O-CARBAMOYL SALICYLATES AND THEIR PREPARATION

Abstract: A number of new compounds useful as analgesics, antipyretics and anti-inflammatory agents in mammals being O-carbamoyl salicylates have been discovered. Only one of the salicylates, being O-carbamoyl methyl salicylate is known but nothing about its pharmacological activity. This invention provides novel O-carbamoyl salicylates with aforesaid properties and a novel method of producing same by reacting a salicylate with a chloro sulphonic acid. A typical compound bears the formula

Description: "O-CARBAMOYL SALICYLATES AND THEIR PREPARATION" This invention relates to O-carbamoyl salicylates, which are useful as analgesics, antipyretics and antiinflammatory agents in mammals. The most readily available and commonly used agents for relief of mild pain are mild analgesics like salicylates and derivatives of salicylic acid which have been used since 1838. The most important derivative of salicylic acid, acetylasalicylic acid (aspirin), was found pharmacologically useful only in 1899. The only other salicylate known is methyl salicylate used for topical application far relief in muscular and joint pains. Use of aspirin, particularly in high doses, produces side effects like gastrointestinal disorders. In view of the severe side effects of aspirin, it was considered of interest to modify its chemical structure to overcome the side effects while retaining its beneficial analgesic action. Accordingly, we turned our attention, amongst others, to O-carbamoyl salicylates, which have been found by us to meet the requirements. Preparation of O-carbamoyl methyl salicylate has been reported by Ernst Grigat and Rlf Putter in chemische Bericht 99 (3), 958 (1966) who obtained same by the reaction of O-cyanatobenzoic acid methyl ester in benzene with p-toluene sulfonic acid. This report contains no hint of the possible pharmacological properties of the compounds. We have now discovered that those compounds possess analgesic, antipyretic and anti-inflammatory activity in mammals and hence may find use as drugs in the treatment of pain and inflammation and also as possible alternate to the widely employed drug, acetyl salicylic acid (aspirin). In one aspect this invention provides novel O-carbamoyl salicylates represented by the general formula I EMI2.1 Wherein R represents H, halogens such as chloro, dichloro, bromo and iodo; alkyl or alkoxy group comprising of one to six carbon atoms and nitro group, in various positions, and n' represents an alkyl or chloro substituted alkyl group, straight or branched, comprising of two to six carbon atoms or an aromatic ring containing one or more substituents such as halogen, alkyl group, either straight or branched, comprising up to fifteen carbon atoms, alkoxy group comprising of one to six carbon atoms and nitro group. In another aspect this invention provides a process for the preparation of O-carbamoyl salicylates of the general formula I, EMI3.1 wherein R represents H, halogen such as chloro, dichloro, bromo and iodo; alkyl or alkoxy group comprising of one to six carbon atoms and nitro group, in-various positions, and R' represents an alkyl or chloro substituted alkyl group, straight or branched, comprising of one to six carbon atoms or an aromatic ring containing one or more substituents such as halogen, alkyl group, either straight or branched, comprising up to fifteen carbon atoms, alkoxy group comprising of one to six carbon atoms and nitro group, which comprises treating a compound of formula II EMI3.2 in which R and R' have the same meaning as before with chlorosulfonyl isocyanate represented by the formula Cl.S02.NCO The above reaction is carried out in the presence of aprotic solvents like aromatic hydrocarbons such as benzene, toluene and xylene, ethers such as diethyl ether, diisopropyl ether, glycol dimethyl ether, diethylene glycol, dimethyl ether, chloro hydrocarbons such as methylene chloride, propylene chloride, chloroform, carbon tetrachloride or trichloro ethylene, or esters such as ethyl acetate, butyl acetate propionic acid methyl ester, at temperatures ranging from -50C to +6O0. The reaction is carried out for a period ranging from 60 minutes to 300 minutes. The compounds so produced are isolated from the reaction mixture by treatment with ice and could be crystallized from organic solvents like ethanol. The compounds of the invention obtained in the present invention are characterized and identified by chemical and spectroscopic methods. The following are some typical examples which illustrate the process of this invention. EXAMPLE 1 O-Carbamoyl ethyl salicylate In a four necked flask fitted with a mechanical stirrer, thermometer, condenser and dropping funnel was taken ethyl salicylate (7.8 gms) in dry methylene chloride (30 ml) Chlorosulfonyl isocyanate (4 ml) in methylene chloride (10 ml) was added dropwise over a period of 15 minutes with stirring and maintaining the temperature 5-100C. On completion of the addition the reaction mixture was stirred and allowed to warm to ambient temperature (280C). The stirring was further continued for another 30 minutes. After removal of methylene chloride under vacuum, the residue obtained, was added to crushed ice (50 gms) and left for 5 hours. The crude product obtained is filtered and recrystallized from ethanol. m.p. 150-1520C Yield: 93% EXAMPLE 2 O-Carbamoyl phenyl salicylate In a four necked flask fitted with a mechanical stirrer, thermometer, condenser and dropping funnel was taken phenyl salicylate (9.85 gms) in dry benzene (40 ml). Chlorosulfonyl isocyanate (4 ml) in benzene (8 ml) was added dropwise over a period of 12 minutes with stirring and maintaining the temperature of 25-300C. After completion of addition, the reaction mixture was stirred for another 45 minutes. The reaction mixture was then added to crushed ice (100 gms) and stirred for 6 hours. Benzene was separated and the solid obtained in the aqueous part was filtered, dried and recrystallized from methanol. m.p. 1410C Yield: 95% EXAMPLE 3 O-Carbamoyl-(3-pentadecylphenyl) salicylate In a four necked flask fitted with a mechanical stirrer, thermometer, condenser and dropping funnel was taken 3-pentadecylphenyl salicylate (9.73 gms) in dry diethyl ether (50 ml). Chlorosulfonyl isocyanate (2 ml) in diethyl ether (6 ml) was added dropwise over a period of 20 minutes with stirring and maintaining the temperature 10-15 C. Once the addition is completed the reaction mixture was stirred and allowed to warm to ambient temperature (230C). Diethyl ether was removed under vacuum. To the residue obtained, was added crushed ice (40 gms) and left for 3 hours. The crude product obtained was filtered and recrystallized from dilute ethanol (80%). m.p. 108-1100C Yield: 87% Employing the procedure as described above in examples 1, 2 and 3, the following additional compounds, which illustrate the invention, were prepared. O-carbamoyl methyl salicylate (m.p. 149-1500C) 0-carbamoyl-5-chloromethyl salicylate (m.p. 151-1 520C) O-carbamoyl-5-chloroethyl salicylate (m.p. 1430C) O-carbamoyl propyl salicylate (m.p. 146-148 C) O-carbamoyl-5-chloro propyl salicylate (m.p. 1400C) O-carbamoyl isopropyl salicylate (m.p. 145-1470C) O-carbamoyl-5-chloro isopropyl salicylate (m.p. 148-1490C) O-carbamoyl butyl salicylate (m.p. 152-1540C) O-carbamoyl isobutyl salicylate (m.p. 148-1490C) O-carbamoyl cyclohexylsalicylate (m.p. 154-155 C) O-carbamoyl-5-chloro-phenyl salicylate (m.p. 128-1300C) O-carbamoyl-(2-methyl-phenyl) salicylate (m.p. 90-920C) O-carbamoyl-5-chloro(2-methyl-phenyl) salicylate (m.p. 94-960C) O-carbamoyl (3-methylphenyl) salicylate (m.p. 95-970C) O-carbamoyl (4-methylphenyl) salicylate (m.p. 98-99 C) O-carbamoyl (2-chlorophenyl) salicylate (m.p. 155-157 C) O-carbamoyl-5-chloro (2-chlorophenyl) salicylate (m.p. 158-1590C) 0-carbamoyl (4-chlorophenyl) salicylate (m.p. 164-165 C) O-carbamoyl-5-chloro (4-chlorophenyl) salicylate (m.p. 158-159 C) O-carbamoyl-(2,4-dichlorophenyl) salicylate (m.p. 158-159 C) 4 O-carbamoyl-5-chloro(2-dichlorophenyl) salicylate (m.p. 1641650C) 0-carbamoyl (2,3-dichlorophenyl) salicylate (m.p. 160-162 C) O-carbamoyl-5-chloro(2,5-dichlorophenyl) salicylate (m.p. 163-164 C) O-carbamoyl(3-methyl-4-chlorophenyl) salicylate (m.p. 1501510C) O-carbamoyl-5-chloro(3-methyl-4-chlorophenyl) salicylate (m.p. 153 C) O-carbamoyl-5-chloro(3-pentadecylphenyl) salicylate (m.p. 109-111 C) 0-carbamoyl (4-methoxyphenyl) salicylate (m.p. 1200C) 0-carbsmoyl (4-ethoxyphenyl) salicylate (m.p. 124-126 C) 0-carbamoyl (2-nitrophenyl) salicylate (m.p. 163 C) 0-carbamoyl (4-nitrophenyl) salicylate (m.p. 165 C) Table I gives analgesic and anti-inflammatory profile of some representative compounds of this invention. TABLE I ANALGESIC AND ANTI-INFLAMATORY PROFILE OF SOME REPRESENTATIVE COMPOUNDS Dose: 200 mg/kg LD20 i.p. mice 800 mg Gross observations: No obvious gross effects pertaining to Central Nervous System or Autonomic Nervous System. Analgesic Anti-inflammatory %Inhibition S1. protection Raw edema Granuloma No. Compound Writhing 1 O-Carbamoyl methyl salicylate 69.78 76.23 46.32 2 O-Carbamoyl ethylsalicylate 95.00 34.86 28.63 3 O-Carbamoyl -5-chloro ethylsalicylate 67.00 34.85 19.79 4 O-Carbamoyl phenylsaicylate 72.00 93.19 57.65 5 O-Carbamoyl (2-chlorophenyl) salicylate 70.00 35.00 35.06 6 O-Carbamoyl (4-chlorophenyl) salicylate 83.00 37.88 41.45 7 O-Carbamoyl (2,4-dichlorophenyl) salicylate 76.00 28.77 34.40 8 O-Carbamoyl (3-methylphenyl) salicylate 84.00 48.50 33.24 9 O-Carbamoyl (3-methyl-4-chlorophenyl) salicylate 68.00 28.90 24.04 10 O-Carbamoyl (3-pentadecylphenyl) salicylate 45.00 12.10 33.55

Claims: CLAIMS 1. O-carbamoyl salicylates represented by the general formula I EMI9.1 wherein R represents H, halogens such as chloro, dichloro, bromo and iodo; alkyl or alkoxy group comprising of one to six carbon atoms and nitro group, in various positions, and R' represents an alkyl or chloro substituted alkyl group, straight or branched, comprising of tlfO to six carbon atoms or an aromatic ring containing one or more substituents such as halogen, alkyl group, either straight or branched, comprising up tofifteen carbon atoms, alkoxy group comprising of one to six carbon atoms and nitro group. 2. A process for the preparation of O-carbamoyl salicylates of the general formula I, EMI9.2 wherein R represents H, halogen such as chloro, dichloro, bromo and iodo; alkyl or alkoxy group comprising of one to six carbon atoms and nitro group, in various positions, and R' represents an alkyl or chloro substituted alkyl group, straight or branched, comprising of one to six carbon atoms or an aromatic ring containing one or more substituents such as halogen, alkyl group, either straight or branched, c comprising up to fifteen carbon atoms, alkoxy -group comprising of one to six carbon atoms and nitro group, which comprises treating a compound of formula II EMI10.1 in which R and R' have the same meaning as before, with chlorosulfonyl isocyanate represented by formula Cl.S02NCO. 3. Process as claimed in claim 2, wherein the reaction is carried out -5 0C to 600C for a period of 60 to 300 minutes. 4. Process as claimed in claim 2 or 3, wherein the solvent used is an aromatic hydrocarbon such as benzene, toluene or xylene, ether such as diethyl, diisopropyl ether, glycol dimethyl ether, diethylene glycol or dimethyl ether. 5. Process as claimed in any of the claims 2 to 4, wherein the solvents used are chlorohydrocarbons such as methylene chloride, propylene chloride, chloroform, carbon tetrachloride or trichloro ethylene, tetrachloroethylene or esters such as ethyl acetate, butyl acetate or propionic acid methyl ester. 6. Process as claimed in any of the foregoing claims 2 to 5, wherein the O-carbamoyl salicylate produced is isolated from the reaction mixture by treatment with ice and crystallized from organic solvents like ethanol. 7. O-carbamoyl salicylates of formula I EMI11.1 as hereinbefore defined as produced by the process claimed in any of the foregoing claims 2 to 6. 8. Process of preparing O-carbamoyl salicylates of general formula I EMI11.2 as defined hereinbefore, substantially as hereinbefore described particularly with reference to examples 1, 2 and 3.

Inventors: KAMAL, AHMED, SATTUR, PRALHAD BALVANT RAO, THYAGARAJAN, GOPALAKRISHNA
Applicants: COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Application year: 1983
Main classification: C07C125
IPC codes: C07C271