Title of Invention

"NOVEL BENZOFUROXAN DERIVATIVES ,AND THEIR PAHARMACEUTICAL COMPOSITIONS"

Abstract

This invention discloses novel compounds of benzofuroxan series and to their use in therapeutics. In particular the invention concerns novel benzofuroxan derivatives, pharmaceutical compositions containing these compounds, and their use as tolerance resistant nitric oxide donors in treatment of angina pectoris. In addition the invention also discloses the use of other carefully chosen derivatives of benzofuroxan series showing tolerance resistance activity as nitric oxide donors and to their pharmaceutically acceptable compositions and formulations.

Full Text

- 2 -Field of Invention This invention relates to novel compounds of benzofuroxan series_and to their use in therapeutics. In particular the invention concerns novel benzofuroxan derivatives, pharmaceutical compositions containing these compounds, and their use as tolerance resistant nitric oxide donors in treatment,of angina_pectoris. In addition the invention also relates to the use of other carefully chosen derivatives of benzofuroxan series showing tolerance resistance activity as nitric oxide donors and to their pharmaceutically acceptable compositions and formulations. This application is divided out of Indian Patent Application No. 462/CAL/99 filed on 18th May, 1999. BACKGROUND OF THE INVENTION After the discovery of endothelium-derived relaxing factor (EDRF) by Furchgott et al (1980), and the elucidation of the biochemistry of EDRF by a number of laboratories (Ignarro, 1989; Vane et al, 1990; Bassenge et al, 1988; and Vanhoutte, 1989), it is now widely accepted that EDRF is the endogenous nitrovasodilator, nitric oxide (NO) donor. The organic nitrates and related compounds owe their pharmacological action to the release of nitric oxide (NO) and these compounds are collectively called nitrovasodilators. NO stimulates the guanylate cyclase enzyme in vascular smooth muscle cells resulting in increased levels - 2A - of cyclic GMP. This leads to dephosphorylation of myosin light chain which results in relaxation of smooth muscles (Murad, 1986). NO is known to be involved in a number of bio- - 3 - regulatory processes like, vasodilatation, platelet deaggregation, vascular smooth .muscle proliferation, etc. Organic nitrates are used in prophylaxis, treatment and management of patients with angina pectoris. These are also useful in congestive heart failure associated with acute myocardial infarction, hypertension associated with surgical procedures and to produce controlled hypotension during surgical procedures. Among organic nitrates, nitroglycerine (sublingual) which is currently in use, is the drug of choice for immediate relief of anginal symptoms. Prophylactic treatment of stable angina pectoris involves the use of one or more drugs such as long acting nitrates like isosorbide dinitrate, a beta-blocker and/or a calcium channel antagonist, particularly in patients likely to experience coronary spasm. In some cases this triple therapy satisfactorily control angina. They are quite effective in the treatment of these conditions when used intermittently. Frequently repeated use of nitrates result in decrease in their pharmacological effects, a phenomenon well recognized as nitrate tolerance. The mechanism of tolerance is not well defined. As early as 1973, Needleman and Johnson (1973) have reported that tolerance to nitroglycerine could occur in isolated rabbit arteries. It was hypothesized by them that depletion of sulphydryl groups was associated with the development of tolerance to nitroglycerine. This is a major problem in the clinical use of organic nitrates (Frampton et al, 1992). Currently, the development of - 4 - tolerance is reduced by the use of intermittent dosing schedule with a nitrate-free interval of 10-12 hrs. However, this intermittent use is associated with decreased exercise tolerance during the last part of nitrate-free interval. This suggests possibility of increased frequency of or severity of angina during nitrate-free interval. The importance of development of tolerance has increased as these drugs are used more commonly in various dosage forms like oral, transdermal, and intravenous preparations and even as sustained-release preparations. Several indirect indices like exercise duration, systemic blood pressure, pulmonary artery pressures and pulmonary artery wedge pressure has been used to assess tolerance to organic nitrates. However, it is not clear whether decreased response to nitrates is due to tolerance of the vascular smooth muscle cells or changes in regulatory factors like activation of neurohumoral factors or fluid retention etc. (Armstrong and Moffat, 1983 ). Irrespective of the mechanisms of tolerance development, clinically it is important to develop nitric oxide donors with least tendency to develop tolerance. P B Ghosh et al. (Journal of Medicinal Chemistry, 1968) disclosed the method of synthesis of various benzo -2,1,3-oxadiazoles (benzofurazans) and their N-oxides (benzofuroxans) and their potential as antileukemic and immuno-suppressive drugs in vitro. P B Ghosh et al. (Journal of Medicinal Chemistry, 1972) tested 4- nitrobenzofurazans and 4- nitrobenzofuroxans - 5 - bearing electron withdrawing substitutents in the 5 and 6 position (relative to NO2) as potential antileukemic and immuno suppressive drugs in vitro. Nishikawa et al. (The Journal of Pharmacology and Experimental Therapeutics, 1982) disclosed effect of N-ethoxycarbonyl -3- morpholinosydnonimine and its metabolites 3- morpholinosydnonimine, cyanomethyleneamino morpholine, N-nitroso -N-morpholinoamino acetonitrile as novel antianginal agents. F. Murad (J. Clin. Invest, 1986) disclosed cyclic guanosine monophosphate as a mediator of vasodilation. James Frampton et al. (Drug Evaluation, Adis International Limited, 1992) give a review of pharmacology and therapeutic efficiency of nicorandil in angina pectoris. Nicorandil, which has both vasodilator and venodilating properties was found to offer an effective alternative to established vasodilator therapy with conventional nitrates and calcium antagonists in the long term treatment of stable angina pectoris. U S Patent No.5,272,164 disclosed novel carboximidamide derivatives particularly N-cyano-N1 -substituted pyridine carboximidamide derivatives having vasodilating effect and hypotensive effect besides other physiological effects which are helpful in treatment of ischemic heart diseases. U S Patent 5,424,326 disclosed phenyl -1,2,5- oxadiazole carboxamide -2- oxide and its derivatives, which are useful for the treatment of disorders of the cardiovascular system. - 6 - F Benedini et. al. (J. Med. Chem. 1995) disclosed a new nitro ester -3- [ (nitroxy) alkyl] -2H- 1,3- b&nzoxazin-4(3H)- ones showing marked inhibitory activity against ischemia-induced electrocardiographic changes, with only limited systemic hemodynamic effects. These nevf nitro ester derivatives, endowed with marked anti-anginal activity, which is not associated with concurrent and pronounced fall in systemic blood pressure, are indicative of a new class of selective nitrovasodilators having a preferential action on large coronary vessels, which could be clinically relevant in the treatment of coronary artery diseases. However, none of the above prior art disclosures on the drugs specifically used as vasodilator for treatment of cardiac ailments tackles the problem associated with the conventional NO-donors to develop tolerance in the patient after continuous use for a period of time. Significantly, the invention identifies the molecules showing vasodilator activity without tendency to develop tolerance unlike the conventional nitric-oxide donors. The molecules identified by this invention are either novel or their NO donor activities were hitherto unknown. Summary of the Invention The present invention provides, in the first aspect, novel benzofuroxan derivatives and pharmaceutically acceptable salts thereof. Such salts include, but are not limited to, oxalate, tartarate, maleate, methyl sulphonate, p-toluene sulphonate, - 7 - The invention further provides the use of the benzofuroxan derivatives as tolerance resistant nitric oxide donors. The invention further provides pharmaceutical formulations comprising benzofuroxan derivatives to be used as tolerance resistant nitric oxide donors- The invention also provides for a method of treatment of mammal including man, of coronary heart diseases by Accordingly, the present invention provides for a compound useful for cardiovascular disorders represented by the formula (I) and pharmaceutically acceptable salts thereof wherein : Ris-0-(CH2)n-X-R'; n = 1-6; X is -NHC(O)- or oxygen; -7A- R' is Ci-C8 alkyl, aromatic, heteroaromatic, substituted or unsubstituted saturated heterocyclic ring with one or two hetero atoms selected from the group consisting of nitrogen and oxygen, wherein substitution is with Ci-Cs alkyl; or R is selected from wherein R" is hydrogen, nitro, Ci-C8 alkyl or-C(O)- R"' wherein Rtpl is hydrogen, Ci-Cs alkyl or aryl, with the proviso that R is not 0CH2CH2nicotinami de. The invention also provides for a pharmaceutical composition comprising an affective amount of a compound of general formula (I), as defined above in association vith a pharmaceutically acceptable earner or excipient -7B- BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figs.l and 2 give the dose response curves for GTN and the test compounds No.8 and 16. Figs.3 and 4 give the dose response curves (percentage relaxation vs the log(M) concentration) for GTN and test compound No.8 and 16 before and after development of tolerance. DETAILED DESCRIPTION OF THE INVENTION The novel compounds of the benzofuroxan series used for cardiovascular disorders are represented by the general formula (I). - 8 - and pharmaceutically acceptable salts thereof wherein : R is -0-(CH2)n-X-R' n= 1 to 6 X is -NHC(0)-or oxygen R1 is lower alkyl (Ci-Ca), aromatic, heteroaromatic, substituted or unsuhstituted saturated heterocyclic ring with one or two hetero atoms such as nitrogen or oxygen wherein substitution is with lower alkyl or R is selected from wherein R" is hydrogen, nitro, lower alkyl or -C(O)-R(tl wherein R'11 is hydrogen, lower alkyl or aryl with proviso that R is not -O-CH2CH2-nicotinamide. - 9 - The .compounds of the invention showing tolerance resistant NO donor activities-as defined above are given in the' Table-1.. Table-1 Novel Benzofuroxan derivatives Compound No R 1 -OCH2CH2-NHCO-4-pyridyl.HCl 2 substitution (e) 3 substitution (f) 4 -0CHzCH2-N-morpholinyl.HCl 5 -OCH2CH2OMe 6 substitution (g) 7 -OCH2CH2O-CH2CH3 8 -OCHz-3-pyridyl.HCl 9 substitution (c) 10 substitution (h) - 10 - In addition the already known compounds o.f the benzofuroxan series,, which this- invention has_ found to be useful for treatment of cardiovascular disorders^-are represented by the general formula (II): and pharmaceutically acceptable salts thereof wherein : Ri is acetoxy, -X-Rz, -C(0)-R4 or carboxy wherein X is oxygen or sulfur R2 is hydrogen or R3 R3 is straight chain or branched lower alkyl (Ci-Cs) R4 is R3 , -NR2R3, -ORs or substituted or unsubstituted heterocyclic ring witli one or two heteroatoms such as nitrogen or oxygen wherein the substitution is with lower alkyl. R5 is straight chain or branched lower alkyl (C2-C8) with proviso that Ri is not -SCHa or -SCH2CH2CH3 The representative compounds of general formula II as defined above showing tolerance resistant NO donor activities are given in Table 2. - 11 - Table-2 Known Benzofuroxan derivatives Compound No Rl 11 -COOH 12 -OC(O)-CH3 13 -OH.HC1 14 -COOC2H5 15 -COOCH2CH2CH3 16 -COOCH(CH3)2 17 -COO 18 -CON(CH3)2 19 substitution (a1) 20 substitution (b') 21 -CONHCH(CH3)2 22 -CONH^Bu (a') (b1) The present invention also provides a process for the preparation of novel benzofuroxan derivatives of the general formula I, and their pharmaceutically acceptable salts, wherein one of the processes comprises, a) reacting chloro carbonyl benzofuroxan and an alcohol in solvent such as tetrahydrofuran at room temperature; b) adding a base such as triethylatnine to the reaction mixture; c) refluxing the reaction mixture till the completion of - 12 - the reaction; d) removal of the solvent .followed by addition of water and extraction with organic solvent such as etl^yl acetate; e) concentration of ethyl acetate layer. f) purification by column chromatography^ and g) optionally transforming into the corresponding pharmacologically acceptable salts. Said products of steps (f) and (g) are characterized by m.p. and the conventional spectroscopic techniques. The present invention also provides a process for the preparation of novel benzofuroxan derivatives of the general formula I, and their pharmaceutically acceptable salts, wherein the said process comprises, a) reacting carboxy benzofuroxan with saturated solution of alcoholic HC1; b) removal of excess of alcohol under reduced pressure to get the residue; c) purification by column chromatography, and d) optionally transforming into the corresponding pharmacologically acceptable salts. Said products of steps (c) and (d) are characterized by m. p. and the conventional spectroscopic techniques. Such products can also be prepared by the other equivalent processes of ester formation, which comprises, (a) reacting carboxy benzofuroxan and an equimolar amount of an alcohol such as N-(2-hydroxyethyl) isonicot-inamide, N-(2-hydroxyethyl) -2- pyrolidinone, N-(2- - 13 - hydroxyethyl) morpholine , propylene glycol, me^thylcellosolve , ethylcellosolve, pyridine -3- methanol, solketal, isosorbide -5- mononitrate, etc., in methylene chloride; (b) adding 4- dimethylamino pyridine and N,N'- dicyclohexyl carbodiimide under stirring and continuing the stirring for a period of 2 to 16 hours at room temperature to complete the reaction; (c) filtering the reaction mixture when the filtrate on evaporation under reduced pressure gives the crude product; (d) purifying the product thus obtained by column chromatography, and (e) optionally transforming into the corresponding pharmaceutically acceptable salts. The said product of steps (d) and (e) are characterized by m.p. and the conventi onal spectroscopic techniques. The invention also provides a process for the preparation of 5(6)- [(2,3- dihydroxy propyloxy) carbonyl] benzofuroxan, wherein said process comprises, (a) reacting a mixture of 5(6)- ((±) 2,2- dimethyl -1,3- dioxolane -4- methyloxy) carbonyl benzofuroxan and an acid such as 75% acetic acid and stirring at 80°C for 4 hours; (b) evaporating the solvent under vacuum to give an oily product; (c) purifying the product of step (b) by column chromatography; Said product of step (c) is characterized by m.p. and the conventional spectroscopic techniques. - 14 - Pharmaceutical compositions for NO-donor molecules: The compounds according to this invention as given by general formula I or II and their salts or complexes can be administered orally, intravenously or parenterally as a pharmaceutical preparation in liquid or solid form. It may also be administered via topical, transdermal, sublingual, buccal or rectal route for example as a suppository, ointment, cream, powder, transdermal patch, metered aerosol or spray. The pharmaceutically acceptable carriers present in the composition of this invention are materials recommended for the purpose of administering the medicament. These may be liquid or solid materials, which are otherwise inert or medically acceptable and are compatible with the active ingredients. EVALUATION OF THE BIOLOGICAL ACTIVITY: Methods: a) In vitro Screening of NO Donors The method adopted was a modified method of Nishikawa et al (1982). Albino rabbits of either sex were stunned and exsanguinated. Thoracic aorta was quickly removed and cut helically (at an angle of 45°) into strips 4-5 mm wide and 25 to 30 mm long, after removal of adventitial connective tissue. The endothelium was rubbed off gently using a cotton swab soaked in Kreb's solution. Two strips were fixed vertically in organ baths containing 20 ml. Kreb's solution maintained at 37°C and bubbled with oxygen. A resting tension of 4 g was applied and the preparation was allowed to - 15 - equilibrate for 30 min. Each preparation was exposed to two primer doses of KC1 (30mM). After the contraction reached a maximum, the bath was drained off and replaced with fresh Kreb1s solution. Half an hour later, cumulative dose response curve for the test compound was taken on one tissue (test) and for glyceryl trinitrate (GTN) in the other (standard). The dose range used was from 10~9 M to 10~3 M with a contact period of 4 min. for each dose. After the maximum relaxation was achieved with the last dose, papaverine (10-" M) was added to obtain the maximum relaxation. Tolerance was induced in both the tissues by adding 440 uM of GTN for 90 minutes. During this period the bath solution was changed every 30 min. and 440 uM of GTN was replaced. Later both the tissues were washed thoroughly and the dose response curve (DRC) for both the test compounds and the standard were repeated. The percentage relaxation with individual doses was calculated by taking the maximum relaxations to 10~4 M papaverine as 100% relaxation. A graph was plotted by taking the percentage relaxation vs the log (M) concentration of the compounds. The relaxant activity of the test compounds was assessed by calculating the mean relative potencies (MRP) and the mean activity ratio (MAR), both before and after tolerance, as defined below: Concentration of GTN producing 50% of its maximum relaxation MRP = Concentration of test compound producing 50% of the maximum relaxation of GTN. - 16 - Maximum relaxation produced by the test compound ¦i MAR = .Maximum relaxation produced by GTN Selection criteria for in vivo study: Compounds having MRP greater than 3 and MAR greater than 1.3 after tolerance were selected for in vivo study. Dose response curves for compounds 8 and 16 are given in Figs.1-4 of the accompanying drawings as an example for the estimation of MRP and MAR. b) In vivo Pharmacological Screening: A modified method of Benedini et al (1995) was adopted for studying the anti-anginal effect of the chosen compounds. Guinea pigs of either sex, weighing approximately 400-600 g were used for this study. Animals were anesthetized with urethane (1.25 g/kg, i.p.) and jugular vein was cannulated for intravenous administration of drugs/vehicle. Mean arterial blood pressure (MABP) was monitored by a cannula inserted into the right carotid artery and connected to a pressure transducer. Standard limb lead II electrocardiogram was recorded continuously. All the recordings were carried out on a MacLab system (AD Instruments, UK). The ability of the test compounds to suppress the vasopressin induced T-wave elevation was used as the model for studying the anti-anginal effects of the compounds. Guinea pigs were divided into two groups for the purpose of this study, i) control group (pretreated with the vehicle for the compound) and ii) drug treated group. i) Control Group In this group of animals the solvent used for dissolving the test compound was administered intravenously in a volume 4 of 1 ml/kg. The basal T-wave heights, heart ra,tes and MABP and changes after vehicle administration were rioted. Thirty seconds later 1 I.U./ml/kg of vasopressin was administered intravenously. The T-wave heights, heart rates and MABP and their changes after vasopressin administration were also noted. The T-wave elevation (after vasop res sin-administration) , maximum rise in MABP, and changes in heart rate were calculated from the above data and expressed as mean ± standard deviation. ii) Drug treated group The effects of the test compound in suppressing the T-wave elevation caused by vasopressin were evaluated with atleast three dose levels. Groups of 6 guinea pigs were used for each dose. The test compound was injected 30 seconds prior to vasopressin administration. Changes in MABP, heart rate and T-waves were recorded as described for the control group. The percentage inhibition of vasopressin induced T-wave elevation was calculated for each dose taking the T-wave height estimated in control group as 100%. From the dose vs percent inhibition relationship, the dose required for 50% inhibition (EDso) for the T-wave elevation was estimated. Determination of the EDzo values for drop in MABP In a separate group of animals the drop in MABP after administration of the test compound (dose range of 0.1 - 1000 ug/kg, i.v.) was studied. Atleast three animals were used for each dose. Care was taken so that the doses were given only - 18 - after the MABP had stabilized from the effects of the previous dose. All doses were injected in a final volume of 1 ml/kg. The drop in MABP was noted for increasing concentrations of the test compound and a dose response curve was drawn. From this graph the dose required to produce a 20% fall in MABP (ED20) was calculated. The specificity of the test compound was defined by the selectivity index, which was calculated as shown below: Selectivity Index Dose required for 20% reduction in MABP (ug/kg) Dose required for 50% inhibition of T-wave elevation (ug/kg.) Compounds having selectivity ratio greater than 30 times that of GTN were selected for initial toxicology evaluation. The selectivity index for GTN was estimated to be 0.017, RESULTS OF IN VITRO Screening of NO Donors: The results of in vitro screening of the NO donors are given in the following Table 3. Compounds 1,2,3,5,6,7,8.9 and 10 amongst the novel molecules and compounds 14,15,16,21 and 22 amongst the known molecules were found to be the suitable compounds for both potency and activity and hence, the selectivity of their action was studied in vivo. TABLE 3 - In vitro activity of NO donors Compound Mean Relate Before Tolerance /e Potency After Tolerance Mean Activity Before Tolerance / Ratio After Tolerance 1 0.06 6.94 1. 19 2.38 2 0.11 25 1.15 1.83 - 19 - 3 0.28 11.22 1.13 1.69 4 0.18 4.12 " 1.08 1.22 5 0.97 17.02 1.74 2.32 6 0.17 3.49 1.16 1.58 7 0.2 11.9 1.04 1.97 8 0.53 8.05 1.23 1.7 9 0.39 10.13 1.05 1.57 10 0.25 7.0 1.37 1.63 11 Low Potency Low Potency 0.5 0.2 12 Low Potency Low Potency 0.7 0.4 13 Low Potency Low Potency 0.32 0.52 14 0.79 16.36 1.17 1.72 15 0.44 9.0 1.06 1.6 16 0.4 10.6 1.1 1.6 17 0.71 11.5 1. 1 1 .25 18 0.028 2.73 0.92 0.88 19 0.06 0.46 1.07 0.92 20 0.017 0.85 0.75 0.85 21 0.046 3.79 0.82 1.43 22 0.06 9.28 1.03 ¦2.07 The compounds, which were selected based on in-vitro studies, were subjected to in-vivo studies t(\ assess their anti-anginal action. Compounds with sufficient selectivity (i.e. lesser hypotension) and anti-anginal action are listed in Table 4. - 20 - TABLE 4 - - In vivo activity of selected Nitrio Oxide donors Compound Dose needed for 20% fall in B.P.(ED20 ug/kg,i.v.) (A) Dose required for 50% inhibition of T- wave (ED50 ug/kg,i.v.) (B) Selectivity Index A/B (C) GTN 8.22 474.40 0 017 2 139.52 675.61 0 152 5 226.34 337.9 0 67 8 227.16 372.85 0 61 9 286 492 0 58 15 248.86 681.68 0 37 16 318.55 113.16 2. 81 It was observed that compounds have a high selectivity index as compared to GTN.. In the case of compounds 5, 8 and 9 amongst the novel molecules and compound 16 amongst the known molecule the index is significantly higher. The index showed that these compounds could elicit anti-anginal activity at a dose, which has minimum systemic effect. Their selectivity in dilating coronary arteries was quite high as compared to a conventional drug like GTN. The high selectivity index of these compounds as compared to nitroglycerine show that they selectively dilate the coronary arteries and have a lower tendency to cause hypotension during clinical usage. For example, the compound with lowest selectivity index, compound 15 is 22 times more selective as compared to GTN. This shows that these compounds have very little tendency to cause hypotension. - 21 - Conventional nitrates like GTN cause tachycardia, retrosternal discomfort, palpitations, collapse, syncope and postural hypotension, etc. as a manifestation of hypotensive effect. This could limit their use in selected patients. However, the compounds described in this invention due to a lower tendency to cause hypotension are superior to conventional nitrates. The benzofuroxans described in this invention can be used in cardiovascular disorders like acute effort angina, angina prophylaxis, mixed angina and silent ischemia, acute myocardial infarction, congestive heart failure, etc. They can be used alone or in combination. They could be combined with beta adrenergic blockers like propranolol, atenolol, carvedilol, etc. and calcium channel antagonists ]ike verapamil, diltiazem, etc. The following examples are presented to" further illustrate the invention, but do not limi t i t in any way. EXAMPLES The method of preparation of the representative novel compounds of this invention as listed in Table 1 are given in the following examples. EXAMPLE 1: Preparation of 5(6)- (2- isonicotinamideethyloxy carbonyl) benzofuroxan. (Compound 1): 5(6)- Carboxy benzofuroxan (1.8g, 0.01 mole) and N- (2-hydroxyethyl) isonicotinamide (1.66 g, 0.01 mole) were dissolved in CH2CI2 (100 ml) and THF (100 ml) mixture. To this solution, 4- dimethylamino pyridine (70 mg) and N,N'- - 22 - dicyclohexyl carbodiimide (3 g, 0.0145 mole) were added under stirring. The reaction mixture was stirred for 16 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product which was purified by column chromatography (EtOAc:n-hexane = 90:10) to give the title compound as yellow solid {0.2 g, 74%) . m.p.: 201°C (HC1 salt) IR (KBr): 3423, 3180, 1720, 1677, 1613, 1585, 1543, 1490 cm-1 PMR (200 MHz, CDC13) 6: 2.58-2.6 (2H,t,J=l.7Hz), 3.55 (1H,S), 4.52-4.57 (2H,t,J=5.26Hz), 7.67-8.45 (3H,m), 8.95-9.65 (4H,dd) Mass: 328 (M+), 298, 229, 181, 164, 147, 117, 105, 77, 50. EXAMPLE 2: Preparation of 5(6)- (2- pyrolidinone ethyloxy carbonyl) benzofuroxan. (Compound 2): 5(6)- Carboxy benzofuroxan (0.9g, 0.005 mole) and 1- (2-hydroxyethyl) -2- pyrolidinone (0.7 g, 0.005 mole) were dissolved in CH2CI2 (40 ml). To this solution, 4- dimethyl amino pyridine (70 mg) and N,N'- dicyclohexyl carbodiimide (2.06 g, 0.01 mole) were added under stirring. The reaction mixture was stirred for 3 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product, which was purified by column chromatography (EtOAc:n- hexane = 50:50) to give the title compound as pale yellow solid (0.7 g, 48%). m.p.: 101-102°C IR (KBr): 1726, 1678, 1611, 1590, 1534 cr1 - 23 - PMR (200 MHz, CDCla) 6: 1.99-2.14 (2H.ni), 2.35-2.43 (2H,tfJ=7.72Hz), 3.49-3.56 (2H, Jt, J = 6.9Hz) t 3.6Q-3.73 (2H,t,J=5.2Hz), 4.48-4.53 (2H,t, J=5.4Hz), 7.6-7.86 (3H,m) Mass: 291 (M+), 273, 225, 111, 98, 70, 56. EXAMPLE 3: Preparation of 5(6)- (2- hydroxy propyloxy carbonyl) benzofuroxan (Compound 3): 5(6)- carboxy benzofuroxan (1.8 g, 0.01 mole) and propylene glycol (0.76 g, 0.01 mole) were dissolved in CH2CI2 (80 ml). To this solution, 4- dimethylamino pyridine (140 mg) and N,Nr-dicyclohexyl carbodiimide (4.4 g, 0.021 mole) were added with stirring. The reaction mixture was stirred for 2 hours at room temperature. It was filtered and the 'filtrate on evaporation under reduced pressure gave crude product which was purified by column chromatography (EtOAc:n- hexane = 20:80) to give the title product as pale yellow solid (1.16 g. 49%) m.p. : 89-90°C IR (KBr): 3500-3100, 1716, 1654, 1613, 1592, 1540, 1491 cm-' PMR (200 MHz, CDCla) 6: 1.3-1.33 (3H,d,J=6Hz), 3.82 (lH.s), 4.22-4.4 (3H,m), 7.6-8.26 (3H,m) Mass: 238 (M- ) , 179, 163, 147, 103, 75, 58, 45,. EXAMPLE 4: Preparation of 5(6)- (2- morpholino ethyloxy carbonyl) benzofuroxan. (Compound 4): 5(6)- Carboxy benzofuroxan (0.9 g, 0.005 mole) and N-(2-hydroxyethyl) morpholine (0.71 g, 0.005 mole) were dissolved in CH2CI2 (50 ml). To this solution, 4-dimethylamino pyridine (70 mg) and N, N1- dicyclohexyl carbodiimide (2.06 g, 0.01 - 24 - mole) were added under stirring. The reaction mixture was s'tirred for 2 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product which was purified by column chromatog-raphy (EtOAcrn-hexane = 50:50) to give the title compound as white solid (0.5 g, 34%). The base (0.2 g) was transformed into the., corresponding HC1 salt, by 5% methanolic HC1 (0.14 g, 64%). m.p.: 210°C (HC1 salt) IR (KBr): 1729, 1613, 1589, 1542 cnr * PMR (200MHzr CDCln) 6: 2.58-2.59 (4H,t,J=4.5Hz), 3.18-3.2 (4H,t,J=13.63Hz), 3.55-3.43 (2H,t), 3.97-4.17 (2H,t), 7.48-7.98 (3H,m) Mass: 293 (M+), 113, 103, 101, 100. EXAMPLE 5: Preparation of 5(6)- (2- methyloxy ethyloxy carbonyl) benzofuroxan. (Compound 5): 5(6)- Carboxy benzofuroxan (1.8 g, 0.01 mole) and methyl cellosolve (0.076 g, 0.01 mole) were dissolved in CH2CI2 (60 ml). To this solution, 4- dimethylamino pyridine (0.3 g) and N,N'- dicyclohexyl carbodiimide (2.3 g, 0.01 mole) were added with stirring. The reaction mixture was stirred for 2 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product as oily liquid. Crude product was purified by column ohromatography (EtOAc:n-hexane'= 5:95) to give the title compound. It was crystallized from n- hexane to yield 5(6)- methyloxy ethyloxy carbonyl benzofuroxan as yellow solid (1.2 g, 50%). - 25 - m.p.: 68-69°C IR (KBr): 1717, 1615, 1582, 1536 cm-i PMR (300 MHz., CDCls) 6: 3.43 (3H,s), 3.72-3.75 (2H, t, J = 6Hz) , 4.5- 4.53 (2H,t,J=6Hz), 7.26-8.26 (3H,m). Mass: 238 (M+), 207, 180, 163, 103, 75, 58. Alternatively, compound 5 can also be prepared by following procedure : 5(6)-Carboxy benzofuroxan (1.0 g) was heated to 80°C in a saturated solution of methyl cellosolve HCl for 16 hours. Excess methyl cellosolve was removed under vacuum and the residue was redissolved in diethylether and washed with aqueous NaOH, followed by water and dried over Na2'SO4 . Ether was removed under vacuum and the residue was purified by column chromatography to get 280 mg of compound 5. EXAMPLE 6: Preparation of 5(6)- (2,3- dihydroxy propyloxy carbonyl) benzofuroxan. (Compound 6): A mixture of 5(6)- ((±)-2, 2- dimethyl -1,3- dioxolane -4- methyloxy) carbonyl benzofuroxan (0.5 g, 0.001 mole) and 5 ml of 75% acetic acid was stirred at 80°C for 4 hours. Evaporation of the solvent under vacuum (40°C) gave oily product, which was purified by column chromatography (hexane:EtOAc = 80:20) to give the title compound as yellow solid (0.4 g, 93%) m.p.:86°C IR (KBr): 3355, 1719, 1606, 1450 cm-1 PMR (300 MHz, CDCI3) 6: 3.89-3.90 (1H,d,J=4.2Hz), 4.03-4.06 (lH,t,J=4.5Hz), 4.36-4.52 (2H,m), 7.61-8.34 (3H,m) - 26 - Mass: 254 (M+), 180, 163, 103 EXAMPLE 7: Preparation of 5(6)-(2- ethyloxy ethoxy carbonyl) benzofuroxan. (Compound 7): 5(6)- Carboxy benzofuroxan (1.8 g, 0.01 mole) and ethylcellosolve (0.8 g, 0.01 mole) were dissolved in CH2CI2 (50 ml). To this solution, 4- dimethylamino pyridine (0.3g) and N,Nf- dicyclohexyl carbodiimide (2.4 g, 0.Q11 mole) were added under stirring. The reaction mixture was stirred for 2 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product as brown oily liquid, which was purified by column chromatography (EtOAcm- hexane = 20:80) to yield the title compound as pale yellow viscous oil (1.0 g, 40%) IR (KBr): 1727, 1598, 1538, 1488cm"1 PMR (200 MHzT CDCI3) 6: 1.2-1.27 (3H,t,J=7Hz), 3.54-3.64 (2H,q,J-7Hz), 3.76-3.81 (2H,t,J=6Hz), 4.5-4.54 (2H,t,J=5Hz), 7.59- 8.26 (3H,m) EXAMPLE 8: Preparation of 5(6)- (3- pyridine methoxy carbonyl) benzofuroxan. (Compound 8): 5(6)- Carboxy benzofuroxan (1.8 g, 0.01 mple) and pyridine -3- methanol (1.1 g, 0.01 mole) were dissolved in CH2CI2 (50 ml). To this solution, 4- dimethylamino pyridine (70 mg) and N,N'- dicyclohexyl carbodiimide (3 g, 0.014 mole) were added with stirring. The reaction mixture was stirred for 2 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product, which was purified by column chromatography - 27 - (EtOAc:n- hexane = 25:75) to give the title compound as a pale yellow solid. The base (0 ...5 g) was transformed into the corresponding HC1 salt, by 5% methanolic HC1 (0.4 g, 71%) m.p.: 200°C (HC1 salt) IR (KBr): 1719, 1616, 1589, 1534 cm-1 PMR (300 MHz, DMSOde) 6: 5.59 (2H,s), 7.88-8.04 (3H,m), 8.63- 9.09 (4H,m) Mass:307 (M++HC1), 271 (M+), 180, 92. EXAMPLE 9: Preparation of 5(6)-((+) 2,2- dimethyl -1,3- dioxolane -4- methyloxy carbonyl) benzofuroxart. (Compound 9): 5(6)- Carboxy benzofuroxan (0.99 g, 0.005 mole) and solketal (0.66 g, 0.005 mole) were dissolved in CH2CI2 (40 ml). To this solution, 4- dimethylamino pyridine (0.2 g) and N,N'-dicyclohexyl carbodiimide (1.33 g, 0.006 mole) were added under stirring. The reaction mixture was stirred for 2 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product as oily liquid, which was purified by column chromatography (EtOAc:n- hexane = 10:90) to give the title compound as pale yellow solid (0.6 g, 41%) m.p.: 51-52°C IR (KBr): 1725, 1586, 1535, 14-84 cm"1 PMR (200 MHz, CDCI3) 6: 1.39 (3H,s), 1.46 (3H;s), 3.83-3.89 (lH,dd,6Hz), 4.13-4.20 (lH,dd,6Hz), 4.39-4.48 (3H,m), 7.85-8.27 (3H,m) Mass: 294 (M+), 279, 163. EXAMPLE 10: Preparation of isosorbide mononitrateoxy - 28 - carbonyl benzofuroxan. (Compound 10): To a solution of 5(6)- caxboxy benzofuroxan (1.0 g, 0.0055 mole) and isosorbide -5- mononitrate (0.09 g, 0.0047 mole) in CH2CI2 (50 ml) were added 4- dimethylamino pyridine (50 mg) and N.N1- dicyclohexyl carbodiimide (2 g, 0.0097 mole) with stirring. The reaction mixture was stirred for 2 hours at room temperature. It was filtered and the filtrate on evaporation under reduced pressure gave crude product, which was purified by column chromatography (EtOAc:n- hexane = 20:80) to give the title product as a yellow solid (1.0 g, 51%) m.p.: 117-118°C IR (KBr): 1721, 1635, 1590, 1537 cm-1 PMR (200 MHz, CDCI3) 6: 3.91-4.16 (4H,m), 4.63-4.66 (lH,d,J=6Hz), 5.07-5.12 (1H,dd,J=4.5Hz), 5.39-5.68 (2H,m), 7.61-8.36 (3H,m} Mass: 353 (M+), 194, 163, 127. The following examples gives method of preparation of representative compounds of Table 2. EXAMPLE 11: Preparation of 5(6)- n- propoxy carbonyl benzofuroxan. (Compound 15) : 5(6)- Carboxy benzofuroxan (2.0g, 0.011 mole) was refluxed in a saturated solution of n- propionolic HC1 for 16 hours. n-Propanol was removed under vacuum and the residue was redissolved in diethyl ether (150 ml). The. solution was then washed with aqueous NaOH (50ml 0.1 mole), followed by water (100 ml) and dried over Na2SO4. Ether was removed under - 29 - vacuum to give an oil which was purified by column chromatography. Yield : 1.0 g, (45%) m.p : 30-22°C I.R.(KBr): 1725, 1613, 1585, 1540, 1490 cm"1 P.M.R. (200MHz, CDC13)6: 1.09-1.08 (2H.t,J=7.4Hz), 1.58-2.17 (2H,m), 4.30-4.36 (3H,t,J=6.6Hz), 7.36-7.86 (3H,m). Mass: 222(M+), 180, 163, 75. Alternatively, compound 15 can also be prepared by the following procedure: 5(6)-Chlorocarbonyl benzofuroxan (100 mg) and n-propyl alcohol (150 mg) were dissolved in THF (10 ml) at room temperature. To the reaction mixture triethylamine (0.1 ml) was added and reaction mixture was refluxed for 24 hours. THF was removed under reduced pressure. To the residue 3 0 ml water was added and extracted with ethyl acetate (3x20 ml). Ethyl acetate was removed under reduced pressure to get sticky mass which was purified by column chromatography using ethylacetate:hexane (1:9) to give 65 mg of compound 15. Compound 15 can also be prepared by the method of preparation of compound 16. EXAMPLE 12: Preparation of 5(6)- isopropoxy carbonyl benzofuroxan. (Compound 16). To a solution of 5(6)- carboxy benzofuroxan (l.Og, 0.0055 mole) and isopropyl alcohol (0.9 ml., 0.01 mole) in CH2CI2 (50 ml) were added 4- dimethylamino pyridine (70 mg) and N, N1-dicyclohexyl carbodiimide (2.28g, 0.011 mole) under - 30 - stirring. The reaction mixture was stirred for 2 hours at room temperature. It was fj.lte.red and the filtrate on evaporation under reduced pressure gave crude product which was purified by column chromatography (n-hexane) to give the title compound as yellow solid (0.7 g, 57%). m.p : 65-67°C IR (KBr): 1716, 1622, 1585, 1537 cnr i PMR (200 MHz, CDCl3)G: 1.31-1.41 (6H, d, J=6.2Hz), 5.15-5.37 (lH,m), 7.51-8.21(3H,m) Mass: 22 (M+), 180, 163, 103, 75. Compound 16 can also be prepared by the methods of preparation of compound 15. Oral Formulations: Orally they may be administered as solid dosage forms for example as pellets, granules, powder, sachet or as discreet units such as tablets or capsules, etc. Other orally administered pharmaceutical preparations include monophasic and biphasic liquid dosage forms either in ready to use form, or forms suitable for reconstitution such as mixtures, syrups, suspensions or emulsions. The preparations in addition may contain diluents, dispersing agents, buffers, stabilizers, solubilizers, surface active agents, preservatives, chelating agents and/or other pharmaceutical additives. Aqueous or non aqueous vehicles or their combination may be used and if desired may contain suitable sweeteners, flavouring agents or similar substances. In the case of a suspension or emulsion a suitable thickening agent, - 31 - suspending, agent or emulsifying agent may be present. Pharmaceutical preparations can have a slow, delayed or controlled release of active ingredients as is provided by a matrix or diffusion controlled system. Parenteral formulations: For parenteral administration, the compounds or their salts or suitable complexes may be presented in a sterile vehicle which may be an aqueous or non aqueous vehicle or a combination thereof. The examples of vehicles are water, ethyl oleate, oils and derivatives of polyols,, glycols and their derivatives. It may contain additives common in injectable preparations like stabilizers, solubili'zers, pH modifiers, buffers, antioxidants, cosolvents, complexing agents, tonicity modifiers, etc. Some suitable, additives are for example tartrate, citrate, or similar buffers, alcohols, sodium chloride, dextrose and high molecular weight liquid polymers. Another alternative is sterile powder for reconstitution. The compound may be administered in the form of injection, intravenous infusion/drip, or suitable depot preparation. When the present invention, its salts or a suitable complex is presented as a discrete unit dosage form like a tablet, it may contain in addition medically inert excipients as are used in art. Diluents such as starch, lactose dicalcium phosphate, lubricants or similar additives like talc, magnesium stearate, polymeric substances, like methyl cellulose, hydroxy propyl cellulose, fatty acids and - 32 - derivatives, sodium starch glycollate, etc. can also be used. Example 13: Preparation of ora.l dosage form of the benzofuroxan derivatives given in Tables 1 and 2. The compounds described in Tables 1 and 2 can be prepared in the form of tablets, containing thei active ingredient in the range of 0.03 to 3 mg per tablet. A typical tablet has the following composition: Active ingredient as given above Starch 27 mg Lactose 70 mg Polyvinyl pyrolidone (k-30) 1.0 mg Talc 1.5 mg Magnesium stearate 0.5 mg Example 14: Preparation of parenteral dosage form of benzofuroxan derivatives given in Tables 1 and 2: A preparation suitable for parenteral administration has the following composition: Active ingredient 1 mg. Poly ethylene glycol - 400 0.5 ml Isotonic saline solution q.s. or water for injection 1 ml These examples are presented by way of illustration alone and in no way limit the scope of the invention. -33-WE CLAIM : 1. A compound useful for cardiovascular disorders represented by the formula (I) and pharmaceutically acceptable salts thereof wherein: R is -0-(CH2)n-X-R'; n = l-6; X is -NHC(O)- or oxygen; R1 is Ci-C8 alkyl, aromatic, heteroaromatic, substituted or unsubstituted saturated heterocyclic ring with one or two hetero atoms selected from the group consisting of nitrogen and oxygen, wherein substitution is with G-Cs alkyl; or R is selected from -34- wherein R" is hydrogen, nitro, Ci-C8 alkyl or -C(O)- R"f wherein R1" is hydrogen, Ci-Cs alkyl or aryl, with the proviso that R is not OCH2CH2nicotinamide. 2. The compound, as claimed in claim 1, wherein the preferred position for the substitution is 5(6). 3. The compound, as claimed in claim 1 or 2, wherein Xis-NHC(O)-; R' is Ci-Cs alkyl, heteroaromatic, substituted or unsubstituted saturated heterocyclic ring with one or two hetero atoms selected from the group consisting of nitrogen and oxygen, wherein substitution is with Ci-Cs alkyl and the preferred value of n is 1 and 2. 4. The compound, as claimed in claim 1 or 2, wherein said compound is 5(6)-(3- pyridine methoxy carbonyl) benzofuroxan. 5. The compound as claimed in claim 1 or 2, wherein said compound is 5(6)-((±) - 2, 2 - dimethyl - 1, 3 - dioxalane - 4 - methyloxycarbonyl) benzofuroxan. 6. The compound, as claimed in claim 1 or 2, wherein said compound is 5(6) - (2 - pyrolidinone ethyloxy carbonyl) benzofuroxan. 7. The compound, as claimed in claims 1 - 3, wherein said compound is 5(6) - (2 - isonicotinamide ethyloxy carbonyl) benzofuroxan hydrochloride. 8. The compound, as claimed in claim 1 or 2, wherein said compound is 5(6) - (2 - ethyloxy ethoxy carbonyl) benzofuroxan. -35- 9. The compound, as claimed in claim 1 or 2, wherein said compound is 5(6) - (2 hydroxy propyloxy caxbonyfylcnijOfwfoXo-n- 10. The compound, as claimed in claim 1 or 2, wherein said compound is 5(6) (isosorbide mononitrate oxycarbonyl) benzofuroxan. 11. The compound, as claimed in claim 1 or 2, wherein said compound is 5(6) - (2, 3 - dihydroxy propyloxy carbonyl) benzofuroxan. 12. Th" compound, as claimed in claim 1 or 2, wherein said compound is 5(6) - (2 - methyloxy ethloxy carbonyl) benzofuroxan. 13. The compound, as claimed in claim 1 or 2, wherein said compound is 5(6) - (2 - morpholino ethyloxy carbonyl) benzofuroxan. 14. A pharmaceutical composition comprising a pharmaceutically effective amount of a compound of general formula (I), as claimed in claim 1, in association with a pharmaceutically acceptable carrier or excipient. 15. The pharmaceutical composition, as claimed in claim 14, useful in cardiovascular disorders like coronary heart diseases. 16. The pharmaceutical composition, as claimed in claim 14, useful as a tolerance resistant anti anginal composition. 17. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (3 - pyridine methoxy carbonyl) - benzofuroxan. -36- 18. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein the said compound is 5(6) ((±) - 2, 2 - dimethyl - 1, 3 - dioxalane - 4 - methyloxycarbonyl) benzofuroxan. 19. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (2 - pyrolidinone ethyloxy carbonyl) benzofuroxan. 20. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (2 - isonicotinamide ethyloxy carbonyl) benzofuroxan hydrochloride. 21. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (2 - ethyloxy ethoxy carbonyl) benzofuroxan. 22. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (2 - hydroxy propyloxy carbonyl) benzofuroxan. 23. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (isosorbide mononitrateoxycarbonyl) benzofuroxan. 24. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (2, 3 - dihydroxy propyloxy carbonyl) benzofuroxan. 25. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (2 - methyloxy ethyloxy carbonyl) benzofuroxan. 26. The pharmaceutical composition, as claimed in claim 14, 15 or 16, wherein said compound is 5(6) - (2 - morpholino ethyloxy carbonyl) benzofuroxan. -37- 27. The pharmaceutical composition of the compound of general formula (I) as claimed in claim 14, wherein the said composition contains pharmaceutically active amount of the compound of general formula (I) and one or more pharmaceutically acceptable carrier ranging from 60% to 99.9% of total weight of the composition. 28. The pharmaceutical composition, as claimed in claim 27, in the form of an oral formulation. 29. The pharmaceutical composition, as claimed in claim 28, wherein said pharmaceutically acceptable carrier is selected from one or more of the compounds like starch, lactose, polyvinyl pyrolidone (K.-30), talc and magnesium stearate. 30. The pharmaceutical composition, as claimed in claim 27, in the form of a parenteral formulation. 31. The pharmaceutical composition, as claimed in any one of the claims 27 - 30, wherein said pharmaceutically acceptable salt of the compound of formula (I) is an oxalate, tartarate, maleate, methyl sulphonate or p-toluene sulphonate. 32. The pharmaceutical composition, substantially as herein described, particularly with reference to the examples. This invention discloses novel compounds of benzofuroxan series and to their use in therapeutics. In particular the invention concerns novel benzofuroxan derivatives, pharmaceutical compositions containing these compounds, and their use as tolerance resistant nitric oxide donors in treatment of angina pectoris. In addition the invention also discloses the use of other carefully chosen derivatives of benzofuroxan series showing tolerance resistance activity as nitric oxide donors and to their pharmaceutically acceptable compositions and formulations.

Documents:

00303-cal-2000 abstract.pdf

00303-cal-2000 assignment.pdf

00303-cal-2000 claims.pdf

00303-cal-2000 correspondence.pdf

00303-cal-2000 description(complete).pdf

00303-cal-2000 drawings.pdf

00303-cal-2000 form-1.pdf

00303-cal-2000 form-18.pdf

00303-cal-2000 form-2.pdf

00303-cal-2000 form-3.pdf

00303-cal-2000 g.p.a.pdf

00303-cal-2000 letters patent.pdf

00303-cal-2000 reply. f.e.r.pdf