Synthesis of Benzo-15-crown-5 polyethers, anticoccidial ionophore analogues.

Synthesis of eight benzo-15-crown-5 derivatives I (R = H, CO2Me, CO2H, Me; R1 = H, CO2H, CO2Me, CHO, CH=CHCO2H, CH2CH2CO2H) designed as rigid cyclic analogues of the anticoccidial ionophores is described. No anticoccidial activity was observed in chickens, but moderate activity in tissue culture was found for I (R = Me, R1 = H; R = R1 = H) and dibenzo-18-crown-6.     

Synthesis and pharmacology of site-specific cocaine abuse treatment agents: 2-substituted-6-amino-5-phenylbicyclo[2.2.2]octanes

A series of 2-substituted-6-amino-5-phenylbicyclo[2.2.2]octanes was synthesized and tested for inhibitor potency in [(3)H]WIN 35,428 (WIN) binding at the dopamine (DA) transporter and [(3)H]DA uptake assays. To demonstrate transporter selectivity for the compounds, inhibitor potency was also tested using [(3)H]nisoxetine and [(3)H]paroxetine binding assays for the norepinephrine (NE) and serotonin (5-HT) transporters, respectively. Synthesis was accomplished by bisannulation of the enamine derived from phenylacetaldehyde and dimethylamine with 2-cyclohexenone to give a mixture of endo- and exo-trans-6-amino-5-phenylbicyclo[2.2. 2]octan-2-ones. The separated ketones were reduced to the four diastereomeric alcohols which were converted to acetyl and benzoyl esters. The ketones, alcohols, and acetyl esters generally have low affinity for the three transporters and do not effectively inhibit the uptake of [(3)H]DA. In all cases, the benzoates show significantly greater inhibition of WIN binding compared to the corresponding ketones, alcohols, or acetate esters. One compound, (1R/S,4R/S)-6R/S-(N,N-dimethylamino)-5R/S-phenylbicyclo[2.2. 2]oct-2S/R-yl benzoate, is almost as potent as cocaine in binding to the DA transporter (IC(50) = 270 nM versus 159 nM for cocaine). The C-2 epimer, (1R/S,4R/S)-6R/S-(N, N-dimethylamino)-5R/S-phenylbicyclo[2.2.2]oct-2R/S-yl benzoate, was selective and potent in binding to the 5-HT transporter (IC(50) = 53 nM versus 1050 nM for cocaine) as compared to the DA transporter (IC(50) = 358 nM). A preliminary molecular modeling study of the benzoyl esters indicates that their relative potencies in the WIN binding assay are not correlated to the nitrogen to benzoate phenyl (centroid) distance or to the deviation of the nitrogen from the plane defined by the benzoate ring.     

Synthesis and calcium channel antagonist activity of dialkyl 1,4-dihydro-2,6-dimethyl-4-[3-(1-methoxy-carbonyl-4-substituted-1,4- dihydro-pyridyl)]-3,5-pyridinedicarboxylates.

A novel class of dialkyl 1,4-dihydro-2,6-dimethyl-4-(3-[1- methoxycarbonyl-4-(H, Me, n-Bu or Ph)-1,4-dihydropyridyl])-3,5-pyridinedicarboxylates (3-29) were synthesized and evaluated as calcium channel antagonists using the muscarinic receptor mediated Ca2+ dependent contraction of guinea pig ileal longitudinal smooth muscle (GPILSM). The differences in activity among members of this new class of compounds was less than one log unit (IC50 range of 8.25 x 10(-6) to 4.36 x 10(-7) M), relative to the reference drug nifedipine (IC50 = 1.43 x 10(-8) M). Compounds possessing symmetrical C-3(5) diethoxycarbonyl ester substituents generally exhibited optimum activity. The R3 substituent (H, Me, n-Bu, Ph) at the 4-position of the 4-[3-(1-methoxycarbonyl-1,4-dihydropyridyl)] moiety was a determinant of activity. In symmetrical diester compounds, a R3 H substituent provided optimum activity for Me, i-Bu and t-Bu dialkyl ester analogues, whereas a R3 Ph substituent provided optimum activity for Et and i-Pr symmetrical diesters. The test results indicate the 4-[3-(1-methoxycarbonyl-4-substituted-1,4-dihydropyridyl)] substituent in this new class of compounds is bioisosteric with a 4-(3-nitrophenyl), or a 4-(3-pyridyl) substituent in classical 1,4-dihydropyridine antagonists. Compounds possessing large symmetrical dialkyl ester substituents (i-Bu, t-Bu), in conjunction with a 4-[3-(1-methoxycarbonyl-4-methyl-1,4-dihydropyridyl)] substituent, permanently inhibited recovery of the KCl-induced response in GPILSM.     

Synthesis and Antimicrobial Activity of 5-(R<Superscript>1</Superscript>-benzyl)-2-(R<Superscript>2</Superscript>-benzylidenehydrazono)-3-(2-furylmethyl)Thiazolidin-4-ones

3-Aryl-2-bromopropanoic acid esters react with furfurylthiosemicarbazones of benzaldehyde and 4-chlorobenzaldehyde to form 5-(R¹-benzyl)-2-(4-R-benzylidenehydrazono)-3-furfuryl-4-thiazolidinones (R = H, 4-Cl; R¹ = 4-Me, 4-F, 4-Cl). The antimicrobial activity of the synthesized compounds was studied, and it was established that only the compounds with R¹ = Me are active. The replacement of methyl group by halogen results in the loss of antimicrobial activity. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 5, pp. 20 – 22, May, 2005.     

Pseudoproline-containing analogues of morphiceptin and endomorphin-2: evidence for a cis Tyr-Pro amide bond in the bioactive conformation.

Analogues of the opioid peptides [D-Phe(3)]morphiceptin (H-Tyr-Pro-D-Phe-Pro-NH(2)) and endomorphin-2 (H-Tyr-Pro-Phe-Phe-NH(2)) containing the pseudoproline (Psi Pro) (4R)-thiazolidine-4-carboxylic acid (Cys[Psi(R1,R2)pro]) or (4S)-oxazolidine-4-carboxylic acid (Ser[Psi(R1,R2)pro]) in place of Pro(2) were synthesized. The pseudoproline ring in these compounds was either unsubstituted (R(1), R(2) = H) or dimethylated (R(1), R(2) = CH(3)) at the 2-C position. 2-C-dimethylated pseudoprolines are known to be quantitative or nearly quantitative inducers of the cis conformation around the Xaa(i-1)-Xaa(i)[Psi(CH(3),CH)(3)pro)] imide bond. All dihydropseudoproline-containing analogues (R(1), R(2) = H) showed good mu opioid agonist potency in the guinea pig ileum (GPI) assay, high mu receptor binding affinity in the rat brain membrane binding assay, and, like their parent peptides, excellent mu receptor binding selectivity. (1)H NMR spectroscopic analysis of the Cys[Psi(H,H)pro](2)- and Ser[Psi(H,H)pro](2)-containing analogues in DMSO-d(6) revealed that they existed in a conformational equilibrium around the Tyr-Xaa[Psi(H,H)pro] peptide bond with cis/trans ratios of 40:60 and 45:55, respectively. The dimethylated thiazolidine- and oxazolidine-containing [D-Phe(3)]morphiceptin- and endomorphin-2 analogues (R(1), R(2) = CH(3)) all retained full mu agonist potency in the GPI assay and displayed mu receptor binding affinities in the nanomolar range and high mu receptor selectivity. As expected, no conformers of the latter analogues with a trans conformation around the Tyr-Xaa[Psi(CH(3),CH(3)pro)] imide bond were detected by (1)H NMR spectral analysis, indicating that in these compounds the cis conformation is highly predominant (>98%). These results represent the most direct evidence obtained so far to indicate that morphiceptin and endomorphin-2 have the cis conformation around the Tyr-Pro peptide bond in their bioactive conformations.     

Different modes of potentiation by beta-eudesmol, a main compound from Atractylodes lancea, depending on neuromuscular blocking actions of p-phenylene-polymethylene bis-ammonium derivatives in isolated phrenic nerve-diaphragm muscles of normal and alloxan-diabetic mice.

The essential moieties in p-phenylene-polymethylene bis-ammonium (PMBA) derivatives, C6H4[X(CH2)nN+R3]2, on the potentiating effects by beta-eudesmol, a main component of Atractylodes lancea, of their neuromuscular blockades were investigated in isolated phrenic nerve-diaphragm muscle preparations of normal and alloxan-diabetic mice. PMBA derivatives were separated into the following three groups based on the patterns of the potentiating effects: group I: PMBA-23 (n = 6, R = Me) and PMBA-24 (n = 6, R = Et); group II: PMBA-1 (n = 4, R = Me), PMBA-21 (n = 4, R = Et) and PMBA-2 (X = O, n = 3, R = Me); and group III: PMBA-31 (X = S, n = 3, R = Me), PMBA-3 (X = CO, n = 3, R = Me) and PMBA-4 (X = CHOH, n = 3, R = Me). The pretreatment with 80 microM beta-eudesmol for 60 min did not affect group I-induced neuromuscular blocking action, and it potentiated group II- and group III-induced ones. The potentiating effect of beta-eudesmol on group III was greater in diabetic muscles than in normal one and that on group II was to the same extent in both muscles. These results suggest that the four-methylene length of the side chains in normal muscles and the hydrophilic moieties adjacent to a phenylene ring in diabetic muscles are related to the potentiating effect by beta-eudesmol on PMBA derivatives.     

Synthesis and antifungal properties of certain 7-alkylaminopyrazolo[1,5-a]pyrimidines.

A series of 7-alkylaminopyrazolo[1,5-alpha]pyrimidines (5-25) and one 7-alkylthiopyrazolo[1,5-alpha]pyrimidine (4) were synthesized from the corresponding 7-chloro precursors 3, which were prepared in turn from the 7-hydroxy analogues 2, obtained via condensation of 3-aminopyrazoles with acetoacetate esters, malonate esters, or acetylenedicarboxylate ester. Compounds 4-25 were found to inhibit Trichophyton mentagrophytes (in vitro). The degree of inhibition increased with increasing 7-alkylamino chain length up to C8 units and then began to decrease with longer chain lengths. Unsaturated chains were more fungitoxic than saturated chains, 5-methyl-7-oleylaminopyrazolo[1,5alpha]pyrimidine [22, R7=NH(CH2)8CH=CH(CH2)7CH3] being four times more inhibitory and 16 times more fungicidal (against T. mentagrophytes) than 5-methyl-7-n-octylaminopyrazolo[1,5-alpha] pyrimidine [11, R7=NH(CH2)7CH3]. Although 11 and 22 appeared to have some efficacy as topical antifungeal agents, when applied to T. mentagrophytes infections in vivo, both caused irritation (of abraded and unabraded guinea pig skin) as did compound 4 (R5=Me; R7=SC8H17).     

The structural basis for peptidomimetic inhibition of eukaryotic ribonucleotide reductase: a conformationally flexible pharmacophore

Eukaryotic ribonucleotide reductase (RR) catalyzes nucleoside diphosphate conversion to deoxynucleoside diphosphate. Crucial for rapidly dividing cells, RR is a target for cancer therapy. RR activity requires formation of a complex between subunits R1 and R2 in which the R2 C-terminal peptide binds to R1. Here we report crystal structures of heterocomplexes containing mammalian R2 C-terminal heptapeptide, P7 (Ac-1FTLDADF7) and its peptidomimetic P6 (1Fmoc(Me)PhgLDChaDF7) bound to Saccharomyces cerevisiae R1 (ScR1). P7 and P6, both of which inhibit ScRR, each bind at two contiguous sites containing residues that are highly conserved among eukaryotes. Such binding is quite distinct from that reported for prokaryotes. The Fmoc group in P6 peptide makes several hydrophobic interactions that contribute to its enhanced potency in binding to ScR1. Combining all of our results, we observe three distinct conformations for peptide binding to ScR1. These structures provide pharmacophores for designing highly potent nonpeptide class I RR inhibitors.     

Nitrosative guanine deamination: ab initio study of deglycation of N-protonated 5-cyanoimino-4-oxomethylene-4,5-dihydroimidazoles

5-Cyanoimino-4-oxomethylene-4,5-dihydroimidazoles (1) (R at N1) have been discussed as possible intermediates in nitrosative guanine deamination, which are formed by dediazoniation and deprotonation of guaninediazonium ion. The parent system 1 (R = H) and its N1 derivatives 2 (R = Me) and 3 (R = MOM) are considered here. Protonation of 1-3, respectively, may occur either at the cyano-N to form cations 4 (R = H), 6 (R = Me), and 8 (R = MOM) or at the imino-N to form cations 5 (R = H), 7 (R = Me), and 9 (R = MOM), respectively. This protonation is the first step in the acid-catalyzed water addition to form 5-cyanoimino-imidazole-4-carboxylic acid, which then leads to oxanosine. There also exists the option of a substitution reaction by water at the R group of 6-9, and this dealkylation forms N-[4-(oxomethylene)-imidazol-5-yl]carbodiimide (10) and N-[4-(oxomethylene)-imidazol-5-yl]cyanamide (11). In the case of DNA, the R group is a deoxyribose sugar, and attack by water leads to deglycation. To explore this reaction option, the S(N)1 and S(N)2 reactions of 6-9 with water were studied at the MP2/6-31G*//RHF/6-31G* and CCSD/6-31G*//RHF/6-31G* levels, with the inclusion of implicit solvation at the IPCM(MP2/6-31G*)//RHF/6-31G* level, and the electron density distributions of tautomers 1, 10, and 11 were analyzed. The low barriers determined for the MOM transfer show that the deglycation could occur at room temperature but that the process cannot compete with water addition.     

Synthesis and analgesic activity of 2-methyl-2-[1-(3-benzoyl-4-substituted-1,4-dihydropyridyl)]acetic acid methyl esters, acetic acids, and acetamides.

A group of 2-methyl-2-[1-(3-benzoyl-4-substituted-1,4-dihydropyridyl)]acetic acid methyl esters (7), weak acetic acids (8), and acetamides (9) were designed for evaluation as less acidic non-ulcerogenic non-steroidal antiinflammatory drugs (NSAIDs). In this respect, the model compound 2-methyl-2-[1-(3-benzoyl-4-phenyl-1,4-dihydropyridyl)]acetic acid (8a), unlike traditional arylacetic acid NSAIDs, was shown to be a weak acid with a pKa of 9.17. In contrast to arylacetic acid NSAIDs, the alpha-methylacetic acid sodium salt of 8a, or the methyl alpha-methylacetate ester (7a) did not inhibit cyclooxygenase-1 (COX-1) or -2 (COX-2). In vitro stability studies showed that the methyl alpha-methylacetate ester (7a) acts as a prodrug to the alpha-methylacetic acid derivative (8a), undergoing rapid (< 10 minutes) and quantitative conversion upon incubation with rat plasma, or incubation with rat liver homogenate (t1/2 = 25 min). In contrast, the alpha-methylacetamide (9a) underwent negligible (< 2%) conversion to the alpha-methylacetic acid derivative (8a) upon incubation with either rat plasma, or rat liver homogenate, for incubation times up to 24 h. The effect of a C-3 para-substituted-benzoyl substituent (R1 = H, Cl, Me), a C-4 substituent (R2 = aryl, benzyl, cyclohexyl, alkyl), and the nature of the N1-acetic acid moiety [methyl ester (R3 = OMe), acetic acid (R3 = OH), acetamide (R3 = NH2)] on analgesic activity was determined using the 4% NaCl-induced abdominal constriction (writhing) assay. Compounds 7-9 inhibited writhing 27-95% relative to the reference drug aspirin (58% inhibition). The analgesic potency with respect to the para-benzoyl substituent was H > Cl or Me. Although the effect of the C-4 R2-substituent on analgesic activity was variable within the ester, acid and amide sub-groups of compounds, compounds having a R2-cyclohexyl substituent generally provided superior analgesic activity relative to those having a lipophilic alkyl substituent. The nature of the R3-substituent (OMe, OH, NH2) was a determinant of analgesic activity where the potency order was acetic acid methyl ester > acetic acid or acetamide, except when the C-4 R2-substituent was cyclohexyl or benzyl where the potency order was acetamide > acetic acid methyl ester or acetic acid. Reduction of the 5,6-olefinic bond of the 1,4-dihydropyridyl compound (9a, 94% inhibition) to the corresponding 1,2,3,4-tetrahydropyidyl derivative (10, 69% inhibition) reduced analgesic activity.     

Demonstration of the heterogeneity of the kappa-opioid receptors in guinea-pig cerebellum using selective and nonselective drugs

In guinea-pig cerebellum, saturation studies reveal that the nonselective opioid [3H]ethylketazocine has a binding capacity (R) of 6.79 pmol/g tissue which is similar to the sum of the individual R values of the mu-, delta- and kappa 1-selective opioids. Conversely, the binding parameters of the nonselective opioid [3H]bremazocine are best-fitted to a two-site model (Kd1 = 0.12 nM, R1 = 11.3 pmol/g tissue; Kd2 = 6.03 nM, R2 = 9.09 pmol/g tissue) with an R TOTAL value of 20.3 pmol/g tissue which is statistically different from the R value of [3H]ethylketazocine or the sum of R mu + R delta + R kappa 1. This suggests that [3H]bremazocine labels additional opioid binding sites. After suppression of the mu-, delta- and kappa 1-receptors, [3H]bremazocine binding is then best-fitted to a one-site model with a Kd value of 1.48 nM and an R value of 11.2 pmol/g tissue. Competition studies done against the binding of [3H]U69593 indicate that the opioid receptors labelled with this ligand are related to the kappa 1-receptor subtype. However, competition studies performed against the binding of [3H]bremazocine (under suppressed conditions) display a pharmacological profile related to another subtype of kappa-receptors previously described in guinea-pig brain as the kappa 2-receptors.     

Synthesis and antibacterial activities of new (alpha-hydrazinobenzyl)cephalosporins

Some (alpha-hydrazinobenzyl)cephalosporins, I (R = Me, CH2OAc, Cl) and II (R = Me, CH2OAc), structurally related (formula; see text) to cephalexin, cephaloglycin, and cefaclor have been prepared and evaluated in vitro for their antimicrobial activity. The synthesis involves the condensation of the chloride hydrochloride III (R = H or Me) with the 7-aminocephem derivatives IV. The hydrazino compound I (R = Cl), an analogue of cefaclor, resulted in being the most active compound of the series.     

Involvement of imidazoline receptors in the centrally acting muscle-relaxant effects of tizanidine

BIBN4096BS [[R-(R,(R*,S*)]-N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl] pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-,1-Piperidinecarboxamide] is a selective calcitonin gene-related peptide (CGRP) receptor antagonist with a picomolar affinity to the CGRP receptor in human neuroblastoma SK-N-MC cells. Here, we describe the characterisation of the binding properties of the tritiated radioanalogue of BIBN4096BS in SK-N-MC cells as well as in marmoset tissue. [(3)H]BIBN4096BS showed reversible and saturable binding to SK-N-MC cells with a K(D) of 0.045 nM. In competition experiments, [3(H)]BIBN4096BS is concentration-dependently displaced from SK-N-MC cell membranes by BIBN4096BS as well as by the endogenous ligand CGRP and its analogues with the rank order of affinity BIBN4096BS>human alpha-CGRP=human beta-CGRP>[Cys(Et)(2,7)]human alpha-CGRP>adrenomedullin (high affinity site)=human alpha-CGRP-(8-37)=human beta-CGRP-(8-37)>calcitonin=amylin. In the marmoset cortex, saturable [(3)H]BIBN4096BS binding was observed with a K(D) of 0.077 nM. CGRP showed biphasic competition of [(3)H]BIBN4096BS binding, whilst BIBN4096BS monophasically displaced its radioanalogue with a K(i) of 0.099 nM. These data, using [(3)H]BIBN4096BS, confirm the high affinity of this novel antagonist for the primate CGRP receptor and demonstrate furthermore that this radioligand is a useful tool to study CGRP receptor pharmacology.     

An evaluation of certain chain-extended analogues of 9-beta-D-arabinofuranosyladenine for antiviral and cardiovascular activity

Several nucleosides modified and chain extended at the 5'-position have been synthesized as follows: N6-benzamido- 9-(2,3-di-O-benzoyl-beta-D-arabino-pentodialdo-1,4-furanosyl)adenine, O=CHR, a leads to (E)-EtOCOCH=CHR (2) b leads to EtOCOCH2CH2R (3) c leads to H2NCOCH2CH2R (6) d leads to 1-(adenin-9- yl)-1,5,6-trideoxy-beta-D-arabino-hepto-1,4-furanuronamide (8); 3 e leads to ethyl 1-(adenin-9-yl)-1,5,6-trideoxy-beta-D-arabino-hepto-1, 4-furanuronate (5) f leads to 1-(adenin-9-yl)-1, 5,6-trideoxy-beta-D-arabino-hepto-1,4-furanuronic acid (4); 5 g leads to 9-(5,6-dideoxy-beta-D-arabino-hepto-1,4-furanosyl)adenine (7) [where a = EtOCOCH=PPh3; b = H2, Pd/C; c = Me2A1NH2; d = NH3/MeOH; e = NaOEt/EtOH; f = NaOH/MeOH; g = LiA1H4]. Both 7 and 8 show activity against herpes simplex virus type 1. The mechanism for such activity is unknown. Compounds 5 and 8 exhibited weak coronary vasodilation effects in dogs.     

D-Amino acid scan of gamma-melanocyte-stimulating hormone: importance of Trp(8) on human MC3 receptor selectivity

In our search for potent and receptor-selective agonists and antagonists, we report here the results of D-amino acid substitution at each position of the short peptide gamma-melanocyte-stimulating hormone (gamma-MSH). The native gamma-MSH shows weak binding at all three receptors (i.e., the human MC3, MC4, and MC5) and a selectivity of 1-2 orders of magnitude at the MC3R over the MC4R and MC5R. Sequential replacement of each residue in the gamma-MSH sequence with the corresponding D-isomer results in analogues which mostly have weaker binding affinity than the native peptide, except for two analogues. For the DTrp(8) analogue, there is an increase in binding affinity by about 1 order of magnitude (IC(50) = 6 nM) at the MC3R compared with that of the natural molecule and an increase in selectivity for the MC3R by 2 orders of magnitude compared with the activity at the MC4R and MC5R. The DPhe(6) analogue is about 10-fold more potent (IC(50) = 8.8 nM) at the MC3R compared with the native peptide but lacks subtype selectivity. Measurement of the intracellular cAMP accumulation in human MC3R, MC4R, and MC5R revealed that the native peptide shows potent activity at the MC3R (EC(50) = 5.9 nM) and is about 50-100-fold selective at this receptor compared with the MC4R and MC5R. The DArg(10) (EC(50) = 35 nM) and DPhe(11) (EC(50) = 11 nM) analogues are selective for the MC3R by 1 and 2 orders of magnitude compared with the MC4R and MC5R, respectively. The DTrp(8) compound (EC(50) = 0.33 nM) shows about 300- and 250-fold increase in selectivity at the MC3R compared with the MC4R and MC5R, respectively. Finally, the DTyr(1) peptide is selective for the MC3R (EC(50) = 12 nM) by 40-200-fold compared with the MC4R and MC5R. In general, the trend is that D-amino acid substitutions of the aromatic residues 1, 6, 8, and 11 and the basic residue Arg(10), but not Arg(7), result in an increase in MC3R selectivity over the MC4R and MC5R and only agonist activity is observed. Thus, the key residues of gamma-MSH identified in this study include the aromatic residues 1, 6, 8, and 11 and the basic residue Arg(10) (but not Arg(7)), as important for MC3 selectivity over the MC4 and MC5 subtypes. Further, the study reveals the extreme importance of DTrp at position 8 in imparting potency and selectivity since this is the most selective analogue for the human MC3R reported thus far.     

Synthesis and evaluation of alpha-[[(2-haloethyl)amino]methyl]-2- nitro-1H-imidazole-1-ethanols as prodrugs of alpha-[(1-aziridinyl)methyl]-2- nitro-1H-imidazole-1-ethanol (RSU-1069) and its analogues which are radiosensitizers and bioreductively activated cytotoxins

alpha-[(1-Aziridinyl)methyl]-2-nitro-1H-imidazole-1-ethanols, of general formula ImCH2CH(OH)CH2NCR1R2CR3R4, where Im = 2-nitroimidazole and R1, R2, R3, R4 = H, Me, are radiosensitizers and selective bioreductively activated cytotoxins toward hypoxic tumor cells in vitro and in vivo. Treatment of the aziridines with hydrogen halide in acetone or aqueous acetone gave the corresponding 2-haloethylamines of general formula ImCH2CH(OH)CH2(+)-NH2CR1R2CR3R4X X-, where R1, R2, R3, R4 = H, Me, and X = F, Cl, Br, I. These 2-haloethylamines were evaluated as prodrugs of the parent aziridines. The rates of ring closure in aqueous solution at pH approximately 6 were found to increase with increasing methyl substitution and to depend on the nature of the leaving group (I approximately Br greater than Cl much greater than F). A competing reaction of ImCH2CH(OH)CH2+NH2CH2CH2X X- (X = Cl, Br) with aqueous HCO3- ions gives 3-[2-hyroxy-3-(2-nitro-1H-imidazol-1-yl)propyl]-2-oxazolidinone. The activities of these prodrugs as radiosensitizers or as bioreductively activated cytotoxins were consistent with the proportion converted to the parent aziridine during the course of the experiment. alpha-[[(2-Bromoethyl)amino]methyl]-2-nitro-1H-imidazole-1- ethanol (RB 6145, 10), the prodrug of alpha-[(1-aziridinyl)methyl]-2-nitro-1H-imidazole-1-ethanol (RSU-1069, 3), is identified as the most useful compound in terms of biological activity and rate of ring closure under physiological conditions.     

Quantitative analysis of multiple kappa-opioid receptors by selective and nonselective ligand binding in guinea pig spinal cord: resolution of high and low affinity states of the kappa 2 receptors by a computerized model-fitting technique

The binding characteristics of selective and nonselective opioids have been studied in whole guinea pig spinal cord, using a computer fitting method to analyze the data obtained from saturation and competition studies. The delineation of specific binding sites labeled by the mu-selective opioid [3H]D-Ala2,MePhe4,Gly-ol5-enkephalin (Kd = 2.58 nM, R = 4.52 pmol/g of tissue) and by the delta-selective opioid [3H]D-Pen2, D-Pen5-enkephalin (Kd = 2.02 nM, R = 1.47 pmol/g of tissue) suggests the presence of mu and delta-receptors in the spinal cord tissue. The presence of kappa receptors was probed by the kappa-selective opioid [3H]U69593 (Kd = 3.31 nM, R = 2.00 pmol/g of tissue). The pharmacological characterization of the sites labeled by [3H]U69593 confirms the assumption that this ligand discriminates kappa receptors in guinea pig spinal cord. The benzomorphan [3H]ethylketazocine labels a population of receptors with one homogeneous affinity state (Kd = 0.65 nM, R = 7.39 pmol/g of tissue). The total binding capacity of this ligand was not different from the sum of the binding capacities of mu, delta-, and kappa-selective ligands. Under mu- and delta-suppressed conditions, [3H]ethylketazocine still binds to receptors with one homogeneous affinity state (Kd = 0.45 nM, R = 1.69 pmol/g of tissue). Competition studies performed against the binding of [3H]ethylketazocine under these experimental conditions reveal that the pharmacological profile of the radiolabeled receptors is similar to the profile of the kappa receptors labeled with [3H]U69593. Saturation studies using the nonselective opioid [3H]bremazocine demonstrate that this ligand binds to spinal cord membranes with heterogeneous affinities (Kd1 = 0.28 nM, R1 = 7.91 pmol/g of tissue; Kd2 = 3.24 nM, R2 = 11.2 pmol/g of tissue). The total binding capacity obtained with [3H]bremazocine (Rtotal = 19.1 pmol/g of tissue) was different from either the sum of the binding capacities of mu-, delta, and kappa-selective ligands or the binding capacity of [3H]ethylketazocine obtained under unsuppressed conditions. These results suggest that [3H]bremazocine labels additional opioid sites, namely the kappa 2 receptors, in contrast to kappa 1 sites labeled with [3H]U69593. In experimental conditions where the binding of [3H]bremazocine at mu, delta, and kappa 1 receptors was quenched by selective blockers, [3H]bremazocine recognizes the kappa 2 receptors with one homogeneous affinity state (Kd = 3.45 nM, R = 8.23 pmol/g of tissue). However, competition studies suggest that some opioids bind to these kappa 2 receptors with heterogeneous affinity states (high and low affinity states), whereas others bind with one apparently homogeneous affinity state.(ABSTRACT TRUNCATED AT 400 WORDS)     

Evaluation of methylthio-, methylsulfinyl-, and methylsulfonyl-analogs of alkanes and alkanoic acids as cardiac inotropic and antifungal agents

A group of alkane and alkanoic acid compounds of general formula MeS(O)m(CH2)nR [m = 0-2; n = 1, 5, 13; R = Me, CO2H(Na)] were synthesized for evaluation as cardiac inotropic and antifungal agents. Inotropic activity was determined as the ability of the test compound to modulate in vitro guinea pig atrium contractility. The oxidation state of the S-atom was an important determinant of inotropic modulation since the thio (m = 0) analogs exhibited a positive inotropic effect. In contrast, the sulfinyl (m = 1) and sulfonyl (m = 2) analogs exhibited a negative inotropic effect. A pentyl spacer (n = 5) provided the largest positive or negative inotropic effect. The relative positive, and negative, inotropic potency orders with respect to the R-substituent were Me > or = CO2H, and CO2Na > or = Me, respectively. The most potent positive inotrope MeS(CH2)5Me (EC50 = 4.49 x 10(-6) M) could serve as a useful lead-compound for the design of a new class of positive inotropic agents. In a broad spectrum antifungal screen, the minimal inhibitory concentration (MIC) range for the five most active compounds was MeSO2(CH2)5Me (0.46-1.83 mM), MeS(CH2)13Me (0.31-1.23 mM), MeSO(CH2)13Me (< 0.009-1.87 mM), MeSO2(CH2)13Me (0.27-1.09 mM), and MeS(CH2)13CO2H (0.27-1.09 mM), relative to the reference drug Ampotericin B (< 0.0002-0.002 mM). The most active antifungal agent MeSO(CH2)13Me was selective against C. guillermondi, C. neoformans, S. cerevisiae, and A. fumigatus (strain TIMM 1776).     

Synthesis and calcium channel antagonist activity of new 1,4-dihydropyridine derivatives containing dichloroimidazolyl substituents

A group of dialkyl, dicycloalkyl and diaryl ester analogues of nifedipine (CAS 21829-25-4), in which the ortho-nitrophenyl group at position 4 is replaced by a 4,5-dichloroimidazolyl substituent, were synthesized and evaluated as calcium channel antagonists using the high K+ contraction of guinea-pig ileal longitudinal smooth muscle. The results for the symmetrical esters in alkyl esters series showed that increasing the length of the methylene chain in C3 and C5 ester substituents (from n = 0 to n = 2) increased the activity. When increasing of the length was accompanied by increase of the hindrance, the activity decreased. In the unsymmetrical diester series, the results showed when R1 is a small substituent (R1 = Me), increasing of the lipophilic property in R2 substituent increases the activity if this high lipophilicity is not accompanied by steric hindrance. The results demonstrate that in the unsymmetrical series, several compounds (benzyl methyl, benzyl isopropyl and cyclohexyl ethyl) had activity similar to that of the reference drug nifedipine. In symmetrical diesters compounds, the most active compound was the diphenethyl ester derivative being more active than nifedipine. These structure-activity data indicate that the 4-(4,5-dichloroimidazolyl) moiety is the bioisoester of 3-nitrophenyl and 2,3-dichlorophenyl moieties.