Cyclohexylamine derivatives as subtype selective nmda receptor antagonists

Described are cyclobexylamine derivatives of Formula I, Formula II, or Formula III and their pharmaceutically acceptable salts thereof: The compounds are antagonists of NMDA receptor channel complexes useful for treating cerebral vascular disorders such as, for example, cerebral ischemia, cardiac arrest, stroke, and Parkinson's disease. The substituents are described in the specification.

FIELD OF THE INVENTION

The invention pertains to cyclohexylamine derivatives as N-Methyl-D-Aspartate Antagonists (NMDA).

BACKGROUND OF THE INVENTION

Over excitation of NMDA receptor channel complexes on postsynaptic neurons following excessive release of glutamic acid from synaptosomes and glutamic acid from synaptosomes and glial cells result in a massive calcium ion influx into the neuronal cells, which leads to their death. This is believed to occur under ischemic or hypoxic conditions such as stroke, hypoglycemic, cardiac arrest and physical trauma. An NMDA receptor antagonist might be therapeutically useful because it may minimize damage of the central nervous system (CNS) induced by ischemic or hypoxic conditions. The NMDA receptor channel complex consists of at least three binding domains including glutamic acid (or NMDA) recognition site, channel blocking binding site, and strychnine-insensitive glycine binding type. Physiologically, a blockade of at least one of these sites terminates the channel opening of the NMDA receptor to prevent a calcium ion influx (Nagata R. et al., J. Med. Chem., 1994;37:3956-3968).

Excessive excitation by neurotransmitters may be responsible for the loss of neurons in cerebral vascular disorders such as cerebral ischemia or cerebral infauxtion resulting in a range of conditions such as thromboembolic or hemorrhagic stroke, cerebral vasospasm, hypoglycemia, cardiac arrest, status epilepticus, perinatal, asphyxia anoxia, such as from near drowning, pulmonary surgery and cerebral trauma, as well as lathyrism, Alzheimer's disease, and Huntington's disease. Such conditions likewise suggest the use of agents that may act as antagonists in the receptors identified above may lead to treatment of amyotrophic lateral sclerosis (ALS), schizophrenia, parkinsonism, epilepsy, anxiety, pain, and drug addiction (PCT/EPO 94/01492 having publication number WO 94/26747 published Nov. 24, 1994, Watjen et al.).

L-glutamic acid, L-aspartic acid, and a number of other closely related amino acids have the ability to activate neurons in the nervous system and therefor the vast majority of excitatory neurons in the mammalian CNS. Interaction with glutamic acid mediated neurotransmission is considered a useful approach in the treatment of neurological and psychiatric diseases (WO 94/26746, published Nov. 24, 1994, Jacobsen et al.).

Excitatory amino acid receptor antagonists that block NMDA receptors are recognized for usefulness in the treatment of a variety of disorders. NMDA receptors are intimately involved in the phenomenon of excitotoxicity, which may be a critical determinant of outcome of several neurological disorders. Disorders known to be responsive to blockade of the NMDA receptor include acute cerebral ischemia (stroke or cerebral trauma, for example), muscular spasm, convulsive disorders, neuropathic pain and anxiety, and may be a significant causal factor in chronic neurodegenerative disorders such as Parkinson's disease (Klockgether T., Turski L., Ann. Neurol., 1993;34:585-593); human immunodeficiency virus (HIV) related neuronal injury, amyotrophic laterial sclerosis (ALS), Alzheimer's disease (Francis P. T., Sims N. R., Procter A. W., Bowen D. M., J. Neurochem., 1993;60(5):1589-1604); and Huntington's disease (see Lipton S., TINS, 1933;16(12):527-532; Lipton V, Rosenberg P. A., New Eng. J. Med., 1994;330(9):613-622; and Bigge C. F., Biochem. Pharmacol., 1993;45:1547-1561, and references cited therein). NMDA receptor antagonists may also be used to prevent tolerance to opiate analgesia or to help control withdrawal symptoms from addictive drugs (European Patent Application 488,959A).

Many of the properties of native NMDA receptors are seen in recombinant homomeric NR1 receptors. These properties are altered by the NR2 subunits. Recombinant NMDA receptors expressed in Xenopus Oocytes have been studied by voltage-clamp recording, and has developmental and regional expression of the mRNAs encoding NMDA receptor subunits. Electrophysiological assays were utilized to characterize the actions of compounds at NMDA receptors expressed in Xenopus Oocytes. The compounds were assayed at four subunit combinations at cloned rat NMDA receptors, corresponding to three putative NMDA receptor subtypes (Moriyoshi et al., Nature, 1991;354:31-37; Monyer et al., Science, 1992; 256:1217-1221; Kutsuwada et al, Nature, 1992;358:36-41; Sugihara et al., Biochem. Biophys Res. Commun., 1992;185:826-832).

Expression cloning of the first NMDA receptor subunit, NMDAR1 (NR1) in Nakanishi's lab in 1991 provided an initial view of the molecular structure of the NMDA receptor (Moriyoshi, supra., 1991). There are several other structurally related subunits (NMDAR2A through NMDAR2D) that join NR1 in heteromeric assemblies to form the functional ion channel complex of the receptor ( Annu. Rev. Neurosci., 1994; 17:31-108). The molecular heterogeneity of NMDA receptors implies a future potential for agents with subtype selective pharmacology.

SUMMARY OF THE INVENTION

Described are cyclohexylamines derivatives of Formula I and their pharmaceutically acceptable salts thereof

Ar is substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl, which heteroaryl is from 5 to 14 atoms having from 1 to 2 heteroatoms selected from the group consisting of N, O, and S with from 0 to 2 substituents for each; the substituents are from the groups F, Cl, Br, I, CN, NO 2 , OCH 3 , OC(O)CH 3 , CF 3 , OCH 2 CH 2 OH or N(CH 3 ) 2 ;

E is hydrogen or OH;

d is an integer of from 0 to 2;

n is an integer from 1 to 6;

q is an integer from 0 to 6;

X is independently selected from hydrogen or an electron withdrawing group;

Y is a hydrogen bond donor group; and

* denotes cis or trans or a mixture thereof.

The invention also relates to compounds of Formula II

or a pharmaceutically acceptable salt thereof wherein:

Ar is substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl, which heteroaryl is from 5 to 14 atoms having from 1 to 2 heteroatoms selected from the group consisting of N, O, and S with from 0 to 2 substituents for each; the substituents are from the groups F, Cl, Br, I, CN, NO 2 , OCH 3 , OC(O)CH 3 , CF 3 , OCH 2 CH 2 OH, or N(CH 3 ) 2 ;

E is hydrogen or OH;

d is an integer from 0 to 2;

t is an integer from 1 to 3;

X is independently selected from hydrogen or an electron withdrawing group;

Y is a hydrogen bond donor group; and

* denotes cis or trans or a mixture thereof.

The invention is also concerned with a pharmaceutical composition useful for treating disorders responsive to the selective blockade of N-methyl-D-aspartate receptor subtypes in a mammal, including a human, suffering therefrom which comprises a therapeutically effective amount of at least one compound of Formula I, or Formula II or Formula III, and the pharmaceutically acceptable salts thereof. The composition is useful for treating optionally disorders such as stroke, cerebral ischemia, trauma, hypoglycemia, neurodegenerative disorders, anxiety, depression, migraine headache, convulsions, aminoglycoside antibiotic-induced hearing loss, psychosis, glaucoma, CMV retinitis, opioid tolerance or withdrawal, chronic pain, or urinary incontinence.

The invention is also concerned with a method of treating disorders responsive to the selective blockade of the N-methyl-D-aspartate receptor subtypes in a mammal, including a human, suffering therefrom which comprises administering in unit dosage form, at least one compound represented by Formulas I-III or their pharmaceutically acceptable salts thereof.

DETAILED DESCRIPTION OF THE INVENTION

In the compounds of the present invention preferred are compounds of Formula I or pharmaceutically acceptable salts thereof. Even more preferred are those compounds of Formula I wherein:

X is independently selected from hydrogen or an electron withdrawing group selected from the group consisting of halogen, nitro, cyano, aminoalkyl, CF 3 , C(O)CH 3 , and haloalkyl; and

Y is a hydrogen bond donor group selected from the group consisting of OH, heterocycle, which heterocycle is a carboxylic acid or an amide isostere, NH 2 , SH, and NHR 7 , wherein R 7 is alkyl, aralkyl, C(O)R 8 , C(O)OR 8 , C(O)NHR 8 , SO 2 R 8 , or SO 2 NHR 8 , and R 8 is alkyl, aralkyl, or aryl.

More preferred are compounds of Formula I or pharmaceutically acceptable salts thereof wherein:

Ar is unsubstituted or substituted phenyl;

E is hydrogen;

X is independently selected from hydrogen or an electron withdrawing group selected from the group consisting of halogen, nitro, cyano, aminoalkyl, CF 3 , C(O)CH 3 , and haloalkyl; and

Y is a hydrogen bond donor group selected from the group consisting of OH, heterocycle, which heterocycle is a carboxylic acid or an amide isostere, NH 2 , SH, and NHR 7 , wherein R 7 is alkyl, aralkyl, C(O)R 8 , C(O)OR 8 , C(O)NHR 8 , SO 2 R 8 , or SO 2 NHR 8 , and R 8 is alkyl, aralkyl, or aryl; and

Still more preferred are compounds of Formula I or pharmaceutically acceptable salts thereof wherein:

E is hydrogen;

Ar is unsubstituted or substituted phenyl;

Z is as defined above and further a group wherein:

Ar and the nitrogen atom in Formula I are separated by from 2 to 4 atoms;

X is hydrogen or an electron withdrawing group selected from the group consisting of halogen, nitro, cyano, aminoalkyl, alkyl, CF 3 , C(O)CH 3 , and haloalkyl;

Y is a hydrogen bond donor group selected from the group consisting of OH, heterocycle, which heterocycle is a carboxylic acid or an amide isostere, NH 2 , SH, and NHR 7 , wherein R 7 is alkyl, aralkyl, C(O)R 8 , C(O)OR 8 , C(O)NHR 8 , SO 2 R 8 , or SO 2 NHR 8 , and R 8 is alkyl, aralkyl, or aryl; and

Still more preferred are compounds of Formula I or pharmaceutically acceptable salts thereof wherein:

Ar is unsubstituted or substituted phenyl;

E is hydrogen;

Y is OH;

wherein m is an integer of from 1 to 3;

X is hydrogen; and

Most preferred is a compound selected from those listed below:

Preferred are compounds of Formula II or pharmaceutically acceptable salts thereof wherein:

X is independently selected from hydrogen or an electron withdrawing group selected from the group consisting of halogen, nitro, cyano, aminoalkyl, CF 3 , C(O)CH 3 , and haloalkyl; and

Y is a hydrogen bond donor group selected from the group consisting of OH, heterocycle, which heterocycle is a carboxylic acid or an amide isostere, NH 2 , SH, and NHR 7 , wherein R 7 is alkyl, aralkyl, C(O)R 8 , C(O)OR 8 , C(O)NHR 8 , SO 2 R 8 , or SO 2 NHR 8 , and R 8 is alkyl, aralkyl, or aryl.

More preferred are compounds of Formula II or pharmaceutically acceptable salts thereof wherein:

E is hydrogen;

Ar is unsubstituted or substituted phenyl;

Y is a hydrogen bond donor group selected from the group consisting of OH, heterocycle, which heterocycle is a carboxylic acid or an amide isostere, NH 2 , SH, and NHR 7 , wherein R 7 is alkyl, aralkyl, C(O)R 8 , C(O)OR 8 , C(O)NHR 8 , SO 2 R 8 , or SO 2 NHR 8 , and R 8 is alkyl, aralkyl, or aryl;

X is independently selected from hydrogen or an electron withdrawing group selected from the group consisting of halogen, nitro, cyano, aminoalkyl, CF 3 , C(O)CH 3 , and haloalkyl; and

Still more preferred are compounds of Formula II or pharmaceutically acceptable salts thereof wherein:

E is hydrogen;

Ar is unsubstituted or substituted phenyl;

T is a group wherein Ar and the nitrogen atom bearing R are separated by 3 or 4 atoms;

Y is a hydrogen bond donor group selected from the group consisting of OH, heterocycle, which heterocycle is a carboxylic acid or an amide isostere, NH 2 , SH, and NHR 7 , wherein R 7 is alkyl, aralkyl, C(O)R 8 , C(O)OR 8 , C(O)NHR 8 , SO 2 R 8 , or SO 2 NHR 8 , and R 8 is alkyl, aralkyl, or aryl;

X is independently selected from hydrogen or an electron withdrawing group selected from the group consisting of halogen, nitro, cyano, CF 3 , C(O)CH 3 , and haloalkyl; and

Still more preferred are compounds of Formula II or pharmaceutically acceptable salts thereof wherein:

Ar is unsubstituted or substituted phenyl;

E is hydrogen;

Y is OH;

X is hydrogen; and

Another preferred compound is that of Formula III

with the substituents Y, X, d, W, R 1 , R 2 , V, R, E, and Ar are as described above for Formula I.

Other preferred compounds of Formulas I-III are those above where * denotes cis instead of trans.

Alkyl groups having two or more carbons may optionally contain 1 or 2 sites of unsaturation, the groups being known as alkenyl groups or radicals. Illustrative examples of an alkenyl group or radical having from 2 to 12 carbon atoms, also known as a C 2 to C 12 alkenyl, include ethenyl, 1-propenyl, 2-propenyl, 1-buten-1-yl, 2-buten-1-yl, 1-penten-1-yl, 2-penten-1-yl, 1-penten-3-yl, 1-penten-5-yl, 1-hexen-1-yl, 1-hexen-4-yl, 2-hexen-1-yl, 3-hexen-1-yl, 2-octen 3-yl, 5-nonen-2-yl, 4-undecen-4-yl, and 5-dodecen-2-yl.

The term aryl means an aromatic carbocyclic ring having from 6 to 10 carbon atoms. Illustrative examples of an aryl group or radical include phenyl, 1-naphthyl, and 2-naphthyl. Aryl groups may be unsubstituted or independently substituted by from 1 to 3 substituents selected from F, Cl, Br, I, CN, NO 2 , OCH 3 , OC(O)CH 3 , CF 3 , OCH 2 CH 2 OH, or N(CH 3 ) 2 . Phenyl is not substituted in the 4-position with a hydrogen bond donor group Y.

The term aralkyl means an aryl-alkyl-group or radical wherein aryl and alkyl have the meanings as defined above. Illustrative examples of an arylalkyl group or radical include benzyl, 4-fluorophenylmethyl, 2-phenylethyl, 3-phenylpropyl, 4-phenylbutyl, 3-methyl-3-phenylpropyl, 1-naphthylmethyl, 1-naphthylethyl, 3-(1-naphthyl)-propyl, 4-(1-naphthyl)-butyl, 4-(2-naphthyl)-butyl, 4-phenylheptyl, and 12-(2-hydroxyphenyl)-dodec-3-yl.

The terms (C 3 -C 7 cycloalkyl)alkyl or cycloalkyl (3-7 carbon atoms) alkyl means an alkyl group (as described above) substituted thereon by a cycloalkyl group of from 3 to 7 carbon atoms as cyclopentyl, cyclopropyl, cyclohexyl, and cycloheptyl.

The term heteroatom means nitrogen, oxygen, or sulfur.

As used above, a fused bicyclic group or radical is a group wherein two ring systems share two and only two atoms.

As used above, a fused tricyclic group or radical is a group wherein three ring systems share four and only four atoms.

The term heteroaralkyl means a heteroaryl-alkyl-group or radical wherein heteroaryl and alkyl have the meanings as defined above. Illustrative examples of an heteroaralkyl group or radical include 4-pyridyl-methyl, (4-fluoro-quinolin-2-yl)methyl, 2-(isoxazol-3-yl)ethyl, and 12-(5-chlorothiophen-2-yl)-dodec-3-yl.

The term halogen means bromine, chlorine, fluorine, or iodine.

The term aminoalkyl means an H 2 N-alkyl-group or radical wherein alkyl has the meaning as defined above, which is a substituted alkyl or radical containing from 1 to 3 substituents wherein at least one substituent is NH 2 .

The term hydroxyalkyl means an HO-alkyl-group or radical wherein alkyl has the meaning as defined above, which is a substituted alkyl group or radical containing from 1 to 3 substituents wherein at least one substituent is OH.

The term amino(hydroxy)alkyl means an H 2 N(HO)-alkyl-group or radical wherein alkyl has the meaning as defined above, which is a substituted alkyl group or radical containing from 2 or 3 substituents wherein at least one substituent is OH and one substituent is NH 2 .

The term (aminocarbonyl)alkyl means an H 2 NC(O)-alkyl-group or radical wherein alkyl has the meaning as defined above, which is a substituted alkyl group or radical containing from 1 to 3 substituents wherein at least one substituent is (O)C NH 2 .

The term thioalkyl means an HS-alkyl-group or radical wherein alkyl has the meaning as defined above, which is a substituted alkyl group or radical containing from 1 to 3 substituents wherein at least one substituent is SH.

The term (methylthio)-alkyl- means a CH 3 S-alkyl-group or radical wherein alkyl has the meaning as defined above, which is a substituted alkyl group or radical containing from 1 to 3 substituents wherein at least one substituent is SCH 3 .

The term carboxyalkyl means an HO 2 C-alkyl-group or radical wherein alkyl has the meaning as defined above, which is a substituted alkyl group or radical containing from 1 to 3 substituents wherein at least one substituent is CO 2 H.

The term haloalkyl means a halogen-alkyl-group or radical wherein halogen and alkyl have the meanings as defined above, which is a substituted alkyl group or radical containing from 1 to 3 substituents wherein at least one substituent is selected from F, Cl, Br, or I.

The term ureidoalkyl means an H 2 N (C O) NH-alkyl-group or radical wherein alkyl has the meanings as defined above, which is a substituted alkyl group or radical containing from 1 to 3 substituents wherein at least one substituent is H 2 N (C O) NH .

The term alkenylalkyl means a (C 2 -C 12 alkenyl)-(C 1 -C 12 alkyl)-group or radical wherein alkenyl and alkyl have the meanings defined above.

The phrase heterocycle, which heterocycle is a carboxylic acid or an amide isostere means a 5- or 6-membered monocyclic ring containing from 1 to 4 heteroatoms selected from N, O, and S and providing a hydrogen bond donor moiety selected from NH, OH, and SH. Illustrative examples include the following structures:

The term entgegen means the stereoisomerism about a carbon-carbon double bond wherein the highest ranking substituent on each carbon are on opposite sides, which substituent ranking is based on the sequence rules of the Cahn-Ingold-Prelog system (March J., supra., 1993:109,127 and references cited therein).

The term zusammen means the stereoisomerism about a carbon-carbon double bond wherein the highest ranking substituent on each carbon are on the same side, which substituent ranking is based on the sequence rules of the Cahn-Ingold-Prelog system (March J., Advanced Organic Chemistry, 4 th ed., New York: John Wiley & Sons, 1992;109, 127-133 and references cited therein).

The term cis means the stereoisomerism about a carbon-carbon double bond, a monocyclic ring, a fused bicyclic ring, or a bridged bicyclic ring wherein the highest ranking substituent on each of the two carbons of relevance are on the same side, which substituent ranking is based on the sequence rules of the Cahn-Ingold-Prelog system (March, J., Advanced Organic Chemistry, 4 th ed., 1992, New York: John Wiley & Sons, 1992:109, 127-133 and references cited therein).

The term trans means the stereoisomerism about a carbon-carbon double bond, a monocyclic ring, a fused bicyclic ring, or a bridged bicyclic ring wherein the highest ranking substituent on each of the two carbons of relevance are on opposite sides, which substituent ranking is based on the sequence rules of the Cahn-Ingold-Prelog system (March J., supra., 1992; 109:127-133 and references cited therein).

The terms cis or trans refers to the relative stereochemistry of the groups attached to the cyclohexyl rings of Formulas I or II at the carbon atoms denoted by *.

The term (X) d wherein d is an integer from 0 to 2 means the group X is present 0 to 2 times on the phenylene to which it is attached, which group is independently selected from hydrogen or an electron withdrawing group wherein the electron withdrawing group is as defined above unless otherwise stated. The groups X can be the same or different.

The terms

wherein n is an integer of from 1 to 6 and q is an integer of from 0 to 6 mean a chain of from 1 to 6 carbons or from 0 to 6 carbons, respectively, wherein each carbon is independently substituted, which substituents are the groups R 1 and R 2 , wherein R 1 and R 2 are independently (R 1 and R 2 in each occurrence can be the same or different) selected from the groups consisting of hydrogen, alkyl, OH, hydroxyalkyl, aminolkyl, aralkyl, or N(R 4 )(R 5 ) wherein R 4 and R 5 are independently selected from hydrogen, alkyl, aralkyl, heteroaryl, heteroaralkyl, aminoalkyl, hydroxyalkyl and thioalkyl, unless otherwise stated. The groups R 1 can be the same or different and the groups R 2 can be the same or different.

For purposes of the syntheses of the compounds of the present invention, reactive functional groups present in starting materials, reaction intermediates, or reaction products may be protected during chemical reactions using protecting groups which render the reactive functional groups substantially inert to the reaction conditions (see for example, Green T. W., Wuts P. G., Protective Groups in Organic Synthesis, 2nd ed. New York: John Wiley & Sons, 1991). Thus, for example, protecting groups such as the following may be utilized to protect suitable amino, hydroxyl, and other groups of related reactivity: carboxylic acyl groups, such as formyl, acetyl, trifluoroacetyl; alkoxycarbonyl groups, such as ethoxycarbonyl, t-butoxycarbonyl (BOC), , , -trichloroethoxycarbonyl (TCEC), -iodoethoxycarbonyl; aryloxycarbonyl groups, such as benzyloxycarbonyl, methoxybenzyloxycarbonyl, phenoxycarbonyl; trialkyl silyl groups, such as trimethylsilyl and t-butyldimethylsilyl (TBDMS); and groups such as trityl, tetrahydropyranyl, vinyloxycarbonyl, o-nitrophenylsulfenyl, diphenylphosphinyl, toluenesulfonyl, and benzyl may all be utilized. The protecting group may be removed, after completion of the synthetic reaction of interest, by procedures known to those skilled in the art. For example, a BOC group may be removed by acidolysis, a trityl group by hydrogenolysis, TBDMS by treatment with fluoride ions, and TCEC by treatment with zinc.

It is to be appreciated that the compounds of Formulas I-III may have chiral centers in which case, all stereoisomers thereof both separately and as racemic and/or diastereoisomeric mixtures are included.

Some of the compounds of Formulas I-III are capable of further forming pharmaceutically acceptable acid-addition and/or base salts. All of these forms are within the scope of the present invention.

The acid addition salt of said basic compounds are prepared by contacting the free base form with a sufficient amount of the desired acid to produce the salt in the conventional manner.

Pharmaceutically acceptable base addition salts are formed with metals or amines, such as alkali and alkaline earth metals or organic amines. Examples of metals used as cations are sodium, potassium, magnesium, calcium, and the like. Examples of suitable amines are N,N-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine, dicyclohexylamine, ethylenediamine, N-methylglucamine, and procaine (see, for example, Berge, supra., 1977).

The base addition salts of said acidic compounds are prepared by contacting the free acid form with a sufficient amount of the desired base to produce the salt in the conventional manner.

Certain of the compounds of the present invention can exist in unsolvated forms as well as solvated forms, including hydrated forms. In general, the solvated forms, including hydrated forms, are equivalent to unsolvated forms and are intended to be encompassed within the scope of the present invention.

The compounds of the present invention can be prepared and administered in a wide variety of oral and parenteral dosage forms. Thus, the compounds of the present invention can be administered by injection, that is, intravenously, intramuscularly, intracutaneously, subcutaneously, intraduodenally, or intraperitoneally. Also, the compounds of the present invention can be administered by inhalation, for example, intranasally. Additionally, the compounds of the present invention can be administered transdermally. It will be obvious to those skilled in the art that the following dosage forms may comprise as the active component, either a compound of Formulas I-III or a corresponding pharmaceutically acceptable salt of a compound of Formulas I-III.

In tablets, the active component is mixed with the carrier having the necessary binding properties in suitable proportions and compacted in the shape and size desired.

For preparing suppositories, a low-melting wax, such as a mixture of fatty acid glycerides or cocoa butter, is first melted, and the active component is dispersed homogeneously therein, as by stirring. The molten homogenous mixture is then poured into convenient sized molds, allowed to cool, and thereby to solidify.

Aqueous solutions suitable for oral use can be prepared by dissolving the active component in water and adding suitable colorants, flavors, stabilizing and thickening agents as desired.

The quantity of active component in a unit dose preparation may be varied or adjusted from 0.1 mg to 100 mg preferably 0.5 mg to 100 mg according to the particular application and the potency of the active component. The composition can, if desired, also contain other compatible therapeutic agents.

In therapeutic use as antagonists or as agents for the treatment of diseases, the compounds utilized in the pharmaceutical method of this invention are administered at the initial dosage of about 0.01 mg to about 100 mg/kg daily. A daily dose range of about 0.01 mg to about 10 mg/kg is preferred. The dosages, however, may be varied depending upon the requirements of the patient, the severity of the condition being treated, the compound being employed. Determination of the proper dosage for a particular situation is within the skill of the art. Generally, treatment is initiated with smaller dosages, which are less than the optimum dose of the compound. Thereafter, the dosage is increased by small increments until the optimum effect under the circumstances is reached. For convenience, the total daily dosage may be divided and administered in portions during the day, if desired.

Tablet Formulation Ingredient Amount (mg) Compound 1 25 Lactose 50 Cornstarch (for mix) 10 Cornstarch (paste) 10 Magnesium stearate (1%) 5 Total 100 Compound 1 lactose and cornstarch (for mix) are blended to uniformity. The cornstarch (for paste) is suspended in 200 mL of water and heated with stirring to form a paste. The paste is used to granulate the mixed powders. The wet granules are passed through a No. 8 hand screen and dried at 80 C. The dry granules are lubricated with the 1% magnesium stearate and pressed into a tablet. Such tablets can be administered to a human from one to four times a day for treatment of disease caused by over excitation of NMDA receptor channel complexes.

The compounds of the present invention can be prepared according to the various synthetic schemes that follow. Protecting groups may be used when appropriate throughout many of the schemes. Although specifically noted in certain schemes, the appropriate use and choice of protecting groups is well-known by one skilled in the art, and is not limited to the specific examples below. It is also understood that such groups not only serve to protect chemically reactive sites, but also to enhance solubility or otherwise change physical properties. A good general reference for protecting group preparation and deprotection is Protective Groups in Organic Synthesis by Green, supra., 1991. A number of general reactions such as oxidations and reductions are not shown in detail but can be done by methods understood by one skilled in the art. General transformations are well reviewed in Comprehensive Organic Transformation by Richard Larock, and the series Compendium of Organic Synthetic Methods published by Wiley-Interscience, 1989. In general, the starting materials were obtained from commercial sources unless otherwise indicated.

Preparation of Compounds

These compounds can be prepared following the procedures described in the examples below.

General Methods

HCl salts were prepared by treatment of a MeOH solution of the amine with excess HCl in Et 2 O (1 M). The salts were isolated either by filtration if they precipitated directly from the etherial solution, or by first removal of the solvent under reduced pressure, and then crystallization (Et 2 O/MeOH).

Purity was determined by reversed phase HPLC by the following methods:

Preparation of trans-1-Amino-4-phenylcyclohexane 5

Preparation of trans-4- 2-(4-Phenylcyclohexylamino)ethyl phenol

Electrophysiological Assays at NMDA Receptor Subunits

Preparation of RNA. cDNA clones encoding the NR1A, NR2A, NR2B, and NR 2 C rat NMDA receptor subtypes were used. (See Moriyoshi et al., Nature , (Lond.), 1991;354:31-37); Kutsuwada et al., Nature (Lond.), 1992;358:36-41; Monyer et al., Science (Washington, D.C.), 1992;256:1217-1221; Ikeda et al., FEBS Lett., 1992;313:34-38; Ishii et al., J. Biol. Chem., 1993;268:2836-2843 for details of these clones or their mouse homologs.) The clones were transformed into appropriate host bacteria, and plasmid preparations were made with conventional DNA purification techniques. A sample of each clone was linearized by restriction enzyme digestion of cRNA was synthesized with T3 RNA polymerase. The cRNA was diluted to 400 ng/ L and stored in 1- L aliquots at 80 C. until injection.

Electrical recordings were made using a conventional two-electrode voltage clamp (Dagan TEV-200) over periods ranging between 3 to 21 days following injection (Woodward et al., Mol. Pharmacol., 1992;41:89-103). Oocytes were placed in a 0.1 mL recording chamber continuously perfused (5-15 mL min 1 ) with frog Ringer's solution containing (in mM): NaCl, 115; KCL, 2; BaCl 2 , 1.8; HEPES, 5; pH 7.4. Drugs were applied by bath perfusion. Using oocytes expressing different subunit combinations of NMDA receptor, NMDA currents were activated by co-application of glutamate (100 M) and glycine (1-100 M). Inhibitory potency of the novel antagonists was assessed on responses elicited by fixed concentrations of glutamate and glycine, by measuring reductions in current induced by progressively increasing concentrations of antagonist.

Concentration-inhibition curves were fit with Equation 1.

In which I control is the current evoked by agonists alone, pIC 50 log IC 50 , IC 50 is the concentration of antagonist that produced half maximal inhibition, and n is the slope factor (De Lean et al., Am. J. Physiol., 1978;235:E97-102). For incomplete curves, analysis by fitting was unreliable, and IC 50 values were calculated by simple regression over linear portions of the curves (Origin: Microcal Software). The electrophysiological assay results are set forth in Table 1.

6-Hydroxydopamine-lesioned rats were used (see Ungerstedt, U., Arbuthnott, G. W., Quantitative recording of rotational behavior in rats after 6-hydroxy-dopamine lesions of the nigrostraiatal dopamine system. Brain Res., 1971;24(3):485-93). Adult male Sprague-Dawley rats were anesthetized with chloral hydrate, and unilateral lesions of the nigrostriatal dopamine system were accomplished by infusion of 8 g of 6-hydroxydopamine HBr (6-OHDA) into the right medial forebrain bundle. Rats were pretreated 30 minutes before surgery with desipramine HCl 25 mg/kg intraperitoneally (IP) to protect noradrenegic neurons, and pargyline 25 mg/kg IP to potentiate the effects of 6-OHDA. A minimum of 3 weeks after surgery, the rotational behavior induced by apomorphine HCL 50 g/kg subcutaneously (SC) was assessed. Only rats demonstrating more than 100 contraversive turns/hour to apomorphine were used for the present experiments.

Rotational behavior was measured using an automatic rotometer system (Rotorat Rotational Activity System, MED Associates, Georgia, Vt.). Antiparkinsonian activity was assessed as the ability of the compound to potentiate the contraversive rotation induced by L-DOPA methyl ester, 10 mg/kg SC, over a 6-hour period. Experiments were conducted using a crossover paradigm where each rat received either a vehicle plus L-DOPA, or the test compound plus L-DOPA, in randomized order. Rats were tested at 7-day intervals. In experiments in which the compound was tested orally, rats were food deprived for 16 hours. Statistical analysis between treatment groups were performed using a paired t-test. The results were reported in Table 1 as the minimum effective dose (MED) of compound (mg/kg) required to produce a statistically-significant increase in total contraversive rotations compared to rats receiving L-DOPA only.

3 H Ifenprodil Binding Assay Protocol

Materials and Methods

All buffers and reagents used in assay incubations or to dissolve drugs were prepared using water purified through a Milli-Q reverse osmosis system (Millipore Corp, Bedford, Mass.) and treated with UV emissions. Prior to use in the assays, buffers were further filtered through a sterile Corning filtration unit (Corning Glass Works, Corning, N.Y.) containing a 0.2- m filter. Buffer used to rinse the membranes on the assay filters was prepared with purified water, but was not refiltered and was stored no longer than 5 days. Stock solutions of the drugs (usually 10 mM) were dissolved in 20 mM HEPES-KOH buffer pH 7.4 (assay buffer) with the addition of 1 to 5 L of glacial AcOH, if needed, to keep them in solution. For eliprodil the stock solution was buffer with the addition of 10% DMSO. All subsequent dilutions from stock were made in buffer.

Membrane Preparation

An extensively washed buffy coat membrane fraction was prepared from frozen adult rat forebrains (Zivic-Miller Laboratories, Inc, Zelienople, Pa.) as described previously (Coughenour L. L.; Cordon, J. J., J. Pharmacol. Exp. Ther., 1997;280:584-592) and stored at 80 C. On the day of the assay, pellets were resuspended in 35 mL of assay buffer at pH 7.4 using a Polytron setting 6. After incubation at 37 C. for 30 minutes in a shaking water bath, the homogenate was centrifuged 40,000 g for 10 minutes at 4 C. The pellets were resuspended in fresh buffer and centrifuged 3 more times before final suspension for use in the assay.

Binding Studies

3 H Ifenprodil Binding. Triplicate incubations were carried out in a volume of 0.5 mL in 1.3 mL polypropylene tubes (Marsh Biomedical Products Inc, Rochester, N.Y.) for 2 hours at room temperature. Incubations contained test agents, membranes (100-200 g protein) and 4 nM 3 H -ifenprodil in 20 mM HEPES-KOH buffer, pH 7.4 (assay buffer). Assays were started by addition of the membranes. Bound radioligand was separated by filtration under reduced pressure using a Tomtec Mach II, 96-well cell harvester (Tomtec Inc, Orange, Colo.). Filtration was through Whatman GF/B glass fiber filters (Whatman Ltd, Maidstone, England), which had been soaked for at least 15 minutes in 0.3% polyethylenimine and allowed to air dry. The filters were rinsed with 3 mL of ice-cold assay buffer within 6 seconds. Air was allowed to pass through the filters for an additional 10 seconds to remove residual moisture. The filter mat was supported on a cold ( 20 C.) teflon support, and filters from individual wells were separated and placed in Mini Poly-Q vials (Beckman Instruments Inc, Fullerton, Calif.) and filled with 4 mL of scintillation cocktail (Beckman Ready Protein ). Radioactivity retained on the filter was determined by liquid scintillation spectrophotometry. Nonspecific binding was defined as the binding in the presence of 1 mM ifenprodil. Specific binding was 90%.

3 H -TCP Binding. Binding assays were carried out essentially as described for 3 H ifenprodil binding. Incubations contained test agents, 100 g to 200 g protein, 2 nM 3 H TCP and 10 M glutamate, glycine, and spermidine. Incubations were for 10 m to allow assays to be carried out under nonequilibrium conditions for the detection of binding selective to NMDA receptors of the NR2B subtype. Specific binding was defined as the binding displaced by 100 M ( )MK-801 and was 90% of the total binding.

Control data was entered as 100%, and no parameters were constrained. Inhibition curves were compared by ANOVA with posttest comparisons of the log IC 50 using Dunnett's multiple comparisons posttest or Student's nonpaired, two-tailed t-test (GraphPad InStat software).