GB2343180A - Process for making pyrazinone compounds used as thrombin inhibitors - Google Patents

Abstract

The invention is a process for making thrombin inhibitor <EMI ID=1.1 HE=22 WI=66 LX=1013 LY=237 TI=CF> compounds of formula which comprises<BR> <SL COMPACT=COMPACT> <LI>```a) reacting <EMI ID=1.2 HE=11 WI=44 LX=1118 LY=555 TI=CF> with R<SP>3</SP>CN ad R<SP>2</SP>CH<SB>2</SB>CHO in a base selected from a trialkylamine and a metal alkoxide to form <EMI ID=1.3 HE=17 WI=51 LX=1094 LY=823 TI=CF> wherein<BR> ```R<SP>1</SP> is C<SB>1</SB>-C<SB>6</SB> alkyl or benzyl;<BR> ```R<SP>2</SP> is hydrogen,<BR> ```aryl, or<BR> ```C<SB>1</SB>-C<SB>6</SB> alkyl;<BR> HX is selected from hydrochloric acid, sulfuric acid, methanesulfonic acid, phosphoric acid, acetic acid, oxalic acid and hydrogen bromide;<BR> R<SP>3</SP> is potassium, sodium, lithium or trimethylsilyl;<BR> <LI>```b) cyclizing <U>II</U> with oxalyl chloride to form <EMI ID=1.4 HE=126 WI=73 LX=999 LY=1527 TI=CF> <LI>c) aminating <U>III</U> with phenethylamine to produce <LI>d) saponifying and hydrogenating <U>IV</U> to produce <LI>e) coupling <U>V</U> to </SL> to form

Description

TITLE OF THE INVENTION PROCESS FOR MAKING A THROMBIN INHIBITOR BACKGROUND OF THE INVENTION The synthesis of alpha-aminonitriles using timethylsilylcyanide, an aldehyde and a primary amine was described by Gibson et al., Tetrahedron Letters 1992, p. 6295. The Strecker reaction of ethyl glycine and acetaldehyde with potassium cyanide is described in Chem. Berichte. 59 p. 1500 (1926).

Neber et al., Ann., 515,283 (1935) describe rearrangement of oxime tosylates and isolation of an azirine-pyridine-hydrochloride complex from 2,4dinitrodesoxybenzoin oxime tosylate. O'Brien, Chemical Reviews Vol. 64, Number 2, pp. 81-89 (1964) describes Neber rearrangement of ketoxime O-sulfonates to amino ketones. LaMattina et al., SYNTHESIS April 1980 pp. 329-330, describes the use of the Neber rearrangement for the synthesis of alpha-amino acetals.

Patent publications WO 9740024 and WO 9808840 describe synthesis of 3-aminopyrazinones as thrombin inhibitors (e. g. 3-(2-phenylethylamino)6-methyl-1-(2-amino-6-methyl-5-methylene-carboxamidomethylpyndinyl)-2pyridinone) and integrin antagonists respectively. Specifically, synthesis of the pyridinone is described in WO 9740024 on pages 52-58. The described procedure employs a step for forming a glycine free base starting material. The procedure also employs halogenated solvents such as methylene chloride. The present invention employs glycine ethyl ester hydrochloride, eliminating the need for the extra process step for forming the glycine free base. Furthermore, the process of the invention does not use halogenated solvents.

SUMMARY OF THE INVENTION THE INVENTION IS A PROCESS FOR MAKING

which comprises a) reacting

with R3CN and R2CH2CHO and a base selected from the group consisting of a trialkylamine and a metal alkoxide to form

wherein R is Ci-C6 alkyi or benzyl; R is hydrogen, aryl, or C,-C6 alkyl ; HX is selected from the group consisting of hydrochloric acid, sulfuric acid, methanesulfonic acid, phosphoric acid, acetic acid, oxalic acid and hydrogen bromide ; R3 is potassium, sodium, lithium or trimethylsilyl; b) cyclizing II with oxalyl chloride to form

c) aminating III with phenethylamine to produce

d) saponifying and hydrogenating IV to produce

e) coupling V with

to form

DETAILED DESCRIPTION OF THE INVENTION In one embodiment of this process, R'is ethyl or benzyl; R2 is hydrogen; the base is tributylamine; HX is HCI ; and R3 is trimethylsilyl.

The invention also includes a process for forming

which comprises saponifying and hydrogenating

The invention also includes the compound

The invention also includes a process for making

which comprises reducing

with hydrogen in the presence of a porous metallic nickel catalyst, e. g. Raney nickel.

The invention also includes a process for making

which comprises cyanating

The invention also includes a process for making

comprising coupling

with

The invention also includes a process for forming 1 (Ethoxycarbonylmethyl)-3-hydroxy-pyrazinone

which comprises cyclizing

1- (Ethoxycarbonylmethyl)-3-hydroxy-pyrazinone can be used, following procedures similar to the one outlined in Example 7 on pages 50-53 of WO 9911267, to make thrombin inhibitors such as 3-(2, 2-difluoro-2-phenylethylamino)-1-(2-amino-6- methyl-5-methylenecarboxamido-methylpyridinyl)-pyrazin (lH)-2-one bis-TFA salt.

The invention also includes a process for making chloroacid

which comprises chlorinating dione

The invention also includes a process for making mesyloxime

which comprises treating acetone oxime with methanesulfonyl chloride and triethylamine.

The invention also includes a process for making oxamide acetal

which comprises adding ethyl oxamate

to aminoacetal

Reaction step a) proceeds by adding the amino ester salt to a solvent such as tetrahydrofuran, an acetate solvent (e. g., isopropyl acetate, ethyl acetate) or an alcoholic solvent (e. g. ethanol, methanol) after which the base and cyano compound and aldehyde are added to provide the desired cyano ester salt.

Cyclizing step b) proceeds by adding the cyano ester salt to a solvent such as an acetate solvent (e. g., ethyl acetate, isopropyl acetate) or toluene, and then using oxal chloride or oxalyl bromide to form the desired pyrazinone. Amination step c) proceeds by adding aqueous carbonate or bicarbonate (e. g. potassium carbonate, lithium carbonate, sodium carbonate, potassium bicarbonate, lithium bicarbonate, sodium bicarbonate) to the pyrazinone, and adding phenylethylamine under heated conditions to form the amidine. Saponification step d) proceeds under standard saponification conditions with a metal hydroxide (e. g. lithium hydroxide, sodium hydroxide, potassium hydroxide) in an alcoholic solvent (e. g. methanol, ethanol).

The amidine is combined with a branched or n-alcool (e. g., methanol, ethanol, butanol, propanol) and a metal hydroxide (e. g. sodium hydroxide, lithium hydroxide, potassium hydroxide) and hydrogenated to form the desired acid. Coupling step e) proceeds under standard coupling conditions using the acid, pyridine diamine dihydrochloride and an imide coupling reagent (e. g., diisopropylcarbodiimide, 1- (3- Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, dicyclohexyldiimide).

Reduction of 2-amino-S-bromo-6-picoline to pyridine diamine dihydrochloride is achieved using a porous metallic nickel catalyst such as Raney Nickel under standard reducing conditions, first forming cyanopyridine from the picoline derivative using copper cyanide, sodium cyanide, potassium cyanide, zinc cyanide, Co (CN) 2, Ni (CN) 2, Pd (CN) 2 alone or in the presence of a lead catalyst or in case of Co (CN) 2, Ni (CN) 2, or Pd (CN) 2 in the presence of a reducing agent such as zinc alone or in the presence of a ligand such as PPh3, and then subjecting the aminopyridine to reducing conditions.

Hydrogenation with a porous metallic catalyst according to the procedure of the present invention is achieved using a commercially available activated, hydrogen containing porous metallic nickel catalyst, e. g. commercially available from the Raney Catalyst Co., Inc. (Chattanooga, TN) and Girdler Catalysts, Chemical Products Division, Chemetron Corporation, (Louisville, KY). In one example, the catalyst is Raney NickelS of the type that is prepared by fusing equal parts of nickel with aluminum in the presence of sodium hydroxide, leading to a material having the formula Ni2H with residual amounts of aluminum. The catalyst may be preapred in various grades differentiated by catalyst concentration (for grade W-2, see R. Mozingo, Org. Syn., Coll. Vol. 3,181 (1955); for grades W-3 to W-7, see H. R. Billica and H. Adkins, Org. Syn., Coll. Vol. 3,176 (1955) and X. A. Dominguez et al., J. Org. Chem., 26,1625 (1961).

The term"Cl-C6 alkyl"as used herein except where noted, means an alkyl group having between 1 and 6 straight chain carbons which may be unsubstituted or which may be substituted at 1,2,3,4,5 or 6 carbon atoms with C- C6 alkyl, hydroxy, C,-C6 alkoxy, halogen, or amino.

The term"halogen"includes fluoro, chloro, bromo and iodo.

The term"aryl"as used herein except where noted, represents a stable 6-to 10-membered mono-or bicyclic ring system. The aryl ring can be unsubstituted or substituted with one or more of C1 4 lower alkyl, hydroxy, alkoxy, halogen, or amino. Examples of"aryl"groups include phenyl and naphthyl.

The term"trialkylamine"includes triethylamine, tributylamine, diisopropylethylamine, tripropylamine, DBU, and N-methylmorpholine and the like.

The term"metal alkoxide"includes sodium methoxide, sodium ethoxide, sodium pentoxide, sodium butoxide, potassium methoxide, potassium ethoxide, potassium pentoxide, potassium butoxide, lithium methoxide, lithium ethoxide, lithium pentoxide, lithium butoxide, cesium methoxide, cesium ethoxide, cesium pentoxide, and cesium butoxide and the like.

The abbreviations listed below are used in the specification and have the meanings indicated below: TMS-CN Trimethylsilylcyanide PEG Polyethylene glycol KOH Potassium hydroxide DMSO Dimethylsulfoxide DMF Dimethylformamide EtOAc Ethyl acetate MeOH Methanol EDC 1- (3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride HOBT 1-hydroxybenzotriazole hydrate DBU diazabicyclo [5.4.0] undec-7-ene TRIS 2-Amino-2-hydroxymethyl-1, 3-propanediol DIC Diisopropylcarbodiimide NMP N-methyl pyrrolidine DPPF Bis [diphenylphosphino] ferrocene Pharmaceutically-acceptable salts of compounds prepared according to the process of the invention (in the form of water-or oil-soluble or dispersible products) include the conventional non-toxic salts such as those derived from inorganic acids, e. g. hydrochloric, hydrobromoic, sulfuric, sulfamic, phosphoric, nitric and the like, or the quaternary ammonium salts which are formed, e. g., from inorganic or organic acids or bases. Examples of acid addition salts include acetate, adipate, alginate, aspartate, benzoate, benzenesulfonate, bisulfate, butyrate, citrate, camphorate, camphorsulfonate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptanoate, glycerophosphate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, 2hydroxyethanesulfonate, lactate, maleate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oxalate, pamoate, pectinate, persulfate, 3-phenylpropionate, picrate, pivalate, propionate, succinate, sulfate, tartrate, thiocyanate, tosylate, and undecanoate. Base salts include ammonium salts, alkali metal salts such as sodium and potassium salts, alkaline earth metal salts such as calcium and magnesium salts, salts with organic bases such as dicyclohexylamine salts, N-methyl-D-glucamine, and salts with amino acids such as arginine, lysine, and so forth. Also, the basic nitrogencontaining groups may be quaternized with such agents as lower alkyl halides, such as methyl, ethyl, propyl, and butyl chloride, bromides and iodides; dialkyl sulfates like dimethyl, diethyl, dibutyl; and diamyl sulfates, long chain halides such as decyl, lauryl, myristyl and stearyl chlorides, bromides and iodides, aralkyl halides like benzyl and phenethyl bromides and others.

In order to determine activitiy of compounds prepared according to the process of the invention, assays of human a-thrombin and human trypsin were performed by the methods substantially as described in Thrombosis Research, Issue No. 70, page 173 (1993) by S. D. Lewis et al.

The assays were carried out at 25 C in 0.05 M TRIS buffer pH 7.4, 0.15 M NaCI, 0.1% PEG. Trypsin assays also contained 1 mM CaCl2. In assays wherein rates of hydrolysis of ap-nitroanilide (pna) substrate were determined, a Thermomax 96-well plate reader was used was used to measure (at 405 nm) the time dependent appearance ofp-nitroaniline. sar-PR-pna was used to assay humanthrombin (Km=125 I1M) and bovine trypsin (Km=125 IlM). p-Nitroanilide substrate concentration was determined from measurements of absorbance at 342 nm using an extinction coefficient of 8270 cm~lM~l.

In certain studies with potent inhibitors (Ki'10 nM) where the degree of inhibition of thrombin was high, a more sensitive activity assay was employed. In this assay the rate of thrombin catalyzed hydrolysis of the fluorogenic substrate Z GPR-afc (Km=27 uM) was determined from the increase in fluorescence at 500 nm (excitation at 400 nm) associated with production of 7-amino-4-trifluoromethyl coumarin. Concentrations of stock solutions of Z-GPR-afc were determined from measurements of absorbance at 380 nm of the 7-amino-4-trifluoromethyl coumarin produced upon complete hydrolysis of an aliquot of the stock solution by thrombin.

Activity assays were performed by diluting a stock solution of substrate at least tenfold to a final concentration : 20. 1 Km into a solution containing enzyme or enzyme equilibrated with inhibitor. Times required to achieve equilibration between enzyme and inhibitor were determined in control experiments.

Initial velocities of product formation in the absence (Vo) or presence of inhibitor (Vi) were measured. Assuming competitive inhibition, and that unity is negligible compared Km/ [S], [I]/e, and [I]/e (where [S], [I], and e respectively represent the total concentrations, of substrate, inhibitor and enzyme), the equilibrium constant (Ki) for dissociation of the inhibitor from the enzyme can be obtained from the dependence of Vo/Vi on [1] shown in equation 1: Vo/Vi = 1 + [Il/Ki (1).

The activities shown by this assay indicate that the compounds are therapeutically useful for treating various conditions in patients suffering from unstable angina, refractory angina, myocardial infarction, transient ischemic attacks, atrial fibrillation, thrombotic stroke, embolic stroke, deep vein thrombosis, disseminated intravascular coagulation, and reocclusion or restenosis of recanalized vessels. The compounds are selective compounds, as evidenced by their inhibitory activity against human trypsin (represented by Ki), which is at least 1000 nM.

Anticoagulant therapy is indicated for the treatment and prevention of a variety of thrombotic conditions, particularly coronary artery and cerebrovascular disease. Those experienced in this field are readily aware of the circumstances requiring anticoagulant therapy. The term"patient"used herein is taken to mean mammals such as primates, including humans, sheep, horses, cattle, pigs, dogs, cats, rats, and mice.

Thrombin inhibition is useful not only in the anticoagulant therapy of individuals having thrombotic conditions, but is useful whenever inhibition of blood coagulation is required such as to prevent coagulation of stored whole blood and to prevent coagulation in other biological samples for testing or storage. Thus, the thrombin inhibitors can be added to or contacted with any medium containing or suspected of containing thrombin and in which it is desired that blood coagulation be inhibited, e. g., when contacting the mammal's blood with material selected from the group consisting of vascular grafts, stents, orthopedic prosthesis, cardiac prosthesis, and extracorporeal circulation systems.

Compounds prepared according to the process of the invention are useful for treating or preventing venous thromboembolism (e. g. obstruction or occlusion of a vein by a detached thrombus; obstruction or occlusion of a lung artery by a detached thrombus), cardiogenic thromboembolism (e. g. obstruction or occlusion of the heart by a detached thrombus), arterial thrombosis (e. g. formation of a thrombus within an artery that may cause infarction of tissue supplied by the artery), atherosclerosis (e. g. arteriosclerosis characterized by irregularly distributed lipid deposits) in mammals, and for lowering the propensity of devices that come into contact with blood to clot blood.

Examples of venous thromboembolism which may be treated or prevented with the compounds include obstruction of a vein, obstruction of a lung artery (pulmonary embolism), deep vein thrombosis, thrombosis associated with cancer and cancer chemotherapy, thrombosis inherited with thrombophilic diseases such as Protein C deficiency, Protein S deficiency, antithrombin III deficiency, and Factor V Leiden, and thrombosis resulting from acquired thrombophilic disorders such as systemic lupus erythematosus (inflammatory connective tissue disease). Also with regard to venous thromboembolism, compounds of the invention are useful for maintaining patency of indwelling catheters.

Examples of cardiogenic thromboembolism which may be treated or prevented with the compounds include thromboembolic stroke (detached thrombus causing neurological affliction related to impaired cerebral blood supply), cardiogenic thromboembolism associated with atrial fibrillation (rapid, irregular twitching of upper heart chamber muscular fibrils), cardiogenic thromboembolism associated with prosthetic heart valves such as mechanical heart valves, and cardiogenic thromboembolism associated with heart disease.

Examples of arterial thrombosis include unstable angina (severe constrictive pain in chest of coronary origin), myocardial infarction (heart muscle cell death resulting from insufficient blood supply), ischemic heart disease (local anemia due to obstruction (such as by arterial narrowing) of blood supply), reocclusion during or after percutaneous transluminal coronary angioplasty, restenosis after percutaneous transluminal coronary angioplasty, occlusion of coronary artery bypass grafts, and occlusive cerebrovascular disease. Also with regard to arterial thrombosis, the compounds are useful for maintaining patency in arteriovenous cannulas.

Examples of atherosclerosis include arteriosclerosis.

Examples of devices that come into contact with blood include vascular grafts, stents, orthopedic prosthesis, cardiac prosthesis, and extracorporeal circulation systems The thrombin inhibitors can be administered in such oral forms as tablets, capsules (each of which includes sustained release or timed release formulations), pills, powders, granules, elixers, tinctures, suspensions, syrups, and emulsions. Likewise, they may be administered in intravenous (bolus or infusion), intraperitoneal, subcutaneous, or intramuscular form, all using forms well known to those of ordinary skill in the pharmaceutical arts. An effective but non-toxic amount of the compound desired can be employed as an anti-aggregation agent. For treating ocular build up of fibrin, the compounds may be administered intraocularly or topically as well as orally or parenterally.

The thrombin inhibitors can be administered in the form of a depot injection or implant preparation which may be formulated in such a manner as to permit a sustained release of the active ingredient. The active ingredient can be compressed into pellets or small cylinders and implanted subcutaneously or intramuscularly as depot injections or implants. Implants may employ inert materials such as biodegradable polymers or synthetic silicones, for example, Silastic, silicone rubber or other polymers manufactured by the Dow-Corning Corporation.

The thrombin inhibitors can also be administered in the form of liposome delivery systems, such as small unilamellar vesicles, large unilamellar vesicles and multilamellar vesicles. Liposomes can be formed from a variety of phospholipids, such as cholesterol, stearylamine or phosphatidylcholines.

The thrombin inhibitors may also be delivered by the use of monoclonal antibodies as individual carriers to which the compound molecules are coupled. The thrombin inhibitors may also be coupled with soluble polymers as targetable drug carriers. Such polymers can include polyvinlypyrrolidone, pyran copolymer, polyhydroxy-propyl-methacrylamide-phenol, polyhydroxyethylaspartamide-phenol, or polyethyleneoxide-polylysine substituted with palmitoyl residues. Furthermore, the thrombin inhibitors may be coupled to a class of biodegradable polymers useful in achieving controlled release of a drug, for example, polylactic acid, polyglycolic acid, copolymers of polylactic and polyglycolic acid, polyepsilon caprolactone, polyhydroxy butyric acid, polyorthoesters, polyacetals, polydihydropyrans, polycyanoacrylates and cross linked or amphipathic block copolymers of hydrogels.

The dosage regimen utilizing the thrombin inhibitors is selected in accordance with a variety of factors including type, species, age, weight, sex and medical condition of the patient; the severity of the condition to be treated; the route of administration; the renal and hepatic function of the patient; and the particular compound or salt thereof employed. An ordinarily skilled physician or veterinarian can readily determine and prescribe the effective amount of the drug required to prevent, counter, or arrest the progress of the condition.

Oral dosages of the thrombin inhibitors, when used for the indicated effects, will range between about 0.01 mg per kg of body weight per day (mg/kg/day) to about 30 mg/kg/day, preferably 0.025-7.5 mg/kg/day, more preferably 0.1-2.5 mg/kg/day, and most preferably 0.1-0.5 mg/kg/day (unless specificed otherwise, amounts of active ingredients are on free base basis). For example, an 80 kg patient would receive between about 0.8 mg/day and 2.4 g/day, preferably 2-600 mg/day, more preferably 8-200 mglday, and most preferably 8-40 mg/kg/day. A suitably prepared medicament for once a day administration would thus contain between 0.8 mg and 2.4 g, preferably between 2 mg and 600 mg, more preferably between 8 mg and 200 mg, and most preferably 8 mg and 40 mg, e. g., 8 mg, 10 mg, 20 mg and 40 mg. Advantageously, the thrombin inhibitors may be administered in divided doses of two, three, or four times daily. For administration twice a day, a suitably prepared medicament would contain between 0.4 mg and 4 g, preferably between 1 mg and 300 mg, more preferably between 4 mg and 100 mg, and most preferably 4 mg and 20 mg, e. g., 4 mg, 5 mg, 10 mg and 20 mg.

Intravenously, the patient would receive the active ingredient in quantities sufficient to deliver between 0.025-7.5 mg/kg/day, preferably 0.1-2.5 mg/kg/day, and more preferably 0.1-0.5 mg/kg/day. Such quantities may be administered in a number of suitable ways, e. g. large volumes of low concentrations of active ingredient during one extended period of time or several times a day, low volumes of high concentrations of active ingredient during a short period of time, e. g. once a day. Typically, a conventional intravenous formulation may be prepared which contains a concentration of active ingredient of between about 0.01-1.0 mg/ml, e. g. 0.1 mg/ml, 0.3 mg/ml, and 0.6 mg/ml, and administered in amounts per day of between 0.01 ml/kg patient weight and 10.0 ml/kg patient weight, e. g. 0.1 ml/kg, 0.2 ml/kg, 0.5 ml/kg. In one example, an 80 kg patient, receiving 8 ml twice a day of an intravenous formulation having a concentration of active ingredient of 0.5 mg/ml, receives 8 mg of active ingredient per day. Glucuronic acid, L-lactic acid, acetic acid, citric acid or any pharmaceutically acceptable acid/conjugate base with reasonable buffering capacity in the pH range acceptable for intravenous administration may be used as buffers. Consideration should be given to the solubility of the drug in choosing an The choice of appropriate buffer and pH of a formulation, depending on solubility of the drug to be administered, is readily made by a person having ordinary skill in the art.

The compounds can also be administered in intranasal form via topical use of suitable intranasal vehicles, or via transdermal routes, using those forms of transdermal skin patches well known to those of ordinary skill in that art. To be administered in the form of a transdermal delivery system, the dosage administration will, or course, be continuous rather than intermittent throughout the dosage regime.

The thrombin inhibitors are typically administered as active ingredients in mixture with suitable pharmaceutical diluents, excipients or carriers (collectively referred to herein as"carrier"materials) suitably selected with respect to the intended form of administration, that is, oral tablets, capsules, elixers, syrups and the like, and consistent with convention pharmaceutical practices.

For instance, for oral administration in the form of a tablet or capsule, the active drug component can be combined with an oral, non-toxic, pharmaceutically acceptable, inert carrier such as lactose, starch, sucrose, glucose, methyl cellulose, magnesium stearate, dicalcium phosphate, calcium sulfate, mannitol, sorbitol and the like; for oral administration in liquid form, the oral drug components can be combined with any oral, non-toxic, pharmaceutically acceptable inert carrier such as ethanol, glycerol, water and the like. Moreover, when desired or necessary, suitable binders, lubricants, distintegrating agents and coloring agents can also be incorporated into the mixture. Suitable binders include starch, gelatin, natural sugars such as glucose or beta-lactose, com-sweeteners, natural and synthetic gums such as acacia, tragacanth or sodium alginate, carboxymethylcellulose, polyethylene glycol, waxes and the like.

Lubricants used in these dosage forms include sodium oleate, sodium stearate, magnesium stearate, sodium benzoate, sodium acetate, sodium chloride and the like.

Disintegrators include, without limitation, starch methyl cellulose, agar, bentonite, xanthan gum and the like.

Typical uncoated tablet cores suitable for administration of thrombin inhibitors are comprised of, but not limited to, the following amounts of standard ingredients: EXCIPIENT GENERAL PREFERRED MOST PREFERRED RANGE (%) RANGE (%) (%) MANNITOL 10-90 25-75 30-60 MICROCRYSTALLI 10-90 25-75 30-60 NE CELLULOSE MAGNESIUM 0.1-5.0 0.1-2.5 0.5-1.5 STEARATE Mannitol, microcrystalline cellulose and magnesium stearate may be substituted with alternative pharmaceutically acceptable excipients.

The thrombin inhibitors can also be co-administered with suitable antiplatelet agents, including, but not limited to, fibrinogen receptor antagonists (e. g. to treat or prevent unstable angina or to prevent reocclusion after angioplasty and restenosis), anticoagulants such as aspirin, thrombolytic agents such as plasminogen activators or streptokinase to achieve synergistic effects in the treatment of various vascular pathologies, or lipid lowering agents including antihypercholesterolemics (e. g. HMG CoA reductase inhibitors such as lovastatin or simvastatin, HMG CoA synthase inhibitors, etc.) to treat or prevent atherosclerosis. For example, patients suffering from coronary artery disease, and patients subjected to angioplasty procedures, would benefit from coadministration of fibrinogen receptor antagonists and thrombin inhibitors. Also, thrombin inhibitors enhance the efficiency of tissue plasminogen activator-mediated thrombolytic reperfusion. Thrombin inhibitors may be administered first following thrombus formation, and tissue plasminogen activator or other plasminogen activator is administered thereafter.

Typical doses of the thrombin inhibitors in combination with other suitable anti-platelet agents, anticoagulation agents, or thrombolytic agents may be the same as those doses of thrombin inhibitors administered without coadministration of additional anti-platelet agents, anticoagulation agents, or thrombolytic agents, or may be substantially less that those doses of thrombin inhibitors administered without coadministration of additional anti-platelet agents, anticoagulation agents, or thrombolytic agents, depending on a patient's therapeutic needs.

The following examples of the invention are exemplary and should not be interpreted as limiting the scope of the invention as defined above.

EXAMPLE 1

A nitrogen-purged 1-liter vessel was charged with 450 mL isopropyl acetate, followed by additional of glycine ethyl ester salt 1 (50 grams; 0.357 moles) at 20 C. The slurry was cooled to 0 C during which time 0.357 moles (85 mL) tributylamine was charged, followed by 0.411 moles (55 mL) trimethylsilylcyanide. No increase in temperature was observed during any of the above additions. The slurry was cooled to-10 C and 0.643 moles acetaldehyde (36 mL) was added dropwise to the reaction mixture over 30 minutes during which time the temperature rose to a maximum of 5 C. The reaction mixture was warmed to 5 10 C and aged for 2 hours during which time the mixture became homogeneous.

The reaction mixture was cooled to-10 C, seeded with 1.5 grams of authentic material and sparged with anhydrous HCI gas (ca. 21 g) over 60 minutes during which time the internal temperature rose to a maximum of 10 C. The slurry was cooled to 0 C and aged for 1 hour. The solids were isolated on a filter pot and the flask and cake rinsed with chilled isopropyl acetate (3 x 50 ml). The salt was dried, in vacuo with a nitrogen stream, at ambient temperature overnight to provide 52 grams of 2.'H NMR (300Mhz ; DMSO): 84.64 (q, 1H, 7.0 Hz), 4.19 (q, 2H, 7.1 Hz), 3.98 (d, 2H, 5.7 Hz), 1.63 (d, 3H, 7.0 Hz), 1.22 (t, 3H, 7.1 Hz). 13C (75.5 Mhz ; DMSO); Se 166.1,116.4,61.7,45.3,43.2,15.4,13.8.

EXAMPLE 1A

A nitrogen-purged 1-liter vessel was charged with 250 mL ethyl acetate, followed by additional of glycine ethyl ester salt la (30 grams) at 20 C.

The slurry was cooled to-10 C during which time 147 mmoles (35 mL) tributylamine was charged, followed by 172 mmoles (23 mL) trimethylsilylcyanide. 269 mmoles acetaldehyde (15 mL) was added dropwise to the reaction mixture over 30 minutes during which time the temperature rose to a maximum of 5 C. The reaction mixture was warmed to 10 C and aged for 1 hour during which time the mixture became homogeneous.

The reaction mixture was cooled to-10 C and sparged with HCI gas for 70 minutes during which time the intemal temperature rose to a maximum of 14 C. The slurry was cooled to 5 C and aged for 35 minutes. The solids were isolated on a filter pot and the flask and cake rinsed with chilled ethyl acetate (3 x 30 ml). The 2a was dried, in vacuo, with a nitrogen stream, at ambient temperature overnight to provide 35 grams of material.'H NMR (300Mhz ; DMSO): 1.49 (d, 3H), 3.59 (d, 2H), 3.73 (q, 1H), 5.18 (s, 2H), 7.3-7.45 (br m, 5H). 13C : 167.34, 135.24,128.39,128.23,128.12,117.63,66.62,45.98,43.44,16.28.

EXAMPLE 2

A 5 liter flask was charged with 1.5 L isopropyl acetate and 192 grams (1.0 mole) 2 at ambient temperature. 4.0 moles (350 ml) oxalyl chloride was added via addition funnel over 20 minutes during which time the temperature rose about 5 C. The reaction mixture was warmed to 50 C and aged for 12 hours to form a reaction mixture containing 3.

EXAMPLE 3

The reaction mixture containing 3 was cooled to 15 C and aqueous potassium carbonate (17% solution; 1.3 kg, providing 2.2 moles or 212 grams) was added slowly (CO2 evolution). The final batch pH was adjusted to greater than 7.0.1.7 moles (213 ml) phenylethylamine was added to the biphasic reaction mixture resulting in a pH of 9.3. The contents were heated to 75 C for 4 hours. The bottom layer was removed and discarded. The organic layer was washed with water (3 x 1.2 L) at 75 C. The organic layer was cooled to 0 C over 2 hours and aged for 1 hour. The solids were isolated by filtration and the cake washed with chilled isopropyl acetate (3 x 200 ml). The product was dried in vacuo at 25 C to provide 228 grams of 4.'H NMR (300MHz ; DMSO): 57. 52 (t, 1H), 7.20-7.32 (m, 5H), 4.81 (s, 2 H), 4.17 (q, 2H, 7 Hz), 3.47 (m, 2 H), 2.86 (m, 2H), 2.21 (s, 3H), 1.21 (t, 3H, 7 Hz).

EXAMPLE 4

Amidine 4 was combined with methanol (1.2 L) at 25 C and 5 N KOH (400 ml). The solution was warmed to 40 C and aged for 0.5 hours. The reaction mixture was filtered through a bed on Solka Floc in a sintered-glass funnel and the cake washed with 100 ml methanol. The filtrate was combined with 42 grams of 10% Pd/C and hydrogenated at 40 psi at 50 C for 18 hours. The reaction mixture was filtered through a bed of Solka-Floc and then through a 5 4 frit. The filtrate pH was adjusted to 1.8 with concentrated HCI that precipitated the product. The slurry was aged at 20 C for 2 hours and filtered. The cake was washed with water (2 x 250 ml) and dried in vacuo at 40 C to constant weight to provide 242 grams of 5.13C NMR (75.5 MHz ; DMSO): 8c 169.2,151.3,149.0,139.7,128.5,128.3,125.9,123.9, 119.2,46.1,41.7,34.5,15.4.

EXAMPLE 5

To a 50 liter round bottom flask equipped with mechanical stirrer, thermocouple, heating mantle and nitrogen inlet was added degassed NMP (8.00 liters), 2-amino-5-bromo-6-picoline 6 (4.034 kg, 21.57 mol) and CuCN (2.125 kg, 23.73 mol). The thick slurry was warmed to 160 C and stirred for 10 hours at 160 C. The dark solution was easily stirred at 160 C for the first 8 hours, after which the reaction began to get thick. A glass filled banana type Teflon stirrer blade (Ace Glass prototype) was necessary to insure continuous stirring.

The reaction mixture was allowed to cool with stirring (the top heating mantle was removed). When the temperature fell to 85 C, concentrated NH40H (2.0 liters) was added. The mixture was continually cooled to 45 C, and NH40H (18.0 liters) was added. The slurry was stirred 6 hours at ambient temperature and then CH2C12 (4.0 liters) was added. The mixture was stirred for 5 min and then transferred to a 50 liters cylindrical extraction vessel. CH2C12 (6.0 liters) was added and the slurry was thoroughly stirred. The organic layer was separated and the aqueous slurry was extracted again with CH2C12 (2 x 9.0 liters).

To a 50 liters round bottom flask was charged the CH2C12 extracts (44.1 kg) and Darco G-60 decolorizing charcoal (0.40 kg). The suspension was stirred 2 hours and then filtered through a 1.5" bed of solka floc. Filtration time was 3 hours when using a 6 liters sintered glass funnel and 1 hour in a filter pot 17"in diameter. The filtrate contained 2.60 kg (90.4%) product by LC. The filtrate (80.14 kg) was slowly vacuum transferred to a 50 liters round bottom flask equipped with a mechanical stirrer, thermocouple and batch concentrator. The solution was concentrated to give a slurry of cyanopyridine 7 in NMP (approx. 19 liters).

The filtrates from two batches of cyanopyridine were combined at this point.

EXAMPLE 5A Alternatively, a 2-liter 3-neck round bottom flask was equipped with a mechanical stirrer, thermocouple probe and nitrogen inlet adapter. The flask was charged with 1 mol (187.05 grams) 2-amino-5-bromo-6-picoline 6,333 mL DMF, 3 mL water, 0.6 mol (70.45 grams) Zn (CN) 2 and 0.0012 mol DPPF. The yellow suspension was degassed via two vacuum degas/nitrogen cycles. 0.0005 mol (0.458 grams) Pd2DBA3 was added and the mixture was again degassed via two vacuum degas/nitrogen cycles. The mixture was heated to 120 C and aged at 120 C for 20 hours under nitrogen.

The mixture was cooled to 95-100 C (the total reaction volume at this point is 540 mL). and gradually diluted with 1000 mL of 4 : 1 NH4CI-NH40H solution (cooled to 10 C) (saturated aqueous NH4CI and concentrated aqueous NH40H were combined to provide 1500 mL of 4 : 1 NH4CI-NH40H solution) over 20 minutes. The warm 40 C mixture was transferred gradually via pump or vacuum over 15 minutes to a 3 liter flask containing 500 mL water using 300 mL water to complete the transfer. The tan slurry was gradually cooled to-5 C over 1.5 hours and filtered. The tan crystalline solid was washed with 500 mL of 4: 1 NH4CI- NH40H solution and 500 mL water and finally with 500 mL water.

The tan solid was suspended in 500 mL water and 200 mL 5M aqueous HCl were added to bring the pH to 3.0. The mixture was heated to 60 C, treated with 1 gram DarcoG60 at 60 C and filtered at 60 C using 200 mL water to rinse the filter.

The homogenous pale yellow solution was basified via the addition of 85-90 grams of 50% aqueous NaOH maintaining the temperature at 45 55 C. The mixture was cooled to 5 C over 1 hour and filtered. The crystalline solid was washed with 1000 mL of water at 5 C and dried under a stream of nitrogen to provide 120 grams (90%) of cyanopicoline product 7 as an off white crystalline solid.

Alternatively, the tan solid can be wasjed with toluene (840 mL) and dried to provide 120 grams of 7 as an off white crystal solid.

EXAMPLE 6

The cyanopyridine 7/NMP slurry was dissolved in 2: 1 MeOH/NH40H (13.6 liters). A portion of the solution (8.06 kg by weight, 1.07 kg cyanopyridine by assay) was further diluted with 2: 1 MeOH/NH40H (3.4'liters). The batch was divided in to 4 portions to be used in a 5 gal stirred autoclave. The autoclave was preconditioned with 2: 1 MeOH/NH40H (3.4 liters) and Raney Ni (50 grams) and stirred at 50 C and 100 psi for 4 hours.

To a preconditioned 5 gal stirred autoclave was added the cyanopyridine solution (-11 liters) and Raney Ni (0.22 kg). The reaction was stirred at 100 psi H2 and 50 C for 7 hours. The suspension was filtered through a 3"bed of solka floc and the filter cake was washed with MeOH (7 liters). No exotherm was detected when air passed over Raney Ni on Solka floc. When filtered through celite the Raney Ni quickly heats up. Assay of the filtrate (15.3 kg) was 1.37 kg (84.3%) of the diaminopyridine free base.

The filtrate (30.80 kg) was slowly vacuum transferred to a 50 liters round bottom flask equipped with a mechanical stirrer, thermocouple and batch concentrator. The solution was concentrated to give a slurry of diaminopyridine free base in NMP/H20 (~11 liters). The filtrates from two hydrogenation runs were combined. Concentration was done under vacuum at 29 in. Hg and 10-25 C over 2 hours. n-PrOH (8.4 liters) was added and the mixture was concentrated back to a slurry of diaminopyridine free base in NMPfH2O (~10 liters).

The flush with n-PrOH was necessary to remove all NH40H. Concentration was done under vacuum at 29 in. Hg and 25-40 C over 1.5 hours. n-PrOH (8.4 liters), concentrated HCl (3.35 liters, 2.5 eq.) and finally H20 (3.00 liters) were added. The resulting diaminopyridine bis HCl salt solution was concentrated until turbid.

The temperature rose from 27 to 50 C after adding the HCI and then just enough H20 was added to dissolve all the solids. The volume of the solution was-25 liters. Concentration was done under vacuum at 29 in. Hg and 20 30 C over 1.0 hour.

The seedbed slurry was allowed to stir for 3 hours at 30 C and then diluted back to the original volume (-25 liters) with n-PrOH (5. 50 liters). H20 was azeotropically removed by concentrating the mixture to-60 % volume and then replenishing with n-PrOH (10 liters) back to the original volume. The procedure was repeated until the mother liquor contained 7 mg/mL pyridine diamine dihydrochloride product 8.

A sample of the slurry was removed via pipette and filtered. A 0.25 g sample of the filtrate was diluted (100X dilution) and analyzed by HPLC.

The slurry (25 liters) was stirred for 10 hours at ambient temperature and then filtered. The filter cake was slurry washed with n-PrOH (2 x 4.5 liters) and then dried over nitrogen. The weight of the filter cake was 2.3 kg (58 % bromopyridine).

EXAMPLE 6A Alternatively, 3.1 kg ethanol and 50% aqueous sodium hydroxide (0.97) kg were added to a 10 L glass jug. The slurry was shaken to dissolve solid, and 2-amino-5cyano-6-picoline (1.3 kg) was added with shaking to form a slurry. The mixture was introduced into a 5 gallon autoclave. Raney nickel A7063 (0.45 kg) was added as a water wet solid. Ethanol (1.3 kg) was used to facilitate the transfer of the reaction mixture and the nickel. The slurry was hydrogenated at 100 psi, room temperature, for 4 hours.

The reaction mixture was transferred into a carboy. The hydrogenation was repeated two times. The three batches were then filtered through a bed of solkaflok on a 5 L sintered glass funnel via vacuum filtration. Each carboy was rinsed with 1 L of IPA that was then filtered through the solkaflok bed. The combined filtrates were transferred via residual vacuum to a 100 L 4 neck round bottom flask equipped with mechanical stirrer, thermocouple probe, nitrogen inlet adapter, and additional funnel. HCI in IPA (7.4 L) was added by addition funnel over 30 minutes. A mild exotherm was noted with the temperature rising from 20 C to 40 C. The slurry was aged for 1.5 hours while cooling to 26 C. The mixture was filtered through a bed of solkaflok on a 5 L sintered glass funnel via vacuum filtration. IPA (3 L) was used to facilitate the transfer. The solkaflok bed was washed with an additional 5 L of IPA. The combined filtrates were transferred via pump into a 100 L cylindrical extractor equipped with addition funnel and nitrogen inlet. HCl in IPA (14.6 L) was added over 45 minutes, maintaining the temperature at 15-25 C using glycol. The slurry was aged at 16-17 C for 1.5 hours. The slurry was filtered on an 18"filter pot. The off-white solid was washed with 24 L of room temperature IPA (6 L displacement, 6 L slurry, 6 L slurry, 6 L displacement). The solid was dried in the filter pot under a stream of nitrogen at 20-25 C for 72 hours to provide the diamine (5.76 kg, 96.0 wt%, 94.2% yield).

EXAMPLE 7

Coupling of the pyrazinoic acid 5 with the pyridine diamine dihydrochloride 8 was performed under standard peptide coupling conditions using diisopropylcarbodiimide, HOBT, N-methylmorpholine in DMF solvent.

At 22 C, a nitrogen-purged flask was charged with DMF (325 ml), N-methylmorpholine (55 ml), the pyridine diamine salt 8 (27.3 grams), the pyrazinoic acid derivative 5 (36.0 grams) and HOBT (18.6 grams). The slurry was aged for 15 minutes and was then treated with a DIC/DMF solution (22 ml in 25 ml, respectively) dropwise over 5 minutes. The slurry was aged at 25 C for 2.5 hours.

Water (600 ml) was added slowly to the reaction mixture at < 40 C. The slurry was aged for 1 hour and the solids isolated by filtration. The cake was washed with 1/1 MeOH/water (1 x 400 ml), then 7/3 MeOH/EtOAc (1 x 100 ml), then with EtOAc (1 x 300 ml). The product was dried in vacuo at 25 C to give 43.1 grams of final product free base 9.

The free base (40.0 grams) was combined with 2N HCl (98 ml) and water (20 ml) and heated to 80-82 C. The solution was aged for 15 minutes and then clarified through a 0.5 inch pad of water-wet solka floc on a sintered glass funnel. The flask and funnel were rinsed with hot water (40 ml). The filtrate was reheated to 75 C and then cooled to 25 C over 2.5 hours. Concentrated HCI (16 ml) was added slowly to the solution that was cooled to 19 C and aged for 1 hour. The solids were isolated via filtration and were washed with IN HCI (2 x 40 ml) and ethanol (3 x 75 ml). Drying in vacuo provides 44.6 grams of 10 dihydrochloride salt.

Other standard coupling procedures, including procedures employing EDC hydrochloride instead of diisopropylcarbodiimide, may be used to achieve desired coupling.

EXAMPLE 8

Treating acetone oxime 11 (Aldrich) with methanesulfonyl chloride and triethylamine in THF at 0 C resulted in a rapid conversion to the mesyloxime 12. Once complete, the addition of hexanes reduced the solubility of the triethylamine hydrochloride by-product, which was removed by filtration. Simple concentration of the filtrate yielded 12 in quantitative crude yield. The filtrate was concentrated until a 2.5 M solution of 12 in THF was obtained.

Preparation of 12: To a solution of acetone oxime 11 (37.0 g, 496 mmol) and triethylamine (74.0 mL, 537 mmol) in THF (500 mL) was added methanesulfonyl chloride (41.0 mL, 519 mL) at Ti S +22 C. The, heterogeneous mixture was stirred 75 min, whereupon hexanes (200 mL) was added. After stirring 20 min, the mixture was filtered through a sintered glass funnel, washing the white solid with 3: 2 hexanes/THF (2 x 250 mL).

The combined filtrate was concentrated on a rotary evaporator (110-175 torr, 35 C bath heating) until 1 L of distillate had been collected. H NMR of the solution indicated clean mesyloxime 12 in THF. Concentration of the solution to dryness provides solid L2 ;'H NMR (CDC13) : 5 3.23 (s, 3H), 2.01 (s, 3H), 1.99 (s, 3H) ppm; "C NMR (CDCI3) 8 166.0,36.3,21.0,16.5 ppm; IR (CH2Cl2) 1652 (weak), 1363, 1181 cl''.

A sodium cation was used to reduced viscosity. Use of lithium counterion resulted in a thin slurry. Treating this slurry with HCI yielded amino acetal 13 as a solution in THF/EtOH that could be used directly in the next synthetic step. Solid 95% EtOLi (32.8 g, 599 mmol) was added to EtOH (550 mL) and cooled to 0 C. The 2.5 M solution of 12 in THF (496 mmol) was added to the ethanolic solution of EtOLi. The ice bath was removed, and the turbid solution stirred 24 h. The mixture containing intermediate 2H-azirene was cooled to 0 C, whereupon a 6.0 M solution of HCI in EtOH (110 mL, 660 mmol) was added while maintaining Ts'+18 C. The ice bath was removed, and the mixture stirred 2 h at 23 C. IH NMR of the crude solution indicated an 83: 17 mixture of 13 and 14, respectively. For 13 ;'H NMR (DMSO-d6) 8 2.92 (br q, J = 5.5 Hz, 2H,-CHrNH3CI), 34 (s, (s, 3H,-CH3) ppm; Ethyl ether resonances of 13 were buried under solvent (ethanol) signals; For 14 ;'H NMR (DMSO-d6) 8 3.92 (br q, J = 5.7 Hz,-CH2NH3CI), 2.18 (s, 3H,-CH3) ppm.

EXAMPLE 9

Ethyl oxamate 17 was prepared in 97% yield by treating ethyl oxalyl chloride 15 (Aldrich, E. Merck) with glycine ethyl ester hydrochloride 16 (Aldrich) in the presence of triethylamine. To a mixture of ethyl glycine hydrochloride 15 (50.9 g, 364 mmol) and triethylamine (107 mL, 765 mmol) in CH2CI2 (365 mL) was added ethyl chlorooxalate 16 (40.7 mL, 364 mmol) over 25 min, such that Ti + 14 C. The slurry was stirred 1 h, whereupon H20 (500 mL was added. The organic layer was separated, washed with H20 (500 mL), and dried over MgSO4. Concentration of the solution provided 17 as an oil ;'H NMR (CDCI3) 8 7. 62-7.5 (br, 1H), 4.36 (q, J = 7. 0 Hz, 2H), 4.23 (q, J = 7. 2 Hz, 2H), 4.11 (d, J = 5.5 Hz, 1H), 1.38 (t, J = 7.2 Hz, 3H), 1.29 (t, J = 7.0 Hz, 3H) ppm ;'3C NMR (CDCl3) 8 168.7,159.9,156.7,63.2,61.7,41.4,14.0,13.9 ppm; IR (CCL4) 1752,1710 cm-t.

To the crude reaction solution containing protected aminoacetone 13 was added 17 and excess diisopropylethylamine. After heating overnight at 64 C, acylation was affected, affording the unsymmetrical oxamide acetal 18 (83%) following an aqueous workup.' To the crude mixture of 13 (reference 14) was added 17 (50.2 g, 247 mmol) and diisopropylethylamine (130 mL, 739 mmol). The mixture was heated to Ti = 64 C and stirred overnight. The mixture was diluted with H20 (200 mL) while still at Ti 64 C, then allowed to cool to 23 C. To the homogenous solution was added halfsaturated NaCl (aq) (400 mL) and MTBE. The organic phase was separated, and the aqueous phase extracted with 1: 1 THF/MTBE (300 mL). The combined organic extracts were washed with brine (150 mL), saturated NaHC03 (150 mL), and brine (150 mL). The solution was concentrated on a rotary evaporator, then partitioned between EtOAc (500 mL) and brine (60 mL). The organic phase was separated, washed with brine (60 mL), and dried over MgSO4. Concentration of this solution provided the oxamide 18 ;'H NMR (CDC13) 8 8.02 (br t, J = 5.2 Hz, 1H), 7.47 (br t, J = 5.6 Hz, 1 H), 4.16 (q, J = 7.1 Hz, 2H), 4.02 (d, J = 5. 6 Hz, 2H), 3.49-3.38 (m, 6H), 1.24 (s, 3H), 1.23 (t, J = 7.1 Hz, 3H), 1.11 (t, J = 7. 1 Hz, 6H) ppm ; 13C NMR (CDC13) 8 168.5,159.9,159.2,99.6,61.6,56.2,44.7,41.4,21.2,15.3,14.1 ppm; IR (CC14) 1752,1679 cmi'.

Treating 18 with trifluoroacetic acid and trifluoroacetic anhydride in acetic acid at 80 C provided crystalline pyrazine-2,3-dione 19 upon solventswitching to an isopropyl acetate/ethanol solvent mixture.

Trifluoroacetic acid (1.1 mL, 14.2 mL) and trifluoroacetic anhydride (1.0 mL, 7.1 mmol) were added to a solution of oxamide 18 (1. 03 g, 3.38 mmol) in acetic acid (8 mL). The solution was heated to reflux and stirred 31 h. The solution was concentrated to dryness on a rotary evaporator, then diluted with EtOH (10 mL).

After concentrated to dryness again, EtOH (10 mL) was added, resulting in the formation of a white solid. The mixture was heated to 65 C and aged 30 min. IPAc (20 mL) was added to the mixture over 20 min. After aging an additional 30 min at 65 C, the mixture was concentrated to 10 mL total volume. The crystals were filtered, washing with 4: 1 IPAc/EtOH (2 x 5 mL). Drying the crystals yielded 19 ;'H NMR (CDCl3) 8 11.24 (br, 1H), 6.20 (br, 1H), 4.60 (br, 3H), 4.15 (q, J = 7.1 Hz, 2H), 1.99 (s, 3H), 1.20 (t, J = 7.1 Hz) ppm ; 13C NMR (DMSO-d6) 8 167.9,157.1,154.2, 119.8,106. 3,61.3,45.4,15.3,13. 9 ppm; IR (CCl4) 1748,1684,1649,1618 cm-'.

Cyclization of 18 to 19 could also be effected by treating with methanesulfonic acid or HCI in refluxing ethanol.

EXAMPLE 10 Formation of pyrazinoic acid 5 from dione 19

Combine dione 19 (100.0 g; 470 mmols) with THF (660 ml) in a N2-purged flask at RT. Add DMF (15 ml) and age for 15 min. At 22 C, add POC13 (44 ml; 475 mmols) slowly over 20 min. Warm solution to 50-2 C over 30 min and age for 100 min.

Assay for extent of reaction. Cool the solution to-5 C and slowly add 30% aq NaOH (365 g; 2.7 moles mmols) over 30 minutes, keeping the internal temp below +5 C.

Warm the solution to 20 C over 30 min and age at 20-22 C for 1 hr. Assay for extent of reaction. Adjust pH to 7 with conc HCl at 15-20 C. Evaporate volatiles in vacuo at < 30 C, initially at 70-90 torr. Once distillation slows at these conditions, reduce pressure to 30 torr at 25 C to collect last traces of volatiles. Add water (110 ml) to the rxn mixture (a slurry). Warm to 30 C and slowly adjust pH to 1.8 with conc HCl (keep solution temp < 40 C during pH adjustment). Solution should clarify at pH 3.1. Add seed (1 g) at pH 2.0 and continue pH adjustment to 1.8. Cool the developing slurry to 5 C over 30 min and age for 1 hr. Isolate solids and rinse flask and cake with cold (10 C) water (2 x 15 ml). Dry in vacuo overnight at 40 C.

Yields 88 g (92% yield) of chloroacid 20.

Combine chloroacid 20 (45 g; 222 mmols) with n-propanol (320 ml) and phenethylamine (66 ml; 529 mmols). Heat to reflux (100 C) and age for 21 hr. Cool to 80 C and add 1 N Hcl (460 ml) slowly so as to keep batch temp above 60 C.

After 100 ml has been added, add seed (1 g). Age at 60 C for 1 hr and cool to 22 C.

Age at 22 C for 1 hr and filter. The cake was washed with chilled 3/2 water/MeOH (2 x 100 ml) and dried in vacuo at 50 C to provide 48.5 g of the amidine acid (78% yield; 97.0 A% purity) 5.

5 can be coupled with 8 to form the finished thrombin inhibitor and and subsequently to form the dihydrochloride salt 10, as in Example 7.

Claims (1)

1. WHAT IS CLAIMED IS:

   1. A process for forming

   which comprises saponifying and hydrogenating

   2. The compound having the structure

   3. A process for making

   which comprises reducing

   with hydrogen in the presence of a porous metallic nickel catalyst. 4. A process of claim 3 wherein the catalyst is Raney nickel.

   5. A process for making

   which comprises cyanating

   6. A process for making

   which comprises a) reacting

   with R3 CN and R CH2CHO in a base selected from the group consisting of a trialkylamine and a metal alkoxide to form

   wherein R1 is C1-C6 alkyl or benzyl; R is hydrogen, aryl, or Cl-C6 alkyl ; HX is selected from the group consisting of hydrochloric acid, sulfuric acid, methanesulfonic acid, phosphoric acid, acetic acid, oxalic acid and hydrogen bromide; R is potassium, sodium, lithium or trimethylsilyl; b) cyclizing II with oxalyl chloride to form

   c) aminating III with phenethylamine to produce

   d) saponifying and hydrogenating IV to produce

   e) coupling V with

   to form

   7. A process of claim 6 wherein R1 is ethyl or benzyl; R is methyl; the base is trbutylamine; HX is HCI ; and R is trimethylsilyl.

   8. A process for forming

   comprising coupling

   with

   9. A process for forming

   which comprises cyclizing oxamide acetal

   which comprises chlorinating

   11. A process for making mesyloxime

   which comprises treating acetone oxime with methanesulfonyl chloride and triethylamine.

   12. A process for making oxamide acetal

   which comprises adding ethyl oxamate

   to aminoacetal