2-AZA-BICYCLO[2.2.2]OCTANE NMDA/NR2B ANTAGONISTS

Abstract: Novel 2-aza-bicyclo[2.2.2]octanes substituted in the 2-position are effective as NMDA NR2B antagonists useful for relieving pain.

Description: TITLE OF THE INVENTION 2-AZA-BICYCLO[2.2.2]OCTANE NMDA NR2B ANTAGONISTS BACKGROUND OF THE INVENTION Field of the Invention This invention relates to novel 2-aza-bιcyclo[2.2.2]octanes In particular, this invention relates to novel 2-aza-bιcyclo[2.2.2]octanes substituted in the 2-posιtιon that are effective as NMDA NR2B antagonists useful for relieving pain Ions such as glutamate play a key role in processes related to chronic pam and pam-associated neurotoxicity - pπmaπly by acting through N-methyl-D- aspartate ("NMDA") receptors. Thus, inhibition of such action - by employing ion channel antagonists, particularly NMDA antagonists - can be beneficial in the treatment and control of pain. Known NMDA antagonists include ketamine, dextromophan, and 3-(2- carboxypιperazm-4-yl)-propyl-l-phosphonιc acid ("CPP"). Although these compounds have been reported (J.D. Kπstensen, et al., Pain, 51:249-253 (1992), K Eide, et al., Pain, 61:221-228 (1995); D.J. Knox, et al., Anaesth. Intensive Care 23:620-622 (1995); and M.B. Max, et al., Chn Neuropharmacol. 18:360-368 (1995)) to produce symptomatic relief in a number of neuropathies including postherpetic neuralgia, central pam from spinal cord injury, and phantom limb pain, widespread use of these compounds is precluded by their undesirable side effects Such side effects at analgesic doses include psychotomimetic effects such as dizziness, headache, hallucinations, dysphoπa, and disturbances of cognitive and motor function. Additionally, more severe hallucinations, sedation, and ataxia are produced at doses only marginally higher than analgesic doses. Thus, it would be desirable to provide novel NMDA antagonists that are absent of undesirable side effects or that produces fewer and/or milder side effects NMDA receptors are heteromeπc assemblies of subumts, of which two major subunit families designated NR1 and NR2 have been cloned. Without being bound by theory, it is generally believed that the various functional NMDA receptors in the mammalian central nervous system ("'CNS") are only formed by combinations of NR1 and NR2 subunits, which respectively express glycine and glutamate recognition sites The NR2 subunit family is in turn divided into four individual subunit types: NR2A, NR2B, NR2C, and NR2D I Ishii, et al., J. Biol. Chem., 268.2836-2843 (1993), A. Wenel, et al., NeuralReport, 7:45-48 (1995), and D.J Laurie et al., Mol. Brain Res., 51:23-32 (1997) descπbe how the various resulting combinations produce a vaπety of NMDA receptors diffeπng in physiological and pharmacological properties such as ion gating properties, magnesium sensitivity, pharmacological profile, as well as in anatomical distπbution. For example, while NR1 is found throughout the brain, NR2 subunits are differentially distπbuted. In particular, it is believed that the distπbution map for NR2B lowers the probability of side effects while producing pain relief. For example, S. Boyce, et al., Neuropharmacology, 38:611-623(1999) descπbes the effect of selective NMDA NR2B antagonists on pain with reduced side-effects. Thus, it would be desirable to provide novel NMDA antagonists that target the NR2B receptor. International Patent Publication WO94/21615 descπbes benzimidazole-pipeπdme compounds utilized as dopamme D4 antagonists. Phenol compounds descπbed as NMDA antagonists are descπbed m U.S. patent Nos. 5,306,723 and 5,436,255, and in International Patent Publications WO91/17156, WO92/19502, WO93/02052, WO94/29571, WO95/28057, WO96/37226, and EP 04422506. Benzyl pipeπdines substituted with phenols or imidazoles are descπbed in Z.-L. Zhou, et al., J. Medicinal Chemistry, 42:2993-3000(1999); T.F. Gregory, et al., Poster #94, 218 th National Meeting Ameπcan Chemical Society, New Orleans, Louisiana, August 22-26, 1999. Other NMDA NR2B selective compounds are descπbed in European Patent Publication EP 787493 and British J. Pharmacol, 123:463(1998). However, there continues to be a need for novel NMDA antagonists that target the NR2B receptor. SUMMARY OF THE INVENTION The present invention relates to 2-aza-bιcyclo[2.2.2]octanes substituted the 2-posιtιon with benzimidazoles, lmidazopyπdines, phenols or imidazoles either directly or through a Cι-C4alkyl, cycloalkyl, hydroxyalkyl, alkoxy or ammoalkyl chain. The present invention also forms novel pharmaceutical compositions utilizing these novel compounds. Further, this invention includes novel methods to treat pam by utilizing the novel compounds. DETAILED DESCRIPTION OF THE INVENTION In one aspect, the compounds of this invention are represented by Formula (I) (I) or pharmaceutically acceptable salts thereof, wherein Rl is 2-benzιmιdazole, 4-ιmιdazole, 2-ιmιdazopyπdme, 2-ιndole, 2- quinazolme, or 4-phenol, R2 is phenyl, optionally substituted with one to five substituents, each substituent independently being chloro, fluoro, bromo, Cι -C4alkyl, tπfluoromethyl, hydroxy, or carboxy, Li is Ci-C4alkyl, Ci-C4alkenyl, Ci-C4alkynyl, Cι-C4alkoxy, ammoCι-C4alkyl, hydroxyCι-C4alkyl, carbonyl, cycloC3-C6alkyl or aminocarbonyl, L2 is phenylmethyl or phenylmethylaminocarbonyl, optionally substituted with chloro, fluoro, bromo, or methyl, and optionally substituted at any of the 3, 5, 6, 7, or 8 positions independently with X, wherein X is hydroxy, ammo, Cι-C4alkylamιno, dι(C[- C4)alkylamιno, Cι-C4alkyl, ester, carbamate, carbonate, or ether In an embodiment, the compound of this invention is represented by Formula (I) or a pharmaceutically acceptable salt thereof, wherein Rl is 2-benzιmιdazole, R2 is phenyl, optionally substituted with one to five substituents, each substituent independently being chloro, fluoro, bromo, Ci -C4alkyl, tπfluoromethyl, hydroxy, or carboxy, L] is Cι-C4alkyl, Cι-C4alkenyl, Cι-C4alkynyl, Cι-C4alkoxy, ammoCι-C4alkyl, hydroxyCi-C4alkyl, carbonyl, cycloC3-C6alkyl or aminocarbonyl; L2 is phenylmethyl or phenylmethylammocarbonyl, optionally substituted with chloro, fluoro, bromo, or methyl; and optionally substituted at any of the 3, 5, 6, 7, or 8 positions independently with X, wherein X is hydroxy, ammo, Cι-C4alkylamιno, dι(Ci- C4)alkylamιno, Cι-C4alkyl, ester, carbamate, carbonate, or ether In another embodiment, the compound of this invention is represented by Formula (I) or a pharmaceutically acceptable salt thereof, wherein Rl is 2-ιmιdazopyπdme; R2 is phenyl, optionally substituted with one to five substituents, each substituent independently being chloro, fluoro, bromo, Cι-C4alkyl, tπfluoromethyl, hydroxy, or carboxy; Li is Ci-C4alkyl, Ci-C4alkenyl, Ci-C4alkynyl, Cι-C4alkoxy, ammoCι-C4alkyl, hydroxyCι-C4alkyl, carbonyl, cycloC3-C6alkyl or aminocarbonyl; L2 is phenylmethyl or phenylmethylammocarbonyl, optionally substituted with chloro, fluoro, bromo, or methyl; and optionally substituted at any of the 3, 5, 6, 7, or 8 positions independently with X, wherein X is hydroxy, ammo, Cι-C4alkylamιno, dι(Cι- C4)alkylammo, Cι-C4alkyl, ester, carbamate, carbonate, or ether. As used herein, "alkyl" as well as other groups having the prefix "alk" such as, for example, alkoxy, alkanoyl, alkenyl, alkynyl and the like, means carbon chains which may be linear or branched or combinations thereof Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, sec- and tert-butyl, pentyl, hexyl, heptyl and the like. "Alkenyl", "alkynyl" and other like terms include carbon chains containing at least one unsaturated C-C bond. The term "cycloalkyl" means carbocycles containing no heteroatoms, and includes mono-, bi- and tπcychc saturated carbocycles, as well as fused πng systems Such fused πng systems can include one πng that is partially or fully unsaturated such as a benzene πng to form fused πng systems such as benzofused carbocycles. Cycloalkyl includes such fused πng systems as spirofused πng systems. Examples of cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, decahydronaphthalene, adamantane, mdanyl, denyl, fluorenyl, 1,2,3,4- tetrahydronaphalene and the like. Similarly, "cycloalkenyl" means carbocycles containing no heteroatoms and at least one non-aromatic C-C double bond, and include mono-, bi- and tπcychc partially saturated carbocycles, as well as benzofused cycloalkenes. Examples of cycloalkenyl include cyclohexenyl, indenyl, and the like Unless otherwise stated, the terms "carbonyl" and "aminocarbonyl" include short C1-C2 termini. The terms include, for example, -CH2CONH-, -CH2CO-, -C2H4CONHCH2-, and -CH2COC2H4- Unless otherwise stated, the term "carbamate" is used to include -OCOOCι-C4alkyl, -NHCOOCι-C4alkyl, and -OCONHCι-C4alkyl. The term "halogen" includes fluoπne, chloπne, bromine and iodine atoms. The term "SEM" is used to descπbe -CH2-O-CH2CH2-Sι(CH3)3. The term "Co" means that the carbon is not present. Thus, "C0-C5" means that there are from none to five carbons present - that is, five, four, three, two, one, or no carbons present. The term "optionally substituted" is intended to include both substituted and unsubstituted. Thus, for example, optionally substituted aryl could represent a pentafluorophenyl or a phenyl πng. Compounds described herein contain one or more asyrnrnetπc centers and may thus give πse to diastereomers and optical isomers. The present invention includes all such possible diastereomers as well as their racem c mixtures, their substantially pure resolved enantiomers, all possible geometπc isomers, and pharmaceutically acceptable salts thereof. The above Formula I is shown without a definitive stereochemistry at certain positions. The present invention includes all stereoisomers of Formula I and pharmaceutically acceptable salts thereof. Further, mixtures of stereoisomers as well as isolated specific stereoisomers are also included. Duπng the course of the synthetic procedures used to prepare such compounds, or using racemization or epimenzation procedures known to those skilled in the art, the products of such procedures can be a mixture of stereoisomers. The term "pharmaceutically acceptable salts" refers to salts prepared from pharmaceutically acceptable non-toxic bases or acids. When the compound of the present invention is acidic, its coπesponding salt can be conveniently prepared from pharmaceutically acceptable non-toxic bases, including inorganic bases and organic bases. Salts deπved from such inorganic bases include aluminum, ammonium, calcium, copper (IC and ous), feme, feπous, lithium, magnesium, manganese (ic and ous), potassium, sodium, zinc and the like salts Particularly prefeπed are the ammonium, calcium, magnesium, potassium and sodium salts Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of pπmary, secondary, and tertiary amines, as well as cyclic amines and substituted amines such as naturally occurπng and synthesized substituted ammes Other pharmaceutically acceptable organic non-toxic bases from which salts can be formed include ion exchange resins such as, for example, arginine, betaine, caffeine, chohne, N,N -dibenzylethylenediamme, diethylamme, 2-dιethylamιnoethanol, 2- dimethylaminoethanol, ethanolamme, ethylenediamine, N-ethylmorphohne, N- ethylpipeπdine, glucamine, glucosamine, histidine, hydrabamine, isopropylamine, lysme, methylglucamme, morphohne, piperazine, pipeπdine, polyamme resins, proca e, puπnes, theobromine, tπethylamine, tπmethylamme, tπpropylamme, tromethamine and the like. When the compound of the present invention is basic, its coπespondmg salt can be conveniently prepared from pharmaceutically acceptable non-toxic acids, including inorganic and organic acids. Such acids include, for example, acetic, benzenesulfonic, benzoic, camphorsulfomc, citπc, ethanesulfomc, fumaπc, glucomc, glutamic, hydrobromic, hydrochloπc, lsethiomc, lactic, maleic, malic, mandelic, methanesulfomc, mucic, nitπc, pamoic, pantothenic, phosphoπc, succimc, sulfuπc, tartaπc, p-toluenesulfonic acid and the like. Particularly prefeπed are citπc, hydrobromic, hydrochloπc, maleic, phosphoπc, sulfuπc, and tartaπc acids The pharmaceutical compositions of the present invention compose a compound represented by Formula I (or pharmaceutically acceptable salts thereof) as an active ingredient, a pharmaceutically acceptable earner and optionally other therapeutic ingredients or adjuvants. The compositions include compositions suitable for oral, rectal, topical, and parenteral (including subcutaneous, intramuscular, and intravenous) administration, although the most suitable route in any given case will depend on the particular host, and nature and seventy of the conditions for which the active ingredient is being administered The pharmaceutical compositions may be conveniently presented m unit dosage form and prepared by any of the methods well known in the art of pharmacy. In practice, the compounds represented by Formula I, or pharmaceutically acceptable salts thereof, of this invention can be combined as the active ingredient m intimate admixture with a pharmaceutical earner according to conventional pharmaceutical compounding techniques The earner may take a wide vaπety of forms depending on the form of preparation desired for administration, e g , oral or parenteral (including intravenous) Thus, the pharmaceutical compositions of the present invention can be presented as discrete units suitable for oral administration such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient. Further, the compositions can be presented as a powder, as granules, as a solution, as a suspension m an aqueous liquid, as a non-aqueous liquid, as an oil-in-water emulsion or as a water-in-oil liquid emulsion In addition to the common dosage forms set out above, the compound represented by Formula I, or pharmaceutically acceptable salts thereof, may also be administered by controlled release means and/or delivery devices The compositions may be prepared by any of the methods of pharmacy. In general, such methods include a step of bπngmg into association the active ingredient with the earner that constitutes one or more necessary ingredients. In general, the compositions are prepared by uniformly and intimately admixing the active ingredient with liquid earners or finely divided solid earners or both. The product can then be conveniently shaped into the desired presentation. Thus, the pharmaceutical compositions of this invention may include a pharmaceutically acceptable earner and a compound or a pharmaceutically acceptable salt of Formula I. The compounds of Formula I, or pharmaceutically acceptable salts thereof, can also be included in pharmaceutical compositions in combination with one or more other therapeutically active compounds. The pharmaceutical earner employed can be, for example, a solid, liquid, or gas. Examples of solid earners include lactose, teπa alba, sucrose, talc, gelatin, agar, pectin, acacia, magnesium stearate, and steanc acid Examples of liquid earners are sugar syrup, peanut oil, olive oil, and water Examples of gaseous earners include carbon dioxide and nitrogen. In prepaπng the compositions for oral dosage form, any convenient pharmaceutical media may be employed. For example, water, glycols, oils, alcohols, flavoπng agents, preservatives, colonng agents and the like may be used to form oral liquid preparations such as suspensions, elixirs and solutions, while earners such as starches, sugars, microcrystalline cellulose, diluents, granulating agents, lubncants, binders, disintegrating agents, and the like may be used to form oral solid preparations such as powders, capsules and tablets. Because of their ease of administration, tablets and capsules are the prefeπed oral dosage units whereby solid pharmaceutical earners are employed Optionally, tablets may be coated by standard aqueous or nonaqueous techniques A tablet containing the composition of this invention may be prepared by compression or molding, optionally with one or more accessory ingredients or adjuvants. Compressed tablets may be prepared by compressing, in a suitable machine, the active ingredient in a free-flowing form such as powder or granules, optionally mixed with a binder, lubncant, inert diluent, surface active or dispersing agent. Molded tablets may be made by molding in a suitable machine, a mixture of the powdered compound moistened with an inert liquid diluent. Each tablet preferably contains from about lmg to about 500mg of the active ingredient and each cachet or capsule preferably containing from about 1 to about 500mg of the active ingredient. Pharmaceutical compositions of the present invention suitable for parenteral administration may be prepared as solutions or suspensions of the active compounds in water A suitable surfactant can be included such as, for example, hydroxypropylcellulose. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, and mixtures thereof oils. Further, a preservative can be included to prevent the detπmental growth of microorganisms. Pharmaceutical compositions of the present invention suitable for injectable use include steπle aqueous solutions or dispersions. Furthermore, the compositions can be in the form of steπle powders for the extemporaneous preparation of such steπle injectable solutions or dispersions. In all cases, the final injectable form must be steπle and must be effectively fluid for easy syπngabihty The pharmaceutical compositions must be stable under the conditions of manufacture and storage; thus, preferably should be preserved against the contaminating action of microorganisms such as bacteπa and fungi. The earner can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (e.g. glycerol, propylene glycol and liquid polyethylene glycol), vegetable oils, and suitable mixtures thereof Pharmaceutical compositions of the present invention can be in a form suitable for topical use such as, for example, an aerosol, cream, ointment, lotion, dusting powder, or the like. Further, the compositions can be in a form suitable for use in transdermal devices. These formulations may be prepared, utilizing a compound represented by Formula I of this invention, or pharmaceutically acceptable salts thereof, via conventional processing methods. As an example, a cream or ointment is prepared by mixing hydrophilic mateπal and water, together with about 5 wt% to about 10 wt% of the compound, to produce a cream or ointment having a desired consistency. Pharmaceutical compositions of this invention can be in a form suitable for rectal administration wherein the carrier is a solid. It is preferable that the mixture forms unit dose suppositories. Suitable carriers include cocoa butter and other materials commonly used in the art. The suppositories may be conveniently formed by first admixing the composition with the softened or melted carrier(s) followed by chilling and shaping in moulds. In addition to the aforementioned carrier ingredients, the pharmaceutical formulations described above may include, as appropriate, one or more additional carrier ingredients such as diluents, buffers, flavoring agents, binders, surface-active agents, thickeners, lubricants, preservatives (including anti-oxidants) and the like. Furthermore, other adjuvants can be included to render the formulation isotonic with the blood of the intended recipient. Compositions containing a compound described by Formula I, or pharmaceutically acceptable salts thereof, may also be prepared in powder or liquid concentrate form. Experimental Protocols Assessing the Activity of Selected Compounds to Inhibit NR1A/2B NMDA Receptor Activation (FLIPR Assay) The activity of selected compounds to inhibit NR1A/2B NMDA receptor activation measured as NR1A/2B receptor-mediated Ca 2+ influx is assessed by the following procedure: NR1 A/2B receptor transfected L(tk) cells are plated in 96-well format at 3 x 10 6 cells per plate and grown for one - two days in normal growth media (Dulbeccos MEM with Na pyruvate, 4500 mgglucose, pen/strep, glutamine, 10% FCS and 0.5mg/ml geneticin). NR1A/2B -expression in these cells is induced by the addition of 4nM dexamethasone in the presence of 500μM ketamine for 16 - 24 hours. After receptor induction cells are washed using a Labsystem Cellwasher two times with assay buffer (Hanks balanced salt solution (HBSS-Mg ++ free) containing 20mM HEPES, 0.1% BSA, 2mM CaCl 2 and 250μM probenecid). The cells of each 96 well cell plate are loaded with the Ca ++ sensitive dye Fluo-3 (Molecular Probes, Inc.) at 4μM in assay buffer containing 0.5% FBS, and 0.04% pluronic F-127 (Molecular Probes, Inc.) for lh at 37 °C avoiding light. The cells are then washed with the Cellwasher four times with assay buffer leaving them in lOOμl buffer Test compounds in solution are pipetted by FLIPR (Fluorometnc Imaging Plate Reader) into each test well for a 2mιn pretreatment Duπng this time the fluorescence intensity is recorded (excitation at 488nm and emission at 530nm) The glutamate/glycine 50μL agonist solution (final concentration lμM/lμM) is then added by FLIPR into each well already containing 150μL of buffer (containing the test compound or vehicle) and the fluorescence is continuously monitored for lOmin The endpomt fluorescence values are used to determine an IC 50 value companng the agonist-stimulated signal for the vehicle alone sample and that for the cells incubated with each concentration of test compound Determining the Apparent Dissociation Constant (Ki) of Compounds for Human NR1A/NR2B Receptors (Binding Assay) The radio gand binding assay is performed at room temperature in 96-well microtiter plates with a final assay volume of l.OmL in 20mM Hepes buffer (pH 7.4) containing 150mM NaCl. Solutions of test compounds were prepared in DMSO and serially diluted with DMSO to yield 20μL of each of 10 solutions differing by 3-fold in concentration. Non-specific binding (NSB) using hot AMD-1 (lOμM final concentration) and total binding (TB) by using DMSO (2% final concentration). A solution of NR1A NR2B receptors (40pM final concentration) and tπtiated AMD-2 (InM final concentration) were added to the test compounds. After 3h of incubation at room temperature, samples are filtered through Packard GF/B filters (presoaked in 0.05% PEI, polyethylenmine Sigma P-3143) and washed 10 times with lmL of cold 20mM Hepes buffer per wash. After vacuum drying of the filter plates, 40μL of Packard Mιcroscιnt-20 was added and bound radioactivity determined in a Packard TopCount. The apparent dissociation constant (Ki), the maximum percentage inhibition (%Imax) > the minimum percentage inhibition (%Imιn) an the hill slope (nH) were determined by a non-linear least squares fitting the bound CPM data to Equation #1 below Equatιon#l: (SB) (%I max - %I mιn ) CPM Bound = + NSB + (SB) (1 - %Imax) (1 + ( [Drug] / (Ki [L-844,345]/K D ) ) n π H π ) where, K D IS the apparent dissociation constant for the radioligand for the receptor as determined by hot saturation and SB is the specifically bound CPM determined from the difference of TB and NSB AMD-1 AMD-2 Compounds AMD-1 and AMD-2 can be synthesized in accordance with the following general reaction schemes. SCHEME 1 la In accordance with scheme 1, hydrogen chlonde is bubbled through a solution of the appropπately substituted benzonitπle 1 in methanol at room temperature The volatiles are removed under reduced pressure and the resulting residue is tnturated with ether and filtered to yield the desired imidate 2 Imidate 2 is dissolved in methanol at ambient temperature, treated with amine 3 at ambient temperature and stiπed under argon The volatiles are removed under reduced pressure and the residue punfied by preparative HPLC or tπturation with ether to afford amidme la SCHEME 2 R -C 0 6 alkyl-NR 3 H HCI Me 3 AI -»- Me 2 CI AI-NH 2 -C 0 6 alkyl A 3a 6 la In accordance with scheme 2, at room temperature under argon, amme 3a is dissolved in ether and was treated with 1-M hydrogen chlonde in ether (1 equiv ) m a single portion The resulting precipitate is stiπed vigorously for 10 minutes The volatiles are removed under reduced pressure The residue is suspended in toluene, cooled to 0°C under argon, treated with 2 0-M tnmethylaluminum (1 05 equiv ) in a dropwise manner, and stiπed for 45 minutes at room temperature to afford intermediate 6 (not isolated) Compound 6 is added to a solution of nitnle 1 in toluene The reaction is heated to 80°C without stirring in a sealed tube for 18h, cooled to ambient temperature, poured onto a silica gel column and eluted with methanol/dichloromethane to give the ami dine 4 Preparation of [ 125 I]AMD-1 Tritiated AMD-1 was prepared by the following procedure: A mixture of AMD-1, hydrochloride salt, (5mg, 0.012mmol) in dioxane (0.2mL) containing triethylamine (4μL) was treated with hexamethylditin (5μL), a catalytic amount of palladium catalyst and heated at 100°C for 45 minutes. The reaction was cooled to room temperature, filtered through a glass wool plug, rinsed with methanol and concentrated in vacuo to give 10.7mg of a brown oil. The oil was dissolved in methylene chloride and passed through a small silica column eluting with methylene chloride followed by 5% methanol/methylene chloride. Fractions containing the trimethylstannane (Rf 0.26 in 10% methanol/methylene chloride) were pooled and concentrated in vacuo to give 4.5mg of the trimethylstannane as a clear colorless oil. This material was further purified by HPLC (C18 Econosil, 10x250mm, 20 minute linear gradient, 30% MeCN:70% H 2 O (0.1% TFA) to 90% MeCN, 3mL/min, 254nm, retention time 15 minutes) to give 3mg of the trimethylstannane. A Na l25 I shipping vial (lOmCi, Amersham) was charged with a stir bar, an iodobead, 50μL of methanol and stiπed five minutes at room temperature. A solution of the trimethylstannane (O.lmg) in 50μL of methanol containing 5μL of trifluoroacetic acid was added and the reaction was stiπed for five minutes. The reaction was quenched with 50μL of ammonium hydroxide and purified by HPLC (C18 Vydac protein and peptide column, 4.6 x 250 mm, 20 minute linear gradient, 30% MeCN 70% H 2 O (0 1% TFA) to 90% MeCN, lmL min, retention time 11 minutes) Fractions containing the radioactive product were pooled and concentrated in vacuo to give 989μCι of [ 12D I]AMD-1 with a specific activity of 898Cι/mmol as measured by UV absorbance at 272nm Synthesis of Tritiated AMD-2 Tπtiated AMD-2 was prepared by the following procedure The phenol of AMD-2 (2mg, 0 008mmol) dissolved in dimethylformamide (0 6mL) and potasium carbonate (1 2mg) for lhr High specific activity tπtiated methyl iodide (50mCι, 0 0006mmol, in toluene ImL, Amencan Radiolabeled Chemicals) was added at room temperature and stiπed for 2 hours The reaction mixture was filtered using a Whatman PTFE 0 45μm syπngeless filter device to remove any msoluable potassium carbonate, washed with Abs ethanol (2mL, Pharmco), and the combined filtrates were concentrated to dryness at room temperature using a rotary evaporator, this also removed any unreacted tπtiated methyl iodide The residue was punfied by HPLC chromatography on a Phenomenx Luna C8 semi-prep column ( Luna 5 micro C8(2), 250x10 0 mm) using a gradient system of 20/80 acetomtπle/water with 0 1% tnfluoroacetic acid to 100% acetronitπle with 0 1% tnfluoroacetic acid in 20mιn Total activity of the product was 8mCι Further purification was effected by absorption onto a Waters C-18 Sep-pak column (Waters Sep-Pak PLUS C18) and elution with water followed by absolute ethanol The product was diluted with absolute ethanol (lOmL) before submission for final analysis The compounds of this invention exhibit less than 50μM in the FLIBR and binding assays Thus, the compounds and pharmaceutical compositions of this invention have been found to exhibit biological activity as NMDA NR2B antagonists Accordingly, another aspect of the invention is the treatment of pam, migraine, depression, anxiety, schizophrenia, Parkinson's disease, or stroke - maladies that are amenable to amelioration through inhibition of NMDA NR2B receptors - by the administration of an effective amount of the compounds of this invention The following examples are provided to more fully illustrate the present invention, and are not to be construed as limiting the scope of the claims in any manner EXAMPLES Compounds of this invention can be prepared by Scheme 1 below. Scheme 1 Compounds of this invention can be prepared by Scheme 2 below. Scheme 2 EtOoC EtOoC In Schemes 1 and 2, in place of the l-SEM-benzimidole-2- carboxaldehyde SEM any of the following aldehydes, ketones, or bromides can be used to prepare the compounds of this invention: n = 0,1 ,2,3 EXAMPLE 1 2-(lH-Benzimidazol-2-ylmethyl)-5-(4-chloro-benzyl)-2-aza-bicyclo[2.2.2]octane Example 1 was prepared by the following procedure Step 1: 1 - (2-Trimethylsilylethoxymethyl)- lH-benzoimidazole : A mixture of KH, from 7g of 30% oil dispersion, and 5g of benzimidazole in lOOmL of THF was stiπed under nitrogen at room temperature for 18h. To the stiπed suspension was added 7g of 2-tnmethylsιlylethoxymethyl chlonde and the mixture kept at room temperature for 24h, cooled in an ice bath, cautiously quenched with 50mL of water, and extracted into ether The combined ether extracts were dned over magnesium sulfate and concentrated. Low pressure chromatography over silica gel eluting with a gradient of 3:1 ethyl acetate :hexane to 100% ethyl acetate gave 9.5g of 1-SEM-benzιmιdazole as a colorless oil. Step 2: l-(2-Trimethylsilylethoxymethyl)-lH-benzoimidazole-2-carbaldehyde: To a solution of 40mmole of lithium dnsopropyl amide in lOOmL of THF cooled to -78°C was added 5g of 1-SEM-benzιmιdazole in 50mL of THF After 1.5h at or below -70°C, the red solution was quenched by rapid addition of 6mL of methyl formate. After warming to room temperature over 30mm, 50mL of water and 200mL of ethyl acetate were added The organic layer was separated and dned over magnesium sulfate then concentrated under reduced pressure to 5.3g of a thick oil that solidified in the freezer Step 3: 5-(4-Chloro-benzylidene)-2-aza-bicyclo[2.2.2]octane-2-carboxylic acid ethyl ester: To a stiπed solution of 2g of 5-Oxo-2-aza-bιcyclo[2.2.2]octane-2- carboxyhc acid ethyl ester (G. Krow, R. Rodebaugh, M. Gnppi and R. Carmosin, Synthetic Communications, 2f2\ 1-214(1972)) and 3.5g of diethyl 4- chlorobenzylphosphonate in lOmL of l,3-dιmethyl-2-ιmιdazohdmone dned over 4 A mol sieves was added 0.50g of 60% sodium hydnde oil dispersion. The mixture was allowed to stir overnight, diluted with 200mL of water and extracted with 3X100mL of ether. Combined extracts were dned over magnesium sulfate and concentrated under reduced pressure. Low pressure chromatography over silica gel eluting with a gradient of 5:95 ethyl acetate:hexane to 1:5 ethyl acetate: hex ane gave 2g of 5-(4- chloro-benzyhdene)-2-aza-bιcyclo[2.2.2]octane-2-carboxylιc acid ethyl ester as a colorless oil. Step 4: 5-(4-Chloro-benzyl)-2-aza-bicycIo[2.2.2]octane-2-carboxylic acid ethyl ester: A solution of 2g of 5-(4-chloro-benzyhdene)-2-aza- bιcyclo[2.2.2]octane-2-carboxyhc acid ethyl ester and 0 5g of 5% platinum on carbon in lOOmL of ethanol was allowed to stir overnight under latm of hydrogen. The catalyst was filtered off and the solution concentrated to give 2g of a racemic mixture of exo:endo isomers of 5-(4-chloro-benzyl)-2-aza-bιcyclo[2.2.2]octane-2-carboxyhc acid ethyl ester as an oil Step 5: 5-(4-Chloro-benzyl)-2-aza-bicyclo[2.2.2]octane: A mixture of 2g of 3-(4-chloro-benzyl)-8-aza-bιcyclo[3.2.1]octane-8- carboxyhc acid ethyl ester, 20mL of 48% HBr and 5mL of acetic acid was heated to reflux for 2h. After cooling in an ice bath the solution was basified to pH 10 by addition of NaOH pellets, extracted with 3X100mL of chloroform and the combined extracts dned over magnesium sulfate. Removal of solvents under reduced pressure gave 1.5g of racemic exo and endo 5-(4-chloro-benzyl)-2-aza-bιcyclo[2.2.2]octane as a thick oil Step 6: 2-[3-(4-Chloro-benzyl)-8-aza-bicyclo[3.2.1]oct-8-ylmethyl]-lH-benzimidazole: A mixture of 0.5g of racemic exo and endo 5-(4-chloro-benzyl)-2-aza- bicyclo[2.2.2]octane, 0.5g of l-(2-trimethylsilylethoxymethyl)-lH-benzoimidazole-2- carbaldehyde, 5mL of 1 ,2-dichloroethane and 0.5g of sodium triacetoxyborohydride was stiπed at room temperature for 48h. The reaction mixture was diluted with 50mL chloroform and lOmL saturated aqueous Na2CO3 and the layers separated. The aqueous layer was extracted with 2X25mL of chloroform and the combined organic layers dried over magnesium sulfate and concentrated under reduced pressure. The crude SEM ether was heated to reflux in 50mL of ethanol containing 5mL of 3N HC1 for 2h, cooled, concentrated and partitioned between lOmL of saturated aqueous sodium carbonate and 3X25mL of chloroform. The chloroform extracts were dried over magnesium sulfate and concentrated. Purification by chromatography eluting with 90: 10 CHCl3:MeOH gave 0.8g of 2-[3-(4-chloro-benzyl)-8-aza- bicyclo[3.2.1]oct-8-ylmethyl]-lH-benzimidazole as a mixture of exo and endo isomers. Chromatography on a Chiralpak™ OD column eluting with a 90:10 mixture of hexane with 0.10% diethylamine and isopropanol gave 0.2g of 2-(lH- benzimidazol-2-ylmethyl)-5-ejco-(4-chloro-benzyl)-2-aza-bicyclo[2.2.2]octane, enantiomer A: RT = 8.75min; MS (m+1) =366.9; l H NMR (400MHz, CDCI3) 7.6 (br, 2H), 7.22 (d, 2H), 7.08 (d, 2H), 4.05 (s, 2H), 3.05 (d, IH), 2.8 (d, IH), 2.7 (m, 2H), 2 (m, 2H), 1.8-1.5 (complex, 6H), 1.25 (m, IH). Later fractions gave 0.2g of 2-(lH-benzimidazol-2-ylmethyl)-5- exo - (4-chloro-benzyl)-2-aza-bicyclo[2.2.2]octane, enantiomer B: RT = 10.7min; MS (m+1) =366.9; l H NMR (400MHz, CDCI3) 7.6 (br, 2H), 7.22 (d, 2H), 7.08 (d, 2H), 4.05 (s, 2H), 3.05 (d, IH), 2.8 (d, IH), 2.7 (m, 2H), 2 (m, 2H), 1.8-1.5 (complex, 6H), 1.25 (m, lH). Even later fractions gave 0.4g of racemic 2-(lH-benzimidazol-2- ylmethyl)-5- endo -(4-chloro-benzyl)-2-aza-bicyclo[2.2.2]octane: RT = 12.52min; MS (m+1) =366.9; ^ NMR (400MHz, CDCI3) 7.6 (br, 2H), 7.22 (d, 2H), 7.08 (d, 2H), 4.05 (s, 2H), 2.85 (dd, 2H), 2.6 (m, 3H), 2.2 (m, 2H), 2.1 (m, IH), 1.85 (m, IH), 1.7 (m, IH), 1.55 (m, 3H). EXAMPLE 2 2-(lH-Benzimidazol-2-ylmethyl)-5-benzyl-2-aza-bicyclo[2.2.2]octane Example 2 was prepared following the procedures described for Example 1, but substituting diethyl benzylphosphonate for di ethyl 4- chlorophosphonate. Chromatography on a Chiralpak™ AD column eluting with a 90:10 mixture of hexane with 0.10% diethylamine and isopropanol, yielded 2-(lH- benzimidazol-2-ylmethyl)-5-exø-(benzyl)-2-aza-bicyclo[2.2.2]octane, enantiomer A: RT = 6.97min; MS (m+1) =332.2; l U NMR (400MHz, CDCI3 1.50-1.60(m, 2H), 1.62-1.80 (m, 4H), 1.92-2.10 (m, 2H), 2.60(s, IH), 2.70-2.81 (m, 3H), 3.05 (d, J=17 Hz IH), 4.05 (s, 2H), 7.20-7.25 (m, 2H), 7.26-7.35 (m, 5H), 7.45-7.50 (br s, IH), 7.75 (br s, IH), 9.70 (br s,lH). Later fractions gave 2-(lH-benzimidazol-2-ylmethyl)-5-ej o -(benzyl )- 2-aza-bicyclo[2.2.2]octane, enantiomer B: RT = 8.5min; MS (m+1) =332.2; 1H NMR (400MHz, CDCI3) 1.50-1.60(m, 2H), 1.62-1.80 (m, 4H), 1.92-2.10 (m, 2H), 2.60(s, IH), 2.70-2.81 (m, 3H), 3.05 (d, J=17 Hz IH), 4.05 (s, 2H), 7.20-7.25 (m, 2H), 7.26- 7.35 (m, 5H), 7.45-7.50 (br s, IH), 7.75 (br s, IH), 9.70 (br s, IH). Still later fractions gave racemic 2-(lH-benzimidazol-2-ylmethyl)-5- endo -(benzyl)-2-aza-bicyclo[2.2.2]octane: RT = 10.2 and 12.15min; MS (m+1) =332.2; iH NMR (400MHz, CDCI3) 1.95-1.22 (m, IH), 1.45-1.65 (m, 3H), 1.80-1.90 (m, IH), 1.92-2.10 (m, IH), 2.20-2.25 (m,2H), 2.60-2.80 (m, 4H), 2.85 (d, J=18 Hz IH), 4.00 (s, 2H), 7.15-7.25 (m, 5H), 7.30-7.35 (m, 2H), 7.42 (br s, IH), 7.70 (br s, lH), 9.95 (br s,lH). EXAMPLE 3 5-(4-Chloro-benzyl)-2-(3H-imidazo[4,5-b]pyridin-2-ylmethyl)-2-aza- bicyclo[2.2.2]octane Example 3 was prepared in a similar manner to Example 1, Steps 1-6, but substituting 3H-imidazo[4,5-b]pyridine for benzimidazole in Step 2. Chromatography on a Chiralpak™ AD column eluting with a 90:10 mixture of hexane with 0.10% diethylamine and isopropanol gave racemic 5-exo-(4-chloro-benzyl)-2- (3H-imidazo[4,5-b]pyridin-2-ylmethyl)-2-aza-bicyclo[2.2.2]octane: RT = 6.03min; MS (m+1) =367.2; ^ NMR (400MHz, CDCI3) 8.4 (S, IH), 8.0 (s, IH), 7.35-7.2 (m, 3H), 7.1 (d, 2H), 4.05 (s, 2H), 3.1 (d, IH), 2.8-2.62 (m, 4H), 2.60 (s, IH), 2.1-1.90 (m, 2H), 1.8-1.72 (m, 2H), 1.70-1.61 (m,lH). Later fractions gave 5-en<Jø-(4-chloro-benzyl)-2-(3H-imidazo[4,5- b]pyridin-2-ylmethyl)-2-aza-bicyclo[2.2.2]octane, enantiomer A: RT = 7.5min; MS (m+1) = 367.2; l H NMR (400MHz, CDCI3) 8.4 (S, IH), 8.0 (s, IH), 7.35-7.2 (m, 3H), 7.1 (d, 2H), 4.05 (s, 2H), 2.9-2.8 (dd, 2H), 2.62 (m, 3H), 2.2 (m, 2H), 2.0 (m, IH), 1.5 (m, 3H) 1.3 (m, IH), 1.08 (m, IH). Still later fractions gave 5-exo -(4-chloro-benzyl)-2-(3H-imidazo[4,5- b]pyridin-2-ylmethyl)-2-aza-bicyclo[2.2.2]octane, enantiomer B: RT = 8.1min; MS (m+1) =367.2; l ¥L NMR (400MHz, CDCI3) 8.4 (S, IH), 8.0 (s, IH), 7.35-7.2 (m, 3H), 7.1 (d, 2H), 4.05 (s, 2H), 2.9-2.8 (dd, 2H), 2.62 (m, 3H), 2.2 (m, 2H), 2.0 (m, IH), 1.5 (m, 3H) 1.3 (m, IH), 1.08 (m, IH). EXAMPLE 4 2-(3-Benzyl-8-aza-bicyclo[3.2.1]oct-8-ylmethyl)-3H-imidazo[4,5-b]pyridine Example 4 was prepared in a similar manner to Example 3, but substituting racemic exo and endo 5-(benzyl)-2-aza-bicyclo[2.2.2]octane for racemic exo and endo 5-(4-chloro-benzyl)-2-aza-bicyclo[2.2.2]octane. Chromatography on a Chiralpak™ AD column eluting with a 95:5 mixture of hexane with 0.10% diethylamine and isopropanol gave racemic 5-exø-(benzyl)-2-(3H-imidazo[4,5- b]pyridin-2-ylmethyl)-2-aza-bicyclo[2.2.2]octane: RT = 6.03min; MS (m+1) =333.2; *H NMR (400MHz, CDCI3 4.10 (s, 2H), 3.15 (d, 2H), 2.8 (d, 2H. Later fractions gave 5-eradø-(benzyl)-2-(3H-imidazo[4,5-b]pyridin-2- ylmethyl)-2-aza-bicyclo[2.2.2]octane, enantiomer A: RT = 7.53min; MS (m+1) = 333.2; l U NMR (400MHz, CDCI3) 4.05 (s, 2H), 2.90 (d,2H), 2.8 (d, 2H). Still later fractions gave 5-exo -(benzyl)-2-(3H-imidazo[4,5-b]pyridin- 2-ylmethyl)-2-aza-bicyclo[2.2.2]octane, enantiomer B: RT = 8.09min; MS (m+1) =333.2; *H NMR (400MHz, CDCI3) 4.05 (s, 2H), 2.90 (d,2H), 2.8 (d, 2H).

Claims: WHAT IS CLAIMED IS: 1. A compound having the formula: 7 or a pharmaceutically acceptable salt thereof, wherein R is 2-benzimidazole, 4-imidazole, 2-imidazopyridine, 2-indole, 2- quinazoline, or 4-phenol; R2 is phenyl, optionally substituted with one to five substituents, each substituent independently being chloro, fluoro, bromo, Cι-C4alkyl, trifluoromethyl, hydroxy, or carboxy; Li is Cι-C4alkyl, Cι-C4alkenyl, Cι-C4alkynyl, Cι-C4alkoxy, aminoCι-C4alkyl, hydroxyCι-C4alkyl, carbonyl, cycloC3-C6alkyl or aminocarbonyl; L2 is phenylmethyl or phenylmethylammocarbonyl, optionally substituted with chloro, fluoro, bromo, or methyl; and optionally substituted at any of the 3, 4, 5, 6, 7, or 8 positions independently with X, wherein X is hydroxy, amino, Cι-C4alkylamino, di(Cι- C4)alkylamino, Cι-C4alkyl, ester, carbamate, carbonate, or ether. 2. The compound according to claim 1, wherein R is 2- benzimidazole. 3. The compound according to claim 1, wherein R] is 2- imidazopyridine. 4. The compound according to claim 1, wherein said compound is 2-(lH-Benzimidazol-2-ylmethyl)-5-(4-chloro-benzyl)-2-aza-bicyclo[2.2.2]octane; 2-(lH-Benzιmιdazol-2-ylmethyl)-5-benzyl-2-aza-bιcyclo[2.2.2]octane; 5-(4-Chloro-benzyl)-2-(3H-ιmιdazo[4,5-b]pyndιn-2-ylmethyl)-2-aza- bιcyclo[2.2.2]octane; or 2-(3-Benzyl-8-aza-bιcyclo[3.2 l]oct-8-ylmethyl)-3H-ιmιdazo[4,5-b]pyπdιne 5. The compound according to claim 1, wherein said compound is or 6 A pharmaceutical composition compnsmg an inert earner and an effective amount of a compound according to claim 1 7 The pharmaceutical composition according to claim 6 useful for the treatment of pam 8 The pharmaceutical composition according to claim 6 useful for the treatment of migraine, depression, anxiety, schizophrenia, Parkinson's disease, or stroke 9. A method of treating pam compnsmg a step of admimstenng to one in need of such treatment an effective amount of a compound according to claim 1 10 A method of treating migraine, depression, anxiety, schizophrenia, Parkinson's disease, or stroke compnsmg a step of administeπng to one in need of such treatment an effective amount of a compound according to claim 1

Inventors: CLAREMON DAVID A, MUNSON PETER M, THOMPSON WAYNE, CLAREMON, DAVID, A., MUNSON, PETER, M., THOMPSON, WAYNE
Applicants: CLAREMON DAVID A, MERCK & CO INC, MUNSON PETER M, THOMPSON WAYNE, CLAREMON, DAVID, A., MERCK & CO., INC., MUNSON, PETER, M., THOMPSON, WAYNE
Application year: 2000
Main classification: A61K31
IPC codes: A61K31, A61P25, C07D453, C07D519