Synthesis and biological activity of several amino analogues of thymidine

3',5'-Diamino-3',5'-dideoxythymidine (7) was synthesized via a nine-step synthesis from thymidine in good overall yield. 3'-Amino-3'-deoxythymidine (8) and 5'-amino-5'-deoxythymidine (12) were prepared with a minor modification of the procedure reported by Horwitz and co-workers. Although the 5'-amino analogue 12 had potent antiviral activity relative to the 3'-amino analogue 8, the latter is a potent inhibitor of the replication of both murine sarcoma 180 cells (ED50 = 5 micrometer) and of murine L1210 cells (ED50 = 1 micrometer) in vitro. Most unexpectedly, however, was the finding of complete lack of either antiviral or antineoplastic activity by the 3',5'-diamino analogue 7 which appears to have acquired the undesirable qualities of both the 3'-amino and 5'-amino analogues of thymidine.     

Ionization, lipophilicity and solubility properties of repaglinide

Potentiometric and spectrophotometric titrations were used for the determination of ionization behaviour, lipophilicity and solubility profile of repaglinide. Acid-base equilibria were characterized by means of protonation macro- and microconstants using Target Factor Analysis of spectrophotometric data. Lipophilicity profiles were evaluated by determination of partition coefficients of neutral and ionized forms of repaglinide in biphasic octanol/water system. The intrinsic solubilities of repaglinide were determined from the solubility data and temperature dependence of intrinsic solubilities were evaluated using van't Hoff equation. Repaglinide possesses two protonation sites and in aqueous solutions exhibits ampholitic properties. At isoelectric pH the zwitterionic form of the molecule predominates over the uncharged form with the tautomeric ratio, logKz=1.9. The difference between calculated and measured logP values, as well as the difference between logP values of uncharged form of repaglinide, HR0, and either one of mono-charged forms indicated the significant partition of zwitterion into octanol. Temperature dependence of solubility data revealed exothermic dissolution process with DeltasolH=-36 kJmol-1 and negative entropy of solution of DeltasolS=-0.19 kJK-1mol-1.     

若干抗真菌甾体生物碱类似物的合成

为寻找新型抗真菌药物,从易得原料3β-乙酰氧基-5,16-孕甾二烯-20-酮(6)经10或11步反应合成了7个抗真菌甾体生物碱类似物,其中19个为新化合物,化合物3a～c和5体外试验抗真菌活性与氟康唑等同或更强。     

Synthesis and DNA-binding properties of polyamine analogues

The synthesis of a series of novel polyamine analogues is reported. The DNA binding of these compounds and a variety of other polyamines were compared with their IC50 values against HeLa cell. There seemed to be no apparent correlation between the DNA binding and toxicity against HeLa cells.     

Synthesis and antitumor activity of several new analogues of penclomedine and its metabolites

Analogues of penclomedine (PEN, 3,5-dichloro-4,6-dimethoxy-2-(trichloromethyl)pyridine) and its metabolites have been synthesized and evaluated as potential antitumor agents. PEN and 4-DMPEN (3,5-dichloro-4-hydroxy-6-methoxy2-(trichloromethyl)pyridine (3a)), the major plasma metabolite in patients, were modified at 4- and 6-positions with different alkyl, aryl, and ester groups. All of the analogues and many of the intermediates were evaluated against the PEN-sensitive MX-1 human breast tumor xenograft in vivo, and several analogues of PEN and 4-DMPEN showed modest to curative activity.     

Synthesis and cardiovascular properties of fluorenyl derivatives related to verapamil.

A series of fluorenyl analogues of verapamil were synthesized and their cardiovascular properties on guinea pig isolated atria and isolated perfused heart evaluated. The compounds were also tested for their calcium antagonistic activity on guinea pig aorta. They were found to be poor calcium antagonists, but showed negative inotropic and antiarrhythmic properties. The results obtained seem to indicate that their mechanism of action differs from that of verapamil.     

Synthesis and antitumor properties of activated cyclophosphamide analogues

A series of 5- and 6-substituted cyclophosphamide analogues has been prepared, and their 31P NMR kinetics of phosphoramide mustard (PDA) release and in vitro and in vivo cytotoxicity have been evaluated. cis-4-Hydroxy-5-methoxycyclophosphamide equilibrated very slowly and to a minor extent with the ring-opened aldophosphamide analogues in aqueous buffer; release of PDA was observed to a minor extent and only at high (1 M) buffer concentrations. This analogue was essentially inactive in vitro against L1210 and P388 leukemia cells. 6-Phenylcyclophosphamide and its 4-hydroperoxy derivative were potent inhibitors of blood acetylcholinesterase and were lethal at therapeutic doses in mice. In contrast, 4-hydroperoxy-6-(4-pyridyl)cyclophosphamide did not inhibit acetylcholinesterase and showed significant antitumor activity in vitro and in vivo against both wild-type and cyclophosphamide-resistant L1210 leukemia. The 4-hydroperoxy-6-arylcyclophosphamides were generally active in vitro against both wild-type and cyclophosphamide-resistant L1210 and P388 cells, and several analogues showed significant activity in vivo. Surprisingly, there was no correlation between antitumor activity in vitro and the rate of PDA release in aqueous buffer. Several compounds that showed essentially no release of PDA in aqueous buffer over several hours were highly cytotoxic to leukemia cells following a 1-h exposure in vitro. These results show that activated cyclophosphamide analogues substituted at the 6-position are not cross-resistant in these leukemia cell lines, and that a specific intracellular activation mechanism may be catalyzing PDA release in these analogues.     

Lipid membrane-binding properties of tryptophan analogues of linear amphipathic beta-sheet cationic antimicrobial peptides using surface plasmon resonance

Using a surface plasmon resonance (SPR) system, we investigated the lipid membrane-binding properties of four analogues of the 18-residue linear amphipathic beta-sheet cationic antimicrobial peptide (KIGAKI)3-NH2, each of which contains a single isoleucine-to-tryptophan substitution. The results of the SPR study revealed significant differences in the binding characteristics of the peptides depending upon the position of tryptophan residues. These peptides showed higher binding affinity to membranes containing acidic phospholipids than zwitterionic phospholipids. The addition of dimethylsulfoxide to the running buffer was effective in maintaining the solubility of these peptide solutions and obtaining concentration-dependent sensorgrams for the kinetic analysis in this study. The kinetic binding data of SPR correlated closely with both the ability of the peptides to lyse liposomes with the same phospholipid composition and bactericidal activity. The results demonstrate that SPR may be a valuable tool to predict the membrane lytic properties of antimicrobial peptides.     

Actions of the verapamil analogues, anipamil and ronipamil, against ischaemia-induced arrhythmias in conscious rats.

Two analogues of verapamil, ronipamil and anipamil, were tested for their ability to reduce arrhythmias induced by occlusion of the left anterior descending coronary artery in conscious rats. Only anipamil (50 and 150 mg kg-1 orally) produced a statistically significant reduction in arrhythmias; it was most effective against ventricular fibrillation. Ronipamil at the same doses had limited antiarrhythmic actions. Only anipamil delayed the development of ECG signs of ischaemia, while both drugs reduced the magnitude of such changes. Anipamil has a more favourable ratio of antiarrhythmic to hypotensive effects when compared with verapamil.     

Effects of verapamil on the cellular accumulations and toxicity of several antitumor drugs in 9-hydroxy-ellipticine-resistant cells

9-OH-Ellipticine (9-OH-E)-resistant cells are not only resistant to the DNA topoisomerase II inhibitors, but also to some other antitumor agents, such as actinomycin D (AD), adriamycin (ADM), daunorubicin and vincristine. It was previously shown that a decreased uptake accounts for the cross-resistance of these cells to AD and ADM which then suggested that the 9-OH-E-resistant cells might display some of the properties usually associated with the multidrug resistance phenotype. In this work, we have examined the effects of verapamil, a drug which is known to overcome the multidrug resistance, on the toxicity and the cellular accumulation of four cytotoxic agents: 9-OH-E, 2N-methyl-9-hydroxy-ellipticinium (NMHE), AD and ADM, either on 9-OH-E resistant cells or on a multidrug resistant subline derived from the same sensitive parental cells. Verapamil inhibited the cellular accumulation of the ellipticine derivatives in the sensitive DC-3F cells, and the toxicity of these drugs on these cells was correspondingly decreased. On either one of the resistant cell lines, verapamil had no effect on the toxicity and the cellular accumulation of 9-OH-E. In contrast, in the presence of verapamil, the cellular accumulation of NMHE by the 9-OH-E and the multidrug resistant cells was about 50% and 300% increased, respectively. The increased NMHE cellular concentration in the multidrug resistant cells was associated with an 8-fold increased toxicity. The major structural characteristics which might account for this difference between the sensitivities of both ellipticine derivatives to the effects of verapamil on the multidrug resistant cells is the presence of a positive charge on the nitrogen in position 2 of the 6H-pyridocarbazole molecule. Finally, verapamil circumvented partially the cross-resistance of DC-3F/9-OH-E cells to AD and ADM by increasing the accumulation of these drugs inside the cells.     

Studies on the effects of several pentamidine analogues on the NMDA receptor

We have investigated the interactions of six analogues of pentamidine with the N-methyl-D-aspartate (NMDA) receptor complex. All six compounds were effective NMDA receptor antagonists based upon their ability to inhibit [³H]dizocilpine binding to rat brain membranes. IC₅₀ values ranged from 2 to 18 μM, and all compounds had Hill coefficients in excess of 1 suggesting a non-competitive interaction with [³H]dizocilpine. All compounds also inhibited NMDA- and glycine-induced intracellular Ca²⁺ changes measured in cultured rat forebrain neurons using the fluorescent indicator, fura-2. IC₅₀ values in this assay ranged from 0.4 to 4.7 μM. Whereas pentamidine is directly toxic to cultured neurons, this was not a consistent finding with the pentamidine analogues tested, indicating that the toxic effects are not related to NMDA receptor antagonism. Finally, all of the agents tested were also effective in protecting neurons from NMDA-induced neurotoxicity. These data emphasize the possible utility of pentamidine-like drugs as neuroprotective agents and suggest that it is possible to generate compounds with a wider margin of safety than pentamidine itself.     

The adrenergic properties of ring-brominated isoprenaline analogues

The beta 1- and beta 2-adrenoceptor activity of the 2- and 6-ring-brominated analogues of isoprenaline were evaluated in vitro. The 2-bromo-substituted analogue exhibits a far greater activity on beta 1- and beta 2-receptors than the 6-bromo-substituted analogue.     

Serotonin receptor binding affinities of several hallucinogenic phenylalkylamine and N,N-dimethyltryptamine analogues.

Hallucinogenic phenylalkylamine and N,N-dimethyltryptamine analogues are known to affect serotonergic systems both in vivo and in vitro. Using a rat stomach fundus model, the 5-HT receptor binding affinities of several of these analogues were determined and compared. The most behaviorally potent analogues examined, DOB, DOM, and 5-methoxy-N,N-dimethyltryptamine, were found to possess rather high affirmities (pA2 = 7.35, 7.12, and 7.08, respectively) for the 5-HT receptors of the model system.     

Immunological properties of vitamin D analogues and metabolites.

This commentary has attempted to describe some of the new aspects of our knowledge of the immunological properties of 1 alpha,25(OH)2D3, the physiologically active metabolite of vitamin D3, and its new analogues. These analogues will, in the future, serve as tools to increase our understanding of the role of vitamin D in immunobiology, not only in basal research but also, hopefully, in the therapy of immune-mediated diseases.     

Preparation and diuretic properties of novel amiloride analogues.

Fifteen novel amiloride analogues were synthesized and their diuretic properties compared to amiloride and triamterene in white wistar rats. Whereas none of the 6-substituted derivatives exhibited significant natriuretic and antikaliuretic effects, five of the compounds modified in the 2-position were found equal or better than standards. The results are discussed with respect to chemical structure and physiochemical properties.     

Relative activities on and uptake by human blood platelets of 5-hydroxytryptamine and several analogues

1. The specificity of platelet receptor sites for 5-HT uptake and for the rapid morphological change and aggregation was investigated with 5-hydroxy-tryptamine (5-HT) and seventeen analogues as well as with some antagonists of 5-HT.2. The analogues, with the exception of 5-hydroxy-N'N'-dibutyltryptamine, caused the rapid morphological change in platelets. In concentrations below those needed to produce the agonistic action (viz. 0.05-2.0 muM), these analogues themselves inhibited competitively the shape change caused by 5-HT.3. The velocity of change in shape caused by 5-HT was reduced in low Na media.4. Ten analogues produced platelet aggregation; three of these, viz. 5-methoxy-alpha-methyltryptamine, 5-hydroxy-alpha-methyltryptamine and 5-hydroxy-N'N'-diisopropyltryptamine), were approximately equipotent with 5-HT. Six analogues did not induce platelet aggregation.5. All the analogues which prevented the initial change in shape of platelets caused by 5-HT also inhibited its aggregating effect, apparently competitively with low K(i) values (0.02-1.6 muM).6. As with the inhibition of shape change, the inhibition of aggregation shows relatively low structural specificity of the receptor site.7. Methysergide was a potent inhibitor of shape change and aggregation (K(i) approximately 0.03 muM); imipramine was much less inhibitory (K(i) approximately 5-10 muM).8. Only one analogue (5-hydroxy-alpha-methyltryptamine) was taken up like 5-HT by platelets. All the other analogues inhibited the uptake of 5-HT by platelets (K(i)=0.2-2.7 muM).9. Methysergide was a weak inhibitor of 5-HT uptake (K(i) approximately 125 muM) whereas imipramine was very effective (K(i) approximately 0.3 muM).10. Our results show that the initial change in shape of platelets is required for and precedes aggregation. The structural specificity of the platelet receptor concerned with shape change and aggregation caused by 5-HT appears low whereas the uptake mechanism is a highly specific one. The uptake probably proceeds through more than one step, the relationship between the steps is not yet clear.     

Syntheses and properties of conformationally restrained nucleosides and oligonucleotides analogues

This review summarizes our efficient syntheses of novel bicyclic nucleoside analogues, 3'-O,4'-C-methyleneribonucleosides (1) (4-BC type nucleoside analogue), 2'-O,4'-C-methyleneribonucleosides (2) (5-BC), 3'-amino-3'-deoxy-3'-N,4'-C-methyleneribonucleosides (3) (aza 4-BC), and 3'-azido- and 3'-amino-3'-deoxy-2'-O,4'-C-methyleneribonucleosides (4, 5) (aza 5-BC). From 1H-NMR and X-ray crystallographic analyses, the 4-BC and aza 4-BC type nucleoside analogues (1, 3) were found to have a S-conformation predominantly, while the conformations of 5-BC and aza 5-BC type nucleoside analogues (2, 4, 5) were exclusively locked in N-form. The 4-BC and 5-BC type nucleoside analogues (1, 2) were effectively introduced into oligonucleotides using a DNA synthesizer. Furthermore, unprecedented hybridizing ability towards complementary RNA and DNA, RNA selectivity, potent triplex forming ability, and sufficient enzymatic stability of these modified oligonucleotides were also confirmed. These results should reveal a promising route to the development of antisense/antigene methodology.     

Discriminative stimulus properties of DOM and several molecular modifications

Rats trained to discriminate racemic 2,5-dimethoxy-4-methylphenylisopropylamine, (±)-DOM (1.0 mg/kg), from saline in a two-lever drug discrimination task were challenged with the optical isomers of DOM as well as with several related agents which represent minor molecular modifications of the DOM structure. Generalization of the (±)-DOM stimulus was found to occur to R(?)-DOM, S(+)-DOM, (±)-2,5-dimethoxyphenylisopropylamine (2,5-DMA), R(?)-2,-5-DMA, and the 2-demethyl derivative of (±)-DOM. The 3-methyl positional isomer of (±)-DOM was found to produce only 34% DOM-appropriate responding at the highest dose tested while administration of S(+)-2,5-DMA and the 5-demethyl derivative of (±)-DOM resulted in disruption of behavior.