A PROCESS FOR THE PREPARATION OF A THROMBUS IMAGING AGENT

Abstract: The present invention relates generally to the synthesis of reagents useful for the preparation of radiopharmaceuticals which serve as imaging agents for the diagnosis of cardiovascular disorders, infection, inflammation, and cancer. They have formula (I). It is also claimed a method for preparing pertinent intermediates.

Description: TITLE A PROCESS FOR THE PREPARATION OF A THROMBUS IMAGING AGENT FIELD OF THE INVENTION The present invention relates generally to an efficient and practical commercial synthesis of novel reagents for the preparation of radiopharmaceuticals useful as imaging agents for the diagnosis of cardiovascular disorders, infection, inflammation and cancer, and to intermediate compounds useful for the preparation of these reagents . These reagents are comprised of stable hydrazine-modified biologically active molecules that react with gamma emitting radioisotopes to form radiopharmaceuticals that selectively localize at sites of disease, allowing an image to be obtained of the loci using gamma scintigraphy . BACKGROUND There is a current need for methods for the non-invasive diagnosis of a variety of diseases such as thromboembolic disease, atherosclerosis, infection and cancer. Radiopharmaceuticals comprised of gamma-ray emitting radionuclide labeled biologically active molecules fulfill this need. The biologically active molecules serve to localize the radionuclides at the sites of disease and thus allow the sites to be visualized by gamma scintigraphy. The molecules are generally proteins, antibodies, antibody fragments, peptides, polypeptides, or peptidomimetics . The molecules interact with a receptor or binding site expressed at the sites of the disease or with a receptor or binding site on an endogenous blood component, such as platelets and leukocytes, that accumulates at the sites. This interaction results in selective localization of a percentage of the injected radiopharmaceutical while the remainder is cleared either through the renal or hepatobiliary systems. The localized radiopharmaceutical is then imaged externally using gamma scintigraphy. A number of radiopharmaceuticals comprised of radionuclide labeled proteins, antibodies or antibody fragments are under development. A combination of factors make the development of these radiopharmaceuticals difficult, including manufacturing and quality control, non- optimal sequestration and clearance rates, and the occurence of antigenic or allergic responses to the radiopharmaceuticals . These problems are mainly due to the macromolecular nature of the proteins, antibodies and antibody fragments. Their high molecular weight makes direct chemical synthesis impractical, therefore they must be synthesized by recombinant or cloning techniques that typically give low yields and require extensive isolation and purification protocols. The use of lower molecular weight peptides, polypeptides or peptidomimetics as the biologically active molecules obviates a number of these problems . They tend to clear more rapidly from the circulation by an active elimination pathway resulting in a lower background in the images. They are also usually not immunogenic . The use of hydrazines and hydrazides as chelators to modify proteins for labeling with radionuclides has been disclosed by Schwartz et . al . in U.S. Patent 5,206,370. The protein is modified by reaction with bifunctional aromatic hydrazines or hydrazides having a protein reactive substituent. For labeling with technetium-99m, the hydrazino-modified protein is reacted with a reduced technetium species, formed by reacting pertechnetate with a reducing agent in the presence of a chelating dioxygen ligand. The technetium becomes bound to the protein through what are believed to be hydrazido or diazenido linkages with the coordination sphere completed by the ancillary dioxygen ligands . U.S. Patent 5,750,088 indicates the value of the compound of formula (I) as a novel reagent for the described imaging agents. A viable chemical synthesis which permits its commercial manufacture is therefore desirable. The present invention describes a convergent process for the preparation of (I) which reduces production time through the consolidation of several key chemical transformations. The process described herein supresses the formation of undesired side-products, thus maximizing product purity. Moreover, the present invention provides an environmentally favorable alternative to the use of reactions and purification protocols which employ the use of carcinogenic and other hazardous solvents . (I) . SUMMARY OF THE INVENTION The present invention relates generally to processes for the efficient production of (I) which has been acheived by the inventors' discovery that a compound of formula (I), which is an important precursor to radiopharmaceuticals useful as imaging agents , and intermediate compounds useful for the preparation of these reagents, may be formed by high yielding and commercially viable processes described herein. DETAILED DESCRIPTION OF THE INVENTION [ 1] Thus , in a first embodiment , the present invention provides a novel process for the preparation of a compound of formula (I) : ( I ) or a pharmaceutically acceptable salt form thereof, the process comprising: (11) cyclizing a compound of formula (XV) : (XV) ; or a salf form thereof, to form a compound of formula (XVI) (XVI) (12) depro tec ting the compound of formula (XVI) to form a compound of formula (XVII) : or a salt form thereof; (13) contacting the compound of formula (XVII) with a compound of formula (IX) : (IX) in the presence of a first base. (13-i) contacting the reaction solution from step (13) with a quenching agent to form a compound of formula (XVIII) : (XVIII) or an alternative salt form thereof; and, (14) desalting the compound of formula (XVIII) to give the compound of formula (I) . [2] In a preferred embodiment, cyclizing comprises contacting the compound of formula (XV) with a cyclizing agent in a cyclizing solvent, in the presence of a second base; deprotecting comprises contacting the compound of formula (XVI) with strong acid at a suitable temperature; and, desalting comprises dissolving the compound of formula (XVIII) in an aqueous base solution, followed by adjusting the pH of the solution to give a compound of formula (I) . [3] In a more preferred embodiment, the cyclizing agent is O- (lH-benzotriazol-1-yl) -N,N,N' ,N' -tetramethyluronium tetraflouroborate; the cyclizing solvent is acetonitrile; the second base is N,N-diisopropylethylamine; the strong acid is a mixture of trifluoroacetic acid and trifluoromethanesulfonic acid; the suitable temperature is from about -30 °C to about 5 °C; the compound of formula (XVII) is its di (trifluoromethanesulfonic acid) salt form; the first base is N,N-diisopropylethylamine; the quenching agent is ammonium acetate; the aqueous base solution comprises sodium hydroxide in water; and, adjusting the pH comprises the addition of aqueous hydrochloric acid to the solution until a pH in the range of about 4.1 to about 4.4 is achieved. [4] In another more preferred embodiment, the compound of formula (XVI) is purified using a C-18 column by loading about 369 g of the reaction solution from step 11 per L of bed volume . [5] In another more preferred embodiment, the compound of formula (XVIII) is purified using a C-18 column by loading about 33 g of the reaction product from step 13i per L of bed volume. [6] In another preferred embodiment, the compound of formula (XV) is prepared by a process comprising: (9) coupling a compound of formula (VI) : (VI ) or a salt form thereof, with a compound of formula (XIII) (XIII ) or a salt form thereof, to form a compound of formula (XIV) (XIV) ; and (10) deprotecting the compound of formula (XIV) to form the compound of formula (XV), or a salt form thereof. [7] In another more preferred embodiment, coupling comprises contacting the compound of formula (VI) with the compound of formula (XIII) in the presence of a coupling agent and a third base; and, deprotecting comprises hydrogenating the compound of formula (XIV) under suitable hydrogen pressure in the presence of a hydrogenation catalyst in a hydrogenation solvent. [8] In an even more preferred embodiment, the compound of formula (VI) is in its trifluoroacetic acid salt form; the coupling agent is 0- (lH-benzotriazol-1-yl) - N,N,N' ,N' -tetramethyluronium hexaflourophosphate; the third base is N,N-diisopropylethylamine; the suitable pressure is about 14.7 psi; the hydrogenation catalyst is palladium on carbon; and, the hydrogenation solvent is methanol . [9] In another preferred embodiment, the compound of formula (IX) is prepared by the process comprising: (4) contacting a compound of formula (VII) : (VII ) with hydrazine to form a compound of formula (VIII ) (VIII ) ; ( 5 ) contacting the compound of formula (VIII ) with a compound of formula (VHI-a) : α S0 3 - Na + c» (VHI-a) and N-hydroxysuccinimide in a polar aprotic solvent in the presence of a second coupling agent to form a compound of formula (IX) . [10] In another more preferred embodiment, the polar aprotic solvent is N,N-dimethylformamide, and the second coupling agent is N,N' -dicyclohexylcarbodiimide. [11] In a second embodiment, the present invention provides a novel process for preparation of a compound of formula (VI) : (VI) or a salt form thereof, the process comprising: (3) contacting a compound of formula (V): (V) or a salt form thereof, with a compound of formula (V-a) (V-a) in the presence of a coupling agent and a base to form a compound of formula (V-b) : (V-b) ; and (3-i) deprotecting the compound of formula (V-b) to form a compound of formula (VI), or a salt form thereof. [12] In another preferred embodiment, the compound of formula (VI) is its trifluoroacetic acid salt form; the coupling agent is O- (lH-benzotriazol-1-yl) - N,N,N' ,N' -tetramethyluronium hexaflourophosphate; the base is N,N-diisopropylethylamine; deprotecting comprises contacting the compound of formula (V-b) with trifluoroacetic acid at a temperature in the range of about -20 °C to about 0 °C; and, the compound of formula (V) is its hydrochloric acid salt form. [13] In another preferred embodiment, the compound of formula (V) is prepared by the process comprising: (2) contacting a compound of formula (IV) : ( IV) with a compound of formula (IV-a) : (IV-a) or a salt form thereof; in the presence of a second coupling agent and a second base to form a compound of formula (IV- b) : ( I V-b) ; and, (2-i) deprotecting the compound of formula (IV-b) to form the compound of formula (V), or a salt form thereof. [14] In another more preferred embodiment, the compound of formula (IV-a) is its p-toluenesulfonic acid salt form; the second coupling agent is 0- (lH-benzotriazol-1-yl) - N,N,N' ,N' -tetramethyluronium hexaflourophosphate; the second base is N,N-diisopropylethylamine; deprotecting comprises contacting the compound of formula (V-b) with hydrochloric acid at a temperature in the range of about -20 °C to about 0 °C; and, the compound of formula (V) is its hydrochloric acid salt form. [15] In a third embodiment, the present invention provides a novel process for the preparation of a compound of formula or salt form thereof, the process comprising: (8) saponifying a compound of formula (XII) : (XII) or a salt form thereof and contacting the resulting product with a compound of formula (Xll-a) : (XII-a) to form a compound of formula (Xll-b) (XII -b) ; or a salt form thereof; and, (8-i) contacting the compound of formula (XII-b) with a compound of formula (III) : (III) to form the compound of formula (XIII) , or a salt form thereof . [16] In another preferred embodiment, the compound of formula (XII) is its di (hydrochloric acid) salt; and, the compound of formula (XII-b) is its sodium salt form. [17] In another preferred embodiment, the compound of formula (XII) is prepared by the process comprising: (6) contacting a compound of formula (X) : (X) with thionyl chloride, tetramethylene sulfone, and sulfamide at a temperature suitable to form a compound of formula (XI) : (7) reducing the compound of formula (XI) to form a compound of formula (XII), or a salt form thereof. [18] In another more preferred embodiment, the suitable temperature is in the range of about 100 °C to about 125 °C; the compound of formula (XII) is the di (hydrochloric acid) salt; and, reducing comprises hydrogenating the compound of formula (XI) under hydrogen pressure of about 50 psi to about 70 psi, in the presence of platinum (IV) oxide as a hydrogenation catalyst. [19] In another preferred embodiment, the compound of formula (III) is prepared by the process comprising: (1) contacting a compound of formula (II) : with a coupling agent to form a compound of formula (III) [20] In another more preferred embodiment, the coupling agent is 1- (3-dimethylamino propyl) -3-ethylcarbodiimide and the coupling is performed in acetonitrile and at a temperature in the range of about -10 °C to about 10 °C. [21] In another preferred emodiment, the compound of formula (XII-b) is prepared by the process comprising: (8a) contacting a compound of formula (XII-c) : or a salt form thereof with a base and contacting the resulting product with a compound of formula (Xll-a) : (Xll-a) to form a compound of formula (XII-b) or salt form therof DEFINITIONS The following terms and abbreviations are used herein and defined as follows. The abbreviation: "Ts" or "tosyl" as used herein means a 4-methylphenylsulfonyl protecting group, "Boc" as used herein means a butyloxycarbonyl protecting group, "DMF" as used herein means N,N- dimethylformamide, "THF" as used herein means tetrahydrofuran, "EtOAc" as used herein means ethyl acetate, "MTBE" as used herein means methyl t-butyl ether, "TFA" as used herein means trifluoroacetic acid, "TFMSA" as used herein means trifluoromethanesulfonic acid, "OSu" as used herein means N-hydroxysuccinimido, "RT" as used herein means room temperature, "psi" as used herein means pounds per square inch, "HPLC" as used herein means high performance liquid chromatography, "DIEA" as used herein means N,N- diisopropylethylamine, "HBTU" as used herein means 0-(lH- benzotriazol-1-yl) -N,N,N' ,N' -tetramethyluronium hexaflourophosphate, "DCC" as used herein means N,N'- dicyclohexylcarbodiimide, and "EDC" as used herein means 1- (3-dimethylamino propyl ) -3-ethylcarbodiimide . The reactions of the synthetic methods claimed herein are carried out in suitable solvents which may be readily selected by one of skill in the art of organic synthesis, said suitable solvents generally being any solvent which is substantially nonreactive with the starting materials (reactants) , the intermediates, or products at the temperatures at which the reactions are carried out, i.e., temperatures which may range from the solvent's freezing temperature to the solvent's boiling temperature. A given reaction may be carried out in one solvent or a mixture of more than one solvent. Depending on the particular reaction step, suitable solvents for a particular reaction step may be selected. Such suitable solvents may include, by way of example and without limitation, chlorinated solvents, hydrocarbon solvents, ether solvents, polar protic solvents and polar aprotic solvents. Suitable halogenated solvents include, but are not limited to carbon tetrachloride, bromodichloromethane, dibromochloromethane, bromoform, chloroform, bromochloromethane, dibromomethane, butyl chloride, dichloromethane, tetrachloroethylene, trichloroethylene, 1, 1, 1-trichloroethane, 1, 1, 2-trichloroethane, 1,1- dichloroethane, 2-chloropropane, hexafluorobenzene, 1, 2, 4-trichlorobenzene, o-dichlorobenzene, chlorobenzene, fluorobenzene , fluorotrichloromethane, chlorotrifluoromethane, bromotrifluoromethane, carbon tetrafluoride, dichlorofluoromethane, chlorodifluoromethane, trifluoromethane, 1, 2-dichlorotetrafluorethane and hexafluoroethane . Suitable hydrocarbon solvents include, but are not limited to benzene, cyclohexane, pentane, hexane, toluene, cycloheptane, methylcyclohexane, heptane, ethylbenzene, m-, o-, or p-xylene, octane, indane, nonane, chlorobenzene, or naphthalene . Suitable ether solvents include, but are not limited to dimethoxymethane, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, furan, diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, anisole, or t-butyl methyl ether. Suitable polar protic solvents include, but are not limited to methanol, ethanol, 2-nitroethanol, 2- fluoroethanol, 2 , 2 , 2-trifluoroethanol, ethylene glycol, 1- propanol, 2-propanol, 2-methoxyethanol, 1-butanol, 2- butanol, i-butyl alcohol, t-butyl alcohol, 2-ethoxyethanol, diethylene glycol, 1-, 2-, or 3- pentanol, neo-pentyl alcohol, t-pentyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, cyclohexanol, benzyl alcohol, phenol, and glycerol . Suitable polar aprotic solvents include, but are not limited to dimethylformamide (DMF) , dimethylacetamide (DMAC) , 1, 3-dimethyl-3 , 4, 5, 6-tetrahydro-2 (1H) -pyrimidinone (DMPU) , 1,3 -dimethyl-2-imidazolidinone (DMI), N-methylpyrrolidinone (NMP) , formamide, N-methylacetamide, N-methylformamide, acetonitrile, dimethylsulfoxide, propionitrile, ethyl formate, methyl acetate, hexachloroacetone, acetone, ethyl methyl ketone, ethyl acetate, isopropyl acetate, t-butyl acetate, sulfolane, N,N- dimethylpropionamide, nitromethane, nitrobenzene, hexamethylphosphoramide . As used herein, "coupling solvent" refers to any solvent in which an amine may be reacted with an carboxylic acid derivative to form an amide. Examples of such coupling solvents include, but are not limited to ether, halogenated, hydrocarbon, and polar aprotic solvents. As used herein, "strong acid" includes, but is not limited to mineral acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, lithium bisulfate, potassium bisulfate, sodium bisulfate, and ammonium chloride; and organic acids such as formic acid, acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, ethanoic acid, propionic acid, butyric acid, valeric acid and caproic acid. As used herein, "suitable base" includes any of a variety of bases, the presence of which in a reaction facilitates the synthesis of the desired product. Suitable bases may be selected by one of skill in the art of organic synthesis. Suitable bases include, but are not limited to, inorganic bases such as alkali metal, alkali earth metal, thallium, and ammonium hydroxides, alkoxides, phosphates, and carbonates, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, thallium hydroxide, thallium carbonate, tetra-n- butylammonium carbonate, and ammonium hydroxide. Suitable bases also include organic bases, including but not limited to aromatic and aliphatic amines, such as pyridine; trialkyl amines such as triethylamine, N,N-diisopropylethylamine, N,N-diethylcyclohexylamine, N,N-dimethylcyclohexylamine, N,N,N' -triethylenediamine, N,N-dimethyloctylamine; 1, 5-diazabicyclo[4.3.0] non-5-ene (DBN) ; 1, 4-diazabicyclo[2.2.2] octane (DABCO) ; 1, 8-diazabicyclo[5.4.0 ]undec-7-ene (DBU) ; tetramethylethylenediamine (TMEDA) ; substituted pyridines such as N,N-dimethylaminopyridine (DMAP) , 4-pyrrolidinopyridine, 4-piperidinopyridine and morpholines such as N-methyl morpholine. As used herein, "aqueous base" includes, but is not limited to lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium bicarbonate, sodium bicarbonate and potassium bicarbonate. As used herein, "aqueous base solution" includes, but is not limited to aqueous systems in which aqueous bases are dissolved, which may or may not include additional organic solvent constituents . An example of an aqueous base solution includes, but is not limited to, sodium hydroxide in water. As used herein, "coupling agents" refers to any agent known in the art of organic synthesis or peptide chemistry, which is capable of facilitating the formation of an amide bond from a carboxylic acid and an amine . Examples of such agents include, but are not limited to dicyclohexyl- carbodiimide (DCC) , diisopropylcarbodiimide (DIC) , carbonyldiimidazole (CDI) , 1- (3-dimethylaminopropyl) -3- ethylcarbodiimide (EDC) , 0- (lH-benzotriazol-1-yl) -N,N,N' ,N' - tetramethyluronium tetraflouroborate (TBTU) , and benzotriazol-1-yl-oxy-tripyrrolidinophosphonium hexafluorophosphate (PyBOP) , (benzotriazolyloxy) tris (dimethylamino)phosphonium hexafluorophosphate (BOP) 2,3- dichloro-5, 6-dicyano-l, 4-benzoquinone (DDQ) , and 0-(lH- benzotriazol-1-yl) -N,N,N' ,N' -tetramethyluronium hexaflourophosphate (HBTU) . As used herein, "cyclizing agent" includes any agent with is capable of facilitating the formation of an intramolecular amide bond from a carboxylic acid and an amine. Examples of such agents include, but are not limited to those named herein as coupling agents. As used herein, "suitable pressures" range from atmospheric to any pressure obtainable in a laboratory or industrial plant. As used herein, "hydrogenation catalysts" are those which facilitate the removal of a protecting group known in the art of organic synthesis to be labile to hydrogen. These catalysts are also those which are known in the art to reduce a nitro group to an amino group and a cyano group to an aminomethyl group. Such hydrogenation catalysts include, but are not limited to palladium on carbon, palladium hydroxide on carbon, palladium on calcium carbonate poisoned with lead, platinum on carbon, and platinum (IV) oxide. As used herein, "hydrogenation solvents" are those solvents known in the art of organic synthesis to be useful solvents for reactions which occur under a hydrogen atmosphere, such as hydrogenations . Examples of such solvents include, but are not limited to polar protic solvents such as methanol, ethanol, propanol, isopropanol and the like, ethers, and hydrocarbons, etc. The compounds described herein may have asymmetric centers. Unless otherwise indicated, all chiral, diastereomeric and racemic forms are included in the present invention. It will be appreciated that compounds of the present invention that contain asymmetrically substituted carbon atoms may be isolated in optically active or racemic forms . Methods on how to prepare optically active forms from optically active starting materials are known in the art, such as by resolution of racemic forms or by synthesis. All chiral, diastereomeric, racemic forms and all geometric isomeric forms of a structure are intended. The present invention includes all isotopes of atoms occurring in the intermediates or final compounds. Isotopes include those atoms having the same atomic number but different mass numbers. By way of general example and without limitation, isotopes of hydrogen include tritium and deuterium; isotopes of carbon include 13 C and 14 C. As used herein, "counterion" refers either a negative or positive ion, which serves as a pairing partner in the salts of the intermediates or products described. Examples of counterions include, but are not limited to, ammonium, trifluoroacetate, chloride, and sodium. As used herein, "pharmaceutically acceptable salts" refer to derivatives of the disclosed compounds wherein the intermediates or final compound are modified by making acid or base salts of the intermediates or final compounds. Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic residues such as amines; alkali or organic salts of acidic residues such as carboxylic acids; and the like. It is to be noted that compounds of the present invention contain a variety of ionic centers. Thus, depending on the pH of the solution, it is likely that more than one ion will be present in some of the compounds of the present invention (i.e., zwitterions) . As a result, both external and internal salts are considered to be part of the present invention. The pharmaceutically acceptable salts of the intermediates or final compounds include the conventional non-toxic salts or the quaternary ammonium salts from non- toxic inorganic or organic acids. For example, such conventional non-toxic salts include those derived from inorganic acids such as hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric, nitric and the like; and the salts prepared from organic acids such as acetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric, citric, ascorbic, pamoic, maleic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicylic, sulfanilic, 2- acetoxybenzoic, fumaric, toluenesulfonic, methanesulfonic, ethane disulfonic, oxalic, isethionic, and the like. The pharmaceutically acceptable salts are generally prepared by reacting the free base or acid with stoichiometric amounts or with an excess of the desired salt-forming inorganic or organic acid or base in a suitable solvent or various combinations of solvents. The pharmaceutically acceptable salts of the acids of the intermediates or final compounds are prepared by combination with an appropriate amount of a base, such as an alkali or alkaline earth metal hydroxide e.g. sodium, potassium, lithium, calcium, or magnesium, or an organic base such as an amine, e.g., dibenzylethylenediamine, trimethylamine, piperidine, pyrrolidine, benzylamine and the like, or a quaternary ammonium hydroxide such as tetramethylammoinum hydroxide and the like. As discussed above, pharmaceutically acceptable salts of the compounds of the invention can be prepared by reacting the free acid or base forms of these compounds with a stoichiometric amount of the appropriate base or acid, respectively, in water or in an organic solvent, or in a mixture of the two; generally, nonaqueous media like ether, ethyl acetate, ethanol, isopropanol, or acetonitrile are preferred. Lists of suitable salts are found in Remington's Pharmaceutical Sciences, 17th ed. , Mack Publishing Company, Easton, PA, 1985, p. 1418, the disclosure of which is hereby incorporated by reference. The present invention is contemplated to be practiced on at least a multigram scale, kilogram scale, multikilogram scale, or industrial scale. Multigram scale, as used herein, is preferably the scale wherein at least one starting material is present in 10 grams or more, more preferably at least 50 grams or more, even more preferably at least 100 grams or more. Multikilogram scale, as used herein, is intended to mean the scale wherein more than one kilogram of at least one starting material is used. Industrial scale as used herein is intended to mean a scale which is other than a laboratory scale and which is sufficient to supply product sufficient for either clinical tests or distribution to consumers. The methods of the present invention, by way of example and without limitation, may be further understood by reference to Schemes 1 through 9 which provide the general synthesis for the compound of formula (I) . Compounds of formula (II) , (VI) , (VII) , and (X) are either commercially available, or can be obtained through the manipulations, well known to the artisan of synthetic organic chemistry, of commercially available materials. SYNTHESIS Scheme 1 BocHN^ ^ \^ C0 2 H ► ( BocHN ' ( ID ( III ) Step 1: The compound of formula (III) can be prepared by contacting a compound of formula (II) with a first coupling agent. The first coupling agent is preferably l-(3- dimethylaminopropyl) -3-ethylcarbodiimide. The coupling reaction is preferably run in a polar aprotic solvent (e.g, CH 3 CN) and at a temperature in the range of about -10 °C to about 10 °C. Scheme 2 ( IV) ( IV-b) ( IV-a ) (V) Step 2: By contacting a compound of formula (IV) with a compound of formula (IV-a) or a salt form thereof (e.g., the p-toluenesulfonic acid salt) in the presence of a second coupling agent and a second base, a compound of formula (IV- b) is prepared. Preferably, the second coupling agent is O- (lH-benzotriazol-1-yl) -N,N,N' ,N' -tetramethyluronium hexaflourophosphate and the second base is N,N- diisopropylethylamine. If desired, in situ intermediate (IV-b) may be isolated. This intermediate may also then be purified. The compound of formula V or a salt form thereof (e.g, the hydrochloric acid salt) can then be arrived at by deprotection of (IV-b) . Deprotection can be performed by contacting the compound of formula (V-b) with a strong acid (e.g., hydrochloric acid) at a temperature in the range of about -20 °C to about 0 °C. Scheme 3 (V-a ) (V-b) (vi ; Step 3 : By contacting a compound of formula (V) or a salt form thereof (e.g., the HC1 salt) with a compound of formula (V-a) in the presence of a coupling agent and a base, one can prepare a compound of formula (V-b) . The coupling agent is preferably O- (lH-benzotriazol-1-yl) -N,N, N' , N' - tetramethyluronium hexaf1ourophosphate and the base is preferably N,N-diisopropylethylamine . If desired, in situ intermediate (V-b) may be isolated and may also then be purified. Step 3-i: Deprotecting the compound of formula (V-b) results in a compound of formula (VI) , or a salt form thereof (e.g., the trifluoroacetic acid salt). Deprotecting comprises contacting the compound of formula (V-b) with a strong acid (e.g., trifluoroacetic acid), preferably at a temperature in the range of about -20 °C to about 0 °C. Scheme 4 (VHI-a) Step 4: The compound of formula (VIII) can be formed by contacting a compound of formula (VII) with hydrazine. Step 5: Contacting the compound of formula (VIII) with a compound of formula (VHI-a) and N-hydroxysuccinimide in a polar aprotic solvent in the presence of a second coupling agent provides a compound of formula (IX) . The polar aprotic solvent is preferably DMF, and the second coupling agent is preferably DCC. Scheme 5 (XIII) (XII-b) Step 6: The compound of formula (XI) can be prepared by contacting a compound of formula (X) with thionyl chloride, tetramethylene sulfone, and sulfamide. Preferably at least one mole equivalent of each of thionyl chloride, tetramethylene sulfone, and sulfamide are used. Even more preferably, 1.6 eq. of thionyl chloride, 9.2 eq. of sulfolane and 1.2 eq. of sulfamide are used. A suitable temperature is in the range of about 100 °C to about 125 °C; Step 7: Reducing the compound of formula (XI) provides a compound of formula (XII), or a salt form thereof (e.g., the di-HCl salt form) . Reducing preferably involves hydrogenating the compound of formula (XI) under hydrogen pressure of about 50 psi to about 70 psi, in the presence of a hydrogenation catalyst (e.g., platinum (IV) oxide). Step 8: Saponifying a compound of formula (XII) or a salt form (e.g., the di-HCl salt form) thereof and contacting the resulting compound with a compound of formula (Xll-a) yields a compound of formula (XII-b) or a salt form thereof (e.g., the Na salt) . Saponification includes contacting a compound of formula (XII) or a salt form thereof with an aqeuous base solution (e.g., NaOH/H 2 θ) and adjusting the aqueous base solution to an appropriate pH. The appropriate pH is preferably in the range of about 7.5 to about 8.5, more preferably 7.9-8.1, and the adjustment is preferably made using a strong acid such as HCl . The compound of formula XII-b can then be manipulated to a compound of formula XIII via Step 8-i. Step 8a: As an alternative to step 8, instead of saponifying a compound of formula (XII) , a compound of formula (XII-c) , or a salt form (e.g., the di-HCl salt form) thereof, can be contacted with a base (e.g., NaOH) and the resulting product contacted with a compound of formula (XII- a) to yield a compound of formula (XII-b) or a salt form thereof (e.g., the Na salt). Step 8-i: Contacting the compound of formula (XII-b) with a compound of formula (III) affords the compound of formula (XIII), or a salt form thereof. Preferably the contacting is performed at a temperature in the range of about 0-5«C. Scheme 6 (XIV) Step 9: Coupling of a compound of formula (VI) or a salt form thereof (e.g., a TFA salt) with a compound of formula (XIII) or a salt form thereof renders a compound of formula (XIV) . Coupling in this step is intended to include contacting the two compounds in the presence of a coupling agent and a third base. Preferably, the coupling agent is 0- (lH-benzotriazol-1-yl) -N,N,N' ,N' -tetramethyluronium hexaflourophosphate and the third base is N,N- diisopropylethylamine . Scheme 7 Step 10: Deprotecting the compound of formula (XIV) yields the compound of formula (XV), or a salt form thereof. Deprotection in this step includes hydrogenating the compound of formula (XIV) under suitable hydrogen pressure (e.g., about 14.7 psi) in the presence of a suitable hydrogenation catalyst (e.g., Pd/C) in a suitable hydrogenation solvent (e.g., MeOH) . Preferably, hydrogen is bubbled through the solution. However, pressures from atmosphere to 60 psi can be used. Scheme 8 Step 11: The compound of formula (XVI) can be prepared by cyclizing a compound of formula (XV) . In this step, cyclizing includes contacting the compound of formula (XV) with a cyclizing agent (e.g., 0- (lH-benzotriazol-1-yl) - N,N,N' ,N' -tetramethyluronium tetraflouroborate) in a cyclizing solvent (e.g., CH 3 CN) , in the presence of a second base (e.g., N,N-diisopropylethylamine) . More preferably, the cyclizing solvent is a mixture of CH 3 CN and THF. Step 11 is preferably performed by reverse addition. In this context, reverse addition is preferably conducted by adding a solution of the compound of formula (XV) (e.g., XV in CH 3 CN) to a solution of cyclizing agent, cyclizing solvent and second base. More preferably the solution containing the compound of formula (XV) also contains the second base. Even more preferably, the cyclizing agent is dissolved in CH 3 CN and THF. Preferably, the solution containing the cyclizing agent is heated to a temperature of from 50-70 «C prior to addition of the solution containing a compound of formula (XV) . Even more preferably, the solution containing the cyclizing agent is heated to a temperature of from 57-63 »C prior to addition of XV. The compound of formula (XVI) may be purified using via column chromatography, preferably a C-18 column (e.g., Shandon Hyperprep HS C-18 (12 μ) column (10 x 55.5 cm)). It is preferred that about 300-400 g, more preferably about 369 g, of reaction mixture per L of bed volume is loaded onto the column. Even though such a large amount of material is loaded onto the column, one can obtain purified material using an appropriate eluent and gradient. Preferably, about 65% water/35% acetonitrile is used with a gradient that brings the mixture to about 42% water/58% acetonitrile over about 120 min. Though the flow rate will affect how quickly the compound of formula (XVI) elutes, at 430 mL/min, one can expect elution when the solvent composition is from about 40-55% acetonitrile. Scheme 9 (XVIII ) Step 12: Deprotecting the compound of formula (XVI) affords a compound of formula (XVII) or a salt form thereof (e.g., the di (trifluoromethanesulfonic acid) salt). This step is preferably performed by contacting the compound of formula (XVI) with strong acid at a suitable temperature. A preferred strong acid is a mixture of trifluoroacetic acid and trifluoromethanesulfonic acid. This acid mixture is preferably in a ratio of about 1 molar equivalent of TFA to about 4 molar equivalents of TFMSA. A preferred suitable temperature is from about -30-5 °C. Step 13: The compound of formula (XVIII), or an alternative salt form thereof, can be prepared by contacting a compound of formula (XVII) with a compound of formula (IX) in the presence of a first base followed by quenching (Step 13 -i) . Preferably, the first base is N,N-diisopropylethylamine . The compound of formula (IX) can be other than a sodium salt (e.g., potassium). Step 13 -i: Step 13 is completed by contacting the compound of formula (XVIII) with a quenching agent. Preferably, the quenching agent is ammonium acetate. The compound of formula (XVIII) may be purified using via column chromatography, preferably a C-18 column (e.g., Shandon Hyperprep HS C-18 (12 μ) column (10 x 55.5 cm)). It is preferred that about 30-40 g, more preferably about 33 g, of reaction product per L of bed volume is loaded onto the column. Even though such a large amount of material is loaded onto the column, one can obtain purified material using an appropriate eluent and gradient. Preferably, the gradient conditions are, start: 10% acetonitrile/90% 50 mM aqueous sodium acetate, end: 17% acetonitrile/83% 50 mM aqueous sodium acetate over about 35 min. Followed by a second gradient to achieve 25% acetonitrile/75% 50 mM aqueous sodium acetate over about 260 min. Though the flow rate will affect how quickly the compound of formula (XVI) elutes, at 450 mL/min, one can expect elution when the solvent composition is from about 19 to 21% acetonitrile. Step 14: Desalting the compound of formula (XVIII) gives the compound of formula (I) . In this context, desalting comprises dissolving the compound of formula (XVIII) in an aqueous base solution (e.g., NaOH/H 2 θ) , followed by adjusting the pH of the solution to give a compound of formula (I) . The pH adjustment of the solution comprises the addition of a strong aqueous acid (e.g., HCI/H 2 O) to the solution until a desired pH is achieved, preferably in the range of about 4.1 to about 4.4. At the desired pH, the compound of formula (I) precipitates in zwitterionic form. EXAMPLES Other features of the invention will become apparent in the course of the following descriptions of exemplary embodiments which are given for illustration of the invention, and are not intended to be limiting thereof. EXAMPLE 1 Synthesis of 6- [ [ (1, 1-Dimethylethoxy) carbonyl] amino]hexanoic anhydride (III) Boc-6-aminohexanoic acid (II; 1553 g) is dissolved in acetonitrile (13,663 g) and then cooled to 0-4 °C. Ethyl-3- (3-dimethyamino)propylcarbodiimide hydrochloride (EDC; 786 g) is added and the solution is stirred for 3 h at 0-5 °C. After rotary evaporation (bath temperature 20-30 °C) , the oil is redissolved in ethyl acetate (14,934 g) and water (8,392 g) , and then partitioned. The organic phase is washed two more times with water (8,392 g each), two times with sodium bicarbonate solution (each wash prepared by adding 772 g of sodium bicarbonate to 8,124 g of water), and one time with brine (prepared by adding 2,652 g of sodium chloride to 7,386 g of water). The organic layer is dried over magnesium sulfate (235 g) for 15-30 min, filtered, and then concentrated by rotary evaporation (bath temperature 20-30 °C) . The residue is slurried in cyclohexane (3,525 g) for 60-90 min at 20-25 °C. Solids are isolated by either filtration or centrifugation, washed with cyclohexane (1 x 3,525 g; 1 x 2,585 g) and dried in a vacuum oven at 25-30 °C to afford 1,222 g (82 %) of (III). EXAMPLE 2 Synthesis of N- [N 5 - [Imino [ [ (4- methylphenyl ) sulfonyl] amino] methyl] -N 2 -methyl-L-ornithyl ] - glycine, Phenylmethyl Ester Monohydrochloride (V) A reaction vessel is charged sequentially with ethyl acetate (2,805 g) , (IV; 850 g) , (IV-a as the tosylate salt; 765 g) , 2- (lJf-benzotriazol-1-yl) -1, 1, 3 , 3 -tetramethyluronium hexafluorophosphate (HBTU; 850 g) , and more ethyl acetate (1,131 g) . N, N-diisopropylethyl amine (DIEA; 757 g) is added dropwise, maintaining a temperature of 20-30 °C. After addition is complete, the mixtue is stirred until analytical HPLC shows disappearance of (IV) . A solution of citric acid (327 g) in water (2,665 g) is added, followed by additional ethyl acetate (748 g) . After mixing, layers are separated and the organic layer is washed two more times with citric acid solution, followed by two washes with sodium bicarbonate solution (each prepared by adding 122 g of sodium bicarbonate to 1,264 g of water), and two washes with brine (each prepared by adding 408 g of sodium chloride to 1,139 g of water). The organic phase is dried over magnesium sulfate for 30-60 min and then filtered. Solids are washed with ethyl acetate (1,326 g) and the filtrate (containing the in si tu intermediate (IV-b)) is transferred to a reaction vessel (rinsing with 128 g of ethyl acetate) . After cooling to -15--21 °C, hydrogen chloride gas (approximately 1,308 g) is added to the mixture such that the temperature does not exceed -10 °C. The solution is stirred for 15 min and then examined by analytical HPLC for the disappearance of intermediate (IV-b) . If necessary, the vessel is charged with additional hydrogen chloride gas (approximately 131 g) . After completion, methyl t-butyl ether (MTBE; 4,956 g) is added while maintaining a temperature of -10--15 °C. After addition is complete, the slurry is warmed to -6-0 °C. Solids are isolated by either filtration or centrifugation and then washed with additional MTBE (1 x 2,508 g and 1 x 5,908 g) . Solids are reslurried in MTBE (6,800 g) for 12-15 h at 20-25 °C and then once again filtered or centrifuged, washing with MTBE (2,465 g) . Vacuum-oven drying (30 °C) affords 1082 g (107 %) of (V) as the hydrochloride salt. EXAMPLE 3 Synthesis of N- [2V 5 - [Imino [ [4-methylphenyl) sulfonyl] amino] methyl] -N 2 -methyl-iV 2 -D-valyl-L- ornithyl]glycine, Phenylmethyl Ester Trifluoroacetate (VI) A reaction vessel is charged sequentially with (V) as the hydrochloride salt (1,077 g) , (V-a) (641 g) , HBTU (1,118 g) , and ethyl acetate (8,190 g) . After dissolution is complete, DIEA is added at a rate such that the temperature remains 20-30 °C. The mixture is then stirred until the reaction is complete by analytical HPLC (typically 18-20 h) . A solution of citric acid (645 g) in water (5,251 g) is added, followed by additional ethyl acetate (205 g) . After mixing, layers are separated and the organic phase is washed one additional time with citric acid solution, followed two washes with sodium bicarbonate solution (each prepared by adding 530 g of sodium bicarbonate to 5,525 g of water), and two washes with brine (each prepared by adding 931 g of sodium chloride to 2,595 g of water) . The organic phase is dried over magnesium sulfate (676 g) for 30-60 min and then filtered. Solids are rinsed with ethyl acetate (1,280 g) and the filtrate is partially concentrated by rotary evaporation (bath temperature 25-35 °C) to a target weight of 2,590 g. If necessary, additional ethyl acetate may be added to achieve this target weight. This solution contains the in si tu intermediate (V-b) . A second reaction vessel is charged with trifluoroacetic acid (2,436 g) and cooled to • -15 °C. A portion of the (V-b) solution from above (1,295 g) is further diluted with ethyl acetate (160 g) and then added to the reaction vessel at a rate such that the temperature remains -15--10 °C. After addition is complete, the addition funnel is rinsed with ethyl acetate (60 g) and the solution is stirred at -7--3 °C until completion by analytical HPLC (typically 22-62 h) . A separate reaction vessel is charged with MTBE (9,322 g) and cooled to 0-5 °C. The reaction mixture from above is added to the MTBE-vessel over the course of 50-70 min. After rinsing with additional MTBE (266 g) , the mixture is stirred for 30-60 min at 0-5 °C, after which solids are collected by filtration or centrifugation. The solids are washed once with MTBE (5,412 g) and once with a mixture of MTBE in cyclohexane (1,623 g each) , and are then slurried in a mixture of MTBE and cyclohexane (5,520 g each) for 2-4 h at 20-25 °C. Solids are once again isolated by either filtration or centrifugation, and then washed once with a mixture of MTBE and cyclohexane (5,520 g each) and once again with a smaller quantity of MTBE and cyclohexane (2,165 g each) . Vacuum- oven drying (30 °C) affords 680 g (92 %) of (VI) as its TFA salt . EXAMPLE 4 Synthesis of 6-Hydrazino-3-pyridinecarboxylic Acid (VIII] A solution of (VII) (340 g) in hydrazine monohydrate (1,532 g) is heated to 98-102 °C for 4 h. After cooling to 45-55 °C, the solution is concentrated by rotary evaporation (bath temperature • 60 °C) and the residue is redissolved in water (1,618 g) . With cooling (10-20 °C) , the pH is brought to 5.4-5.6 by adding concentrated hydrochloric acid (approximately 1,160 g) and the precipitate is collected by either filtration or centrifugation. Solids are rinsed with water (194 g) , ethanol (788 g) , and MTBE (486 g) , and are then dried in a vacuum oven (35-40 °C) to afford 301 g (91 %) of (VIII) . EXAMPLE 5 Synthesis of 2- [[ [5- [[ (2 , 5-Dioxo-l-pyrrolidinyl) oxy] carbonyl] - 2-pyridinyl]hydrazono]methyl]benzenesulfonic acid, Monosodium salt (IX) Compound (VHI-a) (400 g) is stirred in DMF (11,172 g) for 10-20 min at 20-25 °C and (VIII) (294 g) is then added. The suspension is stirred for 4-5 h at 20-25 °C and N- hydrox succinimide (HOSu; 221 g) is added. After stirring for 15-20 min at 20-25 °C. -V,-V'-dicyclohexylcarbodiimide (DCC; 813 g) is added and stirring is continued for 14-24 h at 20-25 °C. After filtratration through a bed of Hyflo Super-Cel or Celite (147 g) and rinsing with DMF (1,682 g) , the filtrate is concentrated by rotary evaporation (35-45 °C) . The residue is slurried in DMF (559 g) for 10-30 min at 20-25 °C and MTBE (9,937 g) is added. The mixture is refluxed (external temperature 60-70 °C) for 30-40 min, cooled to 45-52 °C, and then filtered. Solids are washed with MTBE (1,411 g) and then reslurried in methanol (6,997 g) at 70-75 °C (external) for 50-70 min. After a hot filtration, solids are washed with methanol (3,058 g) and MTBE (882 g) , and then dried in a vacuum oven at 87-93 °C until a volatile impurity at 3.2 ppm is no longer visible by X H NMR spectroscopy to afford 639 g (76 %) of (IX) . EXAMPLE 6 Synthesis of 3-Cyano-5-nitrobenzoic acid, Methyl Ester (XI) A reaction vessel is charged with (X) (904 g) , sulfamide (463 g) , sulfolane (4,416 g) , and thionyl chloride (1,194 g) , and then heated to 115-122 °C for 14-22 h. The mixture is cooled to 50-60 °C and an additional aliquot of thionyl chloride (177 g) is added, followed by reheating to 115-122 °C for 5-8 h. After cooling to 40-45 °C, the reaction mixture is worked-up in two portions as follows : A portion of the reaction solution (2,874 g) is added to a flask containing water (16,260 g) while maintaining a temperature of 15-25 °C. After addition is complete, the solution is stirred for 2-3 h at 15-25 °C and solids are either filtered or centrifuged off, rinsing the solids with additional water (2,710 g) . A total of 771 g of crude product is thus obtained. Crude product (770 g) is dissolved in ethyl acetate (19,423 g) by heating to reflux (external temperature 85-95 °C) and then cooling to 55-65 °C. The solution is filtered through Hyflo Super-Cel or Celite (77 g) which is then washed with ethyl acetate (511 g) . The filtrate is concentrated by rotary evaporation (bath temperature »60 °C) and the resulting residue is slurried in ethanol (475 g) and reconcentrated. The ethanol slurry/concentration process is repeated one more time before suspending the solids in ethanol (19,109 g) and heating to 74-78 °C for 12-18 h. The hot solution is filtered through Hyflo Super-Cel or Celite (110 g) which is then washed with ethanol (511 g) . The filtrate is partially concentrated (target weight 10,230 g; additional ethanol may be added if necessary) , brought to reflux (external temperature 85-95 °C) for 30 min, and then cooled to 0-5 °C. After 2-3 h, solids are isolated by filtration or centrifugation and washed with ethanol (730 g) to afford 591 g (71 %) of (XI) . EXAMPLE 7 Synthesis of 3-Amino-5- (aminomethyl)benzoic acid, Methyl Ester Dihydrochloride (XII) A hydrogenation vessel is charged with (XI) (587 g) , 1- propanol (25,629 g) , and concentrated hydrochloric acid (701 g) . A slurry of platinum (IV) oxide (29 g) in 1-propanol (949 g) is added and the mixture is hydrogenated at approximately 60 psi and 55-60 °C. After analytical HPLC shows completion of reaction (an additional 6 g aliquot of platinum (IV) oxide may be necessary), water (5,695 g) is added and the mixture is cooled to 25-35 °C for 30-60 min. Filtration through either a halar filter or Celite affords a filtrate which is concentrated by rotary evaporation (bath temperature • 45 °C) . The residue is slurried in methanol (1,898 g) for approximately 10 min and then reconcentrated. This slurry/concentration process with methanol is repeated one more time before adding a mixture of acetonitrile (5,430 g) and methanol (664 g) and heating to reflux (external temperature 75-85 °C) for 2-3 h. After cooling to 20-25 °C, the mixture is stirred for an additional 2-3 h, and solids are isolated by either filtration or centrifugation. Product is washed with a mixture of acetonitrile (1,481 g) in methanol (150 g) and then dried in a vacuum oven (45 °C) , giving 616 g (86 %) of (XII) as the dihydrochloride salt. EXAMPLE 8 Synthesis of (S) -3- [ [6- [[ (1, 1-Dimethylethoxy) carbonyl] amino] -1- oxohexyl] amino] -5- [ [ [4- (1, 1-dimethylethoxy) -1, 4-dioxo-2- [ [ (phenylmethoxy) carbonyl] amino] butyl] amino] methyl]benzoic Acid (XIII) Compound (XII) as the dihydrochloride salt (305 g) is saponified by adding a solution of sodium hydroxide pellets (204 g) in water (1,649 g) at • 30 °C . After addition is complete, the mixture is stirred for 60-80 min and then a solution of concentrated hydrochloric acid (284 g) in water (767 g) is added at 18-22 °C until the pH is 7.9-8.1. The reaction vessel is then charged with (Xll-a) (493 g) and acetonitrile (4,144 g) . The pH is periodically adjusted to 7.9-8.1 by the addition of sodium hydroxide solution (prepared by dissolving 120 g of sodium hydroxide pellets in 1084 g of water) . After 40-45 min, the reaction is monitored by analytical HPLC and if necessary, additional aliquots of (Xll-a) (24 g) are added until the reaction is complete. The mixture is partially concentrated (target weight 4,305 g) by rotary evaporation (bath temperature 25- 35 °C) , and sufficient water is added to bring the total volume to approximately 8,914 mL. Ethyl acetate (9,251 g) is added and then the pH is brought to 3.4-3.6 by the addition of a solution of citric acid (474 g) in water (1,133 g) . The aqueous layer is removed and the organic phase is washed three times with water (1,245 g each) and twice with brine (each wash is prepared by adding 588 g of sodium chloride to 1,641 g of water). The organic solution is then dried over magnesium sulfate (169 g) for 15-30 min and filtered (washing with 530 g of ethyl acetate) . The filtrate is concentrated by rotary evaporation (bath temperature 25-35 °C) to afford (XII-b) , redissolved in THF (458 g) , and reconcentrated (bath temperature 25-35 °C) . The THF addition/concentration process is repeated one more time and the residue is then redissolved in a larger quantity of THF (2,590 g) and cooled to 0-3 °C. A solution of (III) (501 g) in THF (1,527 g) is added over 20-60 min such that the temperature remains at 0-5 °C. After addition is complete, the solution is warmed to 20-25 °C over 50-70 min, and then stirred for 16-20 h. Rotary evaporation (bath temperature 30-40 °C) affords an oil which is redissolved at 30-40 °C in ethyl acetate (1,482 g) and reconcentrated. The resulting oil is redissolved in a larger volume of ethyl acetate (8,301 g) and then washed twice with sodium bicarbonate (once by preparing a solution of 623 g of sodium bicarbonate in 6,493 g of water and once by preparing a solution of 311 g of sodium bicarbonate in 3,246 g of water), once with hydrochloric acid solution (prepared by dissolving 129 g of concentrated hydrochloric acid in 6,394 g of water), and once with brine (prepared by adding 1017 g of sodium chloride to 2,837 g of water) . The organic phase is dried over magnesium sulfate (163 g) for 15-30 min, filtered, solids are rinsed with ethyl acetate (667 g) , and the filtrate is partially concentrated (target weight 4,471 g) by rotary evaporation (bath temperature 30- 40 °C) . The solution is cooled to 20-25 °C for 16-20 h, after which solids are filtered or centrifuged off and washed with ethyl acetate (697 g) . Solids are suspended in a mixture of ethyl acetate (504 g) and n-heptane (7,412 g) , and heated to 40-46 °C for 40-60 min. After cooling to 20- 25 °C, solids are isolated by filtration and washed with additional n-heptane . After drying in a vacuum oven (25 °C) , 530 g (65 %) of (XIII) is obtained. EXAMPLE 9 Synthesis of N- [N 2 - [N- [3- [ [6- [ [ (1, 1- Dimethylethoxy) carbonyl] amino] -1-oxohexyl] amino] -5- [ [ [4- (1,1- dimethylethoxy) -1, 4-dioxo-2 [ [ (phenyl- methoxy) carbonyl] amino] butyl] amino] methyl] -benzoyl] -D-valyl] - N 5 - [imino [ [ (4-methylphenyl) sulfonyl] amino] methyl] -N 2 -methyl-L- ornithyl] -glycine, Phenylmethyl Ester (XIV) A reaction vessel is charged with acetonitrile (3,191 g) , HBTU (325 g) , (XIII) (510 g) , (VI) (602 g) , and additional acetonitrile (287 g) . After stirring for 5-10 min, DIEA (443 g) is added such that the temperature remains at 20-30 °C. After addition is complete, the reaction is stirred at 20-25 °C for 6-20 h and monitored by analytical HPLC. If necessary, an additional aliquot of VI (30 g) may be added. Ethyl acetate (6,516 g) is added, followed by a solution of citric acid (530 g of citric acid in 4,774 g of water) . After mixing, the aqueous phase is separated off, and the organic phase is washed two additonal times with citric acid solution, two times with sodium bicarbonate solution (each wash is prepared by adding 473 g of sodium bicarbonate to 4,935 g of water), and two times with brine (each wash is prepared by adding 1,613 g of sodium chloride to 4,507 g of water) . The organic phase is dried over sodium sulfate (1,112 g) , solids are rinsed with ethyl acetate (1,627 g) , and the filtrate is concentrated by rotary evaporation (bath temperature 35-45 °C) to afford (XIV) as an oily foam (1,250 g; 134 %) which is used without extensive drying in the next reaction. EXAMPLE 10 Synthesis of N- [N 2 - [N- [3- [ [ [2-Amino-4- (1, 1-dimethylethoxy) -1, 4- dioxobutyl] amino]methyl] -5- [ [6- [ [ (1, 1-dimethylethoxy) - carbonyl] amino] -1-oxohexyl] amino] benzoyl] -D-valyl] -N 5 - [imino[ [ (4-methylphenyl) sulfonyl] amino] methyl ] -ZV 2 -methyl-L- ornithyl] glycine (XV) Compound (XIV) (2,385 g) is dissolved in methanol (18,889 g) , and palladium on carbon (239 g) is added and hydrogen gas is bubbled through the mixture. After the reaction is complete (analytical HPLC) , the mixture is filtered through Hyflo Super-Cel or Celite (239 g) and solids are rinsed with methanol (1,322 g) . The filtrate is concentrated to a viscous oil by rotary evaporation (bath temperature 25-45 °C) and is further dried on a high vacuum line at 20-25 °C for 18-72 h, affording 1,751 g (118 %) of (XV) . EXAMPLE 11 Synthesis of N- [3- (Aminomethyl) -5- [ [ (6- [ [ (1, 1- dimethylethoxy) carbonyl] amino] -1-oxohexyl) amino] benzoyl] -D- valyl-iV 5 - [imino [ [4-methylphenyl) sulfonyl] amino] methyl] -N 2 - methyl-L-ornithylglycyl-L-aspartic acid, Cyclic (4 1 —>1) -Peptide (XVI) A flask is charged with acetonitrile (1,744 g) , DIEA (498 g) , (XV) (1,744 g) , and additional acetonitrile (302 g) . A second reaction vessel is charged with HBTU (741 g) and acetonitrile (4,773 g) , and stirred at 15-25 °C until everything is in solution. THF (1,006 g) is added and the mixture is heated to 57-63 °C, after which the (XV) solution from above is added over the course of 1.5-2.5 h. After addition is complete, the addition funnel is rinsed with a solution of DIEA (60 g) and acetonitrile (273 g) , and the reaction mixture is stirred for 0.5-5 h and monitored by analytical HPLC. After reaction is complete, the solution is cooled to 15-25 °C (and may be stored for up to 3 weeks at • -5°C) . Portions are removed for preparative HPLC purification . Acetonitrile (13,962 g) is mixed with water (33,150 g) . This mixture is added to a warmed (external temperature 35 °C) portion of the reaction mixture from above (1,625 g) with stirring over 15-30 min. After stirring for 30-90 min at 22-28 °C, the solution is filtered, and the filtrate is purified by preparative HPLC as follows: A Shandon Hyperprep HS C-18 (12 μ) column (10 x 55.5 cm) is equilibrated with 65 % water/35 % acetonitrile. The solution from above is pumped onto the column. After loading is complete, the column is eluded at 430 mL/min under isocratic conditions (65 % water/35 % acetonitrile) for 21 min. This is followed by a linear gradient (to 42 % water/58 % acetonitrile) over 120 min. The main peak typically elutes when the solvent composition is between 40- 55% acetonitrile. The main peak is fractionated and fractions are analyzed by analytical HPLC. Fractions with > 95 % purity are extracted with into ethyl acetate (0.48 g of ethyl acetate per gram of prep HPLC eluant) and the aqueous phase is back-extracted with ethyl acetate (0.24 g of ethyl acetate per gram of prep HPLC eluant; sodium chloride may be added to improve phase separation) . The combined organic phases from all preparative HPLC runs are concentrated down in one flask by rotary evaporation (bath temperature 35-50 °C) . Product is further dried in a vacuum oven at 35-45 °C, to afford 759 g (44 %) of (XVI) . EXAMPLE 12 Synthesis of N- [3- (Aminomethyl) -5- [ ( 6-amino-l-oxohexyl) amino] benzoyl] -D-valyl -N 2 -methyl-L-arginylglycyl-L-aspartic Acid, Cyclic (4 1 —>1) -Peptide, Bis (trifluoromethanesulfonate) (XVII) A reaction vessel is charged with trifluoroacetic acid (1,258 g) and cooled to 12-18 °C. (XVI) (340 g) is added in portions over 10-30 min and the mixture is stirred at 10-20 °C until all solids go into solution. After cooling to -15- -20 °C, trifluoromethanesulfonic acid (2,883 g) is added at a rate such that the temperature remains between -10 and -20 °C. After addition is complete, anisole (274 g) is added, once again maintaining the temperature in the same range. The mixture is stirred at -5--15 °C until completion by analytical HPLC, and then cooled to -30—25 °C. The reaction is quenched by adding diisopropyl ether (9,860 g) at a rate such that the temperature remains • -25 °C. After addition is complete, the mixture is brought to -25--15 °C. Solids are isolated by either filtration or centrifugation, washed with cool (-15--5 °C) diisopropyl ether (2,465 g) , and then slurried for 5-15 min with diisopropyl ether (4,930 g) at 0-20 °C. Solids are isolated by either filtration or centrifugation, and washed with diisopropyl ether (1,849 g) . The slurry/filtration/wash sequence is repeated one more time, and the resulting solids are dried in a vacuum oven (25 °C) affording 381 g (113 %) of (XVII) as the bis (TFMSA) salt . EXAMPLE 13 Synthesis of N- [3- (Aminomethyl) -5- [ [l-oxo-6- [ [ [6- [ [ (2- sulfonyl )methylene] hydrazino] -3- pyridinyl] carbonyl] amino]hexyl] amino] benzoyl] -D-valyl -N 2 - methyl-L-arginylglycyl-L-aspartic Acid, Cyclic (4 1 ->1) -Peptide, Monoammonium Salt (XVIII) A reaction vessel is charged with (XVII) as the bis (TFMSA) salt (798 g) , (IX) (414 g) , and DMF (13,694 g) . The mixture is stirred at 15-30 °C until all solids are in solution. DIEA (363 g) is then added over 5-20 min, while maintaining the temperature at 15-30 °C, and stirring is continued at 15-30 °C for 16-26 h. After the reaction is complete (analytical HPLC) , ammonium acetate (160 g) is added to quench unreacted (IX) and the mixture is concentrated by rotary evaporation (bath temperature 35-45 °C) . The resulting oil is stirred with ethyl acetate (7,980 g) for 20-45 min then transferred to a reaction vessel. Additional ethyl acetate (15,960 g) is added and the suspension is stirred at 20-25 °C for 15-30 min. Crude (XVIII) (741 g; 92 %) is isolated by either filtration or centrifugation and is washed with ethyl acetate (10,785 g) before drying in a vacuum oven (40-50 °C) for 18-72 h. Crude (XVIII) is purified in portions by preparative HPLC. A sample solution is prepared by dissolving crude (XVIII) (147 g) in a solution of 0.1 M aqueous ammonium acetate (4,910 g) and acetonitrile (3,838 g) . After diluting with additional 0.1 M ammonium acetate (40,250 g) , the solution is loaded onto a Shandon Hyperprep HS C-18 (12 μ) column (10 x 55.5 cm), previously equilibrated with 90 % 50 mM ammonium acetate/10 % acetonitrile. After loading is complete, the material is eluted under linear gradient conditions at 450 mL/min. The gradient conditions are: start: 10% acetonitrile/90% 50 mM aqueous sodium acetate, end: 17% acetonitrile/83% 50 mM aqueous sodium acetate over 35 min. A second gradient is then used to achieve 25% acetonitrile/75% 50 mM aqueous sodium acetate over 260 min. The main peak typically elutes when the solvent composition is between 19-21% acetonitrile. The main peak is fractionated and the resulting fractions may be stored under refrigeration (<15 °C) for up to two weeks. Fractions from all runs with >95 % purity (analytical HPLC) are combined for rotary evaporation (bath temperature 40-50 °C) . The resulting solids are redissolved at 40-50 °C in acetonitrile (1,564 g) and water (2,000 g) , the solution is filtered, and the filtrate is reevaporated at 40-50 °C. Solids are once again redissolved in acetonitrile/water and evaporated. Finally, acetonitrile (1,546 g) is added and the suspension evaporated. Drying in a vacuum oven (50-60 °C) affords 529 g (65 %) of purified (XVIII) as the ammonium salt. EXAMPLE 14 Synthesis of N- [3- (Aminomethyl) -5- [ [l-oxo-6- [ [ [6- [ [ (2- sulfonyl)methylene]hydrazino] -3 pyridinyl] carbonyl] amino]hexyl] amino] benzoyl] -D-valyl-I\7 2 - methyl-L-arginylglycyl-L-aspartic Acid, Cyclic (4 1 ->1)- Peptide (I) A reaction vessel is charged with acetonitrile (1,153 g) and a solution of sodium hydroxide pellets (8.4 g) dissolved in water (12,105 g) . (XVIII) as the ammonium salt (525 g) is added in portions over 15-45 min at 15-30 °C. The pH is the brought to 6.1-6.5 by the addition of a sodium hydroxide solution (prepared by dissolving 16 g of sodium hydroxide pellets in water, 315g, 1.3M) and stirred until all solids are in solution. Concentrated hydrochloric acid (301 g) is dissolved in water (902 g) and is added portionwise to the the reaction solution at 15-30 °C to bring the pH to 4.1-4.4. After stirring for 10-20 min, the pH is readjusted if necessary, and solids are isolated by either vacuum or centrifugal filtration. The reactor is rinsed with water (5,402 g) and the solids are rinsed with additional water (5,439 g) . Product is dried in a vacuum oven at 50-60 °C until the water content is < 5 %, to give (I) (294 g; 57% yield) . Although this invention has been described with respect to specific embodiments, the details of these embodiments are not to be construed as limitations. Various equivalents, changes and modifications may be made without departing from the spirit and scope of this invention, and it is understood that such equivalent embodiments are part of this invention.

Claims: WHAT IS CLAIMED AS NEW AND DESIRED TO BE SECURED BY LETTER PATENT OF UNITED STATES IS: 1. A process for the preparation of a compound of formula (I) : (I) ; or a pharmaceutically acceptable salt form thereof, the process comprising: (11) cyclizing a compound of formula (XV) : (XV) ; or a salt form thereof, to form a compound of formula (XVI) (XVI) ; (12) deprotecting the compound of formula (XVI) to form a compound of formula (XVII) : (XVII) or a salt form thereof; (13) contacting the compound of formula (XVII) with a compound of formula (IX) : (IX) in the presence of a first base. (13-i) contacting the reaction solution from step (13) with a quenching agent to form a compound of formula (XVIII) : (XVIII) or an alternative salt form thereof; and, (14) desalting the compound of formula (XVIII) to give the compound of formula (I) . 2. The process according to Claim 1, wherein: cyclizing comprises contacting the compound of formula (XV) with a cyclizing agent in a cyclizing solvent, in the presence of a second base; deprotecting comprises contacting the compound of formula (XVI) with strong acid at a suitable temperature; and, desalting comprises dissolving the compound of formula (XVIII) in an aqueous base solution, followed by adjusting the pH of the solution to give a compound of formula (I) . 3. The process according to Claim 2, wherein: the cyclizing agent is 0- (lH-benzotriazol-1-yl) -N,N, N' ,N' tetramethyluronium tetraflouroborate; the cyclizing solvent is acetonitrile; the second base is N,N-diisopropylethylamine; the strong acid is a mixture of trifluoroacetic acid and trifluoromethanesulfonic acid; the suitable temperature is from about -30 °C to about 5 °C; the compound of formula (XVII) is its di (trifluoromethanesulfonic acid) salt form; the first base is N,N-diisopropylethylamine; the quenching agent is ammonium acetate; the aqueous base solution comprises sodium hydroxide in water; and, adjusting the pH comprises the addition of aqueous hydrochloric acid to the solution until a pH in the range of about 4.1 to about 4.4 is achieved. 4. The process according to Claim 2, wherein the compound of formula (XVI) is purified using a C-18 column by loading about 369 g of the reaction solution from step 11 per L of bed volume. 5. The process according to Claim 2, wherein the compound of formula (XVIII) is purified using a C-18 column by loading about 33 g of the reaction product from step 13i per L of bed volume . 6. The process according to Claim 1, wherein the compound of formula (XV) is prepared by a process comprising: (9) coupling a compound of formula (VI) (VI) or a salt form thereof, with a compound of formula (XIII ; (XIII) or a salt form thereof, to form a compound of formula (XIV) (XIV) ; and (10) deprotecting the compound of formula (XIV) to form the compound of formula (XV), or a salt form thereof. 7. The process according to Claim 6, wherein: coupling comprises contacting the compound of formula (VI) with the compound of formula (XIII) in the presence of a coupling agent and a third base; and, deprotecting comprises hydrogenating the compound of formula (XIV) under suitable hydrogen pressure in the presence of a hydrogenation catalyst in a hydrogenation solvent. 8. The process according to Claim 7, wherein: compound of formula (VI) is in its trifluoroacetic acid salt form; the coupling agent is O- (lH-benzotriazol-1-yl) - N,N,N' ,N' -tetramethyluronium hexaflourophosphate; the third base is N,N-diisopropylethylamine; the suitable pressure is about 14.7 psi; the hydrogenation catalyst is palladium on carbon; and, the hydrogenation solvent is methanol. 9. The process according to Claim 1, wherein the compound of formula (IX) is prepared by the process comprising: (4) contacting a compound of formula (VII) : (vn; with hydrazine to form a compound of formula (VIII) (VIII) ; (5) contacting the compound of formula (VIII) with a compound of formula (VHI-a) : (VHI-a) and N-hydroxysuccinimide in a polar aprotic solvent in the presence of a second coupling agent to form a compound of formula (IX) . 10. The process according to Claim 9, wherein the polar aprotic solvent is N,N-dimethylformamide, and the second coupling agent is N,N' -dicyclohexylcarbodiimide . 11. A process for the preparation of a compound of formula (VI) : (VI ) or a salt form thereof, the process comprising: (3) contacting a compound of formula (V) : (V) or a salt form thereof, with a compound of formula (V-a) (V-a] in the presence of a coupling agent and a base to form a compound of formula (V-b) : (V-b) ; and (3-i) deprotecting the compound of formula (V-b) to form a compound of formula (VI), or a salt form thereof. 12. The process according to Claim 11, wherein: the compound of formula (VI) is its trifluoroacetic acid salt form; the coupling agent is 0- (lH-benzotriazol-1-yl) - N,N,N' , N' -tetramethyluronium hexaflourophosphate; the base is N,N-diisopropylethylamine; deprotecting comprises contacting the compound of formula (V-b) with trifluoroacetic acid at a temperature in the range of about -20 °C to about 0 °C; and, the compound of formula (V) is its hydrochloric acid salt form. 13. The process according the Claim 11, wherein the compound of formula (V) is prepared by the process comprising : (2) contacting a compound of formula (IV) : (IV) with a compound of formula (IV-a) : (IV-a) or a salt form thereof; in the presence of a second coupling agent and a second base to form a compound of formula (IV- b) : (IV-b) ; and, (2-i) deprotecting the compound of formula (IV-b) to form the compound of formula (V), or a salt form thereof. 14. The process according to Claim 13, wherein: the compound of formula (IV-a) is its p-toluenesulfonic acid salt form; the second coupling agent is O- (lH-benzotriazol-1-yl) - N,N,N' ,N' -tetramethyluronium hexaflourophosphate; the second base is N,N-diisopropylethylamine; deprotecting comprises contacting the compound of formula (V-b) with hydrochloric acid at a temperature in the range of about -20 °C to about 0 °C; and, the compound of formula (V) is its hydrochloric acid salt form. 15. A process for the preparation of a compound of formula (XIII) : or salt thereof, the process comprising: (8) saponifying a compound of formula (XII) (XII) or a salt form thereof and contacting the resulting product with a compound of formula (Xll-a) : CBZ H γ γ o, Bu SuO * 0 (Xll-a ) to form a compound of formula (XII-b) (XII-b) ; or a salt form thereof; and, (8-i) contacting the compound of formula (XII-b) with a compound of formula (III) : (III) to form the compound of formula (XIII) , or a salt form thereof . 16. The process according to Claim 15, wherein: the compound of formula (XII) is its di (hydrochloric acid) salt; and, the compound of formula (XII-b) is its sodium salt form. 17. The process according the Claim 15, wherein the compound of formula (XII) is prepared by the process comprising: (6) contacting a compound of formula (X) with thionyl chloride, tetramethylene sulfone, and sulfamide at a temperature suitable to form a compound of formula (XI) : (7) reducing the compound of formula (XI) to form a compound of formula (XII), or a salt form thereof. 18. The process according to Claim 17, wherein: the suitable temperature is in the range of about 100 °C to about 125 °C; the compound of formula (XII) is the di (hydrochloric acid) salt; and, reducing comprises hydrogenating the compound of formula (XI) under hydrogen pressure of about 50 psi to about 70 psi, in the presence of platinum (IV) oxide as a hydrogenation catalyst. 19. The process according to Claim 15, wherein the compound of formula (III) is prepared by the process comprising: (1) contacting a compound of formula (II) : with a coupling agent to form a compound of formula (III) 20. The process according to Claim 19, wherein the coupling agent is 1- (3-dimethylamino propyl) -3- ethylcarbodiimide and the coupling is performed in acetonitrile and at a temperature in the range of about -10 °C to about 10 °C. 21. The process according to Claim 15, wherein the compound of formula (XII-b) is prepared by the process comprising: (8a) contacting a compound of formula (XII-c) : or a salt form thereof with a base and contacting the resulting product with a compound of formula (Xll-a) : (XII-a) to form a compound of formula (XII-b) or salt form therof.

Inventors: BISHOP JOHN, BISHOP, JOHN
Applicants: DU PONT PHARM CO, DU PONT PHARMACEUTICALS COMPANY
Application year: 1999
Main classification: C07K7
IPC codes: A61K51, C07C271, C07K1, C07K5, C07K7, G01T1