Abstract:
The compound (2&#39;,4&#39;-difluoro-4-biphenyl)oxyacetic acid and its pharmaceutically acceptable salts with a metal or an organic base are described. They exhibit high antiinflammatory and analgesic activity and do not cause gastric lesions.

Description:
DESCRIPTION OF THE INVENTION 
     The present invention relates to substituted oxyacetic acids and more specifically to novel compounds exhibiting high antiinflammatory activity, high analgesic activity and free from gastric lesion effects. The novel compounds according to the present invention are represented by the compound (2&#39;,4&#39;-difluoro-4-biphenyl)oxyacetic acid of formula I: ##STR1## and its pharmaceutically acceptable salts with metallic ions, such as sodium, potassium, magnesium, and calcium or with pharmaceutically acceptable organic bases, such as lysine, arginine, diethanolamine. An object of the present invention is to prepare novel compounds exhibiting high antiinflammatory activity and analgesic activity and completely free of gastric lesion effects. 
     Another object of the present invention is to provide a process for the preparation of the acid of formula I and its salts. 
     Still another object of the present invention is to provide pharmaceutical compositions and a method of administration of the novel compounds according to the present invention. 
     The process of preparation of the compound of formula I consists of reacting the sodium salt of 4-(2&#39;,4&#39;-difluorophenyl)phenol II with ethylbromoacetate III, obtaining the ester of formula IV and hydrolyzing the ester in accordance with the reaction scheme hereinbelow: ##STR2## 
     The reaction between compound II and compound III may be carried out in a lower alcohol, preferably ethanol, the compound of formula II being advantageously prepared in situ. The ester of formula IV may be hydrolyzed directly in the crude state with an aqueous solution of an alkali hydroxide. From the solution of the salt of the compound of formula I, the acid of formula I is obtained by acidification with an inorganic acid. 
    
    
     EXAMPLE 1 
     Method of Preparation 
     In a flask of 100 cc capacity, sodium in the amount of 0.22 grams is reacted with 30 cc of absolute ethanol. After the sodium has completely gone in solution, there are added 2 grams of 4-(2&#39;,4&#39;-difluorophenyl)phenol and then 1.1 cc of ethylbromoacetate. The mixture is allowed to reflux for four hours and then the solvent is evaporated on the vacuum. The residue is treated with 30 cc of 10% sodium hydroxide and allowed to reflux for three hours. After cooling, the solution is acidified with dilute hydrochloric acid. The precipitate is filtered with suction and recrystallized from a mixture of ethyl ether-n-hexane. Yield: 2 grams of the acid of formula I (83%). 
     The acid melts at 198°-200° C. It is soluble in hot lower alcohols, insoluble in chlorinated hydrocarbons and essentially insoluble in water. 
     Elementary Analysis: Calcd for C 14  H 10  F 2  O 3  (mol. wt.=264.18); Calcd. %: C=63.65; H=3.81; Found %: C=63.44; H=3.85. 
     Spectrum IR (nujol mull): 1600 cm -1 , 1705 cm -1 , 1730 cm -1  ; 
     Spectrum H 1  NMR (determined in DMSO hexadeuterated, internal reference TMS): 4.7 δ(s, 2H, O--CH 2  --); 6.8-7.7 δ(m, 7H aromatic, 1H mobile). 
     The acid of formula I will be referred hereinbelow with the symbol MR 713. The acid is used to prepare the salts in a conventional manner. The examples which follow illustrate the preparation and the properties of some salts of the acid of formula I, but are not intended to be limitative of the invention. 
     EXAMPLE 2 
     To a warm solution of 50 grams (0.189 moles) of (2&#39;,4&#39;-difluoro-4-biphenyl)oxyacetic acid (I) in 500 cc of ethanol, there are added 10.2 grams (0.189 moles) of pure sodium methoxide. A crystalline solid is formed even in the hot solution and the precipitation is completed by cooling. After recrystallization from water, there are obtained 47 grams of the sodium salt of the compound of formula I; melting point 274°-279° C. (dec.). 
     Infrared Spectrum--(nujol mull): 1255 cm -1 , 1580 cm -1 , 1610 cm -1 . 
     EXAMPLE 3 
     To a warm solution of 0.1 mole of the sodium salt prepared according to Example 2 in 200 cc of water, there is added an aqueous solution of 0.1 moles of calcium chloride in 50 cc of water. By cooling, a crystalline solid precipitates the analytical data of which agree with the following formula: ##STR3## The substance melts with decomposition above 286° C. 
     Infrared Spectrum--(nujol mull): 1260 cm -1 , 1585 cm -1 , 1660 cm -1 . 
     EXAMPLE 4 
     The acid of formula I, 25 grams, (0.094 moles), is dissolved by warming in 150 cc of ethyl acetate; 5.55 grams, (0.094 moles) of ethanolamine is added. The salt which precipitate partially, even from the warm solution, is isolated by filtration and washed on the filter paper first with ethyl acetate and then with diethyl ether. A crystalline solid, in the amount of 17 grams, is obtained, melting point 164°-167° C. 
     Elementary Analysis: Calcd. for C 16  H 17  F 2  NO 4  (Mol. Wt.=325.32); Calcd. %: C=59.07; H=5.27; N=4.30; Found %: C=58.88; H=5.33; N=4.24 
     Infrared Spectrum (nujol mull): 1250 cm -1  (asym. stretch C--O), 1580 cm -1  (stretch C═C), 1610 cm -1  (stretch C═O), 2700-2550 cm -1  (stretch N +  --H), 3400-3200 cm -1  (stretch O--H). 
     H 1  NMR Spectrum (determinated in hexadeuterated DMSO, internal reference TMS): 2.8 δ(t, 2H, CH 2  --OH); 3.5 δ(t, 2H, CH 2  --OH); 4.3 δ(s, 2H, O--CH 2  --CO); 6.4-7.5 δ(m, 11H, aromatic 7H and mobile 4H). 
     EXAMPLE 5 
     In analogy with Example 4, but using L-lysine, instead of ethanolamine as the starting material, there is obtained the corresponding salt of L-lysine, melting point 214°-218° C., [α] D   20  =+6.5°  (c=4.8 methanol). 
     Elementary Analysis: Calcd. for C 20  H 24  F 2  N 2  O 5  (Mol. Wt.=410.41); Calcd. %: C=58.53; H=5.89; N=6.82; Found %: C=58.61; H=5.78; N=6.84. 
     Antiinflammatory Activity 
     The experiments have been carried out with rats and carrageenan has been used as the agent causing edema. The product under examination is administered by the oral route in the dose of 25 mg/kg. The substances which are used for comparison purposes have been acetyl salicylic acid (ASA), ibuprofen, paracetamol (p-acetylaminophenol) and diflunisal. The determination of the volume of the paws due to inflammation has been carried out every hour during the five hours subsequent to the treatment. 
     The results obtained are shown in Table I. On the basis of the data in Table I, it is possible to note that the antiinflammatory activity of MR 713 is essentially the same as diflunisal, is substantially superior to paracetamol even when the latter is used in doses four times larger, lower than that of ibuprofen, (the latter being employed in doses four times larger) and is essentially equivalent to the activity of acetylsalicylic acid, the latter, however, being employed in a dose ten times larger. 
     Analgesic Activity 
     The analgesic activity has been tested in mice using the contorsion test caused by phenylquinone. Even in this case, MR 713 has been administered by the oral route in the dose of 25 mg/kg and the same substances used in the edema test have been used for comparison purposes. Phenylquinone has been administered thirty minutes after the substance under test and the results obtained are reported in Table II. 
     Gastric Tolerability 
     MR 713 has been administered by the oral route in the dose of 25 mg/kg to rats kept fasting for a period of eighteen hours. After a six hours treatment, the animals have been sacrificed, then the stomach has been extracted for the examination of the gastric mucosa for the purpose of determining possible lesions. For the purpose of comparison, there are used under the same experimental conditions, acetylsalicylic acid, ibuprofen, paracetamol, and diflunisal. The optimum tolerability of MR 713 on the gastric level has been demonstrated by the results obtained and reported in Table III, which show that MR 713 causes even less gastric lesions as compared with drugs which are well-known to be tolerated at the gastric level, such as paracetamol and diflunisal. The same experiment, on the other hand, shows quite clearly that ibuprofen and acetylsalicylic acid cause gastric lesions. 
     Acute Toxicity 
     MR 713 presents a very low acute toxicity: its DL 50  in mice by the oral route is 790 mg/kg of body weight. 
     
                                           TABLE I__________________________________________________________________________ANTIINFLAMMATORY ACTIVITYSubplantar Edema Caused by Carrageenan in Rats                                 AREA                                      % Inhi-                                      bition  Dose  Volume of Paw in No. of Hours after the Treatment                                 Absolute                                      vs.Substance  mg/kg/ps        0   1   2   3    4   5   Value                                      Control__________________________________________________________________________Controls  --    21.3            28.1                34.9                    38.2 37.3                             32.6                                 273.2                                      --Acetyl-  250   20.0            23.6                28.0                    29.5 30.5                             31.4                                 182.4                                      33.0SalicyclicAcidIbuprofen  100   20.3            25.2                26.5                    28.7 29.6                             29.9                                 163.7                                      40.0Paracetamol  100   20.4            25.2                31.9                    34.9 33.9                             32.7                                 245.7                                      10.0Diflunisal   25   21.2            25.6                29.7                    31.0 33.4                             33.1                                 190.7                                      30.0MR 713  25   21.3            24.3                29.3                    31.7 33.9                             33.0                                 186.4                                      31.0__________________________________________________________________________ 
    
     
                                           TABLE II__________________________________________________________________________ANALGESIC ACTIVITYContorsions Caused by Phenylquinone in Mice  Dose  Average No. of                % Inhibition vs.                        No. of Animals withTreatment  mg/kg/os        Contorsions                Controls                        Contorsions__________________________________________________________________________Control      23.5 ± 6.1   10/10Acetyl 250   0       100     0/10SalycilicAcidIbuprofen  100    0.2 ± 0.1                99.1    2/10Paracetamol  100    8.6 ± 3.3                63.4    5/10Diflunisal   25    0.2 ± 0.2                99.1    1/9MR 713  25   10.8 ± 2.8                54.0    9/10__________________________________________________________________________ 
    
     
                       TABLE III______________________________________GASTRIC LESION ACTIVITY         Dose      Average Size ofTreatment     mg/kg/os  Ulcer in mm______________________________________Controls      --        0Acetyl        250       3.7 ± 0.8SalicylicAcidIbuprofen     100       2.3 ± 0.7Paracetamol   100       0.6 ± 0.4Diflunisal     25       0.7 ± 0.4MR 713         25       0.3 ± 0.1______________________________________ 
    
     The pharmacodynamic tests carried out in rats and administering MR 713 by the oral route in the doses of 25, 50, and 100 mg/kg, show a half-life time of plasmatic levels, which is possible to calculate in the dose of 25 mg/kg, of about eleven hours. This is a high value at equal dose with respect to common antiinflammatory agents of the nonsteroidal type and particularly substantially superior to the action of diflunisal. The pharmacodynamic tests permit to administer one or at the most two daily doses of MR 713. 
     The present invention also covers all the industrial applications and use of MR 713 and its salts as antiinflammatory and analgesic agents. A substantial aspect of the invention resides in pharmaceutical formulations which contain predetermined amounts of MR 713 or its salts. The compositions according to the present invention may be administered by the oral or parenteral route, for instance in the form of compresses, capsules, powders, which may be dispersed in water and packaged in small envelopes, phthials suitable for injection. By way of example, the following formulations may be used: 
     (a) compresses containing 250 mg of (2&#39;,4&#39;-difluoro-4-biphenyl)oxyacetic acid with excipients and dispersing agents conventionally used in the pharmaceutical industry; 
     (b) compresses containing 375 mg of the acid of formula I containing the additional excipients and dispersing agents as above; 
     (c) phthials containing 400 mg of the lysine salts of (2&#39;,4&#39;-difluoro-4-biphenyl)oxyacetic acid which has been lyophilized, together with a phthial of about 3 cc of solvent for intramuscular injetion.