compared with the R-enantiomer in both groups (young, S: 10.6 ± 2.4 versus R: 6.7 ± 1.1?h; elderly, S: 13.7 ± 1.7 versus R: 10.2 ± 1.2?h).

4. Some 60 and 72% of the dose was excreted in 24-h urine in elderly and young volunteers, respectively, a significantly greater (?p<0.05) proportion of which was of the R-configuration in both age groups (S/R: young, 0.87; elderly, 0.81). The major urinary excretion products were flurbiprofen and 4′-hydroxyflurbiprofen, and their acyl-conjugates in both groups.

5. Age-associated differences in the pharmacokinetics of flurbiprofen occurred in a non-stereoselective manner and were primarily as a consequence of a significant ～ 40% decrease (?p<0.01) in clearance of both enantiomers in the elderly due to reduced metabolic activity. Consequently, the elderly had greater exposure to both enantiomers, as reflected by the AUCs_0–inf being significantly higher (?p<0.05), by 60%, in this age group compared with the young.

6. The findings suggest that age-related alterations in the disposition of flurbiprofen could have significant implications for the use of the drug in the elderly.     

Lack of enantiomeric influence on the brain cytoprotective effect of ibuprofen and flurbiprofen

R(−) enantiomers of the 2-arylpropionic acid derivatives ibuprofen and flurbiprofen weakly inhibit cyclooxygenase (COX) activity. However, a possible cytoprotective effect has been proposed. The aim of the study is to investigate the possible mechanism of this effect. An in vitro hypoxia–reoxygenation model in rat brain slices was used (n = 6 rats per group). After reoxygenation, we measured LDH efflux (neuronal death), brain prostaglandin E₂ (PGE₂) concentration, interleukins (IL)-1β and 10, oxidative and nitrosative stress (lipid peroxides, glutathione, 3-nitrotyrosine, and nitrites/nitrates). Anti-COX activity was measured in human whole blood. Racemic, R(−), and S(+) enantiomers of ibuprofen and flurbiprofen were tested. All compounds had a cytoprotective effect with IC₅₀ values in the range of 10⁻⁵ M. R(−) enantiomers did not significantly inhibit brain PGE₂. The concentration of IL-1β was reduced by 53.1% by the racemic form, 30.6% by the S(+) and 43.2% by the R(−) enantiomer of ibuprofen. The IL-10 concentration increased significantly only with S(+)-flurbiprofen (33.1%) and R(−)-flurbiprofen (26.1%). Lipid peroxidation was significantly reduced by all three forms of flurbiprofen. Nitrite + nitrate concentrations were reduced by racemic, S(+), and R(−)-flurbiprofen. Peroxynitrite formation (3-nitrotyrosine) was significantly reduced by racemic and S(+)-ibuprofen. COX inhibition is not the main mechanism of cytoprotection for these compounds. Their influence on inflammatory mediators and oxidative and nitrosative stress could account for the potential cytoprotective effect of R(−) enantiomers.     

Lack of central 5-hydroxytryptamine influence on the anticonflict activity of diazepam

This study examined the effects of various drug treatments (IP injections) proposed to modify central 5-hydroxytryptamine (5-HT) activity on a conditioned suppression of drinking behavior in water-deprived rats. The subjects were trained to drink their daily water requirement during a 10-min session. Intermittent tone periods of 7 s were then introduced, the last 5 s of which the drinking tube was electrified. The animals gradually suppressed tube contacts during the tone to a low constant level within 2 weeks of training. Diazepam increased punished responding dramatically. The 5-HT antagonists methysergide (1–18 mg/kg), cyproheptadine (1–18 mg/kg), metergoline (0,25–2.0 mg/kg) and cinanserin (10–100 mg/kg) failed to induce large, reliable increases in punished responding. When a low dose of diazepam was combined with 5-HT antagonists, only one treatment, methysergide at 3 mg/kg, potentiated the anticonflict activity of diazepam. Acute or chronic treatment with PCPA increased behavior suppressed by punishment, but this effect was weak, brief, and poorly related to the depletion of brain 5-HT. LSD (0.3–100 g/kg) administered 1,10, or 30 min before the test was ineffective in overcoming suppression by punishment. Mescaline (6–30 mg/kg) had no significant effect on punished responding. 5-HTP (18 mg/kg) decreased the number of shocks accepted, but not after pretreating with carbidopa. Pretreatment with carbidopa plus 5-HTP potentiated the anticonflict effect of diazepam. The 5-HT agonist mCPP (0.25–2.0 mg/kg) enhanced suppression due to punishment, but only in doses that interfered with unpunished responding. The 5-HT-releasing agent fenfluramine (0.25–1.0 mg/kg) did not affect this behavior. Amitriptyline pretreatment in a dose not affecting unpunished behavior (5.6 mg/kg) potentiated the diazepam-induced increase in punished responding. These results are difficult to reconcile with the proposal that suppression of behavior consequent to punishment is related to brain 5-HT activity.     

Lack of influence of histamine antagonists on digitalis cardiotoxicity.

Experiments were carried out in order to study the interaction between cardioactive glycosides and histamine or histamine H1- AND/OR H2-receptor antagonists in anaesthetized cats or guinea pigs. The toxicity of ouabain or digoxin was tested by infusing the glycosides until idioventricular rhythm or death occurred. Histamine increased the toxicity of ouabain, but the histamine H1- and/or H2-receptor antagonists (metiamide and mepyramine)did not influence the toxicity of digitalis. In cats the increase in pulmonary arterial blood pressure caused by digoxin was not affectedby histamine H1- and/or H2-receptor antagonism in spite of the fact that the increase of pulmonary blood pressure caused by histamine could be abolished by H1-receptor antagonists. Our results indicate that histamine is not involved in the toxic effect of cardiac glycosides.     

Lack of influence of cigarette smoking on triazolam pharmacokinetics.

The influence of cigarette smoking on the pharmacokinetics of a single dose of the triazolobenzodiazepine hypnotic triazolam was evaluated in 12 healthy nonsmoking male volunteers and in 12 male subjects, matched for age, height and weight, who smoked an average of 24 cigarettes a day (range: 15-30). Triazolam kinetics were determined from multiple serum concentrations measured during 15 h after a single 0.5 mg dose. There were no significant differences between nonsmoking controls and cigarette smokers in the peak serum triazolam concentration (4.64 vs 4.73 ng ml-1), the time of peak concentration (0.98 vs 1.0 h after dosage), elimination half-life (2.8 vs 2.5 h), or oral clearance of triazolam (506 vs 627 ml min-1). Likewise there were no significant differences between groups in the extent of triazolam binding to serum protein (18.8 vs 18.5% unbound). Altered pharmacodynamics of triazolam in cigarette smokers are not likely to be explained by altered pharmacokinetics.     

Effect of cyclodextrins on the chemical stability of mitomycins in alkaline solution.

The effects of cyclodextrins on the chemical stability of several mitomycin antibiotics in an alkaline medium have been investigated. A stability-indicating high-performance liquid chromatographic method was used to determine the overall degradation rate constants. The influence of various parameters such as structural variations of the cyclodextrins and mitomycins, temperature and pH was studied. It appears that complexation is most favourable with gamma-cyclodextrin. All mitomycin-gamma-cyclodextrin complexes degrade at lower rates than those of the free drugs. Moreover, it was shown that gamma-cyclodextrin influences the equilibrium between mitomycin C and its zwitterion mesomer.     

Nitrilophenoxypropanolamines: influence of ring substitution on beta-receptor blockade

A series of nitrilo-ring-substituted phenoxypropanolamines with N-isopropyland N-t-butyl substituents have been tested for their ability to antagonize isoprenaline-induced responses in ras in vivo (vasodepression and tachycardia), and in isolated rabbit atrial and guinea-pig traceel preparations. In the isolated the tissues the β-receptor antagonism was shown to be of a competitive type. In both N-alkyl series, change of the nitrilo ring substituent through the positions ortho : meta : para produced a decrease in β-receptor blocking potency in all tests. Comparison of β-receptor blocking potencies in different tissues showed that the above changes in the position of the nitrilo ring substituent resulted in an increase in selectivity towards β₁ - as opposed to β₂-receptor antagonism. The para-nitrilo derivatives were more potent than the corresponding ortho and meta compounds in producing increases in effective refracory period and decreases in inotropic activity in guinea-pig driven left atrial preparations.     

2,1-Bensoidoxazoles [anthranils]. Synthesis and opening of the isoxazole ring (review)

Translated from Khimiko-farmatsevticheskii Zhurnal, Vol. 25, No. 1, pp. 57–66, January, 1991.     

The influence of stereochemistry on pKa,rate of quaternization and partition coefficients of corynantheidine-type alkaloids

In alkaloids of the corynantheidine group, the rate of quaternization at N-4 and the pK_a values give a measure of the degree of steric hindrance at this site due to the axial hydrogen at C-3 and the ethyl group at C-20. These hinder the availability of the lone pair of electrons on N-4 to electrophiles. Partition coefficients indicate that lipid solubility is associated with planarity of the molecules; this explains why the more planar isomers (allo and normal) are more highly metabolized in microsomes than the less planar isomers (pseudo and epiallo).     

Lack of influence of brain catecholamines on acute effects of barbiturates

Rats with cerebral electrode implants were tested for sensitivity to EEG burst suppression by intravenously-infused sodium methohexital following manipulation of brain catecholamine function. Although depletion of both norepinephrine (NE) and dopamine (DA) with 6-hydroxydopamine resulted in a slight increase in methohexital sensitivity (MHS), similar depletion with α-methyltyrosine did not alter MHS. In addition, desipramine, an agent which selectively blocks uptake of NE did not affect MHS. The results indicate that brain NE and DA exert little, if any, effect on brain responsiveness to the acute effect of barbiturates.     

Synthesis and biological activity of 6-substituted mitosene analogues of the mitomycins

A series of 1-acetoxymitosene analogues, in which the substituent at C-6 was varied, was prepared by total synthesis and screened for activity against P388 leukemia in mice and induction of lambda phage in Escherichia coli. Among the 6-substituents prepared, none was as effective as the methyl group in conferring biological activity. However, certain N-methylcarbamates were more active than the unsubstituted carbamates.