HETEROSUBSTITUTED PYRIDINE DERIVATIVES AS PDE 4 INHIBITORS

Abstract: The invention encompasses the novel compound of Formula (I) useful in the treatment of diseases, including asthma, by raising the level of cyclic adenosine-3',5'-monophosphate (cAMP) through the inhibition of phosphodiesterase IV (PDE 4). The invention also encompasses pharmaceutical compositions and methods for treatment.

Description: TITLE OF THE INVENTION HETERQSUBSTΓΓUTED PYRIDINE DERIVATIVES AS PDE 4 INHIBITORS BACKGROUND OF THE INVENTION This invention relates to compounds and pharmaceutical compositions containing such compounds useful for treating diseases by raising the level of cyclic adenosine-3 ',5 '-monophosphate (cAMP) through the inhibition of phosphodiesterase rV (PDE 4). Many hormones and neurotransmitters modulate tissue function by elevating intra-cellular levels of 3',5'-cyclic adenosine monophosphate (cAMP). The cellular levels of cAMP are regulated by mechanisms which control synthesis and breakdown. The synthesis of cAMP is controlled by adenyl cyclase which may be directly activated by agents such as forskolin or indirectly activated by the binding of specific agonists to cell surface receptors which are coupled to adenyl cyclase. The breakdown of cAMP is controlled by a family of phosphodiesterase (PDE) isoenzymes, which also control the breakdown of guanosine 3',5 -cyclic monophosphate (cGMP). To date, nine members of the family have been described (PDE 1-9) the distribution of which varies from tissue to tissue. This suggests that specific inhibitors of PDE isoenzymes could achieve differential elevation of cAMP in different tissues, [for reviews of PDE distribution, structure, function and regulation, see Beavo & Reifsnyder (1990) TIPS, 11: 150-155, Nicholson et al (1991) TIPS, 12: 19-27 and Houslay et al (1998) Adv. Pharmacol. 44: 225-342]. The availability of PDE isotype selective inhibitors has enabled the role of PDEs in a variety of cell types to be investigated. In particular it has been established that PDE 4 controls the breakdown of cAMP in many inflammatory cells, for example, basophils (Peachell P.T. et al., (1992) J. Immunol. 148 2503-2510) and eosinophils (Dent G. et al., (1991) Br. J. Pharmacol. 103 1339-1346) and that inhibition of this isotype is associated with the inhibition of cell activation. Furthermore, elevation of cAMP in airway smooth muscle has a spasmolytic effect. Consequently PDE 4 inhibitors are currently being developed as potential anti- inflammatory drugs particularly for the prophylaxis and treatment of asthma, by achieving both anti-inflammatory and bronchodilator effects. The application of molecular cloning to the study of PDEs has revealed that for each isotype there may be one or more isoforms. For PDE 4, it is has been shown that there are four isoforms (A, B, C and D) each coded for by a separate gene in both rodents (Swinnen JN. et al., (1989) Proc. Νatl. Acad. Sci. USA 86 5325- 5329) and man (Bolger G. et al., (1993) Mol. Cell Biol. 13 6558-6571). The existence of multiple PDE 4s raises the prospect of obtaining inhibitors that are selective for individual isoforms, thus increasing the specificity of action of such inhibitors. This assumes that the different PDE 4 isoforms are functionally distinct. Indirect evidence in support of this comes from the selective distribution of these isoforms in different tissues (Swinnen et al., 1989; Bolger et al., 1993; Obernolte R. et al., (1993) Gene 129 239-247, ibid) and the high degree of sequence conservation amongst isoforms of different species. To date full length cDΝAs for human PDE 4 A, B, C and D (Bolger et al., 1993 ibid; Obernolte et al., 1993 ibid; Mclaughlin M. et al., (1993) J. Biol. Chem. 268 6470-6476, Owens et al (1997) Cell. Signal., 9: 575-585) and rat PDE 4A, B and D (Davis R. et al., (1989) Proc. Νatl. Acad. Sci. USA 86 3604-3608; Swinnen JN. et al., (1991) J. Biol. Chem. 266 18370-18377), have been reported, enabling functional recombinant enzymes to be produced by expression of the cDΝAs in an appropriate host cell. These cDΝAs have been isolated by conventional hybridisation methods. The design of PDE 4 inhibitors for the treatment of inflammatory diseases such as asthma, has met with limited success to date. Many of the PDE 4 inhibitors which have been synthesised have lacked potency and/or inhibit more than one type of PDE isoenzyme in a non-selective manner. PDE 4 inhibitors that are relatively potent and selective for PDE 4, are reported to be emetic as well. Indeed this side effect has been so universal that experts have expressed their belief that the emesis experienced upon administration of a PDE 4 inhibitor, may be mechanism based. One object of the present invention is to provide heterosubstituted pyridines derivatives that are inhibitors of PDE 4 at concentrations at which they have little or no inhibitory action on other PDE isoenzymes. These compounds inhibit the human recombinant PDE 4 enzyme and also elevate cAMP in isolated leukocytes. The compounds thus prevent, alleviate or reduce inflammation in the lungs, such as that induced by carrageenan, platelet-activating factor (PAF), interleukin-5 (IL-5) or antigen challenge. The compounds also suppress the hyperresponsiveness of airway smooth muscle seen in inflammed lungs. Another object of the present invention is to provide compounds that have good oral activity and that at orally effective doses, exhibit a reduced incidence of the side-effects associated with known PDE 4 inhibitors, such as rolipram. The compounds of the invention are therefore of use in medicine, especially in the prophylaxis and treatment of asthma and other inflammatory conditions. SUMMARY OF THE INVENTION A compound represented by formula I: or a pharmaceutically acceptable salt or hydrate thereof wherein: Y represents N or N-oxide; y represents 0, 1 or 2; Ri and R^ are independently selected from: H, Ci-6alkyl and haloCi-6 alkyl, R3 and R^ are independently selected from H and Ci-6alkyl, or R^ and R^ attached to the same carbon atom taken together represent a carbonyl oxygen atom, or R3 and R^ attached to different carbon atoms considered in combination with the carbon atoms to which they are attached along with any intervening atoms and represent a saturated 5, 6 or 7 membered carbocyclic ring, n represents an integer of from 0-6; Ar is selected from the group consisting of: (a) thienyl, (b) thiazolyl, (c) pyridyl, (d) phenyl and (e) naphthyl, said Arl bein; g optionally substituted with 1-3 members selected from the group consisting of: (1) halo, (2) Ci-6alkoxy, (3) Ci-γalkylthio, (4) CN, (5) Cι_6alkyl, (6) C i -όhydroxyalkyl, (7) -C(O)C!-. 6 alkyl, -CO2H, -CO2Ci_6alkyl, (8) NH(SO2Me), N(SO2Me)2, (9) SO2Me, S02NH 2 , SO2NHC!. 6 alkyl, 302^^.6 alkyl) 2 (10) NO 2 , (11) Cι_6alkenyl, (12) halo C 1-6 alkyl, and (13) NH 2 , and when Ar^ represents a phenyl or naphthyl group with two or three substituents, two such substituents may be considered in combination and represent a 5 or 6 membered fused lactone ring. Pharmaceutical compositions and methods of treatment are also included. DETAILED DESCRIPTION OF THE INVENTION The present invention includes compounds represented by formula I: as well as pharmaceutically acceptable salts or hydrate thereof wherein: Y represents N or N-oxide; y represents 0, 1 or 2; Ri and R are independently selected from: H, Ci-6alkyl and haloCi-6 alkyl, R3 and R4 are independently selected from H and Cι_6alkyl, or R3 and R4 attached to the same carbon atom taken together represent a carbonyl oxygen atom, or R3 and R4 attached to different carbon atoms considered in combination with the carbon atoms to which they are attached along with any intervening atoms and represent a saturated 5, 6 or 7 membered carbocyclic ring, n represents an integer of from 0-6; Ar is selected from the group consisting of: (a) thienyl, (b) thiazolyl, (c) pyridyl, (d) phenyl and (e) naphthyl, said Arl bein g optionally substituted with 1-3 members selected from the group consistin g of: (1) halo, (2) Cι_6alkoxy, (3) C 1-7 alkylthio, (4) CN, (5) Cι_6alkyl, (6) Ci-6hydroxyalkyl, (7) -C(O)Cι_ 6 alkyl, -CO2H, -CO2Ci_6alkyl, (8) NH(SO2Me), N(SO2Me)2, (9) SO2Me, SO2NH2, SO2NHC!_ 6 alkyl, SO 2 N(C!- 6 alkyl) 2 (10) NO 2 , (11) Cι_6alkenyl, (12) halo Ci-6 alkyl, and (13) NH 2 , and when Arl represents a phenyl or naphthyl group with two or three substituents, two such substituents may be considered in combination and represent a 5 or 6 membered fused lactone ring. The following definitions pertain to the terms used herein unless otherwise indicated. Halo is intended to include F, Cl, Br, and I. HaloCi-6 alkyl refers to an alkyl group having 1-9 halo groups attached. Examples include -CH2F, -CHF2 , - CF3 , -CH 2 CH 2 F , -CHFCH2F , -CF2CH2F , -CF2CHF2 and -CF2CF3. Alkyl groups include straight or branched alkyl groups having 1-7 carbon atoms, and cyclic alkyl groups having from 3-7 carbon atoms. Cycloalkyl groups with alkyl substituent groups attached are also included. Examples of Ci- 6alkyl groups include methyl, ethyl, propyl, 2-propyl, s- and t-butyl, butyl, pentyl, hexyl, 1,1-dimethylethyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. Examples of Ci-βalkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, cyclopropyloxy, cyclohexyloxy, and the like. Likewise, Ci_7alkylthio is intended to include alkylthio groups of from 1 to 7 carbon atoms of a straight, branched or cyclic configuration. Examples of alkylthio groups include methylthio, propylthio, isopropylthio, cycloheptylthio, etc. By way of illustration, the propylthio group signifies -SCH2CH2CH3. Preferred values of R and R2 are -6 alkyl and haloCi-όalkyl. More preferred values are selected from the group consisting of CH3, CH2F, CHF2, CF3 and most preferrably CHF2. Within this subset, all other variables are as originally defined. Preferred values of n are 0, 1, 2 and 3. More preferred values are 0, 1 and 2. Within these subsets, all other variables are as originally defined. Preferred values of Arl are phenyl and naphthyl. More preferred is phenyl. Within these subsets, all other variables are as originally defined. Preferred values of R3 and R are H and Ci-βalkyl. More preferred are H and methyl. Within these subsets, all other variables are as originally defined. Preferred values of R5 and R6 are H and Cι_6alkyl. More preferred is H. Within these subsets, all other variables are as originally defined. Preferably the Y is in the 2, 3 or 4 position relative to the point of attachment to the ethylene group. More preferably the Y is in the 4 position relative to the point of attachment to the ethylene group. Similarly, the pyridyl nitrogen atom shown is preferably in the 2, 3 or 4 position, relative to the attachment to the ethylene group. More preferably it is in the 3 position. A subset of compounds that is of particular interest relates to compounds of formula I wherein: Ri and R are Ci-6alkyl and haloCι_6alkyl selected from the group consisting of CH3, CH2F, CHF2 and CF3 ; n is O, 1, 2 or 3; Arl j s phenyl or naphthyl; R and R4 are H and methyl and R5 and R6 are H or Ci^alkyl. Within this subset, all other variables are as originally defined. More particularly, a subset of compounds that is of particular interest relates to compounds of formula I wherein: Ri and R 2 are CHF2, and n is 0, 1 or 2. Within this subset, all other variables are as defined immediately above. Another subset of compounds that is of particular interest relates to compounds of formula I wherein: Rl and R2 are CHF2; n is 0, 1 or 2; R 3 and R 4 are H or methyl, R5 and R6 are H and Arl j s phenyl. Within this subset, all other variables are as defined immediately above. Examples of compounds falling within the present invention include the following: 1. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-{6-[3- (aminosulfonyl)benzenethiol]3-pyridyl}ethyl}pyridine, 2. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(3-methoxybenzenethiol)3- pyridyl]ethyl Jpyridine, 3. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(3-methoxybenzenesulfonyl)3- pyridyl]ethyl Jpyridine, 4. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-nitrobenzenesulfonyl)3- pyridyl]ethyl } pyridine-N-oxide, 5. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-nitrobenzenethiol)3- pyridyljethyl } pyridine-N-oxide, 6. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-fluorophenylmethanethiol)3- pyridyl]ethyl } pyridine-N-oxide, 7. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-fluorobenzenethiol)3- pyridyl]ethyl } pyridine-N-oxide, 8. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-fluorobenzenesulfonyl)3- pyridyl]ethyl } pyridine-N-oxide, 9. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4- fluorophenylmethanesulfonyl)3-pyridyl]ethyl}pyridine-N-oxide, 10. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-{6-[l-methyl-l-(4- fluorophenyl)ethanethiol]3-pyridyl } ethyl } pyridine-N-oxide, and 11. 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-{6-[l-methyl-l-(4- fluorophenyl)ethanesulfonyl]3-pyridyl } ethyl } pyridine-N-oxide. The compounds described herein contain one or more asymmetric centers and may thus give rise to diastereomers and optical isomers. The present invention is meant to include all such possible isomers and diastereomers as well as their racemic and resolved, enantiomerically pure forms and pharmaceutically acceptable salts thereof. The invention also encompasses a pharmaceutical composition that is comprised of a compound of formula I in combination with a pharmaceutically acceptable carrier. Preferably the composition is comprised of a pharmaceutically acceptable carrier and a non-toxic therapeutically effective amount of compound of formula I as described above. Moreover, within this preferred embodiment, the invention encompasses a pharmaceutical composition for the treatment or prevention of disease by inhibition of PDE 4, resulting in an elevation of cAMP, comprising a pharmaceutically acceptable carrier and a non-toxic therapeutically effective amount of compound of formula I as described above. The term "pharmaceutically acceptable salts" refers to salts prepared from pharmaceutically acceptable non-toxic bases including inorganic bases and organic bases. Salts derived from inorganic bases include aluminum, ammonium, calcium, copper, ferric, ferrous, lithium, magnesium, manganic salts, manganous, potassium, sodium, zinc, and the like. Particularly preferred are the ammonium, calcium, magnesium, potassium, and sodium salts. Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines, and basic ion exchange resins, such as arginine, betaine, caffeine, choline, N,N-dibenzylethylenediamine, diethylamine, 2- diethylaminoethanol, 2-dimethylaminoethanol, ethanolamine, ethylenediamine, N- ethylmorpholine, N-ethylpiperidine, glucamine, glucosamine, histidine, hydrabamine, isopropylamine, lysine, methylglucamine, morpholine, piperazine, piperidine, polyamine resins, procaine, purines, theobromine, triethylamine, trimethylamine, tripropylamine, tromethamine, and the like. It will be understood that references to the compounds of Formula I are meant to also include the pharmaceutically acceptable salts. The compounds of formula I are selective and potent inhibitors of PDE 4. The biological activity and utility of the compounds may be demonstrated as described herein. The compounds according to the invention are thus of particular use in the prophylaxis and treatment of human diseases where an unwanted inflammatory response or muscular spasm (for example bladder or alimentary smooth muscle spasm) is present and where elevation of the cAMP levels may be expected to prevent or alleviate the disease or condition. Particular uses to which the compounds of the invention may be put include the prophylaxis and treatment of asthma, especially inflammed lung associated with asthma, cystic fibrosis, in the treatment of inflammatory airway disease, chronic bronchitis, eosinophilic granuloma, psoriasis and other benign and malignant proliferative skin diseases, endotoxic shock, septic shock, ulcerative colitis, Crohn's disease, reperfusion injury of the myocardium and brain, inflammatory arthritis, chronic glomerulonephritis, atopic dermatitis, urticaria, adult respiratory distress syndrome, diabetes insipidus, allergic rhinitis, allergic conjunctivitis, vernal conjunctivitis, arterial restenosis and atherosclerosis. The compounds of the invention also suppress neurogenic inflammation. They are, therefore, analgesic, antitussive and antihyperalgesic in inflammatory diseases associated with irritation and pain. The compounds also elevate cAMP in lymphocytes and thereby suppress unwanted lymphocyte activation in immune-based diseases such as rheumatoid arthritis, ankylosing spondylitis, transplant rejection and graft versus host disease. The compounds also reduce gastric acid secretion and therefore can be used to treat conditions associated with hypersecretion of gastric acid. The compounds also suppress cytokine synthesis by inflammatory cells in response to immune or infectious stimulation. They are, therefore, useful in the treatment of bacterial, fungal or viral induced sepsis and septic shock in which cytokines such as tumour necrosis factor (TNF) are key mediators. The compounds of the invention also suppress inflammation and pyrexia due to cytokines and are, therefore, useful in the treatment of inflammation and cytokine-mediated chronic tissue degeneration which occurs in diseases such as rheumatoid or osteo-arthritis. The over-production of cytokines such as TNF in bacterial, fungal or viral infections or in diseases such as cancer, leads to cachexia and muscle wasting. Compounds of the invention ameliorate these symptoms as well. The compounds of the invention elevate cAMP in certain areas of the brain and thereby counteract depression and memory impairment. Compounds of the invention suppress cell proliferation in certain tumour cells and can be used, therefore, to prevent tumour growth and invasion of normal tissues. Prophylaxis and prevention are used interchangeably and mean preventing or minimizing the incidence of clinical manifestations of the particular disease or condition. Thus, for example, preventing asthma refers to preventing or minimizing the frequency or severity of asthma attacks. This can be measured using routine skill. For the prophylaxis or treatment of disease the compounds may be administered as pharmaceutical compositions, and according to a further aspect of the invention we provide a pharmaceutical composition which comprises a compound of formula (1) together with one or more pharmaceutically acceptable carriers, excipients or diluents. For the treatment or prevention of any of the diseases or conditions described herein, the compounds of formula I may be administered orally, topically, parenterally, by inhalation spray or rectally in formulations containing conventional non-toxic pharmaceutically acceptable carriers, adjuvants and vehicles. The term parenteral as used herein includes subcutaneous, intradermal, intravenous, intramuscular and intrastemal injection or infusion techniques. In addition to the treatment of warm-blooded animals such as mice, rats, horses, cattle sheep, dogs, cats, etc., the compounds of the invention are useful for the treatment of humans. Oral pharmaceutical compositions containing the active ingredient are typically in the form of tablets, troches, lozenges, aqueous or oily suspensions, dispersible powders or granules, emulsions, hard or soft capsules, syrups or elixirs. Compositions intended for oral use may be prepared according to any method known to the art for the manufacture of pharmaceutical compositions and such compositions may contain one or more agents selected from the group consisting of sweetening agents, flavoring agents, coloring agents and preserving agents in order to provide pharmaceutically elegant and palatable preparations. Tablets contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients which are suitable for the manufacture of tablets. These excipients may be for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, calcium phosphate or sodium phosphate; granulating and disintegrating agents, for example, corn starch, or alginic acid; binding agents, for example starch, gelatin or acacia, and lubricating agents, for example, magnesium stearate, stearic acid or talc. The tablets may be uncoated or they may be coated by known techniques to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monostearate or glyceryl distearate may be employed. They may also be coated by the technique described in the U.S. Patent 4,256,108; 4,166,452; and 4,265,874 to form osmotic therapeutic tablets for control release. In hard gelatin capsules, the active ingredient is typically mixed with an inert solid diluent, for example, calcium carbonate, calcium phosphate or kaolin. In soft gelatin capsules, the active ingredient is typically mixed with water or an oil medium, for example peanut oil, liquid paraffin or olive oil. Aqueous suspensions contain the active material in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients are suspending agents, for example sodium carboxymethyl-cellulose, methylcellulose, hydroxy-propylmethycellulose, sodium alginate, polyvinyl-pyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents may be a naturally-occurring phosphatide, for example lecithin, or condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate, or condensation products of ethylene oxide with long chain aliphatic alcohols, for example heptadecaethylene- oxycetanol, or condensation products of ethylene oxide with partial esters derived from fatty acids and a hexitol such as polyoxyethylene sorbitol monooleate, or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example polyethylene sorbitan monooleate. The aqueous suspensions may also contain one or more preservatives, for example ethyl, or n- propyl, p-hydroxybenzoate, one or more coloring agents, one or more flavoring agents, and one or more sweetening agents, such as sucrose, saccharin or aspartame. Oily suspensions may be formulated by suspending the active ingredient in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents such as those set forth above, and flavoring agents may be added to provide a palatable oral preparation. These compositions may be preserved by the addition of an anti-oxidant such as ascorbic acid. Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active ingredient in admixture with a dispersing or wetting agent, suspending agent and one or more preservatives. Suitable dispersing or wetting agents and suspending agents are exemplified by those already mentioned above. Additional excipients, for example sweetening, flavoring and coloring agents, may also be present. The pharmaceutical compositions of the invention may also be in the form of an oil-in-water emulsion. The oil phase may be a vegetable oil, for example olive oil or arachis oil, or a mineral oil, for example liquid paraffin or mixtures of these. Suitable emulsifying agents may be naturally-occurring phosphatides, for example soy bean, lecithin, and esters or partial esters derived from fatty acids and hexitol anhydrides, for example sorbitan monooleate, and condensation products of the said partial esters with ethylene oxide, for example polyoxyethylene sorbitan monooleate. The emulsions may also contain sweetening and flavouring agents. Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative and flavoring and coloring agents. The pharmaceutical compositions may be in the form of a sterile injectable aqueous or oleagenous suspension. This suspension may be formulated according to the known art using those suitable dispersing or wetting agents and suspending agents which have been mentioned above. The sterile injectable preparation may also be a sterile injectable solution or suspension in a non-toxic parenterally-acceptable diluent or solvent, for example as a solution in 1,3-butane diol. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution and isotonic sodium chloride solution. In addition, sterile, fixed oils may be employed as a solvent or suspending medium. For this purpose any bland fixed oil may be employed including synthetic mono- or diglycerides. In addition, fatty acids such as oleic acid find use in the preparation of injectables. Compounds of formula I may also be administered in the form of suppositories for rectal administration of the drug. These compositions can be prepared by mixing the drug with a suitable non-irritating excipient which is solid at ordinary temperatures but liquid at normal body temperature and will therefore melt to release the drug. Examples of such materials include cocoa butter and polyethylene glycols. For topical use, creams, ointments, jellies, solutions or suspensions, containing the compound of Formula I are employed. (For purposes of this application, topical application also includes mouth washes and gargles.) Dosage levels of the order of from about 0.01 mg to about 140 mg/kg of body weight per day are useful in the treatment of the above-indicated conditions, or alternatively about 0.5 mg to about 7 g per patient per day. For example, inflammation may be effectively treated by the administration of from about 0.01 to 50 mg of the compound per kilogram of body weight per day, or alternatively about 0.5 mg to about 3.5 g per patient per day. The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the host treated and the particular mode of administration. For example, a formulation intended for the oral administration to humans may contain from about 0.5 mg to about 5 g of active agent, compounded with an appropriate and convenient amount of carrier material which may vary from about 5 to about 95 percent of the total composition. Unit dosage forms will generally contain between from about 1 mg to about 500 mg of the active ingredient, typically 25 mg, 50 mg, 100 mg, 200 mg, 300 mg, 400 mg, 500 mg, 600 mg, 800 mg or 1000 mg. It is understood, however, that the specific dose level for any particular patient will depend upon a variety of factors including the age, body weight, general health, sex, diet, time of administration, route of administration, rate of excretion, drug combination and the severity of the particular disease undergoing therapy. The compounds of the invention can be synthesized using the general synthesis schemes provided below. It will be apparent to one skilled in the art that similar methodology could be used to prepare the enantiomers or the racemates of the illustrated compounds. The following abbreviations have the indicated meanings: SCHEME 1 The preparation of bromopyridine intermediate 1 is shown in Scheme 1. Monolithiation of 2,5-dibromopyridine followed by the addition 3,4- bis(difluoromethoxy)benzaldehyde as found in U. S. Pat. No. 5,710,170 gives the secondary alcohol which is subsequently oxidized to the corresponding ketone with an oxidizing agent such as Mnθ2- SCHEME 1 SCHEME 2 The preparation of bromopyridine intermediates 2 and 3 is shown in Scheme 2. The secondary alcohol II is converted to the corresponding chloride in using a chlorinating agent such as thionyl chloride in the presence of a base. This chloride is condensed with the α-anion of ethyl 4-pyridyl acetate, affording the ester IV which upon hydrolysis with a base such as lithium hydroxide, followed by acidification with an acid such as hydrochloric acid affords the decarboxylated intermediate 2. Oxidation of the pyridine to the pyridine-N-oxide 3 is done with an oxidizing agent such as MMPP. SCHEME 2 SCHEME 3 The general method for the preparation of substituted thiols is presented in Scheme 3. Alcohol VU is treated with Lawesson's Reagent to provide the appropriately substituted thiol VEL SCHEME 3 R a represents a substituent group attached to Arl, wherein Arl represents phenyl. Up to 3 R a groups may be present. The alkyl iodide provides the source for R3 and R4, which can be the same or different. SCHEME 4 Preparation of thiol XV is presented in Scheme 4. Sulfonamide XIH is accessed from sulfonyl chloride XII in the presence of tert-butylamine. Coupling of the bromide with 2-(trimethylsilyl)ethanethiol followed by the deprotection of the thioether XTV with a source of fluoride such as tetrabutylamonium fluoride, affords the thiol sulfonamide XV. SCHEME 4 XIV XV SCHEME 5 6-Thio-3-pyridyl derivatives of formula Ie and their sulfone analogs of formula If and Ig are prepared by the general method shown in Scheme 13. The bromopyridine intermediate 2 is coupled with a suitable thiol in the presence of a base such as potassium tert-butoxide. This intermediate Ie may be oxidized to the corresponding sulfone pyridine Ig with an oxidizing agent such as oxone or to the sulfone pyridine-N-oxide If with an oxidizing agent such as MMPP. SCHEME 5 SCHEME 6 6-Thio-3-pyridyl derivatives of formula Ih and their sulfone analogs of formula Ii are prepared by the general method shown in Scheme 6. The bromopyridine intermediate 3 was coupled with a suitable thiol in the presence of a base such as potassium tert-butoxide. This intermediate Ih is then oxidized to the corresponding sulfone pyridine-N-oxide li with an oxidizing agent such as MMPP. SCHEME 6 li SCHEME 7 Sulfonamine Ie2 is prepared by treatment of the corresponding tert- butylsulfonamide Ieχ with an acid such as trifluoroacetic acid. SCHEME 7 Representative compounds of the invention are shown below. α Unless specified, all the compounds are racemic mixture. ASSAYS DEMONSTRATING BIOLOGICAL ACTIVITY LPS and fMLP-Induced TNF-α and LTBj. Assavs in Human Whole Blood Whole blood provides a protein and cell-rich milieu appropriate for the study of biochemical efficacy of anti-inflammatory compounds such as PDE 4- selective inhibitors. Normal non-stimulated human blood does not contain detectable levels of TNF-α and LTB4. Upon stimulation with LPS, activated monocytes expresss and secrete TNF-a up to 8 hours and plasma levels remain stable for 24 hours. Published studies have shown that inhibition of TNF-α by increasing intracellular cAMP via PDE 4 inhibition and/or enhanced adenylyl cyclase activity occurs at the transcriptional level. LTB4 synthesis is also sensitive to levels of intracellular cAMP and can be completely inhibited by PDE 4-selective inhibitors. As there is little LTB4 produced during a 24 hour LPS stimulation of whole blood, an additional LPS stimulation followed by fMLP challenge of human whole blood is necessary for LTB4 synthesis by activated neutrophils. Thus, using the same blood sample it is possible to evaluate the potency of a compound on two surrogate markers of PDE 4 activity in the whole blood. Fresh blood was collected in heparinized tubes by venipuncture from healthy human volunteers (male and female). These subjects had no apparent inflammatory conditions and had not taken any NSAIDs for at least 4 days prior to blood collection. Five hundred μL aliquots of blood were pre-incubated with either 2μL of vehicle (DMSO) or 2μL test compound at varying concentrations for 15 minutes at 37 C. This was followed by the addition of either lOμL vehicle (PBS) as blanks or lOμL LPS (lμg/ml final concentration, Sigma Chem, #L-2630 from E. coli, serotype 0111:B4; diluted in 0.1% w/v BSA (in PBS)). After 24 hours of incubation at 37°C, another lOμL of PBS (blank) or lOμL of LPS (lμg/ml final concentration) was added to blood and incubated for 30 minutes at 37 C. The blood was then challenged with either lOμL of PBS (blank) or lOμL of fMLP (lμM final concentration, Sigma Chem #F-3506; diluted in 1% w/v BSA (in PBS)) for 15 minutes at 37 C. The blood samples were centrifuged at 1500xg for 10 minutes at 4 C to obtain plasma. A 50μL aliquot of plasma was mixed with 200μL methanol for protein precipitation and centrifuged as above. The supernatant was assayed for LTB4 using an enzyme immunoassay kit (Cayman Chemicals #520111) according to the manufacturer's procedure. TNF-α was assayed in diluted plasma (in PBS) using an ELISA kit (Cistron Biotechnology) according to manufacturer's procedure. Anti-allergic Activity in vivo Compounds of the invention have been tested for effects on an IgE- mediated allergic pulmonary inflammation induced by inhalation of antigen by sensitised guinea pigs. Guinea pigs were initially sensitised to ovalbumin under mild cyclophosphamide-induced immunosuppression, by intraperitoneal injection of antigen in combinations with aluminium hydroxide and pertussis vaccine. Booster doses of antigen were given two and four weeks later and at six weeks, animals were challenged with aerosolised ovalbumin whilst under cover of an intraperitoneally administered anti-histamine agent (mepyramine). After a further 48h, bronchial alveolar lavages (BAL) were performed and the numbers of eosinophils and other leukocytes in the BAL fluids were counted. The lungs were also removed for histological examination for inflammatory damage. Administration of compounds of the Examples (0.001-10mg/kg i.p. or p.o.), up to three times during the 48h following antigen challenge, lead to a significant reduction in the eosinophilia and the accumulation of other inflammatory leukocytes. There was also less inflammatory damage in the lungs of animals treated with compounds of the Examples. SPA based PDE activity assay protocol Compounds which inhibit the hydrolysis of cAMP to AMP by the type- IV cAMP-specific phosphodiesterases were screened in 96-well plate format as follows: In a 96 well-plate at 30°C was added the test compound (dissolved in 2 μl DMSO), 188 ml of substrate buffer containing [2,8- 3 H] adenosine ',5 '-cyclic phosphate (cAMP, 100 nM to 50 μM), 10 mM MgCl2, 1 mM EDTA, 50 mM Tris, pH 7.5. The reaction was initiated by the addition of 10 ml of human recombinant PDE- IV (the amount was controlled so that -10% product was formed in 10 min.). The reaction was stopped after 10 min. by the addition of 1 mg of PDE-SPA beads (Amersham). The product AMP generated was quantified on a Microbeta 96-well plate counter. The signal in the absence of enzyme was defined as the background. 100% activity was defined as the signal detected in the presence of enzyme and DMSO with the background subtracted. Percentage of inhibition was calculated accordingly. IC50 value was approximated with a non-linear regression fit using the standard 4-parameter/multiple binding sites equation from a ten point titration. IC50 values shown in Table 7 were determined with 100 nM cAMP using the purified GST fusion protein of the human recombinant phosphodiesterase IVa (met-248) produced from a baculovirus/Sf-9 expression system. The invention will now be illustrated by the following non-limiting examples in which, unless stated otherwise: (i) all operations were carried out at room or ambient temperature, that is, at a temperature in the range 18-25°C; evaporation of solvent was carried out using a rotary evaporator under reduced pressure (600-4000 pascals: 4.5-30 mm. Hg) with a bath temperature of up to 60°C; the course of reactions was followed by thin layer chromatography (TLC) and reaction times are given for illustration only; melting points are uncorrected and 'd' indicates decomposition; the melting points given are those obtained for the materials prepared as described; polymorphism may result in isolation of materials with different melting points in some preparations; the structure and purity of all final products were assured by at least one of the following techniques: TLC, mass spectrometry, nuclear magnetic resonance (NMR) spectrometry or microanalytical data; yields are given for illustration only; when given, NMR data is in the form of delta (δ) values for major diagnostic protons, given in parts per million (ppm) relative to tetramethylsilane (TMS) as internal standard, determined at 300 MHz, 400 MHz or 500 MHz using the indicated solvent; conventional abbreviations used for signal shape are: s. singlet; d. doublet; t. triplet; m. multiplet; br. broad; etc.: in addition "Ar" signifies an aromatic signal; chemical symbols have their usual meanings; the following abbreviations have also been used v (volume), w (weight), b.p. (boiling point), m.p. (melting point), L (liter(s)), mL (milliliters), g (gram(s)), mg (milligrams(s)), mol (moles), mmol (millimoles), eq (equivalent(s)). INTERMEDIATE 1 [3,4-BIS(DIFLUOROMETHOXY)PHENYL]-(6-BROMO-3- PYRIDYL)METHANONE 1 Step 1 r3,4-Bis(difluoromethoxy)phenyll-(6-bromo-3-pyridyl)methanol To a -78 °C suspension of 2,5-dibromopyridine (11.4 g, 48.0 mmol) in 300 mL of Et2θ, was added 40.0 mL (48.0 mmol) of a 1.2 N solution of n- butyllithium in hexane over 10 minutes. The orange mixture was stirred (Mechanical stirrer) 10 minutes at -78 °C followed by the addition over 5 minutes of a precooled solution of bis(difluoromethoxy)benzaldehyde (9.6 g, 40.0 mmol) in 60 mL of Et2θ. This red solution was stirred 1 h at -78 °C and slowly poured into a saturated aqueous solution of NH4CI. The aqueous layer was extracted with ethyl acetate and the combined organic phases were washed with brine, dry over MgSO4 and concentrated under reduced pressure. The residue was purified by chromatography on silica gel (Gradient 20% to 40% ethyl acetate/hexane) to afford 8.3 g (53%) of alcohol. Step 2 r3.4-Bis(difluoromethoxy)phenyll-(6-bromo-3-pyridyl)methanone To a solution of alcohol (3.96 g, 10.0 mmol) from Step 1 above in 60 mL of CH2CI2, was added 8.1 g (93.0 mmol) of Mnθ2- The resulting mixture was stirred 20 h at room temperature and filtered on celite. the volatile were removed under reduced pressure to afford 3.48 g (88%) of ketone. IH NMR (500 MHz, Acetone-d6) δ 8.72 (d, IH), 8.10 (dd, IH), 7.85- 7.78 (m, 3H), 7.55 (d, IH), 7.20 (t, IH), 7.12 (t, IH). INTERMEDIATE 2 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-(6-BROMO-3- PYRIDYL)ETHYL}PYRIDINE Step 1 r3.4-Bis(difluoromethoxy)phenvn-(6-bromo-3-pyridyl)chloromethane To a solution [3,4-Bis(difluoromethoxy)phenyl]-(6-bromo-3- pyridyl)methanol (15.8 g,40.0 mmol) in 400 mL of CH2CI2, was added 3.8 mL (52.0 mmol) of SOCI2. The solution was stirred 45 minutes at room temperature and poured into a saturated aqueous solution of NaHCO3. The aqueous layer was extracted with CH2CI2 and the combined organic layers were dry over MgSO4 and concentrated under reduced pressure. The crude chloride was used directly for the next step without any purification. Step 2 4-{ l-Carbethoxy-2-[3,4-bis(difluoromethoxy)phenyl]-2-(6-bromo-3- pyridvPethyl ) pyridine To a 0 °C solution of ethyl 4-pyridyl acetate (19.8 g, 120 mmol) in 500 mL of THF, was added 21.0 mL ( 120 mmol) of HMPA and 240 mL ( 120 mmol) of a 0.5 M solution KHMDS in toluene. The resulting mixture was stirred 15 minutes at room temperature followed by the addition over 10 minutes of a solution of the crude chloride from Step 1 above in 100 mL of THF. The reaction was stirred 1 h at room temperature, poured into a saturated aqueous solution of NH4CI and the pH was adjusted to 7 with 1 N HCl. The aqueous layer was extracted with ethyl acetate and the combined organic phases were washed with brine, dry over MgSO4 and concentrated under reduced pressure. The residue was used directly for the next step without any purification. Step 3 4-(2-r3.4-Bis(difluoromethoxy)phenyll-2-(6-bromo-3-pyridyl)ethyllpyridine To a solution of crude ester from Step 2 above in a mixture of 540 mL of THF, 180 mL of MeOH and 180 mL of water, was added 180 mL of a 2 N solution of LiOH. The solution was stirred 1.5 h at 65 °C, cooled down to room temperature and 360 mL of 1 N HCl solution were added. The mixture was rotovaped down, the residue was diluted in ethyl acetate and the organic phases was washed with brine, dry over MgSO4 and concentrated under reduced pressure to afford 18.2 g (97%, 3 steps) of pure bromopyridine. IH NMR (500 MHz, Acetone-dό) δ 8.40 (m, 3H), 7.78 (dd, IH), 7.50 (d, IH), 7.43 (s, IH), 7.36 (dd, IH), 7.28 (d, IH), 7.20 (m, 2H), 6.95 (t, IH), 6.94 (t, IH), 4.65 (t, IH), 3.58-3.48 (m, 2H). INTERMEDIATE 3 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-(6-BROMO-3- PYRIDYL)ETHYL}PYRIDINE To a solution of intermediate 2 (2.0 g, 4.2 mmol) in a mixture of 30 mL of CH2CI2 and 3 mL of MeOH was added 1.55 g (2.5 mmol) of 80% MMPP. The reaction was stirred at room temperature for 20 h and purified directly by chromatography on silica gel (Gradient 3% Et3N/ethyl acetate to 30% EtOH/ethyl acetate + 3% Et3N to 40% EtOH/ethyl acetate + 3% Et3N) to afford 1.91 g (93%) of desired pyridine-N-oxide. IH NMR (500 MHz, Acetone-d6) δ 8.38 (d, IH), 7.95 (d, 2H), 7.77 (dd, IH), 7.51 (d, IH), 7.41 (s, IH), 7.35 (dd, IH), 7.29 (d, IH), 7.19 (d, 2H), 6.96 (t, IH), 6.94 (t, IH), 4.60 (t, IH), 3.57-3.47 (m, 2H). EXAMPLE 1 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-{6-[3- (AMINOSULFONYL)BENZENETHIOL]3-PYRIDYL}ETHYL}PYRIDINE Step 1 3-(tert-butylaminosulfonyl) phenylbromide To a 0 °C solution of 3-bromobenzenesulfonyl chloride (3.6 g, 11.7 mmol) in 10 mL of THF, was added 2.7 mL (25.8 mmol) of t-butylamine. The solution was stirred at room temperature for 1 h and diluted with ethyl acetate. The organic layer was washed with 1 N HCl, water and with brine, dried over MgSO4 and concentrated under reduced pressure. The bromide (3.86 g, 93%) was obtained as a white solid. Step 2 3-(rert-butylaminosulfonyl)benzenethiol To a solution of bromide (3.19 g, 10.9 mmol) from Step 1 above in 80 mL of n-BuOH, was added 505 mg (0.437 mmol) of Pd(PPh3)4, 3.45 mL (21.8 mmol) of 2-(trimethylsilyl) ethanethiol and 4.9 g (43.7 mmol) of t-BuOK. The mixture was refluxed for 18 h, cooled down to room temperature and Poured into 800 mL of water. The mixture was neutralized with acetic acid and extracted with ethyl acetate. The organic layer was washed with an NE jOAc solution, with water and with brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (Gradient 10% to 15% ethyl acetate/hexane) to afford 3.35 g (89%) of the protected thiol. This silyl derivative was then dissolved in 70 mL of DMF followed by the addition of 19.3 mL of a 1.0 M solution of TB AF. The solution was stirred at room temperature for 20 h, quenched with water and acidified to pH 3 with 1 N HCl. The aqueous layer was extracted with ethyl acetate and the combined organic phases were washed with brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (30% ethyl acetate/hexane + 0.5% AcOH) to afford 2.17 g (92%) of benzenethiol. Step 3 4- { 2-[3 ,4-Bis(difluoromethoxy)phenyl]-2- { 6-[3-(tert- butylaminosulfonyl)benzenethiol13-pyridyl lethyl Ipyridine To a solution of intermediate 2 (220 mg, 0.47 mmol), 3-(fert- butylaminosulfonyl)benzenethiol (229 mg, 0.93 mmol) and Pd(PPh3)4 (27 mg, 0.023 mmol) in 4 mL of n-BuOH, was added 1.9 mL (1.88 mmol) of a 1.0 M solution ofr- BuOK in THF. The solution was stirred for 15 h at reflux and quenched at room temperature with water. The mixture was acidified to pH 5 with acetic acid and diluted with ethyl acetate. Layers were separated and the organic phase was washed with 25% NH4OAC and with brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (Gradient 40% ethyl acetate/hexane to 100% ethyl acetate) to afford the title compound (215 mg, 73%). Step 4 4-(2-r3,4-Bis(difluoromethoxv)phenvll-2-(6-r3-(aminosulfonyl)benzenethioll3- pyridyl I ethyl) pyridine To a solution t-butyl amine (215 mg, 0.338 mmol) in 3 mL of CH2CI2, was added 1 mL of TFA. The solution was stirred at room temperature for 3 days and evaporated to dryness under reduced pressure. The residue was diluted with ethyl acetate and a 25% solution of NH4OAC, the layers were separated and the organic phase was washed with brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (Gradient 40% ethyl acetate/hexane to 100% ethyl acetate to 5% EtOH/ethyl acetate) to afford the title compound (92 mg, 47%). IH NMR (500 MHz, Acetone-d6) δ 8.8.38-8.33 (m, 3H), 8.02 (t, IH), 7.94-7.89 (m, IH), 7.76-7.58 (m, 3H), 7.40 (s, IH), 7.33 (dd, IH), 7.26 (d, IH), 7.19- 7.14 (m, 2H), 7.06 (d, IH), 6.93 (t, IH), 6.92 (t, IH), 4.58 (t, IH), 3.49 (d, 2H). EXAMPLE 2 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(3- METHOXYBENZENETHIOL)3-PYRIDYL]ETHYL}PYRIDINE Following the procedure described in Example 1, Step 3 but substituting 3-methoxybenzenethiol for 3-(te/?-butylaminosulfonyl) benzenethiol, the title compound was obtained as an oil (57 mg, 43%). EXAMPLE 3 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(3- METHOXYBENZENESULFONYL)3-PYRIDYL]ETHYL}PYRIDINE To a solution of 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(3- methoxybenzenethiol)3-pyridyl]ethyl}pyridine from Example 2 above (43 mg, 0.08 mmol) in 1 mL of MeOH, was added a solution of oxone (60 mg, 0.09 mmol) in 0.3 mL of water. The heterogeneous mixture was stirred 2 days at room temperature. Volatile were removed under reduced pressure and the residue was diluted with ethyl acetate. The organic layer was washed with brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (5% EtOH/ethyl acetate) to afford the title compound (38 mg, 83%). *H NMR (500 MHz, Acetone-d6) δ 8.67 (s, 1 H), 8.35 (d, 2 H), 8.2- 8.1 (m, 2 H), 7.75-7.65 (m, 4 H), 7.63-7.49 (m, 9 H), 7.45 (s, 1 H), 7.35 (d, 1 H), 7.28-7.20 (m, 2 H), 7.18 (d, 2 H), 6.90 (t, large J, 1 H), 6.92 (t, large J, 1 H), 4.77 (t, 1 H), 3.85 (s, 3 H), 3.55 (dd, 2 H). EXAMPLE 4 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(4- NTTROBENZENESULFONYL)3-PYRIDYL]ETHYL)PYRIDINE-N-OXIDE Step l 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-nitrobenzenethiol)3- pyridyllethyl } pyridine To a suspension of 4-nitrobenzenethiol (388 mg, 2.0 mmol) in 5 mL of DMF was added a 2.0 mL of a 1.0 M solution of tBuOK in THF followed by a solution of intermediate 2 (235 mg, 0.5 mmol) in 2 mL of DMF. The solution was stirred 2 days at 160 °C, cooled down to room temperature and quenched with water. The resulting mixture was diluted with ethyl acetate, the organic layer was washed with brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (Gradient 70% ethyl acetate/hexane to 100% ethyl acetate) to afford the title compound (157 mg, 58%). Step 2 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-nitrobenzenesulfonyl)3- pyridyllethyl )pyridine-N-oxide To a solution of 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4- nitrobenzenethiol)3-pyridyl]ethyl}pyridine (44 mg, 0.081 mmol) in a mixture of CH2CI2 (2 mL) and methanol (0.2 mL), was added 110 mg (0.17 mmol) of 80% MMPP. Resulting mixture was stirred at room temperature for 15 h. The reaction mixture was directly purified by flash chromatography (Gradient 100% ethyl acetate + 3% Et3N to 30% EtOH/ethyl acetate + 3% Et3N) to afford the title compound (48 mg, 100%). EXAMPLE 5 4- { 2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(4- NTTROBENZENETHIOL)3-PYRID YL]ETHYL } PYRIDINE-N-OXIDE Following the procedure described in Example 4, Step 1 but substituting intermediate 3 for intermediate 2, the title compound was obtained as a foam (51 mg, 43%). lH NMR (500 MHz, Acetone-d6) δ 8.49 (d, IH), 8.22 (d, 2H), 7.96 (d, 2H), 7.82 (dd, IH), 7.67 (d, 2H), 7.44 (s, IH), 7.38-7.33 (m, 2H), 7.27 (d, IH), 7.20 (d, 2H), 6.96 (t, IH), 6.94 (t, IH), 4.60 (t, IH), 3.58-3.47 (m, 2H). EXAMPLE 6 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(4- FLUOROPHENYLMETHANETfflOL)3-PYRIDYL]ETHYL}PYRIDINE-N-OXIDE The intermediate 3 (361 mg, 0.74 mmol) was mixed with 3.0 mL of a 1.0 M solution of 4-fluorophenylmethanethiol in DMF and 3.0 mL of a 1.0 M solution oft-BuOK in THF. The solution was stirred at 135°C and monitored by TLC. The reaction was cooled down to room temperature, quenched with water and diluted with ethyl acetate. Layers were separated and the organic phase was washed with brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (20% EtOH/ethyl acetate) to afford the title compound (251 mg , 62%). IH NMR (500 MHz, Acetone-d6) δ 8.39 (s, IH), 7.90 (d, 2H), 7.60 (dd, IH), 7.41-7.34 (m, 3H), 7.32-7.19 (m, 2H), 7.18-7.10 (m, 3H), 7.03-6.95 (m, 2H), 6.91 (t, IH), 6.89 (t, IH), 4.49 (t, IH), 4.35 (s, 2H), 3.50-3.40 (m, 2H). EXAMPLE 7 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(4- FLUOROBENZENETHIOL)3-PYRID YLJETHYL } PYRIDINE-N-OXIDE Following the procedure described in Example 6 but substituting 4- fluorobenzenethiol for 4-fluorophenylmethanethiol, the title compound was obtained as a white foam (181 mg, 84%). IH NMR (500 MHz, Acetone-d6) δ 8.38 (s, IH), 7.94 (d, 2H), 7.68- 7.59 (m, 3H), 7.40 (s, IH), 7.32 (d, IH), 7.29-7.22 (m, 3H), 7.19 (d, 2H), 6.96 (t, IH), 6.94 (t, IH), 6.89 (d, IH), 4.53 (t, IH), 3.46 (d, 2H). EXAMPLE 8 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(4- FLUOROBENZENESULFONYL)3-PYRIDYL]ETHYL } PYRIDINE-N-OXIDE To a solution of 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4- fluorobenzenethiol)3-pyridyl]ethyl} pyridine-N-oxide from Example 7 above (266 mg, 0.51 mmol) in a mixture of CH2CI2 (9 mL) and methanol (1 mL), was added 507 mg (1.02 mmol) of MMPP. The resulting mixture was stirred at room temperature for 2 h. The reaction was quenched with a 25% NH4OAC solution and diluted with ethyl acetate. Layers were separated and the organic phase was washed with water and brine, dried over MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (10% MeOH/CH2Cl2) to afford the title compound (258 mg , 91%). IH NMR (500 MHz, Acetone-d6) δ 8.67 (d, IH), 8.27-8.04 (m, 4H), 7.92 (d, 2H), 7.46-7.31 (m, 4H), 7.27 (d, IH), 7.18 (d, 2H), 6.94 (t, IH), 6.92 (t, IH), 4.73 (t, IH), 3.60-3.50 (m, 2H). EXAMPLE 9 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-[6-(4- FLUOROPHENYLMETHANESULFONYL)3-PYRIDYL]ETHYL}PYRIDINE-N- OXIDE The procedure for the oxidation of the sulfide described in Example 8 was applied using the product of Example 6 above as starting material. The title compound was obtained as a white solid (98 mg, 90%). IH NMR (500 MHz, Acetone-d6) δ 8.83 (s, IH), 8.06 (d, IH), 7.97 (d, 2H), 7.72 (d, IH), 7.47 (s, IH), 7.39 (d, IH), 7.32 (d, 1H),7.26-7.17 (m, 4H), 7.03 (t, 2H), 6.97 (t, IH), 6.96 (t, IH), 4.80 (t, IH), 4.67 (s, 2H), 3.60 (d, 2H). EXAMPLE 10 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-{6-[l-METHYL-l-(4- FLUOROPHENYL)ETHANETHIOL]3-PYRIDYL}ETHYL}PYRIDINE-N-OXIDE Step 1 1 -methyl- l-(4-fluorophenyl)ethanethiol To a solution of 1 -methyl- 1 -(4-fluorophenyl )ethanol (689 mg, 4.5 mmol) in 50 mL of toluene was added 1.81 g (4.5 mmol) of Lawesson's reagent. The reaction was stirred at refluxing temperature for 2 h and overnight at room temperature. The mixture was purified by flash chromatography on silica gel (100% hexane) to afford 214 mg (28%) of desired thiol. Step 2 4- { 2- [3 ,4-Bis(difluoromethoxy)phenyl ]-2- { 6- [ 1 -methyl- 1 -(4- fluorophenyl)ethanethioπ3-pyridyl } ethyl } pyridine-N-oxide Following the procedure described in Example 6 but substituting 1- methyl-1 -(4-fluorophenyl )ethanethiol for 4-fluorophenylmethanethiol, the title compound was obtained as a yellow solid (130 mg, 24%). IH NMR (500 MHz, Acetone-d6) d 8.86 (s, IH), 7.95 (d, 2H), 7.61- 7.52 (m, 3H), 7.37 (s, IH), 7.28 (dd, 2H), 7.15 (d, 2H), 7.04-6.97 (m, 3H), 6.96 (t, IH), 6.94 (t, IH), 4.47 (t, IH), 3.37-3.49 (m, 2H), 1.85 (s, 6H). EXAMPLE 11 4-{2-[3,4-BIS(DIFLUOROMETHOXY)PHENYL]-2-{6-[l-METHYL-l-(4- FLUOROPHENYL)ETHANESULFONYL]3-PYRIDYL}ETHYL}PYRIDINE-N- OXIDE The procedure for the oxidation of the sulfide described in Example 8 was applied using the product of Example 10 above as starting material. The title compound was obtained as a white solid (98 mg, 90%). IH NMR (500 MHz, Acetone-d6) δ 8.70 (s, IH), 7.98 (d, 2H), 7.90 (d, IH), 7.41 (d, 2H), 7.38 (d, IH), 7.38-7.30 (m, 4H), 7.20 (d, 2H), 6.97 (d, 2H), 6.95 (t, IH), 6.93 (t, IH), 4.73 (t, IH), 3.55 (d, 2H), 1.82 (s, 6H).

Claims: WHAT IS CLAIMED IS: 1. A compound represented by formula I: or a pharmaceutically acceptable salt or hydrate thereof wherein: Y represents N or N-oxide; y represents 0, 1 or 2; Ri and R are independently selected from: H, Cι_6alkyl and haloCi-6 alkyl, R3 and R4 are independently selected from H and Cι_6alkyl, or R and R4 attached to the same carbon atom taken together represent a carbon yl oxygen atom, or R and R attached to different carbon atoms considered in combination with the carbon atoms to which they are attached along with any intervening atoms and represent a saturated 5, 6 or 7 membered carbocyclic ring, R5 and R6 independently represent a member selected from the group consisting of: H, Ci-6alkyl, haloCi-όalkyl and CN; n represents an integer of from 0-6; Arl i s selected from the group consisting of: (a) thienyl, (b) thiazolyl, (c) pyridyl, (d) phenyl and (e) naphthyl, said Arl being optionally substituted with 1-3 members selected from the group consisting of: (1) halo, (2) Cι_6alkoxy, (3) C 1-7 alkylthio, (4) CN, (5) Ci-βalkyl, (6) C i -όhydroxyalkyl , (7) -C(O)Cι_6 alkyl, -CO2H, -CO2Ci-6alkyl, (8) NH(SO2Me), N(SO2Me)2, (9) SO2Me, SO2NH2, SO2NHC1.6 alkyl, SO 2 N(C 1 . 6 alkyl) 2 (10) NO2, (11) Cι_6alkenyl, (12) halo C 1-6 alkyl, and (13) NH2 , and when Arl represents a phenyl or naphthyl group with two or three substituents, two such substituents may be considered in combination and represent a 5 or 6 membered fused lactone ring. 2. A compound in accordance with claim 1 wherein R and R2 are Ci-6 alkyl or haloCi-6alkyl. 3. A compound in accordance with claim 2 wherein R and R2 are selected from the group consisting of CH3, CH2F, CHF2 and CF3. 4. A compound in accordance with claim 3 wherein Rl and R2 are CHF2- 5. A compound in accordance with claim 1 wherein n is selected from 0, 1, 2 and 3. 6. A compound in accordance with claim 5 wherein n is selected from 0, 1 and 2. 7. A compound in accordance with claim 1 wherein R5 and R6 are independently selected from the group consisting of: H and C\. alkyl. 8. A compound in accordance with claim 7 wherein R5 and R6 represent H. 9. A compound in accordance with claim 1 wherein Arl j s selected from phenyl and naphthyl. 10. A compound in accordance with claim 9 wherein Arl j s phenyl. 11. A compound in accordance with claim 1 wherein R3 and R4 are H or Ci-όalkyl. 12. A compound in accordance with claim 11 wherein R3 and R4 are H or methyl. 13. A compound in accordance with claim 1 wherein: Rl and R2 are Ci-6alkyl or haloCi-6alkyl selected from the group consisting of CH3, CH2F, CHF2 and CF3 ; n is O, 1, 2 or 3; Arl i s phenyl or naphthyl, R3 and R4 are H or methyl and R5 and R6 are H or Cι_6alkyl. 14. A compound in accordance with claim 13 wherein: R 1 and R 2 are CHF2, and n is O, l or 2. 15. A compound in accordance with claim 14 wherein: Rl and R2 are CHF2; n is 0, 1 or 2; R and R4 are H or methyl and Arl is phenyl. 16. A compound selected from the group consisting of: 4-{2-[3,4-Bis(difIuoromethoxy)phenyl]-2-{6-[3- (aminosulfonyl)benzenethiol]3-pyridyl } ethyl } pyridine, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(3-methoxybenzenethiol)3- pyridyljethyl }pyridine, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(3-methoxybenzenesulfonyl)3- pyridyl]ethyl } pyridine, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-nitrobenzenesulfonyl)3- pyridyl]ethyl} pyridine-N-oxide, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-nitrobenzenethiol)3- pyridyl]ethyl } pyridine-N-oxide, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-fluorophenylmethanethiol)3- pyridyl]ethyl } pyridine-N-oxide, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-fluorobenzenethiol)3- pyridyl]ethyl } pyridine-N-oxide, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4-fluorobenzenesulfonyl)3- pyridyljethyl } pyridine-N-oxide, 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-[6-(4- fluorophenylmethanesulfonyl)3-pyridyl]ethyl } pyridine-N-oxide, 4- { 2- [3 ,4-Bis(difluoromethoxy)phenyl]-2- { 6-[ 1 -methyl- 1 -(4- fluorophenyl)ethanethiol]3-pyridyl } ethyl } pyridine-N-oxide, and 4-{2-[3,4-Bis(difluoromethoxy)phenyl]-2-{6-[l-methyl-l-(4- fluorophenyl)ethanesulfonyl]3-pyridyl}ethyl}pyridine-N-oxide or a pharmaceutically acceptable salt or hydrate thereof. 17. A compound in accordance with claim 1 selected from one of the following tables: 18. A pharmaceutical composition that is comprised of a compound in accordance with claim 1 in combination with a pharmaceutically acceptable carrier 19. A method of treating or preventing a disease or condition mediated by PDE 4, comprising administering to a mammalian patient in need thereof, a compound in accordance with claim 1 in an amount that is effective to treat or prevent said disease or condition. 20. A method in accordance with claim 19 wherein the disease or condition is selected from the group consisting of: asthma, inflammed lung associated with asthma, cystic fibrosis, inflammatory airway disease, chronic bronchitis, eosinophilic granuloma, psoriasis, other benign and malignant proliferative skin diseases, endotoxic shock, septic shock, ulcerative colitis, Crohn's disease, reperfusion injury of the myocardium or brain, inflammatory arthritis, chronic glomerulonephritis, atopic dermatitis, urticaria, adult respiratory distress syndrome, diabetes insipidus, allergic rhinitis, allergic conjunctivitis, vernal conjunctivitis, arterial restenosis, atherosclerosis, neurogenic inflammation, pain, cough, rheumatoid arthritis, ankylosing spondylitis, transplant rejection and graft versus host disease, hypersecretion of gastric acid, bacterial, fungal or viral induced sepsis or septic shock, inflammation and cytokine-mediated chronic tissue degeneration, osteoarthritis, cancer, cachexia, muscle wasting, depression, memory impairment, tumour growth and cancerous invasion of normal tissues. 21. A method of treating or preventing asthma or an asthma attack in a mammalian patient in need of such treatment or prevention, comprising administering to said patient a compound in accordance with claim 1 in an amount that is effective for treating or preventing asthma or an asthma attack. 22. A pharmaceutically acceptable salt or hydrate of a compound of Formula I, as defined in any one of claims 1 to 17. 23. A phosphodiesterase IV inhibitor pharmaceutical composition comprising an acceptable phosphodiesterase IV inhibiting amount of a compound of Formula I, as defined in any one of claims 1 to 17, or a pharmaceutically acceptable salt or hydrate thereof, in association with a pharmaceutically acceptable carrier. 24. A compound of formula I, as defined in any one of claims 1 to 17, or a pharmaceutically acceptable salt or hydrate thereof, for use in treatment or prevention of a disease or condition mediated by PDE 4. 25. Use of a compound of formula I, as defined in any one of claims 1 to 17, or a pharmaceutically acceptable salt or hydrate thereof, in the manufacture of a medicament for the treatment or prevention of asthma or an asthma attack.

Inventors: DUCHARME YVES, FRENETTE RICHARD, PRESCOTT SYLVIE, DUCHARME, YVES, FRENETTE, RICHARD, PRESCOTT, SYLVIE
Applicants: DUCHARME YVES, FRENETTE RICHARD, MERCK FROSST CANADA INC, PRESCOTT SYLVIE, DUCHARME, YVES, FRENETTE, RICHARD, MERCK FROSST CANADA & CO., PRESCOTT, SYLVIE
Application year: 2000
Main classification: C07D213
IPC codes: A61K31, A61P1, A61P5, A61P7, A61P9, A61P11, A61P13, A61P17, A61P19, A61P21, A61P25, A61P27, A61P29, A61P31, A61P35, A61P37, A61P43, C07D213, C07D405, C07D409, C07D417