Abstract:
Aminocrotonyl derivatives of 3,5-dinitropyridines are disclosed to have activity in increasing the sensitivity of tumor cells to radiation. Also disclosed are methods of preparing such compounds and pharmaceutical compositions including such compounds.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to aminocrotonyl derivatives of 3,5-dinitropyridine used as sensitizers of tumor cells to therapeutic radiation. It also relates to the process of preparing such compounds starting with 2-fluoro-3,5-dinitropyridine and reacting it with an amino substituted crotonate ester. In addition, the present invention relates to pharmaceutical compositions comprising such aminocrotonyl 3,5-dinitropyridines and to methods of treatment comprising administering such compounds to patients undergoing radiation treatment to enhance the effectiveness of such treatment. 
     At the present time, certain other unrelated compounds are in experimental clinical use as radiation sensitizers. However, these compounds--for example, metronidazole and misonidazole--suffer from the drawback that they also cause neurotoxicity which limits their usefulness. The compounds of the present invention are effective radiation sensitizers, but are believed to have a more favorable therapeutic ratio. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The composition of the present invention which are useful as radiation sensitizers are derivatives of 3,5-dinitropyridines in which the pyridine ring is substituted with a 2-amino (or substituted amino)-1-carboxy (or carboalkoxy)-alken-1-yl radical. 
     More specifically, the invention relates to derivatives of 3,5-dinitropyridines of the formula ##STR1## wherein R, R 1  and R 2  are the same or different and are each selective from the group consisting of hydrogen, C 1-6  -alkyl, C 1-6  mono- or poly-hydroxyalkyl or C 1-6  -aminoalkyl and acid addition salts thereof. 
     Still more specifically this invention comprises 3,5-dinitropyridines of the formula ##STR2## wherein R and R 2  are as defined hereinabove. 
     The substituted 3,5-dinitropyridines described hereinabove are prepared by reaction of 3,5-dinitro-2-fluoropyridine with an amino substituted lower alkenyl ester to produce the desired compound in accordance with the equation set forth below: ##STR3## The reaction of the 2-fluoro-3,5-dinitropyridine is carried out by mixing it with an equimolar amount of the selected loweralkenyl ester in the presence of a equimolar amount of a tertiary amine such as triethyl amine or pyridine and maintaining the reaction mixture at a temperature of 25° or heating at a temperature of 50° for a period of 12 hours to 3 days to accelerate the reaction. Progress of the reaction is followed by thin layer chromatography. It is preferred to carry out the reaction in the presence of a solvent for the reactants. Solvents such as loweralkanols e.g. ethanol, n-propanol or hexamethylphosphorous triamide can be employed for this purpose. 
     As indicated hereinabove acid addition salts of compounds of Formula I may be prepared by mixing a selected compound of Formula I with an equimolar amount of a strong mineral acid in a solvent for the reactants at a temperature of 0° to 50° C. Solvents preferred are lower alkanols such as methanol, ethanol, isopropanol. The salt is precipitated from the alcoholic solution, filtered, washed with a minimal amount of cold alcohol and air dried. 
     The method of treatment of human patients or domestic animals undergoing radiation treatment of malignant disease processes employs the compounds of the present invention in pharmaceutical compositions that are administered orally or parenterally, preferably intravenously. The dose employed depends on the radiation protocol for each individual patient. In protocols where the radition dose is divided into a large number of fractions, the drug can be administered at intervals in the schedule and not necessarily with each radiation treatment. It should be noted that the compounds of the present invention are not intended for chronic administration. In general, the drug is administered from 10  minutes to 5 hours prior to the radiation treatment in a dosage amount of between 0.25 to about 4.0 grams per square meter of body surface, approximately equivalent to a dosage of 6 to 100 mg/kg of patient body weight as set forth in the &#34;Nelson Textbook of Pediatrics&#34; Eleventh Edition (1979) p. 31, edited by Vaughan, McKay, Behrman, and Nelson. 
     The dosage range given is the effective dosage range and the decision as to the exact dosage used must be made by the administering physician based on his judgement of the patient&#39;s general physical condition. In determining the dose for the individual patient, the physician may begin with an initial dose of 0.25 g/square meter of body surface to determine how well the drug is tolerated and increase the dosage with each suceeding radiation treatment, observing the patient carefully for any drug side effect. The composition to be administered is an effective amount of the active compound and a pharmaceutical carrier for said active compound. 
     The dosage form for intravenous administration is a sterile isotonic solution of the drug. Oral dosage forms such as tablets, capsules, or elixirs are preferred. 
     Capsules or tablets containing from 25, 50, 100 or 500 mg of drug/capsule or tablets are satisfactory for use in the method of treatment of our invention. 
     PREPARATION OF REACTANTS 
     Preparation 1 
     Methyl 3-(2,3-dihydroxypropyl)amino-2-butenoate (2) 
     To 5.0 g (0.051 m) methyl-2-butynoate in 25 ml absolute ethanol is added 5.0 g (0.055 m), 2,3-dihydroxypropylamine. This solution is heated at 75°-80° for 18 hours and the solvent is then removed at reduced pressure. The residue oil is chromatographed on silica gel, eluting with 10% methanol/chloroform to afford the desired product as a white solid. m.p. 109°-111°. The yield is 5.6 g (59%). 
     PREPARATION 2 ##STR4## 
     Methyl 3-(1-deoxy--1-arabinyl)amino-2-butenoate (3) 
     To 4.9 g (0.05 m) methyl-2-butynoate in 100 ml dry dimethylsulfoxide is added 6.5 g (0.043 m) 1-amino-1-deoxyarabinitol in one portion. The resulting solution is heated at 70°-75° for 16 hours. The solvent is then removed in vacuo to give a white solid that is triturated with Et 2  O. This suspension is filtered to afford the desired product as a white powder, m.p. 162°-4°. 
     PREPARATION 3 
     Methyl 3-(1,3,4-trihydroxybutylamino-2-butenoate (6) 
     In accordance with the procedure described in J. Med. Chem. Vol. 19, pg. 157 (1976), 1,4-butenediol is oxidized using m-chloroperbenzoic acid to give 2,3-epoxy-1,4-butanediol of the structure ##STR5## The butane epoxide is mixed with an excess of liquid ammonia and the mixture heated at 100° C. in a reaction bomb for 15 hours. The reaction is cooled and pressure released. The ammonia is then evaporated leaving 3-amino-1,2,4-butanetriol. The ester 6 was prepared from 3-amino-1,2,4-butanetriol and methyl-2-butynoate as described for 3. 
    
    
     The following examples are intended to illustrate but do not limit the process of preparation, product, compositions, or method of treatment aspects of the invention. 
     EXAMPLE 1 
     Methyl 3-(2,3-dihydroxypropyl)amino-2-(3,5-dinitropyridin-2-yl)-2-butenoate (4) 
     To a solution of 0.5 g (0.0026 m) 3,5-dinitro-2-fluoropyridine (1) and 0.3 g (0.0026 m) triethylamine in 10 ml isopropanol is added 0.48 g (0.0025 m) methyl 3-(2,3-dihydroxypropyl)amino-2-butenoate (2). This solution is stirred at room temperature for two days, concentrated to an oil in vacuo and the residue is chromatographed on silica gel with 8% methanol/chloroform. The material with R f  =0.5 is collected. This reddish brown material is recrystallized from acetonitrile/n-butylchloride, m.p. 128°-9°. 
     EXAMPLE 2 ##STR6## 
     Methyl 3-(1-deoxy-1-arabinyl)amino-2-(3,5-dinitropyridin-2-yl)-2-butenoate (5) 
     To a solution of 1.0 g (0.004 m) methyl 3-(1-deoxy-1-arabinyl)amino-2-butenoate (3) in 25 ml hexamethyl phosphorus triamide is added 0.5 g (0.005 m) triethylamine and 0.85 g (0.0045 m) 3,5-dinitro-2-fluoropyridine (1). This solution is stirred, the solvent removed in vacuo and the residue is chromatographed on silica gel eluting with 12% methanol/chloroform. Material with R f  =0.4 is collected. If necessary, this is further purified by preparative high pressure liquid chromatography. The desired product is an orange solid, m.p. 132°-6°. 
     EXAMPLE 3 
     When the procedure of Example 2 is repeated but using an equivalent amount of the reactant 6 instead of the butenoate ester of Example 2 the indicated product 7 is obtained. ##STR7## 
     EXAMPLE 4 
     Sterile Isotonic Solutions for Injection 
     Suitable formulations for injection are prepared by dissolving each of the compounds of Examples 1-3 inclusive in isotonic solution in a concentration of about 1 mg/ml and sterilizing the resulting solution. It is suitable for intravenous injection. 
     EXAMPLE 5 
     Capsules 
     Suitable formulations for oral administration are prepared by filling appropriately sized capsules individually with 25 and 50 mg portions of each of the compounds produced in accordance with Examples 1-3 inclusive. 
     EXAMPLE 6 
     
         ______________________________________Tablet FormulationIngredients            Amount______________________________________Product of Examples 1-3                  25     mgCalcium phosphate      120    mgLactose                50     mgStarch                 23     mgMagnesium Stearate     1      mg______________________________________