Synthesis and local anesthetic activity of fluoro-substituted imipramine and its analogues

A series of fluoro-substituted imipramines and its analogues, 6a-6e, were synthesized and evaluated for their in vitro local anesthetic activity. Compound 6b was found to have potency, onset, and duration of action comparable to those of lidocaine (lidocaine hydrochloride, CAS:6108-05-0). Dissociation constants (pK(a)) of these compounds have been determined to be 7.6-7.9.     

SAR analysis of innovative selective small molecule antagonists of sphingosine-1-phosphate 4 (S1P₄) receptor

Recent evidence suggests an innovative application of chemical modulators targeting the S1P(4) receptor as novel mechanism-based drugs for the treatment of influenza virus infection. Modulation of the S1P(4) receptor may also represent an alternative therapeutic approach for clinical conditions where reactive thrombocytosis is an undesired effect or increased megakaryopoiesis is required. With the exception of our recent research program disclosure, we are not aware of any selective S1P(4) antagonists reported in the literature to date. Herein, we describe complementary structure-activity relationships (SAR) of the high-throughput screening (HTS)-derived hit 5-(2,5-dichlorophenyl)-N-(2,6-dimethylphenyl)furan-2-carboxamide and its 2,5-dimethylphenyl analog. Systematic structural modifications of the furan ring showed that both steric and electronic factors in this region have a significant impact on the potency. The furan moiety was successfully replaced with a thiophene or phenyl ring maintaining potency in the low nanomolar range and high selectivity against the other S1P receptor subtypes. By expanding the molecular diversity within the hit-derived class, our SAR study provides innovative small molecule potent and selective S1P(4) antagonists suitable for in vivo pharmacological validation of the target receptor.     

(S,E)-N-[1-(3-heteroarylphenyl)ethyl]-3-(2-fluorophenyl)acrylamides: synthesis and KCNQ2 potassium channel opener activity

Replacement of the morpholinyl moiety in (S,E)-N-[1-(3-morpholinophenyl)ethyl]-3-phenylacrylamide (1) with heteroaryl groups led to the identification of (S,E)-N-1-[3-(6-fluoropyridin-3-yl)phenyl]ethyl-3-(2-fluorophenyl)acrylamide (5) as a potent KCNQ2 potassium channel opener. Among this series of heteroaryl substituted acrylamides, (S,E)-N-1-[3-(1H-pyrazol-1-yl)phenyl]ethyl-3-(2-fluorophenyl)acrylamide (9) exhibits balanced potency and efficacy. The syntheses and the KCNQ2 opener activity of this series of acrylamides are described.     

Infiltration anesthetic lidocaine inhibits cancer cell invasion by modulating ectodomain shedding of heparin-binding epidermal growth factor-like growth factor (HB-EGF)

Although the mechanism is unknown, infiltration anesthetics are believed to have membrane-stabilizing action. We report here that such a most commonly used anesthetic, lidocaine, effectively inhibited the invasive ability of human cancer (HT1080, HOS, and RPMI-7951) cells at concentrations used in surgical operations (5-20 mM). Ectodomain shedding of heparin-binding epidermal growth factor-like growth factor (HB-EGF) from the cell surface plays an important role in invasion by HT1080 cells. Lidocaine reduced the invasion ability of these cells by partly inhibiting the shedding of HB-EGF from the cell surface and modulation of intracellular Ca2+ concentration contributed to this action. The anesthetic action of lidocaine (sodium channel blocking ability) did not contribute to this anti-invasive action. In addition, lidocaine (5-30 mM), infiltrated around the inoculation site, inhibited pulmonary metastases of murine osteosarcoma (LM 8) cells in vivo. These data point to previously unrecognized beneficial actions of lidocaine and suggest that lidocaine might be an ideal infiltration anesthetic for surgical cancer operations.     

Structure activity relationship of lidocaine type local anesthetics.

The structure activity relationship of nine compounds were studied and compared to lidocaine. The extent of local anesthetic activity was ascertained by the tail pinch method in mice, and by the isolated frog sciatic nerve method. The effective and lethal dose in 50% of the animals was also determined. Three of the nine compounds appeared to possess significant local anesthetic activity in the $\text{in vivo}$ studies and thus were selected for further investigation $\text{in vitro}$. The $\text{in vivo}$ studies also indicated that two of the three were more toxic than lidocaine. The $\text{in vitro}$ results demonstrated that methyl substitution at positions 2,3 and 5 on the benzene ring produced a compound of slightly more anesthetic potency in an acid medium. At pH 7.8 all three compounds approached the potency of lidocaine. These data indicate that methyl substitution at other than the ortho position of the benzene ring generally results in compounds of lesser local anesthetic activity while tending to increase the toxicity.     

Phenylimidazole derivatives as new inhibitors of bacterial enoyl-ACP reductase FabK

Novel FabK inhibitors with antibacterial activity against Streptococcus pneumoniae were synthesized and evaluated. Through SAR studies of our initial hit compound 2-(1H-benz[d]imidazol-2-ylthio)-N-(6-methoxycarbonylbenzo[d]thiazol-2-yl)acetamide, a series of novel phenylimidazole derivatives were discovered as potent FabK inhibitors.     

Design,synthesis and evaluation of highly selective pyridone-based class II MET inhibitors

The high incidence of MET oncogene activation in human malignancies has prompted researchers to develop MET inhibitors. As part of our efforts to developing effective and safe therapeutic agents against MET-dependent tumors, a pyridone-based class II MET inhibitor, namely, 1-(4-((2-amino-3-iodopyridin-4-yl)-oxy)-3-fluorophenyl)-N-(4-fluorobenzyl)-4-methoxy-6-oxo-1,6-dihydropyridine-3-carboxamide (3s), was identified. Knowledge of the binding mode of class II MET inhibitors led to the design of new inhibitors that utilize 2-pyridone to conformationally restrain key pharmacophoric groups within the molecule. Integrated molecular docking and SAR studies resulted in the discovery of a novel class of pyridone MET inhibitors with high potency (IC₅₀ of 0.005 μM) and efficient selectivity (>5000 fold) to VEGFR-2, c-Kit and RET kinases.     

Active-site characteristics of CYP2C19 and CYP2C9 probed with hydantoin and barbiturate inhibitors

Three series of N-3 alkyl substituted phenytoin, nirvanol, and barbiturate derivatives were synthesized and their inhibitor potencies were tested against recombinant CYP2C19 and CYP2C9 to probe the interaction of these ligands with the active sites of these enzymes. All compounds were found to be competitive inhibitors of both enzymes, although the degree of inhibitory potency was generally much greater towards CYP2C19. Inhibitor stereochemistry did not markedly influence K(i) towards CYP2C9, and log P adequately predicted inhibitor potency for this enzyme. In contrast, stereochemistry was an important factor in determining inhibitor potency towards CYP2C19. (S)-(+)-N-3-Benzylnirvanol and (R)-(-)-N-3-benzylphenobarbital emerged as the most potent and selective CYP2C19 inhibitors, with K(i) values of < 250nM--at least two orders of magnitude greater inhibitor potency than towards CYP2C9. Both inhibitors were metabolized preferentially at their C-5 phenyl substituents, indicating that CYP2C19 prefers to orient the N-3 substituents away from the active oxygen species. These features were incorporated into expanded CoMFA models for CYP2C9, and a new, validated CoMFA model for CYP2C19.     

Structural activity relationship between Salmonella-mutagenicity and nitro-orientation of nitroazaphenanthrenes

Nitroazaphenanthrenes (NAphs) and their N-oxides (NAphOs) were synthesized as derivatives with nitrogen atoms in the 1, 4, and 9 positions of phenanthrene rings, and as nitrated derivatives substituted at the 1, 2, 3, 4, 5, 6, 7, and 8 positions of phenanthrene rings. To determine the structure activity relationship of these derivatives, all 19 isomers were bioassayed with Salmonella tester strains. NAphs substituted at the 4, 6, 7 and 8 positions were mutagenic for TA98, and 1-, 2-, and 3-N-9-AphOs, 6-N-1-AphO and 6-N-4-AphO were mutagenic for TA98 and TA100 without the S9 mix, while 5-N-1-AphO and 5-N-9-AphO were non- or weakly mutagenic. Nitrated derivatives, 6-N-4-Aph, 6-N-9-Aph, 6-N-1-AphO, and 6-N-4-AphO, were powerful mutagens for TA98 and TA100. Mutagenicity was enhanced by mutant strains producing nitroreductase, such as YG1021 and 1026, and by those producing O-acetyltransferase, such as YG1024 and 1029. Nitro derivatives substituted at positions 4 and 5 in the phenanthrene rings were perpendicular, while those at positions 2, 3, 6 and 7 were coplanar to the phenanthrene rings. NAphs substituted at the 1 and 8 positions were noncoplanar due to steric hindrance of the aromatic proton at the peri position. On the other hand, 1,5- and 1,8-dinitro-4-azaphenanthrenes showed high mutagenicity for strains TA98 and TA100 in the absence of the S9 mix, and were strongly enhanced by nitroreductase and O-acetyltransferase, over-producing mutants. Therefore, it was found that the mutagenic potency of NAphs and NAphOs was closely associated with the chemical properties and orientation of nitro substitution of aromatic rings.     

The potency of fluorinated ether anesthetics correlates with their 19F spin-spin relaxation times in brain tissue

In this study, four fluorinated ether anesthetics and one non-anesthetic fluorinated alkane were observed in rat brain and adipose tissue using 19F-NMR spectroscopy. Measurements of 19F spin-spin relaxation times (T2) of the anesthetics in brain revealed T2 values (0.5-4.5 msec) that correlated linearly with the anesthetic potency (ED50) of the drugs. The non-anesthetic was present at very low concentrations in brain and had a T2 value (18.5 msec) far longer than that of any of the anesthetics. All of the drugs were present at high concentration in peripheral adipose tissue. 19F T2 values for these drugs in adipose tissue (200-400 msec) were far larger than the values observed in brain and did not correlate with anesthetic potency. These results indicate that volatile anesthetic molecules have a specific affinity for neural tissue and that immobilization of anesthetic molecules in brain correlates with anesthetic potency. The results with adipose tissue suggest that the interaction of anesthetic with brain tissue cannot be explained by a simple partition of these drugs into lipid.     

Liquid chromatographic method for the determination of lidocaine and monoethylglycine xylidide in human serum containing various concentrations of bilirubin for the assessment of liver function

A high-performance liquid chromatographic method is described for determination of lidocaine (2-(dietyloamino)-N-(2,6-dimetylofenylo) acetamid) and its metabolite, monoethylglycine xylidide (MEGX), in human serum containing various concentration of bilirubin. Lidocaine and its metabolite were extracted from human serum using dichloromethane. After separation of the layers and freezing at -32 degrees C, the organic layer was decanted and evaporated under a stream of nitrogen. The sample was dissolved in the mobile phase (12% acetonitrile in 15mM potassium dihydrogen orthophosphate, pH 3.0), and after separation on a Supelcosil LC-8-DB column, the analytes were measured by ultraviolet detection at 205nm. Trimethoprim (TMP) was used as the internal standard. The recovery of the examined analytes ranged from 95.7 to 97.9% for lidocaine and from 98.0 to 99.9% for MEGX. The lower limit of quantification (LLOQ) was established at 200microg/l for lidocaine and at 10microg/l for MEGX. The choice of suitable conditions for chromatographic separation of lidocaine and its metabolite MEGX allowed the elimination of the influence of endogenous bilirubin on the result of analysis.     

N-[1-(2-Phenylethyl)pyrrolidin-3-yl]-1-adamantanecarboxamides as novel 5-HT2 receptor antagonists

A series of 1-adamantanecarboxamides was synthesized and examined for their potency as a selective 5-HT2 receptor antagonist. We found (S)-N-[1-[2-(4-fluorophenyl)ethyl]pyrrolidin-3-yl]-1-adamantane carboxamide hydrochloride hydrate (10-(S), Y-39241) to have a high affinity and selectivity for 5-HT2 receptors, and this potent anti-platelet effect of Y-39241 was confirmed both in vitro and in vivo.     

Local Anesthetics Inhibit the Ca2+,Mg2+-ATPase Activity of Rat Brain Synaptosomes

Many biochemical effects of local anesthetics are expressed in Ca2+-dependent processes [Volpi M., Sha'afi R.I., Epstein P.M., Andrenyak P.M., and Feinstein M.B. (1981) Proc. Natl. Acad. Sci. USA 78, 795-799]. In this communication we report that local anesthetics (dibucaine, tetracaine, lidocaine, and procaine and the analogue quinacrine) inhibit the Ca2+-dependent and the Mg2+-dependent ATPase activity of rat brain synaptosomes and of membrane vesicles derived from them by osmotic shock. This inhibition is induced by concentrations of these drugs close to their pharmacological doses, and a good correlation between K0.5 of inhibition and their relative anesthetic potency is found. The Ca2+-dependent ATPase is more selectively inhibited at lower drug concentrations. The physiological relevance of these findings is discussed briefly.     

Interaction of lidocaine with the cardiac sodium channel: effects of low extracellular pH are consistent with an external blocking site

Brief extracellular application of millimolar concentrations of lidocaine affected sodium currents recorded in isolated rat ventricular myocytes in two ways: 1) a reduction of the maximum current consistent with a channel blocking action, and 2) a negative shift in the voltage dependence of inactivation consistent with an interaction with the inactivated state of the channel. Both effects occurred very rapidly (< 1 s). Decreasing extracellular pH to 6.4 increased the potency for channel block (EC50 1.8 +/- 0.2 mM at pH 7.4 and 0.8 +/- 0.1 mM at pH 6.5) and decreased the potency to shift inactivation (V(1/2) shift -42 mV by 1 mM lidocaine at pH 7.4 and -12.6 mV at pH 6.5). Channel block was slightly less at +90 mV compared to -40 mV at either pH (not statistically significant). The increase in potency for block at decreased extracellular pH, while intracellular pH is buffered, and the lack of voltage dependence of block, suggest that the charged form of lidocaine can block the channel by interacting with a site near the extracellular mouth, although alternative explanations are discussed.     

1,2,3-Thiadiazole thioacetanilides as a novel class of potent HIV-1 non-nucleoside reverse transcriptase inhibitors

A novel series of 1,2,3-thiadiazole thioacetanilide (TTA) derivatives have been designed, synthesized and evaluated for its anti-HIV activities in MT-4 cells. Some derivatives proved to be highly effective in inhibiting HIV-1 replication at nanomolar concentrations. Among them, 2-[4-(2,4-dichlorophenyl)-1,2,3-thiadiazol-5-ylthio]-N-(2-nitrophenyl)acetamide 7d2 was identified as the most promising compound (EC(50)=0.059+/-0.02 microM, CC(50)>283.25 microM, SI>4883). The structure-activity relationship (SAR) of these novel structural congeners is discussed.     

SAR study of a subtype selective allosteric potentiator of metabotropic glutamate 2 receptor, N-(4-phenoxyphenyl)-N-(3-pyridinylmethyl)ethanesulfonamide

The major excitatory neurotransmitter in the Central Nervous System is L-glutamic acid. As a result much attention has been given to the discovery of selective modulators of both the ionotropic glutamate receptors (iGluRs) and the metabotropic glutamate receptors (mGluRs). In this study we describe a novel class of subtype selective allosteric potentiators of the mGlu2 receptor. An active compound N-(4-phenoxyphenyl)-N-(3-pyridinylmethyl)ethanesulfonamide, LY181837, was identified in the course of compound screening. The synthesis of two series of analogs examined the structural requirements of the diaryl region of this compound. This SAR study also resulted in compounds with an increase in potency of over 100-fold where the most potent compound reported has EC(50)=14 nM.     

Selective L-nitroargininylaminopyrrolidine and L-nitroargininylaminopiperidine neuronal nitric oxide synthase inhibitors

Selective inhibition of the localized excess production of NO by neuronal nitric oxide synthase (nNOS) has been targeted as a potential means of treating various neurological disorders. Based on observations from the X-ray crystal structures of complexes of nNOS with two nNOS-selective inhibitors, (4S)-N-{4-amino-5-[(2-amino)ethylamino]pentyl}-N'-nitroguanidine (L-Arg(NO2)-L-Dbu-NH2 (1) and 4-N-(Nomega-nitro-L-argininyl)-trans-4-amino-L-proline amide (2), a series of descarboxamide analogues was designed and synthesized (3-7). The most potent compound was aminopyrrolidine analogue 3, which exhibited better potency and selectivity for nNOS than parent compound 2. In addition, 3 provided higher lipophilicity and a lower molecular weight than 2, therefore having better physicochemical properties. Nalpha-Methylated analogues (8-11) also were prepared for increased lipophilicity of the inhibitors, but they had 4- to 5-fold weaker binding affinity compared to their parent compounds.     

Synthesis and biological evaluation of novel 6-nitro-5-substituted aminoquinolines as local anesthetic and anti-arrhythmic agents: molecular modeling study

A series of 6-nitro-5-[1-oxo-2-(substituted amino)ethylamino and 2-(substituted amino)propylamino] quinoline was synthesized and evaluated for their local anesthetic and anti-arrhythmic activity. The detailed synthesis, spectroscopic, and biological data are reported. Molecular modeling methods are used to study the local anesthetic activity of lidocaine and the active compounds by means of the AM1 method. The superposition of the stable conformations of these compounds was studied using the HyperChem 5.11 program.     

Analysis of the action of lidocaine on insect sodium channels

A new class of sodium channel blocker insecticides (SCBIs), which include indoxacarb, its active metabolite, DCJW, and metaflumizone, preferably block inactivated states of both insect and mammalian sodium channels in a manner similar to that by which local anesthetic (LA) drugs block mammalian sodium channels. A recent study showed that two residues in the cockroach sodium channel, F1817 and Y1824, corresponding to two key LA-interacting residues identified in mammalian sodium channels are not important for the action of SCBIs on insect sodium channels, suggesting unique interactions of SCBIs with insect sodium channels. However, the mechanism of action of LAs on insect sodium channels has not been investigated. In this study, we examined the effects of lidocaine on a cockroach sodium channel variant, BgNa(v)1-1a, and determined whether F1817 and Y1824 are also critical for the action of LAs on insect sodium channels. Lidocaine blocked BgNa(v)1-1a channels in the resting state with potency similar to that observed in mammalian sodium channels. Lidocaine also stabilized both fast-inactivated and slow-inactivated states of BgNa(v)1-1a channels, and caused a limited degree of use- and frequency-dependent block, major characteristics of LA action on mammalian sodium channels. Alanine substitutions of F1817 and Y1824 reduced the sensitivity of the BgNa(v)1-1a channel to the use-dependent block by lidocaine, but not to tonic blocking and inactivation stabilizing effects of lidocaine. Thus, similar to those on mammalian sodium channels, F1817 and Y1824 are important for the action of lidocaine on cockroach sodium channels. Our results suggest that the receptor sites for lidocaine and SCBIs are different on insect sodium channels.     

Contributions of dipole moments, quadrupole moments, and molecular polarizabilities to the anesthetic potency of fluorobenzenes

Previous studies have emphasized the role of molecular polarizability and electric moments, especially dipole and quadrupole moments, in binding of drugs to sites of action. A recent publication of ED50s that prevent response to a noxious stimulus for eight fluorobenzenes has made it possible to compare anesthetic potency with ab initio Hartree-Fock calculations of molecular polarizability as well as dipole and quadrupole moments. Fluorobenzenes provide a stringent test of the role of electric moments in anesthetic potency because individual dipole moments range from 0 to 2.84 debye (D) while the quadrupole moment of benzene is large and negative (-30 x 10(-40) C m(2)), that of hexafluorobenzene is large and positive (30 x 10(-40) C m(2)), and that of 1,3,5-trifluorobenzene is nearly zero. We found that anesthetic potency of fluorobenzenes was not affected by the presence of either dipole or quadrupole moments. This result is surprising because fluoroalkanes and fluorocycloalkanes are most potent when half fluorinated and are usually not anesthetics when perfluorinated. The results suggest that electrostatic interactions are not important for binding of fluorobenzenes at sites of anesthetic action and that these sites are different from those that bind conventional anesthetics.