FIELD OF INVENTION The present invention relates to a series of compounds that are potent and selective inhibi- tors of cyclic adenosine 3', 5'-monophosphate spe- cific phosphodiesterase (cAMP specific PDE). In particular, the present invention relates to a se- ries of novel compounds that are useful for inhibit- ing the function of, cAMP specific PDE, in particu- lar, PDE4, as well as methods of making the same, pharmaceutical compositions containing the same, and their use as therapeutic agents, for example, in treating inflammatory diseases and other diseases involving elevated levels of cytokines and proin- flammatory mediators.

BACKGROUND OF THE INVENTION Chronic inflammation is a multi-factorial disease complication characterized by activation of multiple types of inflammatory cells, particularly cells of lymphoid lineage (including T lymphocytes) and myeloid lineage (including granulocytes, macro- phages, and monocytes). Proinflammatory mediators, including cytokines, such as tumor necrosis factor

(TNF) and interleukin-1 (IL-1), are produced by these activated cells. Accordingly, an agent that suppresses the activation of these cells, or their production of proinflammatory cytokines, would be useful in the therapeutic treatment of inflammatory diseases and other diseases involving elevated lev- els of cytokines.

Cyclic adenosine monophosphate (cAMP) is a second messenger that mediates the biologic re- sponses of cells to a wide range of extracellular stimuli. When the appropriate agonist binds to specific cell surface receptors, adenylate cyclase is activated to convert adenosine triphosphate (ATP) to cAMP. It is theorized that the agonist induced actions of cAMP within the cell are mediated predom- inately by the action of cAMP-dependent protein kinases. The intracellular actions of cAMP are terminated by either a transport of the nucleotide to the outside of the cell, or by enzymatic cleavage by cyclic nucleotide phosphodiesterases (PDEs), which hydrolyze the 3'-phosphodiester bond to form 5'-adenosine monophosphat. (5'-AMP). 5'-AMP is an inactive metabolite. The structures of cAMP and 5'- AMP are illustrated below.

cAMP 5'-AMP Elevated levels of cAMP in human myeloid and lymphoid lineage cells are associated with the suppression of cell activation. The intracellular enzyme family of PDEs, therefore, regulates the level of cAMP in cells. PDE4 is a predominant PDE isotype in these cells, and is a major contributor to cAMP degradation. Accordingly, the inhibition of

PDE function would prevent the conversion of cAMP to the inactive metabolite 5'-AMP and, consequently, maintain higher cAMP levels, and, accordingly, sup- press cell activation (see Beavo et al.,"Cyclic Nucleotide Phosphodiesterases : Structure, Regula- tion and Drug Action,"Wiley and Sons, Chichester, pp. 3-14, (1990)) ; Torphy et al., Drug News and Perspectives,-6, pp. 203-214 (1993) ; Giembycz et al., Clin. Exp. Allergy, 22, pp. 337-344 (1992)).

In particular, PDE4 inhibitors, such as rolipram, have been shown to inhibit production of TNFa and partially inhibit IL-1, (3 release by mono- cytes (see Semmler et al., Int. J. Immunopharmacol., 15, pp. 409-413 (1993) ; Molnar-Kimber et al., Media- tors of Inflammation, 1, pp. 411-417 (1992)). PDE4 inhibitors also have been shown to inhibit the pro- duction of superoxide radicals from human poly- morphonuclear leukocytes (see Verghese et al., J.

Mol. Cell. Cardio., 21 (Suppl. 2), S61 (1989) ; Nielson et al., J. Allergy Immunol., 86, pp. 801-808 (1990)) ; to inhibit the release of vasoactive amines and prostanoids from human basophils (see Peachell et al., J. Immunol., 148, pp. 2503-2510 (1992)) ; to inhibit respiratory bursts in eosinophils (see Dent et al., J. Pharmacol., 103, pp. 1339-1346 (1991)) ; and to inhibit the activation of human T-lymphocytes (see Robicsek et al., Biochem. Pharmacol., 42, pp.

869-877 (1991)).

Inflammatory cell activation and excessive or unregulated cytokine (e. g., TNFa and IL-1/3) pro- duction are implicated in allergic, autoimmune, and inflammatory diseases and disorders, such as rheuma-

toid arthritis, osteoarthritis, gouty arthritis, spondylitis, thyroid associated ophthalmopathy, Behcet's disease, sepsis, septic shock, endotoxic shock, gram negative sepsis, gram positive sepsis, toxic shock syndrome, asthma, chronic bronchitis, adult respiratory distress syndrome, chronic pulmo- nary inflammatory disease, such as chronic obstruc- tive pulmonary disease, silicosis, pulmonary sarco- idosis, reperfusion injury of the myocardium, brain, and extremities, fibrosis, cystic fibrosis, keloid formation, scar formation, atherosclerosis, trans- plant rejection disorders, such as graft vs. host reaction and allograft rejection, chronic glomerulo- nephritis, lupus, inflammatory bowel disease, such as Crohn's disease and ulcerative colitis, prolif- erative lymphocyte diseases, such as leukemia, and inflammatory dermatoses, such as atopic dermatitis, psoriasis, and urticaria.

Other conditions characterized by elevated cytokine levels include brain injury due to moderate trauma (see Dhillon et al., J. Neurotrauma, 12, pp.

1035-1043 (1995) ; Suttorp, et al., J. Clin. Invest., 91, pp. 1421-1428 (1993)), cardiomyopathies, such as congestive heart failure (see Bristow et al., Circu- lation, 97, pp. 1340-1341 (1998)), cachexia, cachex- ia secondary to infection or malignancy, cachexia secondary to acquired immune deficiency syndrome (AIDS), ARC (AIDS related complex), fever myalgias due to infection, cerebral malaria, osteoporosis and bone resorption diseases, keloid formation, scar tissue formation, and pyrexia.

In particular, TNFa has been identified as having a role with respect to human acquired immune

deficiency syndrome (AIDS). AIDS results from the infection of T-lymphocytes with Human Immunodefi- ciency Virus (HIV). Although HIV also infects and is maintained in myeloid lineage cells, TNF has been shown to upregulate HIV infection in T-lymphocytic and monocytic cells (see Poli et al., Proc. Natl.

Acad. Sci. USA, 87, pp. 782-785 (1990)).

Several properties of TNFa, such as stimu- lation of collagenases, stimulation of angiogenesis in vivo, stimulation of bone resorption, and an ability to increase the adherence of tumor cells to endothelium, are consistent with a role for TNF in the development and metastatic spread of cancer in the host. TNFa recently has been directly impli- cated in the promotion of growth and metastasis of tumor cells (see Orosz et al., J. Exp. Med., 177, pp. 1391-1398 (1993)).

PDE4 has a wide tissue distribution.

There are at least four genes for PDE4 of which multiple transcripts from any given gene can yield several different proteins that share identical catalytic sites. The amino acid identity between the four possible catalytic sites is greater than 85%. Their shared sensitivity to inhibitors and their kinetic similarity reflect the functional aspect of this level of amino acid identity. It is theorized that the role of these alternatively expressed PDE4 proteins allows a mechanism by which a cell can differentially localize these enzymes intracellularly and/or regulate the catalytic effi- ciency via post translational modification. Any given cell type that expresses the PDE4 enzyme typi-

cally expresses more than one of the four possible genes encoding these proteins.

Investigators have shown considerable interest in the use of PDE4 inhibitors as anti-in- flammatory agents. Early evidence indicates that PDE4 inhibition has beneficial effects on a variety of inflammatory cells such as monocytes, macro- phages, T-cells of the Th-1 lineage, and granulo- cytes. The synthesis and/or release of : many proinflammatory mediators, such as cytokines, lipid mediators, superoxide, and biogenic amines, such as histamine, have been attenuated in these cells by the action of PDE4 inhibitors. The PDE4 inhibitors also affect other cellular functions including T- cell proliferation, granulocyte transmigration in response to chemotoxic substances, and integrity of endothelial cell junctions within the vasculature.

The design, synthesis, and screening of various PDE4 inhibitors have been reported. Methyl- xanthines, such as caffeine and theophylline, were the first PDE inhibitors discovered, but these com- pounds are nonselective with respect to which PDE is inhibited. The drug rolipram, an antidepressant agent, was one of the first reported specific PDE4 inhibitors. Rolipram, having the following struc- tural formula, has a reported 50% Inhibitory Concen- tration (ICso) of about 200 nM (nanomolar) with re- spect to inhibiting recombinant human PDE4.

Rolipram Investigators have continued to search for PDE4 inhibitors that are more selective with respect to inhibiting PDE4, that have a lower IC50 than rolipram, and that avoid the undesirable central nervous system (CNS) side effects, such as retching, vomiting, and sedation, associated with the adminis- tration of rolipram. One class of compounds is dis- closed in Feldman et al. U. S. Patent No. 5, 665, 754.

The compounds disclosed therein are substituted pyrrolidines having a structure similar to rolipram.

One particular compound, having structural formula (I), has an IC51) with respect to human recombinant PDE4 of about 2 nM. Inasmuch as a favorable separa- tion of emetic side effect from efficacy was ob- served, these compounds did not exhibit a reduction in undesirable CNS effects.

In addition, several companies are now undertaking clinical trials of other PDE4 inhibi- tors. However, problems relating to efficacy and adverse side effects, such as emesis and central nervous system disturbances, remain unsolved.

Accordingly, compounds that selectively inhibit PDE4, and that reduce or eliminate the ad- verse CNS side effects associated with prior PDE4 inhibitors, would be useful in the treatment of allergic and inflammatory diseases, and other dis- eases associated with excessive or unregulated pro- duction of cytokines, such as TNF. In addition, selective PDE4 inhibitors would be useful in the treatment of diseases that are associated with ele- vated cAMP levels or PDE4 function in a particular target tissue.

SUMMARY OF THE INVENTION The present invention is directed to po- tent and selective PDE4 inhibitors useful in treat- ment of diseases and conditions where inhibition of PDE4 activity is considered beneficial. The present PDE4 inhibitors unexpectedly reduce or eliminate the

adverse CNS side effects associated with prior PDE4 inhibitors.

In particular, the present invention is directed to compounds having the structural formula (II) : wherein R1 is lower alkyl, bridged alkyl (e. g., norbornyl), aryl, heteroaryl, aralkyl, cyclo- alkyl (e. g., indanyl), a 5-or 6-membered saturated heterocycle (e. g., 3-tetrahydrofuryl), C1-4alkylene- aryl, C1-4alkyleneOaryl, C1-4alkyleneheteroaryl, C1-4alkyleneHet, C2-4alkylenearylOaryl, C1-4alkylene bridged alkyl, C1-3alkylenecycloalkyl (e. g., cyclo- pentylmethyl), substituted or unsubstituted propargyl (e. g.,-CH2C=C-C6H5), substituted or unsub- stituted allyl (e. g.,-CH2CH=CH-C6H5), or halocyclo- alkyl (e. g., fluorocyclopentyl) ; R2 is hydrogen, methyl, or halo-substituted methyl, e. g., CHF2 ; R3 is selected from the group consisting of C (=O) OR, NHC (=O) OR, C (=O) R, C (=NH) NR8R9, C (=O) NR8R9, lower alkyl, bridged alkyl, cycloalkyl, haloalkyl, halocycloalkyl, Cl3alkylenecycloalkyl, a 5-or 6-

membered saturated heterocycle, aryl, heteroaryl, Cl, 3alkyleneC (=O) R7, C (=O) C (=O) NR8R9, Cl. 4alkyleneOR7, C1-3alkylenearyl, SO2heteroaryl, Het, aralkyl., alk- aryl, heteroaralkyl, heteroalkaryl, C1-3alkyleneC- (=O) OR76, C(=O) C1-3alkyleneC(=O) OR7, C1-3alkyleneheter- oaryl, C (=O) C (=O) oR7, C1-3alkylenearyl, SO2heteroaryl, Het, C (=O) Ci3alkyleneC (=O) OR7, C (=O) C13alkylene- NH (C=0) OR7, C(=O) C1-3alkyleneNH2, and NHC (=O) oR7 ; R4 is hydrogen, lower alkyl, haloalkyl, cycloalkyl, or aryl ; Rus vis hydrogen, lower alkyl, alkynyl, halo- alkyl, cycloalkyl, or aryl ; R6 and R12, independently, are hydrogen, lower alkyl, aralkyl, SO2R1l, or C (=O) R7 ; R7 is selected from the group consisting of branched or unbranched lower alkyl, heteroaryl, a heterocycle, aralkyl, and. aryl, and R7 can be option- ally substituted with one or more of OR8, NR8R9, or SR8 ; R8 and R°, same or different ; are selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, heteroaryl, alkaryl, heteroar- alkyl, heteroalkaryl, and aralkyl, or R8 and R9 can be taken together form a 4-membered to 7-membered ring ; Rl° is hydrogen, alkyl, haloalkyl, cyclo- alkyl, aryl, C (=O) alkyl, C (=O) cycloalkyl, C (=O) aryl, C (=O) Oalkyl, C (=O) Ocycloalkyl, C (=O) aryl, CHZOH, CH2Oalkyl, CHO, CN, NO2, or SO2R11; R11 is alkyl, cycloalkyl, trifluoromethyl, aryl, aralkyl, or NR8R9 ; and salts and solvates (e. g., hydrates) thereof.

The present invention also is directed to pharmaceutical compositions containing one or more of the compounds of structural formula (II), to use of the compounds and compositions containing the compounds in the treatment of a disease or disorder, and to methods of preparing compounds and intermedi- ates involved in the synthesis of the compounds of structural formula (II).

The present invention also is directed to methods of treating a mammal having a condition where inhibition of PDE4 provides a benefit, modu- lating cAMP levels in a mammal, reducing TNFa levels in a mammal, suppressing inflammatory cell activa- tion in a mammal, and inhibiting PDE4 function in a mammal by administering therapeutically effective amounts of a compound of structural formula (II), or a composition containing a composition of structural formula (II) to the mammal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to com- pounds having the structural formula (II) :

wherein Ru ils lower alkyl, bridged alkyl (e. g., norbornyl), aryl, heteroaryl, aralkyl, cyclo- alkyl (e. g., indanyl), a 5-or 6-membered saturated heterocycle (e. g., 3-tetrahydrofuryl), C14alkylene- aryl, C1-4alkyleneOaryl, C1-4alkyleneheteroaryl, C1-4alkyleneHet, C2-4alkylenearylOaryl, C1-4alkylene bridged alkyl, C1-3alkylenecycloalkyl (e. g., cyclo- pentylmethyl), substituted or unsubstituted propargyl (i.e., -CH2C#C-C6H5), substituted or unsub- stituted allyl (e. g., -CH2CH=CH-C6H5), or halocyclo- alkyl (e. g., fluorocyclopentyl) ;.

R2 is hydrogen, methyl, or halo-substituted methyl, e. g., CHF2 ; RI is selected from the group consisting of C (=O) OR, NHC (=O) OR, C (=0) R7, C (=NH) NR8R9, C (=O) NR8R9, lower alkyl, bridged alkyl, cycloalkyl, haloalkyl, halocycloalkyl, $C1-3alkylenecyclolkyl, a 5-or 6- membered saturated heterocycle, aryl, heteroaryl, C1-3alkyleneC (=O) R7, C (=O) C (=O) NR8R9, C1-4alkyleneOR7, C13alkylenearyl, SO2heteroaryl, Het, aralkyl, alk- aryl, heteroaralkyl, heteroalkaryl, C1-3alkyleneC- (=O) OR7, C(=O) C1-3alkyleneC (=O) OR7, C1-3alkylenehetero-

aryl, C (=O) C (=O) OR, C (=O) Cl3alkyleneC (=O) OR', C (=O)- Cl3alkyleneNH (C=O) OR7, C (=O) Cl3alkyleneNH2, and NHC (=O) oR7 ; R4 is hydrogen, lower alkyl, haloalkyl, cycloalkyl, or aryl ; Rus vis hydrogen, lower alkyl, alkynyl, halo- alkyl, cycloalkyl, or aryl ; R6 and R12, independently, are hydrogen, lower alkyl, aralkyl, SO2Rll, or C (=O) R7 ; R'is selected from the group consisting of branched or unbranched lower alkyl, heteroaryl, a heterocycle, aralkyl, and aryl, and R7 can be option- ally substituted with one or more of OR", NR8R9, or SR8 ; R8 and R9, same or different, are selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, heteroaryl, alkaryl, heteroar- alkyl, heteroalkaryl, and aralkyl, or R8 and R9 can be taken together form a 4-membered to 7-membered ring ; R1° is hydrogen, alkyl, haloalkyl, cyclo- alkyl, aryl, C (=O) alkyl, C (=O) cycloalkyl, C (=O) aryl, C (=O) Oalkyl, C (=O) Ocycloalkyl, C (=O) aryl, CH2OH, CH2Oalkyl, CHO, CN, NO2, or SO2R11; R11 is alkyl, cycloalkyl, trifluoromethyl, aryl, aralkyl, or NR8R9 ; and salts and solvates (e. g., hydrates) thereof.

As used herein, the term"alkyl,"alone or in combination, is defined to include straight chain and branched chain saturated hydrocarbon groups con- taining one to 16 carbon atoms. The term"lower alkyl"is defined herein as an alkyl group having

one through six carbon atoms (C1-C6). Examples of lower alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, isobutyl, n- butyl, neopentyl, n-hexyl, and the like. The term "alkynyl"refers to an unsaturated alkyl group that contains a carbon-carbon triple bond.

The term"bridged alkyl"is defined herein as a C6-C16 bicyclic or polycyclic hydrocarbon group, for example, norboryl, adamantyl, bicyclo [2. 2. 2]- octyl, bicyclo [2. 2. 1]heptyl, bicyclo [3. 2. 1] octyl, or decahydronaphthyl.

The term"cycloalkyl"is defined herein to include cyclic C3-C7 hydrocarbon groups, optionally fused to an aromatic group. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclohexyl, cyclopentyl, indanyl, and tetrahydronaphthyl.

The term"alkylene"refers to an alkyl group having a substituent. For example, the term ''C13alkylenecycloalkyl''refers to an alkyl group containing one to three carbon atoms, and substi- tuted with a cycloalkyl group.

The term"haloalkyl"is defined herein as an alkyl group substituted with one or more halo substituents, either fluro, chloro, bromo, iodo, or combinations thereof. Similarly,"halocycloalkyl" is defined as a cycloalkyl group having one or more halo substituents.

The term"aryl,"alone or in combination, is defined herein as a monocyclic or polycyclic aromatic group, preferably a monocyclic or bicyclic aromatic group, e. g., phenyl or naphthyl, that can be unsubstituted or substituted, for example, with

one or more, and in particular one to three, sub- stituents selected from halo, alkyl, phenyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, halo- alkyl, nitro, amino, alkylamino, acylamino, alkyl- thio, alkylsulfinyl, and alkylsulfonyl. Exemplary aryl groups include phenyl, naphthyl, tetrahydro- naphthyl, 2-chlorophenyl, 3-chlorophenyl, 4-chloro- phenyl, 2-methylphenyl, 4-methoxyphenyl, 3-tri- fluoromethyl-phenyl, 4-nitrophenyl, and the like.

The term"heteroaryl"is defined herein as a monocyclic or bicyclic ring system containing one or two aromatic rings and containing at least one nitrogen, oxygen, or sulfur atom in an aromatic ring, and which can be unsubstituted or-substituted, for example, with one or more, and in particular one to three, substituents, like halo, alkyl, hydroxy, hydroxyalkyl, alkoxy, alkoxyalkyl, haloalkyl, nitro, amino, alkylamino, acylamino, alkylthio ; alkyl- sulfinyl, and alkylsulfonyl. Examples of heteroaryl groups include thienyl, furyl, pyridyl, oxazolyl, quinolyl, isoquinolyl, indolyl, triazolyl, isothi- azolyl, isoxazolyl, imidizolyl, benzothiazolyl, pyrazinyl, pyrimidinyl, thiazolyl, and thiadiazolyl.

The term"aralkyl"is defined herein as a previously defined alkyl group, wherein one of the hydrogen atoms is replaced by an aryl group as de- fined herein, for example, a phenyl group optionally having one or more substituents, for example, halo, alkyl, alkoxy, and the like. An example of an aralkyl group is a benzyl group.

The term"alkaryl"is defined herein as a previously defined aryl group, wherein one of the

hydrogen atoms is replaced by an alkyl, cycloalkyl, haloalkyl, or halocycloalkyl group.

The terms"heteroaralkyl"and"hetero- alkaryl"are defined similarly as the term"aralkyl" and"alkaryl,"however, the aryl group is replaced by a heteroaryl group as previously defined.

The term"heterocycle"is defined as a 5- or 6-membered nonaromatic ring having one or more heteroatoms selected from oxygen, nitrogen, and sulfur present in the ring. Nonlimiting examples include tetrahydrofuran, piperidine, piperazine, sulfolane, morpholine, tetrahydropyran, dioxane, and the like.

The term"halogen"or"halo"is defined herein to include fluorine, chlorine, bromine, and iodine.

The terms"alkoxy,""aryloxy,"and"aral- koxy"are defined as-OR, wherein R is alkyl, aryl, and aralkyl, respectively.

The term"alkoxyalkyl"is defined as an alkoxy group appended to an alkyl group. The terms "aryloxyalkyl"and"aralkoxyalkyl"are similarly defined as an aryloxy or aralkoxy group appended to an alkyl group.

The term"hydroxy"is defined as-OH.

The term"hydroxyalkyl"is defined as a hydroxy group appended to an alkyl group.

The term"amino"is defined as-NH2.

The term"alkylamino"is defined as-NR2 wherein at least one R is alkyl and the second R is alkyl or hydrogen.

The term"acylamino"is defined as RC (=O) N, wherein R is alkyl or aryl.

The term"nitro"is defined as-NO,.

The term"alkylthio"is defined as-SR, where R is alkyl.

The term"alkylsulfinyl"is defined as R-SO2, where R is alkyl.

The term"alkylsulfonyl"is defined as R-S03, where R is alkyl.

In preferred embodiments, RI is hydrogen or methyl, R'is methyl, R2 is methyl or difluoromethyl, R4 is selected from the group consisting of hydrogen, lower alkyl, benzyl, and phenyl, R12 is hydrogen or methyl, and RI is selected from the group consisting of hydrogen, methyl, ethyl, C (=O) R7, C (=O) OR7, benzyl, So2CH3, and SO2C6Hs. Ru ils selected from the group consisting of

RI is selected from the group consisting of

wherein Ac is CH3C (=O) and tBu is C (CH3) 3.

In most preferred embodiments, Rl is se- lected from the group consisting of cyclopentyl, cyclopropylmethyl, tetrahydrofuryl, indanyl, norbornyl, phenethyl, and phenylbutyl ; RI is selected from the group consisting of methyl and difluoro- methyl ; R3 is selected from the group consisting of benzyl, CO2CH3, C (=O) CHZOH, C (=O) CH (CH3) OH, C (=O) C (CH3) 2OH, and C (=O)-C-OH RI is hydrogen ; Rus vis hydrogen or methyl ; R6 is hy- drogen, methyl, ethyl, benzyl, SO2CH3, S02C6H5, benzoyl, C (=O) C (CH3) 3, or acetyl ; R"is hydrogen or methyl ; and Rl° is hydrogen.

The present invention includes all possi- ble stereoisomers and geometric isomers of compounds of structural formula (II), and includes not only racemic compounds but also the optically active isomers as well. When a compound of structural formula (II) is desired as a single enantiomer, it can be obtained either by resolution of the final product or by stereospecific synthesis from either isomerically pure starting material or use of a chiral auxiliary reagent, for example, see Z. Ma et al., Tetrahedron : Asymmetry, 8 (6), pages 883-888 (1997). Resolution of the final product, an inter- mediate, or a starting material can be achieved by any suitable method known in the art. Additionally, in situations where tautomers of the compounds of

structural formula (II) are possible, the present invention is intended to include all tautomeric forms of the compounds. As demonstrated hereafter, specific stereoisomers exhibit an exceptional abil- ity to inhibit PDE4 without manifesting the adverse CNS side effects typically associated with PDE4 inhibitors.

In particular, it is generally accepted that biological systems can exhibit very sensitive activities with respect to the absolute stereochem- ical nature of compounds. (See, E. J. Ariens, Medic- inal Research Reviews, 6 : 451-466 (1986) ; E. J.

Ariens, Medicinal Research Reviews, 7 : 367-387 (1987) ; K. W. Fowler, Handbook of Stereoisomers : Therapeutic Drugs, CRC Press, edited by Donald P.

Smith, pp. 35-63 (1989) ; and S. C. Stinson, Chemical and Engineering News, 75 : 38-70 (1997).) For example, rolipram is a stereospecific PDE4 inhibitor that'contains one chiral center. The (-)-enantiomer of rolipram has a higher pharmacolog- ical potency than the (+)-enantiomer, which could be related to its potential antidepressant action.

Schultz et al., Naunyn-Schmiedeberg's Arch Pharma- col, 333 : 23-30 (1986). Furthermore, the metabolism of rolipram appears stereospecific with the (+)- enantiomer exhibiting a faster clearance rate than the (-)-enantiomer. Krause et al., Xenobiotica, 18 : 561-571 (1988). Finally, a recent observation indicated that the (-)-enantiomer of rolipram (R- rolipram) is about ten-fold more emetic than the (+)-enantiomer (S-rolipram). A. Robichaud et al., Neuropharmacology, 38 : 289-297 (1999). This observa- tion is not easily reconciled with differences in

test animal disposition to rolipram isomers and the ability of rolipram to inhibit the PDE4 enzyme. The compounds of the present invention can have three or more chiral centers. As shown below, compounds of a specific stereochemical orientation exhibit similar PDE4 inhibitory activity and pharmacological activ- ity, but altered CNS toxicity and emetic potential.

Accordingly, preferred compounds of the present invention have the structural formula (III) : The compounds of structural formula (III) are potent and selective PDE4 inhibitors, and do not manifest the adverse CNS effects and emetic potential demon- strated by stereoisomers of a compound of structural formula (III).

Compounds of structural formula (II) which contain acidic moieties can form pharmaceutically acceptable salts with suitable cations. Suitable pharmaceutically acceptable cations include alkali metal (e. g., sodium or potassium) and alkaline earth metal (e. g., calcium or magnesium) cations. The pharmaceutically acceptable salts of the compounds

of structural formula (II), which contain a basic center, are acid addition salts formed with pharma- ceutically acceptable acids. Examples include the hydrochloride, hydrobromide, sulfate or bisulfate, phosphate or hydrogen phosphate, acetate, benzoate, succinate, fumarate, maleate, lactate, citrate, tartrate, gluconate, methanesulfonate, benzene- sulphonate, and p-toluenesulphonate salts. In light of the foregoing, any reference to compounds of the present invention appearing herein is intended to include compounds of structural formula (II), as well as pharmaceutically acceptable salts and solvates thereof.

The compounds of the present invention can be therapeutically administered as the neat chemi- cal, but it is preferable to administer compounds of structural formula (II) as a pharmaceutical composi- tion or formulation. Accordingly, the present in- vention further provides for pharmaceutical formula- tions comprising a compound of structural formula (II), together with one or more pharmaceutically acceptable carriers and, optionally, other therapeu- tic and/or prophylactic ingredients. The carriers are"acceptable"in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

In particular, a selective PDE4 inhibitor of the present invention is useful alone or in com- bination with a second antiinflammatory therapeutic agent, for example, a therapeutic agent targeting TNFa, such as ENBREL or REMICADE@, which have util- ity in treating rheumatoid arthritis. Likewise, therapeutic utility of IL-1 antagonism has also been

shown in animal models for rheumatoid arthritis.

Thus, it is envisioned that IL-1 antagonism, in combination with PDE4 inhibition, which attenuates TNFa, would be efficacious.

The present PDE4 inhibitors are useful in the treatment of a variety of allergic, autoimmune, and inflammatory diseases.

The term"treatment"includes preventing, lowering, stopping, or reversing the progression of severity of the condition or symptoms being treated.

As such, the term"treatment"includes both medical therapeutic and/or prophylactic administration, as appropriate.

In particular, inflammation is a local- ized, protective response elicited by injury or destruction of tissues, which serves to destroy, dilute or wall off (i. e. sequester) both the inju- rious agent and the injured tissue. The term"in- flammatory disease,"as used herein, means any dis- ease in which an excessive or unregulated inflamma- tory response leads to excessive inflammatory symp- toms, host tissue damage, or loss of tissue func- tion. Additionally, the. term"autoimmune disease," as used herein, means any group of disorders in which tissue injury is associated with humoral or cell-mediated responses to the body's own constitu- ents. The term"allergic disease,"as used herein, means any symptoms, tissue damage, or loss of tissue function resulting from allergy. The term"arth- ritic disease,"as used herein, means any of a large family of diseases that are characterized by inflam- matory lesions of the joints attributable to a vari- ety of etiologies. The term"dermatitis,"as used

herein, means any of a large family of diseases of the skin that are characterized by inflammation of the skin attributable to a variety of etiologies.

The term"transplant rejection,"as used herein, means any immune reaction directed against grafted tissue (including organ and cell (e. g., bone mar- row)), characterized by a loss of function of the grafted and surrounding tissues, pain, swelling, leukocytosis and thrombocytopenia.

The present invention also provides a method of modulating cAMP levels in a mammal, as well as a method of treating diseases characterized by elevated cytokine levels.

The term"cytokine,"as used. herein, means any secreted polypeptide that affects the functions of other cells, and that modulates interactions between cells in the immune or inflammatory re- sponse. Cytokines include, but are not limited to monokines, lymphokines, and chemokines regardless of which cells produce them. For instance, a monokine is generally referred to as being produced and se- creted by a monocyte, however, many other cells produce monokines, such as natural killer cells, fibroblasts, basophils, neutrophils, endothelial cells, brain astrocytes, bone marrow stromal cells, epidermal keratinocytes, and B-lymphocytes. Lympho- kines are generally referred to as being produced by lymphocyte cells. Examples of cytokines include, but are not limited to, interleukin-1 (IL-1), inter- leukin-6 (IL-6), Tumor Necrosis Factor alpha (TNFa),' and Tumor Necrosis Factor beta (TNF).

The present invention further provides a method of reducing TNF levels in a mammal, which

comprises administering an effective amount of a compound of structural formula (II) to the mammal.

The term"reducing TNF levels,"as used herein, means either : a) decreasing excessive in vivo TNF levels in a mammal to normal levels or below normal levels by inhibition of the in vivo release of TNF by all cells, including but not limited to monocytes or macrophages ; or b) inducing a down-regulation, at the translational or transcription level, of excessive in vivo TNF levels in a mammal to normal levels or below normal levels ; or c) inducing a down-regulation, by inhi- bition of the direct synthesis of TNF as a postrans- lational event.

Moreover, the compounds of the present invention are useful in suppressing inflammatory cell activation. The term"inflammatory cell acti- vation,"as used herein, means the induction by a stimulus (including, but not limited to, cytokines, antigens or auto-antibodies) of a proliferative cellular response, the production of soluble media- tors (including but not limited to cytokines, oxygen radicals, enzymes, prostanoids, or vasoactive amines), or cell surface expression of new or in- creased numbers of mediators (including, but not limited to, major histocompatability antigens or cell adhesion molecules) in inflammatory cells (in- cluding but not limited to monocytes, macrophages, T lymphocytes, B lymphocytes, granulocytes, poly- morphonuclear leukocytes, mast cells, basophils, eosinophils, dendritic cells, and endothelial

cells). It will be appreciated by persons skilled in the art that the activation of one or a combina- tion of these phenotypes in these cells can contrib- ute to the initiation, perpetuation, or exacerbation of an inflammatory condition.

The compounds of the present invention also are useful in causing airway smooth muscle relaxation, bronchodilation, and. prevention of bronchoconstriction.

The compounds of the present.. invention, therefore, are useful in treating such diseases as arthritic diseases (such as rheumatoid arthritis), osteoarthritis, gouty arthritis, spondylitis, thyroid-associated ophthalmopathy, Behcet disease, sepsis, septic shock, endotoxic shock, gram negative sepsis, gram positive sepsis, toxic shock syndrome, asthma, chronic bronchitis, allergic rhinitis, al- lergic conjunctivitis, vernal conjunctivitis, eosinophilic granuloma, adult (acute) respiratory distress syndrome (ARDS), chronic pulmonary inflam- matory disease (such as chronic obstructive pulmo- nary disease), silicosis, pulmonary sarcoidosis, reperfusion injury of the myocardium, brain or ex- tremities, brain or spinal cord injury due to minor trauma, fibrosis including cystic fibrosis, keloid formation, scar tissue formation, atherosclerosis, autoimmune diseases, such as systemic lupus erythematosus (SLE) and transplant rejection disor- ders (e. g., graft vs. host (GvH) reaction and. allo- graft rejection), chronic glomerulonephritis, in- flammatory bowel diseases, such as Crohn's disease and ulcerative colitis, proliferative lymphocytic diseases, such as leukemias (e. g. chronic lympho-

cytic leukemia ; CLL) (see Mentz et al., Blood 88, pp. 2172-2182 (1996)), and inflammatory dermatoses, such as atopic dermatitis., psoriasis, or urticaria.

Other examples of such diseases or related conditions include cardiomyopathies, such as conges- tive heart failure, pyrexia, cachexia, cachexia secondary to infection or malignancy, cachexia sec- ondary to acquired immune deficiency syndrome (AIDS), ARC (AIDS-related complex), cerebral ma- laria, osteoporosis and bone resorption diseases, and fever and myalgias due to infection. In addi- tion, the compounds of the present invention are useful in the treatment of diabetes insipidus and central nervous system disorders ; such as depression and multi-infarct dementia.

Compounds of the present invention also have utility outside of that typically known as therapeutic. For example, the present compounds can function as organ transplant preservatives (see Pinsky et al., J. Clin. Invest., 92, pp. 2994-3002 (1993)) as well.

Selective PDE4 inhibitors also can be useful in the treatment of erectile dysfunction, especially vasculogenic impotence (Doherty, Jr. et al. U. S. Patent No. 6, 127, 363), diabetes insipidus (Kidney Int., 37, p. 362 (1990) ; Kidney Int., 35, p.

494, (1989)) and central nervous system disorders, such as multiinfarct dementia (Nicholson, Psycho- pharmacology, 101, p. 147 (1990)), depression (Eckman et al., Curr. Ther. Res., 43, p. 291 (1988)), anxiety and stress responses (Neuropharma- cology, 38, p. 1831 (1991)), cerebral ischemia (Eur.

J. Pharmacol., 272, p. 107 (1995)), tardive dys-

kinesia (J. Clin. Pharmocol., 16, p. 304 (1976)), Parkinson's disease (see Neurology, 25, p. 722 (1975) ; Clin. Exp. Pharmacol, Physiol., 26, p. 421 (1999)), and premenstrual syndrome. With respect to depression, PDE4-selective inhibitors show efficacy in a variety of animal models of depression such as the"behavioral despair"or Porsolt tests (Eur. J.

Pharmacol., 4-7, p. 379 (1978) ; Eur. J. Pharmacol., 57, p. 431 (1979) ; Antidepressants : neurochemical, behavioral and clinical pYospectizres, Enna, Malick, and Richelson, eds., Raven Press, p. 121 (1981)), and the"tail suspension test" (Psychopharmacology, 85, p. 367 (1985)). research findings show that chronic in vivo treatment by a variety of anti- depressants increase the brain-derived expression of PDE4 (J. Neuroscience, 19 ; p. 610 (1999)). There- fore, a selective PDE4 inhibitor can be used alone or in conjunction with a second therapeutic agent in a treatment for the four major classes of antide- pressants : electroconvulsive procedures, monoamine oxidase inhibitors, and selective reuptake inhibi- tors of serotonin or norepinephrine. Selective PDE4 inhibitors also can be useful in applications that modulate bronchodilatory activity via direct action on bronchial smooth muscle cells for the treatment of asthma.

Compounds and pharmaceutical compositions suitable for use in the present invention include those wherein the active ingredient is administered to a mammal in an effective amount to achieve its intended purpose. More specifically, a"therapeuti- cally effective amount"means an amount effective to prevent development of, or to alleviate the existing

symptoms of, the subject being treated. Determina- tion of the effective amounts is well within the capability of those skilled in the art,, especially in light of the detailed disclosure provided herein.

The term"mammal"as used herein includes males and females, and encompasses humans, domestic animals (e. g., cats, dogs), livestock (e. g., cattle, horses, swine), and wildlife (e. g., pri-mates, large cats, zoo specimens).

A"therapeutically effective dose"refers to that amount of the compound that results in. achieving the desired effect. Toxicity and thera- peutic efficacy of such compounds can be determined by standard pharmaceutical procedures in cell cul- tures or experimental animals, e. g., for determining the LD50 (the dose lethal to 50t of the population) and the ED50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index, which is expressed as the ratio between LD50 and ED50. Compounds which exhibit high therapeutic indices are preferred. The data obtained from such data can be used in formulating a dosage range for use in humans. The dosage of such compounds prefer- ably lies within a range of circulating concentra- tions that include the EDso with little or no toxic- ity. The dosage can vary within this range depend- ing upon the dosage form employed, and the route of administration utilized.

The exact formulation, route of adminis- tration, and dosage can be chosen by the individual physician in view of the patient's condition. Dos- age amount and interval can be'adjusted individually

to provide plasma levels of the active moiety which are sufficient to maintain the therapeutic effects.

As appreciated by persons skilled in the art, reference herein to treatment extends to pro- phylaxis, as well as to treatment of established diseases or symptoms. It is further appreciated that the amount of a compound of the invention re- quired for use in treatment varies with the nature of the condition being treated, and with the age and the condition of the patient, and is ultimately determined by the attendant physician or veterinar- ian. In general, however, doses employed for adult human treatment typically are in the range of 0. 001 mg/kg to about 100 mg/kg per day. The desired dose can be conveniently administered in a single dose, or as multiple doses administered at appropriate intervals, for example as. two, three, four or more subdoses per day. In practice, the physician deter- mines the actual dosing regimen which is most suit- able for an individual patient, and the dosage var- ies with the age, weight, and response of the par- ticular patient. The above dosages are exemplary of the average case, but there can-be individual in- stances in which higher or lower dosages are mer- ited, and such are within the scope of the present invention.

Formulations of the present invention can be administered in a standard manner for the treat- ment of the indicated diseases, such as orally, parenterally, transmucosally (e. g., sublingually or via buccal administration), topically, trans- dermally, rectally, via inhalation (e. g., nasal or deep lung inhalation). Parenteral administration

includes, but is not limited to intravenous, intra- arterial, intraperitoneal, subcutaneous, intramuscu- lar, intrathecal, and intraarticular. Parenteral administration also can be accomplished using a high pressure technique, like POWDERJECTTM.

For buccal administration, the composition can be in the form of tablets or lozenges formulated in conventional manner. For example, tablets and capsules for oral administration can contain conven- tional excipients such as binding agents (for exam- ple, syrup, acacia, gelatin, sorbitol, tragacanth, mucilage of starch or polyvinylpyrrolidone), fillers (for example, lactose, sugar, microcrystalline, cellulose, maize-starch, calcium phosphate or sorbi- tol), lubricants (for example, magnesium, stearate, stearic acid, talc, polyethylene glycol or silica), disintegrants (for example, potato starch or sodium starch glycollate), or wetting agents (for example, sodium lauryl sulfate). The tablets can be coated according to methods well known in the art.

Alternatively, the compounds of the pres- ent invention can be incorporated into oral liquid preparations such as aqueous or oily suspensions, solutions, emulsions, syrups, or elixirs, for exam- ple. Moreover, formulations containing these com- pounds can be presented as a dry product for consti- tution with water or other suitable vehicle before use. Such liquid preparations can contain conven- tional additives, such as suspending agents, such as sorbitol syrup, methyl cellulose, glucose/sugar syrup, gelatin, hydroxyethylcellulose, hydroxy- propylmethylcellulose, carboxymethyl cellulose, aluminum stearate gel, and hydrogenated edible fats ;

emulsifying agents, such as lecithin, sorbitan mono- oleate, or acacia ; nonaqueous vehicles (which can include edible oils), such as almond oil, fraction- ated coconut oil, oily esters, propylene glycol, and ethyl alcohol ; and preservatives, such as methyl or propyl p-hydroxybenzoate and sorbic acid.

Such preparations also can be formulated as suppositories, e. g., containing conventional suppository bases, such as cocoa butter or other glycerides. Compositions for inhalation typically can be provided in the form of a solution, suspen- sion, or emulsion that can be administered as a dry powder or in the form of an aerosol using a conven- tional propellant, such as dichlorodifluoromethane or trichlorofluoromethane. Typical topical and transdermal formulations comprise conventional aque- ous or nonaqueous vehicles, such as eye drops, creams, ointments, lotions, and pastes, or are in the form of a medicated plaster, patch, or membrane.

Additionally, compositions of the present invention can be formulated for parenteral adminis- tration by injection or continuous infusion. Formu- lations for injection can be in the form of suspen- sions, solutions, or emulsions in oily or aqueous vehicles, and can contain formulation agents, such as suspending, stabilizing, and/or dispersing agents. Alternatively, the active ingredient can be in powder form for constitution with a suitable vehicle (e. g., sterile, pyrogen-free water) before use.

A composition in accordance with the present invention also can be formulated as a depot preparation. Such long acting formulations can be

administered by implantation (for example, subcuta- neously or intramuscularly) or by intramuscular injection. Accordingly, the compounds of the inven- tion can be formulated with suitable polymeric or hydrophobic materials (e. g., an emulsion in an ac- ceptable oil), ion exchange resins, or as sparingly soluble derivatives (e. g., a sparingly soluble salt). _ For veterinary use, a compound of formula (II), or nontoxic salts thereof, is administered as a suitably acceptable formulation in accordance with normal veterinary practice. The veterinarian can readily determine the dosing regimen and route of administration that is most appropriate for a par- ticular animal.

Thus, the invention provides in a further aspect a pharmaceutical composition comprising a compound of the formula (II), together with a pharmaceutically acceptable diluent or carrier therefor. There is further provided by the present invention a process of preparing a pharmaceutical composition comprising a compound of formula (II), which process comprises mixing a compound of formula (I'I), together with a pharmaceutically acceptable diluent or carrier therefor.

Specific, nonlimiting examples of com- pounds of structural formula (II) are provided be- low, the synthesis of which were performed in accor- dance with the procedures set forth below.

Generally, compounds of structural formula (II) can be prepared according to the following synthetic schemes. In each scheme described below, it is understood in the art that protecting groups

can be employed where necessary in accordance with general principles of synthetic chemistry. These protecting groups are removed in the final steps of the synthesis under basic, acidic, or hydrogenolytic conditions which are readily apparent to those skilled in the art. By employing appropriate manip- ulation and protection of any chemical function- alities, synthesis of compounds of structural for- mula (II) not specifically set forth herein can be accomplished by methods analogous to the schemes set forth below.

Unless otherwise noted, all starting mate- rials were obtained from commercial suppliers and used without further purification. All reactions and chromatography fractions were analyzed by thin- layer chromatography on 250-mm silica gel plates, visualized with W (ultraviolet) or light I2 (iodine) stain. Products and intermediates were purified by flash chromatography, or reverse-phase HPLC.

The compounds of general structural for- mula (II) can be prepared, for example, as set forth in the following synthetic scheme. Other synthetic routes also are known to persons skilled in the art.

The following reaction scheme provides a compound of structural formula (II), wherein R'and R, i. e., CH3 and cyclopentyl, are determined by the starting materials. Proper selection of other starting mate- rials, or performing conversion reactions on inter- mediates and examples, provide compounds of general structural formula (II) having other recited R' through R11 substituents.

Wo Meo beo e 0 PhCH2NH2e N H2 e N H « NaHlOAC) H V H P01C J hHi N O'_O 0''O p0 I Intermedi. ate. 1 I meo -0 N'R \J N. R "'%. O''O s/ Intermediate 1 was prepared by the follow- ing synthetic sequence. Ho Me0 CSHgBr ! (EIOZP (OCH (CHl) COZEI 11 H, HO Ar Dioxane, 80'C Ar KC C Li N/TMS/Z, THF COz£t 2) (COCI) p, C- ! TClI COCU O p 0'C o RT cal. OMF, 0'C lo RT H H E isomer onty O 1t n-BuLi 70FC lo RT Ph A 1) 0. 6eq LAH Ar o TMS^N^OMs Ar Ic L-Ph Ar,,, , j,, N. l N 2) (COCI) 2 DMSO N TFA. CHC13 0 TEA CH2CI2 J Phz 0 C lo RT °) J 80-90% for Iwo sleps dr-10 : 1 (HPLC) 70-75% for 5 sleps Isolated by chromalogaphy 55 6 for major diastereomer purified by EIOAc-Her Isolated by chromalography Iituratan Int. D Int. C Int. B CJC (=O) OCH3 A Int. 1

The following illustrates the synthesis of various intermediates and compounds of structural formula (II). The following examples are provided for illustration and should not be construed as limiting.

Intermediate A Preparation of (E)-3- (3-Cyclopentoxy-4-methoxy- phenyl)-2-methyl-acrylic acid First, (E)-3- (3-cyclopentyloxy-4-methoxy- phenyl)-2-methyl-acrylic acid ethyl ester was pre- pared as follows : To a cooled (O°C), stirred solution of triethylphosphonopropionate (50. 6 mL ; 236 mmol ; 1. 05 eq.) in dry tetrahydrofuran (500 mL) was added a solution of lithium hexamethyldisilylamide in tetrahydrofuran (247 mL of 1. 0 M ; 1. 1 eq.) via sy- ringe under nitrogen atmosphere. The resulting yellow solution was allowed to stir at 0°C for 1. 5 hours, then a solution of 3-cyclopentoxy-4-methoxy- benzaldehyde (49. 4 g ; 225 mmol) in dry tetrahydro- furan (150 mL) was added dropwise via addition fun- nel over 0. 5 hour. The resulting orange solution

was allowed to stir at 0°C for 2 hours, then was warmed to room temperature and stirred overnight.

The reaction then was quenched with the addition of water (400 mL) and extracted with ether (2 x 300 mL). The combined organic layers were washed with IN aqueous hydrochloric acid (250 mL), saturated aqueous bicarbonate (250 mL), and brine (250 mL), then dried over MgSO4, filtered and concentrated in vacuo to provide the unsaturated ester as a brown liquid (68. 4 g ; 100%).

1H NMR (CDCl3, 400 MHz) 5 7. 64 (s, 1H), 7. 01-6. 96 (c, 2H), 6. 87 (m, 1H), 4. 77 (m, 1H), 4. 26 (q, 2H). LRMS (Electrospray, positive) : Da/e 305. 3 (m+1).

A suspension of (E)-3- (3-cyclopentoxy-4- methoxyphenyl)-2-methyl-acrylic acid ethyl ester (30 g, 98. 6 mmol) and LioHH2O (lithium hydroxide hy- drate) (5. 0 g, 119. 2 mmol, 1. 2 equiv.) in methanol- water (4 : 1, 100 mL) was stirred at room temperature for 24 hours. Methanol was removed under reduced pressure and the resulting residue was dissolved in water (100 mL), washed with three 100 mL portions of ethyl acetate, neutralized with 1. 0 N HC1 (hydro- chloric acid) (100 mL), and extracted with two 150 mL portions of ethyl acetate. The extract was washed with brine, dried over anhydrous Na2SO4 (so- dium sulfate), and concentrated under reduced pres- sure to afford the desired product as a light yellow powder (18. 2 g, 66% yield). 1H NMR (300 MHz, CDCl3) (ppm) : 12. 4 (br. s, 1H, COOH), 7. 56 (s, 1H, olefinic), 7. 04 (m, 3H, aromatic), 4. 81 (m, 1H), 3. 78 (s, 3H, OCH3), 2. 06 (s, 3H, CH3), 1. 91-1. 57 (m, 8H, cyclopentyl).

Intermediate A was prepared in an alterna- tive method. as follows : To a stirred solution of the ethyl ester (68. 4 g ; 225 mmol) in dioxane (400 mL) was added a solution of lithium hydroxide monohydrate (14. 0 g ; 332 mmol ; 1. 5 eq.) in water (200 mL) at room temper- ature and under a nitrogen atmosphere. A slight exotherm was observed. The resulting cloudy yellow solution was heated to 80°C (oil bath). for 1. 5 hours. After heating for. 0. 5 hour, the reaction became clear, but required an additional 1. 5 hours to complete the reaction, as evaluated by TLC. The resulting solution was allowed to cool to room tem- perature, diluted with ether (500 mL), then was washed with 1 M aqueous phosphoric acid (H3PO4).

This aqueous layer then. was extracted with ethyl acetate (2 x 200 mL) and the combined ethyl acetate and ether layers were washed with brine (250 mL), <BR> <BR> <BR> <BR> dried over MgSO4, filtered and concentrated in vacuo to provide Intermediate A as an orange solid (55 g ; 88--.).

'-H NMR (CDCl3, 400 MHz) : 5 7. 76 (s, 1H), 7. 06-7. 00 (c, 2H), 6. 89 (m, 1H), 4. 78 (m, 1H), 3. 88 (s, 3H), 2. 17 (s, 3H), 1. 97-1. 83 (c, 6H), 1. 64-1. 61 (c, 2H).

LRMS (Electrospray, negative) : Da/e 275. 3 (M-1).

Intermediate B Preparation of 3- [ (2E)-3- (3-cyclopentyloxy-4- methoxyphenyl)-2-methylprop-2-enoyl]- (4R)-4- phenyl-1, 3-oxazolidin-2-one

To a cooled (0°C), stirred slurry of In- termediate A (55 g ; 199 mmol) in anhydrous dichloro- methane (400 mL) was added a solution of oxalyl chloride in dichloromethane (109 mL of 2. 0 M ; 218 mmol ; 1. 1 eq.) via a syringe under a calcium chloride-dried atmosphere over 10 minutes. Vigorous bubbling was observed. The resulting dark solution was allowed to stir at 0°C for 15 minutes, then a catalytic amount of dimethylformamide was added via syringe (0. 3 mL). The resulting solution was al- lowed to continue stirring at 0°C for 0. 5 hour as the bubbling subsided, and then was allowed to warm to room temperature and stirred overnight (17 hours). The reaction was diluted with ethyl acetate (500 mL) and was carefully quenched with water (250 mL). After vigorously stirring this mixture for 1 hour, the layers were separated, and the organic layer was washed with additional water (400 mL) and brine (400 mL), then dried over MgSO4, filtered and

concentrated in vacuo to provide an acid chloride as a brown solid (57. 5 g ; 98%).

'H NMR (CDC13, 400 MHz) : 5 7. 98 (s, 1H), 7. 11-7. 02 (c, 2H), 6. 92 (m, 1H), 4. 79 (m, 1H), 3. 90 (s, 3H), 2. 22 (s, 3H), 2. 01-1. 82 (c, 6H), 1. 68-1. 62 (c, 2H).

To a cooled (-78°C), mechanically stirred solution of R-phenyl oxazolidinone (10. 0 g ; 61. 3 mmol) in dry tetrahydrofuran (400 mL) was added a solution of n-butylithium in hexanes (27 mL of 2. 5 M ; 1. 1 eq.). via syringe under nitrogen atmosphere.

The resulting solution was allowed to stir at-78°C for 0. 8 hour, then a solution of the acid chloride (19. 9 g ; 67. 4 mmol ; 1. 1 eq.) in tetrahydrofuran (100 mL) was added via cannulae. After stirring at-78°C for 15 minutes, the reaction mixture was allowed to slowly warm to 0°C over 40 minutes, during which time the reaction became a thick slurry. After stirring at 0°C for 2. 5 hours, the reaction was quenched with saturated, aqueous ammonium chloride (300 mL), and the bulk of the tetrahydrofuran was removed at reduced pressure. The residue then was extracted with chloroform (3 x 700 mL) and the com- bined organic layers were washed with water (300 mL) and brine (300 mL), then dried over MgSO4, filtered and concentrated in vacuo to provide about 33 g of a light orange solid. This material was suspended in 10% ethyl acetate in hexane (1. 2 L), and vigorously stirred overnight. The resulting fine powdery sol- ids were collected on a Buchner funnel with suction and then dried in vacuo to provide Intermediate B as a tan powder (21. 8 g ; 88%).

1H NMR (CDCl3, 400 MHz) : 5 7. 41-7. 37 (c, 5H),. 7. 06 (s, 1H), 7. 01-6. 97 (c, 2H), 6. 86 (m, 1H), 5. 54 (t,

1H), 4. 77-4. 73 (c, 2H), 4. 29 (t, 1H), 3. 87 (s, 3H), 2. 17 (s, 3H), 1. 97-1. 82 (c, 6H), 1. 62-1. 56 (c, 2H).

Similarly, the enantiomer of Intermediate B can be prepared using S- (-)-4-phenyl oxazolidi- none.

Intermediate C Preparation of (4R)-3- { [ (3S, 4S)-4- (3-cyclopentyloxy- <BR> <BR> 4-methoxyphenyl)-3-methyl-1-benzylpyrrolidin-3-yl] carbonyl)-4-phenvl-1, 3-oxazolidin-2-one To a cooled (-4°C), stirred slurry of Intermediate B' (9. 30 g ; 22. 8 mmol) and N- (methoxy- methyl)-N- (trimethylsilylmethyl) benzylamine (11. 7 mL ; 45. 6 mmol ; 2 eq.) in chloroform (65 mL) was added a solution of trifluroacetic acid in chloro- form (4. 6 mL of 1. 0 M ; 4. 6 mmol ; 0. 2 eq.) via sy- ringe under nitrogen atmosphere. The resulting slurry was allowed to stir at about 0°C for 4 hours, and then at about 15°C overnight (water bath). The resulting cloudy solution then was recooled to-4°C and treated with additional N- (methoxymethyl)-N- (trimethylsilylmethyl) benzylamine (5. 9 mL ; 22. 8

mmol ; 1 eq.) via syringe, and allowed to stir for 5 hours during which time the reaction became homoge- nous. TLC (5 Et2O in CHzCl2) show the reaction was complete. The bulk of the chloroform was removed at reduced pressure and the residue was diluted with ethyl acetate (250 mL), then washed successively with 1 N aqueous hydrochloric acid (2 x 50 mL), 1 N aqueous sodium hydroxide (50 mL), and brine (50 mL).

The organic layer then was dried over MgSO4, fil- tered, and concentrated in vacuo to give an orange semisolid (13. 9 g). Purification via flash chroma- tography on silica gel (2% ether in dichloromethane) provided the major diastereomer pyrrolidine as a white foam (8. 25 g ; 65%).

Diastereomeric selectivity about 10 : 1 (HPLC).

'H NMR (CDC13 400 MHz) : 7. 42-7. 21 (c, 10H), 6. 95 (s, 1H), 6. 81 (s, 2H), 5. 55 (dd, 1H), 4. 74 (t, 1H), 4. 68 (m, 1H), 4. 10 (dd, 1H), 3. 93 (t, 1H), 3. 70 (d, 1H), 3. 68 (s, 3H), 3. 56 (d, 1H),. 3. 42 (d, 1H), 2. 72 (m, 2H), 2. 64 (d, 1H), 2. 48 (m, 1H), 1. 85-1. 78 (c, 2H), 1. 75-1. 61 (c, 4H), 1. 57-1. 53 (c, 2H), 0. 96 (s, 3H). LRMS (Electrospray, positive) : Da/e 555. 2 (m+1).

Intermediate D Preparation of (3S, 4S)-4- (3-cyclopentyloxy-4- methoxyphenyl)-3-methyl-1-benzylpyrrolidine-3- carbaldehyde Reduction/Oxidation Procedure : To a cooled (-78°C), stirred solution of Intermediate C (15. 09 g ; 27. 2 mmol) in toluene (250mL) was added a solution of lithium aluminum

hydride in tetrahydrofuran (16. 3 mL ; 1. 0 M ; 16. 3 mmol ; 0. 6 eq.) via syringe under'nitrogen atmo- sphere. Vigorous bubbling was observed. The re- sulting solution was allowed to stir at-78°C for 2 hours, then the cooling bath was removed and quenched with the successive addition of water (0. 62 mL), 15% aqueous sodium hydroxide (0. 62 mL) and more water (1. 9 mL). The resulting mixture was allowed to warm to room temperature, stirred for 30 minutes, and then was diluted with ether (500 mL) and dried over MgSO4. Filtration and concentration in vacuo provided the alcohol (with some aldehyde present) as a semisolid (14. 8 g). This material was used imme- diately without further purification.

To a cooled. (-78°C), stirred solution of oxalyl chloride in dichloromethane (10. 9 mL ; 2. 0 M ; 21. 8 mmol ; 0. 8 eq.). in more dichloromethane (75 mL) was added dimethylsulfoxide (3. 1 mL ; 43. 5 mmol ; 1. 6 eq.) via syringe under nitrogen atmosphere. Vigor- ous bubbling was observed. After stirring at-78°C for 20 minutes, a solution of the crude. alcohol in dichloromethane (75 mL) was added via cannulae. The resulting yellow solution was allowed to stir at -78°C for 20 minutes, then triethylamine (15. 2 mL ; 109 mmol ; 4 eq.) was added via syringe. The reac- tion was allowed to stir at-78°C for 20 minutes, then warm to room temperature and stirred for an additional 1 hour. The reaction was quenched with the addition of brine (150 mL), then extracted with dichloromethane (2 x 100 mL). The combined organic fractions were dried over MgSO4, filtered, then concentrated in vacuo to provide the crude aldehyde.

Purification by flash silica gel chromatography (25%

ethyl acetate in hexanes) provided Intermediate D as a clear, colorless oil (9. 8 g ; 92%).

H NMR (CDC13, 400 MHz) : 9. 64. (s, 1H), 7. 37-7. 26 (c, 5H), 6. 78-6. 76 (c, 2H), 6. 70 (m, 1H), 4. 74 (m, 1H), 3. 82 (s, 3H), 3. 70 (m, 1H), 3. 64-3. 62 (c, 2H), 3. 18-3. 13 (c, 2H), 2. 84 (t, 1H), 2. 41 (d, 1H), 1. 94- 1. 83 (c, 6H), 1. 63-1. 59 (c, 2H), 0. 74 (s, 3H).

LRMS (Electrospray, positive) : Da/e 394. 3 (m+1).

Intermediate 1 Preparation of 4- (S)- (3-Cyclopentyloxy-4-methoxy- phenyl)-3- (S)-formyl-3-methylpyrrolidine-l- carboxylic acid methyl ester Intermediate D was dissolved in acetonitrile (4. 8 mL) and treated with methyl chlor- oformate (176 will, 2. 3 mmol). The resulting solution was heated to reflux for 4 hours, and thin layer chromatography indicated complete consumption of Intermediate D. The reaction mixture then was con- centrated in vacuo and purified directly by column chromatography on SiO2 using hexanes/ethyl acetate (3 : 1) as eluant. Intermediate 1 was recovered as a light yellow oil (110 mg).

'H NMR (CDC1,, 400 MHz) 5 : 9. 62 (s, 1H), 6. 83-6. 79 (d, 1H), 6. 65 (dd, 1H), 6. 61 (d, 1H), 4. 74-4. 70 (brd s, 1H), 3. 94-3. 64 (m, 3H), 3. 83 (s, 3H), 3. 76 (s,

3H), 3. 62-3. 55 (m, 1H), 3. 38-3. 28 (dd, 1H), 1. 95- 1. 75 (m, 6H), 1. 66-1. 57 (m, 2H), 0. 91 (s, 3H).

The following illustrates the synthesis of various intermediates and compounds of structural formula (II). The following examples are provided for illustration and should not be construed as limiting. _ In the examples, the following abbrevia- tions are used : NaOH (sodium hydroxide), CH2Cl2 (dichloromethane), Na2SOI.. (sodium sulfate), EtOAc (ethyl acetate), Ph (phenyl), MeOH (methanol), K2CO3 (potassium carbonate), umol (micromole), atm (atmo- sphere), MgSO4 (magnesium sulfate), LiOH (lithium hydroxide), N (normal), mmol (millimole), mL (milli- liter), and H3PO4 (phosphoric acid).

The following general procedures were used to prepare Examples 1-28.

Reductive Amination Procedure : To a stirred solution of aldehyde (0. 24 mmol) in dichloroethane (1 mL) was added benzylamine (0. 24 mmol) followed by sodium triacetoxyborohydride (0. 34 mmol) at room temperature under a nitrogen atmosphere. After stirring for 5 hours, the reac- tion was diluted with 1 N aqueous NaOH (0. 3 mL), and CH2Cl2 (10 mL). The layers were separated and the aqueous layer extracted with another 5 mL of CH2Cl2.

Combined organic layers then were washed with water and brine, dried (Na2SO4), filtered, and concentrated in vacuo. The residue was purified via flash chro-

matography (3 : 2 EtOAc : hexanes on silica gel) to provide the product.

Hydrogenation Procedure : To a stirred solution of the starting material (75 Vmol) in 95% ethanol (1 mL) was treated with Pearlman's catalyst (palladium hydroxide on carbon, 10 mg), then placed under a hydrogen atmo- sphere (1 atm). After stirring at room. temperature for 24 hours, the reaction was filtered through GF/F filter paper with suction on a Buchner funnel and washed with 20 mL of 95% ethanol. Concentration of the filtrate provided the. product.

Sulfonylation Procedure : To a stirred solution of starting material (0. 1 mmol) in 1, 4-dioxane (0. 3 mL) was added, suc- cessively, aqueous K2CO3 (, 0. 6 ml"of 0. 65 M ; 4 eq) and' a solution of the sulfonyl chloride (0. 12 mmol) in 1, 4-dioxane (0. 3 mL) at room temperature. The re- sulting solution was allowed to stir at room temper- ature for 2 hours. The reaction was diluted with 1 : 1 hexanes : EtOAc (30 mL) washed successively with water (20 mL) and brine (20 mL), then dried (MgSO4), filtered, and concentrated in vacuo to provide the sulfonamide.

Hunig's Base Acylation Procedure : To a stirred solution of starting material (0. 14 mmol) and Hunig's base (0. 20 mmol) in dry

CH, Cl-, (1 mL) was added the acid chloride (0. 14 mmol) via syringe at room temperature under a nitrogen atmosphere. After stirring for 1 hour, the reaciton was diluted with CH2Cl2 (30 mL) and washed succes- sively with 1 N aqueous HCl (2 x 10 mL, and brine (10 mL), then dried (Na2SO4), filtered, and concen- trated in vacuo. The residue was purified via ra- dial chromatography (1 mm chromatotron plate with 3% MeOH in CH2Cl2) to provide the amide.

Example 1 R=CH2Ph Methyl (4S, 3R)-4- (3-cyclopentyloxy-4-methoxyphenyl)- 3-methyl-3- methyl]} pyrrolidine carboxylate Prepared by the reductive amination procedure.

H NMR (CDCl3, 400 MHz ; mixture of rotomers) 5 : 7. 34-7. 28 (m, 5H), 6. 77 (d, 1H), 6. 67-6. 64 (m, 2H), 4. 70 (c, 1H), 3. 84-3. 65 (m, 9H), 3. 45-3. 24 (m, 4H), 2. 54 (q, 2H), 1. 86-1. 79 (m, 6H), 1. 62-1. 55 (m, 2H), 0. 78 (d, 3H). LRMS (Electrospray, positive) : Da/e 453. 2 (m+1).

Example 2

R=H Methyl (4S, 3R)-3- (aminomethyl)-4- (3-cyclopentyloxy- 4-methoxyphenyl)-3-methylpyrrolidinecarboxylate Prepared via the hydrogenation procedure.

H NMR (CDCl3, 400 MHz ; mixture of rotomers) 5 : 6. 80 (d, lH), 6. 71-6. 65 (m, 2H), 4. 73 (c, lH), 3. 86-3. 68 (m, 7H), 3. 43-3. 17 (m, 4H), 2. 65 (br s, 2H), 1. 97- 1. 80 (m, 6H), 1. 69-1. 56 (m, 2H), 0. 77 (d, 3H).

LRMS (Electrospray, positive) : Da/e 363. 3 (mol1).

Example 3

R=SO2CH3 Methyl (3S, 4S)-4- (3-cyclopentyloxy-4-methoxyphenyl)- 3-methyl-3- amino] methyl} pyrroli- dinecarboxylate Prepared via the sulfonylation procedure.

'H NMR (CDCl3, 400 MHz ; mixture of rotomers) 5 : 6. 80 (d, 1H), 6. 69-6. 67 (m, 2H), 4. 81-4. 72 (m, 1. 5H), 4. 61 (t, 0. 5H), 3. 88-3. 66 (m, 8H), 3. 44-3. 35 (m, 2H), 3. 20 I% t, 0. 5H), 3. 14-3. 05 (m, 2. 5H), 2. 95 (s, 3H), 1. 91-1. 80 (m, 6H), 1. 63-1. 56 (m, 2H), 0. 82 (d, 3H).

LRMS (Electrospray, positive) : Da/e 441. 2 (m+1).

LRMS (Electrospray, negative) : Da/e 439. 2 (m-1).

Example 4

R=COCH3 Methyl (4S, 3R)-3-[(acetylamino)methyl]-4-(3- <BR> cyclopentyloxy-4-methoxyphenyl)-3-methylpyrrolidine- carboxylate Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDCl3, 400 MHz ; mixture of rotomers) 5 : 6. 80 (d, 1H), 6. 69-6. 67 (m, 2H), 5. 58 (br t, 0. 5H), 5. 52 (br t, 0. 5H), 4. 74 (c, 1H), 3. 86-3. 64 (m, 7H), 3. 39- 3. 19 (m, 5H), 3. 08 (t, 1H), 1. 94 (s, 3H), 1. 91-1. 79 (m, 6H), 1. 63-1. 58 (m, 2H), 0. 80 (d, 3H).

LRMS (Electrospray, positive) : Da/e 405. 3 (m4. l).

Example 5

R=COPh Methyl (4S, 3R)-4- (3-cyclopentyloxy-4-methoxyphenyl)- 3-methyl-3-[(phenylcarbonylamino) methyl] pyrroli- dinecarboxylate Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDC13, 400 MHz ; mixture of rotomers) zu : 7. 55-7. 45 (m, 3H), 7. 37 (t, 2H), 6. 83 (d, 1H), 6. 77- 6. 74 (m, 2H), 6. 14 (br s, 1H), 4. 73 (c, 1H), 3. 90- 3. 59 (m, 9H), 3. 50-3. 30 (m, 3H), 3. 18 (t, 1H), 1. 97- 1. 74 (m, 6H), 1. 64-1. 55 (m, 2H), 0. 94 (d, 3H).

LRMS (Electrospray, positive) : Da/e 467. 3 (m+1).

Example 6

R=SO2Ph Methyl (3S, 4S)-4- (3-cyclopentyloxy-4-methoxyphenyl)- 3-methyl-3- [phenylsulfonyl)amino] methyl}pyrroli- dinecarboxylate Prepared via the sulfonylation procedure.

-'H NMR CDCl3, 400 MHz ; mixture of rotomers) 5 : 7. 84 (dd, 2H), 7. 61-7. 50 (m, 3H), 6. 77 7 (dd, 1H), 6. 64- 6. 60 (m, 2H), 5. 01 (t, 0. 5H), 4. 93 (t,. 0. 5H), 4. 72 (c, 1H), 3. 95-3. 59 (m, 9H), 3. 32 (c, 1H), 3. 19 (t, 0. 5H), 3. 07 (t, 0. 5H), 2. 93-2. 82 (m, 2H), 1. 97-1. 74 (m, 5H), 1. 64-1. 53 (m, 2H), 0. 75 (s, 3H).

LRMS (Electrospray, positive) : Da/e 503. 2 (m+1).

LRMS (Electrospray, negative) : Da/e 501. 2 (m-1).

Example 7

R=DIMER Bis { [ (4S, 3R)-4- (3-cyclopentyloxy-4-methoxyphenyl)-3- methyl-1-carboxymethylpyrrolidin-3-yl] methyl} amine Prepared via the reductive amination procedure with ammonium acetate. in NMR (CDCl3, 400 MHz ; mixture of rotomers) 6. 80 (dd, 2H), 6. 72-6. 64 (m, 4H), 4. 74 (m, 2H), 3. 93-3. 67 (m, 16H), 3. 56-3. 23 (m, 8H), 2. 51 (q, 1H), 2. 05-1. 81 (m, 2H), 1. 70-1. 53 (m, 4H), d, 3H).

LRMS (Electrospray, positive) : Da/e 708. 1 (m+1).

Example 8

R=H <BR> <BR> <BR> <BR> 1- [ (3S, 4S)-4- (. 3-Cyclopentyloxy-4-methoxyphenyl)-3- methyl-l-benzylpyrrolidin-3-yl] ethylamine Less Polar Diastereomer Prepared via the reductive amination procedure.

H NMR (CDCl3, 400 MHz) #: 7. 37-7. 21 (c, 5H), 6. 78 (d, 1H), 6. 69-6. 67 (c, 2H), 4. 75 (m, 1H), 3. 82 (s, 3H), 3. 56 (s, 2H), 2. 86 (m, 1H), 2. 73 (m, 2H), 2. 50 (t, 1H), 2. 01 (t, 1H), 1. 93-1. 78 (c, 7H), 1. 67-1. 56 (c, 2H), 1. 28 (br s, 2H), 0. 89 (d, 3H), 0. 86 (s, 3H).

LRMS (Electrospray, positive) : Da/e 409. 3 (m+1).

Example 9

R=H 1-{(3S,4S)-4-(3-Cyclopentyloxy-4-methoxyphenyl)-3- methyl-l-benzylpyrrolidin-3-yl] ethylamine More Polar Diastereomer Prepared via the reductive amination procedure.

1H NMR (CDCl* 400 MHz) #: 7. 39-7. 22 (c, 5H), 6. 93 (s, 1H), 6. 78-6. 69 (c, 2H), 4. 75 (m, 1H), 3. 82 (s, 3H), 3. 68 (d, 1H), 3. 56 (d, 1H), 3. 17 (t, 1H), 2. 92- 2. 81 (c, 3H), 2. 62 (d, 1H), 2. 37 (d, 1H), 1. 98-1. 81 (c, 6H), 1. 67-1. 57 (c, 2H), 1. 05 (d, 3H), 0. 63 (s, 3H).

LRMS (Electrospray, positive) : Da/e 409. 3 (m+1).

Example 10

R=COPh<BR> <BR> <BR> <BR> N-{1-[(3S, 4S)-4-(3-Cyclopentyloxy-4-methoxyphenyl)-<BR> <BR> <BR> <BR> 3-methyl-1-benzylpyrrolidin-3-yl] ethyl} benzamide Less Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

1H NMR (CDCl3, 400 MHz) 5 : 8. 47 (d, 1H), 7. 81 (d, 2H), 7. 51 (t, 1H), 7. 42 (t, 2H), 7.38-7. 29 (m, 5H), 6. 77 (t, 1H), 6. 73 (d, 2H), 4. 78 (c, 1H), 4. 01 (c, 1H), 3. 82 (s, 3H), 3. 72 (d, 1H), 3. 62 (d, 1H), 3. 40- 3. 26 (m, 3H), 2. 58 (t, 1H), 2. 13 (d, 1H), 1. 96-1. 74 (m, 6H), 1. 70-1. 53 (m, 2H), 1. 22 (d, 3H), 0. 60 (s, 3H).

LRMS (Elecrospray, positive) : Da/e 513. 3 (m+l).

Example 11

R=COPh N- {l- [ (3S, 4S)-4- (3-Cyclopentyloxy-4-methoxyphenyl)- 3-methyl-1-benzylpyrrolidin-3-yl] ethyl} benzamide More Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDCl,, 400 MHz) 7. 92 (br s, 1H), 7. 81 (d, 2H), 7. 53 (t, 1H), 7. 46 (t, 2H), 7. 20-. 7. 13 (m, 5H), 6. 78-6. 72 (m, 3H), 4. 64 (c, 1H), 4. 00 (c, 1H), 3. 84- 3. 77. (m, 4H), 3. 57 (q, 2H), 3. 43 (t, 1H), 3. 25 (t, 1H), 2. 81 (d, 1H), 2. 65 (t, 1H), 2. 34 (d, 1H), 1. 87- 1. 79 (m, 6H), 1. 65-1. 52 (m, 2H), 1. 29 (d, 3H), 0. 80 (s, 3H).

LRMS (Electrospray, positive) : Da/e 513. 3 (m+1).

Example 12

R=COCH3<BR> <BR> <BR> <BR> N-{1-[(3S, 4S)-4-(3-Cyclopentyloxy-4-methoxyphenyl)-<BR> <BR> <BR> <BR> 3-methyl-1-benzylpyrrolidin-3-yl] ethyl} acetamide Less Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDC13, 400 MHz) 5 : 7. 35-7. 24 (m, 5H), 6. 87 (br s, 1H), 6. 82 (d, 1H), 6. 75 (d, 1H), 6. 71 (dd, 1H), 4. 74 (c, 1H), 3. 85-3. 80 (m, 4H), 3. 68 (d, 1H), 3. 49 (d, 1H), 3. 26 (t, 1H), 3. 12 (t, 1H), 2. 66 (t, 1H), 2. 31 (d, 1H), 1. 96 (s, 3H), 1. 95-1. 80 (m, 6H), 1. 64-1. 58 (m, 2H), 1. 15 (d, 3H), 0. 72 (s, 3H).

LRMS (Electrospray, positive) : Da/e 451. 3 (m+1).

Example 13

R=COCH3 N-{1-[(3S,$S)-4-(3-Cyclopentyloxy-4-methoxyphenyl)- 3-methyl-1-benzylpyrrolidin-3-yl] acetamid More Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure. oh NMR (CDC1., 400 MHz) 5 :. 7. 61 (br d, 1H), 7. 36- 7. 26 (m, 5H), 6. 78-6. 70 (m, 3H), 4. 77 (c, 1H), 3. 86- 3. 78 (m, 5H), 3. 63 (d, 1H), 3. 27 (t, 1H), 3. 22 (t, 1H), 3. 06 (d, 1H), 2. 58 (t, 1H), 2. 03 (s, 3H), 1. 96- 1. 80 (m, 6H), 1. 62-1. 57 (m, 2H), 1. 09 (d, 3H), 0. 53 (s, 3H).

LRMS (Electrospray, positive) : Da/e 451. 3 (m+1).

Example 14

R=COCH3 <BR> <BR> <BR> 3- (S)- (l-Acetylaminoethyl)-4- (S)- (3-cyclopentyloxy- 4-methoxyphenyl).-3-methylpyrrolidine-1-carboxic acid methyl ester Less Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDCl3, 400 MHz) 5 : 7. 61 (br d, 1H), 7. 38- 7. 26 (m, 5H), 6. 78-6. 70 (m, 3H), 4. 77 (c, 1H), 3. 86- 3. 76 (m, 4H), 3. 63 (d, 2H), 3. 27. (t, 1H), 3. 22 (t, 1H), 3. 06 (d, 1H), 2. 58 (t, 1H), 2. 06 (d, 1H), 2. 03 (s, 3H), 1. 96-1. 78 (m, 6H), 1. 65-1. 55 (m, 2H), 1. 09 (d, 3H), 0. 53 (s, 3H).

LRMS (Electrospray, positive) : Da/e 451. 3 (m+1).

Example 15

R=SO2Ph<BR> {l- [ (3S, 4S)-4- (3-Cyclopentyloxy-4-methoxyphenyl)-3-<BR> methyl-l-benzylpyrrolidin-3-yl] ethyl}- (phenylsulfonyl) amine More Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDC13, 400 MHz) #: 7. 89 (d, 2H), 7. 54-7. 41 (m, 2H), 7. 40-7. 34 (m, 5H), 7. 31. (c, 1H), 6. 66 (dd, 1H), 6. 34 (s, 1H), 6. 24 (d, 1H), 4. 67 (c, 1H), 3. 78 (s, 3H), 3. 66 (d, iH), 3. 57 (d, 1H), 3. 14-3. 06 (m, 3H), 2. 69 (t, 1H), 2. 39 (t, 1H), 1. 96 (d, 1H), 1. 91- 1. 77 (m, 6H), 1. 69-1. 55 (rn, 2H), 1. 11 (d, 3H), 0. 40 (s, 3H).

LRMS (Elecrospray, positive) : Da/e 549. 2 (m+l).

Example 16

R=SO, PH<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> {1- [ (3S, 4S)-4- (3-cyclopentyloxy-4-methoxyphenyl)-3-<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> methyl-l-benzylpyrrolidin-3-yl] ethyl}- (phenylsufonyl) amine Less Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDCl, 400 MHz) #: 7. 64 (d 2H), 7. 52 (t, 1H), 7. 43-7. 31 (m, 7H), 6. 77-6. 66 (m, 3H), 4. 73 (c, 1H), 3. 80 (s, 3H), 3. 53 (d, 2H), 3. 47 (t, 1H), 3. 29 (t, 1H), 2. 87 (q, 1H), 2. 44 (t, 1H), 2. 29 (d, 1H), 2. 11 (d, 1H), 1. 93-1. 77 (m, 6H), 1. 61-1. 56 (m, 2H) 1. 21 (d, 3H), 0. 54 (s, 3H).

LRMS (Electrospray, positive) : Da/e 549. 2 (m+1).

Example 17

R=S02CH3<BR> {1- [ (3S, 4S)-4- (3-Cyclopentyloxy-4-methoxyphenyl)-3-<BR> methyl-1-benzylpyrrolidin-3-yl] ethyl}- (methylsulfonyl) amine More Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

OH NMR (CDCl3, 400 MHz) 5 : 7. 37-7. 28 (m, 5H), 6. 78- 6. 71 (m, 3H), 4. 76 (c, 1H), 3. 81 (s, 3H), 3. 70 (d, 1H), 3. 54 (d, 1H), 3. 50 (d, 1H), 3. 32 (t, 1H), 3. 01 (d, 1H), 2. 98 (s, 3H), 2. 56 (t, 1H), 2. 02 (t, 1H), 1. 98-1. 83 (m, 6H), 1. 62-1. 53 (m, 2H), 1. 18 (d, 3H), 0. 52 (s, 3H).

LRMS (Electrospray, positive) : Da/e 487. 3 (m+1).

Example 18

R=SO2CH3 {1- [ (3S, 4S)-4- (3-Cyclopentyloxy-4-methoxyphenyl)-3- methyl-l-benzylpyrrolidin-3-yl. lethyl}- (methylsulfonyl) amine Less Polar Diastereomer Prepared via the Hunig's base mediated acylation procedure.

'H NMR (CDC1,, 400 MHz) 5 : 7. 40-7. 27 (m, 5H), 6. 80- 6. 75 (m, 3H), 4. 75 (c, 1H), 3. 87-3. 78 (m, 4H), 3. 47 (t, 1H), 3. 38 (d, 1H), 3. 36 (t, 1H), 3. 22 (q, 1H), 2. 78 (d, 1H), 2. 63-2. 57 (m, 4H), 2. 26 (d, 1H), 1. 95- 1. 79 (m, 1H), 1. 70-1. 58 (m, 2H), 1. 28 (d, 3H), 0. 68 (s, 3H).

LRMS (Electrospray, positive) : Da/e 487. 3 (m+1).

Example 19

R=CH3 Methyl (3S, 4S)-4- (3-cyclopentyloxy-4-methoxyphenyl)- 3-methyl-3-[(methylamino) ethylpyrrolidine carbox- ylate Mixture of Diastereomers Prepared from the methyl ketone via the reductive amination procedure with methylamine.

1H NMR (CDCl., 400 MHz) #: 6. 79 (d, 1H), 6. 68-5. 65 (m, 2H), 4. 71 (c, 1H), 3. 96-3. 62 (m, 11H), 3. 37 (d, 0. 5H), 3. 27 (d, 0. 5H), 2. 15 (d, 3H), 2. 01-1. 74 (m, 6H), 1. 62-1. 55 (m, 2H), 1. 01 (d, 3H).

LRMS (Electrospray, positive) : Da/e 391. 4 (m+1).

Example 20 Example 21

Example 22 Example 23 Example 24

Example 25 Example 26 Example 27

Example 28 The compounds of structural formula (II) were tested for an ability to inhibit PDE4. The ability of a compound to inhibit PDE4 activity is related to the IC50 value for the compound, i. e., the concentration of inhibitor required for 50% inhibi- tion of enzyme activity. The In50 value for com- pounds of structural formula (II) were determined using recombinant human PDE4.

The compounds of the present invention typically exhibit an IC., value against recombinant human PDE4 of less than about 100 µM, and preferably less than about 50 vM, and more preferably less than about 25 gIm. The compounds of the present invention

typically exhibit an IC50 value against recombinant human PDE4 of less than about 5 uM, and often less than about 1 AZM. To achieve the full advantage of the present invention, a present PDE4 inhibitor has an IC50 of about 1 nM to about 25 uM.

The IC50 values for the compounds were determined from concentration-response curves typi- cally using concentrations ranging from 0. 1 pM to 500 uM. Tests against other PDE enzymes using stan- dard methodology, as described in Loughney et al., J. Biol. Chem., 271, pp. 796-806 (1996), also showed that compounds of the present invention are highly selective for the cAMP-specific PDE4 enzyme.

The compounds of structural formula (II) also were tested for an ability to reduce TNFa se- cretion in human peripheral blood lymphocytes. The ability to reduce TNFa secretion is related to the EC50 values (i. e., the effective concentration of the compound capable of inhibiting 50% of the total TNFa).

The compounds of the present invention typically exhibit an EC50 value of less than about 50 µM, and preferably less than about 25 µM, and more preferably less than about 15 µM. The compounds of the present invention preferably exhibit a PBL/TNFa EC, o value of less than about 5 AZM, and often less than about 0. 10 tIM. To achieve the full advantage of the present invention, a present PDE4 inhibitor has an EC50 value of about 10 nM to about 20 µM.

The production of recombinant human PDEs and the Iso and EC50 determinations can. be accom- plished by well-known methods in the art. Exemplary methods are described as follows :

EXPRESSION OF HUMAN PDEs Expression in Baculovirus-Infected Spodoptera fugiperda (Sf9) Cells Baculovirus transfer plasmids were con- struted using either pBlueBacIII (Invitrogen) or pFastBac (BRL-Gibco). The structure of all plasmids was verified by sequencing across the vector junc- tions and by fully sequencing all regions generated by PCR. Plasmid pBB-PDElA3/6 contained the complete open reading frame of PDElA3 (Loughney et al., J.

Biol. Chem., 271, pp. 796-806 (1996)) in pBlue- BacIII. Plasmid Hcam3aBB contained the. complete open reading frame of PDE1C3 (Loughney et al.

(1996)) in pBlueBacIII. Plasmid pBB-PDE3A contained the complete open reading frame of PDE3A (Meacci et al., Proc. Natl. Acad. Sci., USA, 89, pp. 3721-3725 (1992)) in pBlueBacIII.

Recombinant virus stocks were produced using either the MaxBac system (Invitrogen) or the FastBac system (Gibco-BRL) according to the manufac- turer's protocols. In both cases, expression of recombinant human PDEs in the resultant viruses was driven off the viral polyhedron promoter. When (D using the MaxBac system, virus was plaque purified twice in order to insure that no wild type (occ+) virus contaminated the preparation. Protein expres- sion was carried out as follows. Sf9 cells were grown at 27°C in Grace's Insect culture medium (Gibco-BRL) supplemented with 10% fetal bovine se- rum, 0. 33% TC yeastolate, 0. 33% lactalbumin hydro- lysate, 4. 2 mM NaHCO3, 10 Sg/mL gentamycin, 100

units/mL penicillin, and 100 Sg/mL streptomycin.

Exponentially growing cells were infected at a mul- tiplicity of approximately 2 to 3 virus. particles per cell and incubated for 48 hours. Cells were collected by centrifugation, washed with nonsup- plemented Grace's medium, and quick-frozen for stor- age.

Expression in Saccharomyces cerevisiae (Yeast) Recombinant production of human PDE1B, PDE2, PDE4A, PDE4B, PDE4C, PDE4D, PDE5, and PDE7 was carried out similarly to that described in Example 7 of U. S. Patent No. 5, 702, 936, incorporated herein by reference, except that the yeast transformation vector employed, which is derived from the basic ADH2 plasmid described in Price'et al., Methods in Enzymology, 18S, pp. 308-318 (1990), incorporated yeast ADH2 promoter and terminator sequences and the Saccharomyces cerevisiae'host was the protease-defi- cient strain BJ2-54 deposited on August 31, 1998 with the American Type Culture Collection, Manassas, Virginia, under accession number ATCC 74465. Trans- formed host cells were grown in 2X SC-leu medium, pH 6. 2, with trace metals, and vitamins. After 24 hours, YEP medium-containing glycerol was added to a final concentration of 2X YET/3% glycerol. Approxi- mately 24 hr later, cells were harvested, washed, and stored at-70°C.

HUMAN PHOSPHODIESTERASE PREPARATIONS Phosphodiesterase Activity Determinations Phosphodiesterase activity of the prepara- tions was determined as follows. PDE assays utiliz- ing a charcoal separation technique were performed essentially as described in Loughney et al. (1996).

In this assay, PDE activity converts [32P] cAMP or [32P] cGMP to the corresponding [32P] 5'-AMP or [32P] 5'-GMP in proportion to the amount of PDE ac- tivity present. The [32P] 5'-AMP or [32P] 5'-GMP then was quantitatively converted to free [32P] phosphate and unlabeled adenosine or guanosine by the action of snake venom 5'-nucleottdase. Hence, the amount of [32P] phosphate liberated is proportional to en- zyme activity. The assay was performed at 30°C in a 100 iL reaction mixture containing (final concentra- tions) 40 mM Tris HCl (pH 8. 0), 1, uM ZnS04, 5 mM MgCl2, and 0. 1 mg/mL bovine serum albumin (BSA).

Alternatively, in assays assessing PDEl-specific activity, incubation mixtures further incorporated the use of 0. 1 mM CaCl2 and 10, ug/mL calmodulin.

PDE enzyme was present in quantities that yield <30% total hydrolysis of substrate (linear assay condi- tions). The assay was initiated by addition of substrate (1 mM [32P] cAMP or cGMP), and the mixture was incubated for 12 minutes. Seventy-five (75) ug of Crotalus atrox venom then was added, and the incubation was continued for 3 minutes (15 minutes total). The reaction was stopped by addition of 200 , uL of activated charcoal (25 mg/mL suspension in 0. 1 M NaH, PO,, pH 4). After centrifugation (750 X g for

3 minutes) to sediment the charcoal, a sample of the supernatant was taken for radioactivity determina- tion in a scintillation counter and the PDE activity was calculated.

Inhibitor analyses were performed simi- larly to the method described in Loughney et al., J.

B701. Chem., 271, pp. 796-806 (1996), except both cGMP and cAMP were used, and substrate concentra- tions were kept below 32 nM, which is far below the Km of the tested PDEs.

Human PDE4A, 4B, 4C, 4D Preparations Preparation of PDE4A from S. cerevisiae Yeast cells (50 g of yeast strain YI26 harboring HDUN1. 46) were thawed at room temperature by mixing with 50 mL of Lysis Buffer (50 mM MOPS pH 7. 5, 10 SM ZnSO4, 2 mM MgCl2, 14. 2 mM 2-mercapto- ethanol, 5 µg/mL each of pepstatin, leupeptin, aprotinin, 20 Sg/mL each-of calpain inhibitors I and II, and 2 mM benzamidine HCl). Cells were lysed in o @ a French pressure cell (SLM-Aminco, Spectronic Instruments) at 10°C. The extract was centrifuged in a Beckman JA-10 rotor at 9, 000 rpm for 22 minutes at 4°C. The supernatant was removed and centrifuged in a Beckman TI45 rotor at 36, 000 rpm for 45 minutes at 4°C.

PDE4A was precipitated from the high-speed supernatant by the addition of solid ammonium sul- fate (0. 26 g/mL supernatant) while stirring in an ice bath and maintaining the. pH between 7. 0 and 7. 5.

The precipitated proteins containing PDE4A were

collected via centrifugation in a Beckman JA-10 rotor at 9, 000 rpm for 22 minutes. The precipitate was resuspended in 50 mL of Buffer G (50 mM MOPS pH 7. 5, 10 SM ZnSO4, 5 mM MgCl2, 100 mM NaCl, 14. 2 mM 2- mercaptoethanol, 2 mM benzamidine HCl, 5 Sg/mL each of leupeptin, pepstatin, and aprotinin, and 20 µg/mL each of calpain inhibitors I and II) and passed through a 0. 4-5 tzm filter.

The resuspended sample (50 to 100 mL) was loaded onto a 5 X 100 cm column of Pharmacia SEPHACRYL S-300 equilibrated in Buffer G. Enzyme activity was eluted at a flow rate of 2 mL/min and pooled for later fractionation.

The PDE4A isolated from gel filtration chromatography was applied to a 1. 6 X 20 cm column of Sigma Cibacron Blue Agarose-type 300.- (10 mL) equilibrated in Buffer A (50 mM MOPS pH 7. 5, 10 SM ZnSO4, 5 mM MgCl2, 14. 2 mM 2-mercaptoethanol, and 100 mM benzamidine HCl). The column was washed in suc- cession with 50 to 100 ml, of Buffer A, 20 to 30 mL of Buffer A containing 20 mM 5'-AMP, 50 to 100 mL of Buffer A containing 1. 5 M NaCl, and 10 to 20 mL of Buffer C (50 mM Tris HCl pH 8, 10 M ZnSO, 14. 2 mM 2-mercaptoethanol, and 2 mM benzamidine HC1). The enzyme was eluted with 20 to 30 mL of Buffer C con- taining 20 mM cAMP.

The PDE activity peak was pooled, and precipitated with ammonium sulfate (0. 33 g/mL enzyme pool) to remove excess cyclic nucleotide. The pre- cipitated proteins were resuspended in Buffer X (25 mM MOPS pH 7. 5, 5 M ZnSO,, 50 mM NaCl, 1 mM DTT, and 1 mM benzamidine HCl), and desalted via gel filtration on a Pharmacia PD-10# column per manufac-

turer's instructions. The enzyme was quick-frozen in a dry ice/ethanol bath and stored at-70°C.

The resultant preparations were about >80% pure by SDS-PAGE. These preparations had specific activities of about 10 to 40 gImol cAMP hydrolyzed per minute per milligram protein.

Preparation of PDE4B from'-S. cerevisiae Yeast cells (150 g of yeast strain YI23 harboring HDUN2. 32) were thawed by mixing with 100 mL glass beads (0. 5 mM, acid washed) and 150 mL Lysis Buffer (50 mM MOPS pH 7. 2 ; 2 mM EDTA, 2 mM EGTA, 1 mM DTT, 2 mM benzamidine HC1, 5 Sg/mL each of pepstatin, leupeptin, aprotinin, calpain inhibi- tors I and II) at room temperature. The mixture was @ cooled to 4°C, transferred to a Bead-Beater, and the cells lysed by rapid mixing for 6 cycles of 30 seconds each. The homogenate was centrifuged for 22 minutes in. a Beckman J2-21M centrifuge using a JA-10 rotor at 9, 000 rpm and 4°C. The supernatant was recovered and centrifuged in a Beckman XL-80 ultra- centrifuge using a TI45 rotor at 36, 000 rpm for 45 minutes at 4°C. The supernatant was recovered and PDE4B was precipitated by the addition of solid ammonium sulfate (0. 26 g/mL supernatant) while stir- ring in an ice bath and maintaining the pH between 7. 0 and 7. 5. This mixture was then centrifuged for 22 minutes in a Beckman J2 centrifuge using a JA-10 rotor at 9, 000 rpm (12, 000 X g).. The supernatant was discarded and the pellet was dissolved in 200 mL of Buffer A (50 mM MOPS pH 7. 5, 5 mM MgCl2, 1 mM DTT, 1 mM benzamidine HC1, and 5 vg/mL each of leupeptin,

pepstatin, and aprotinin). The pH and conductivity were corrected to 7. 5 and 15-20 mS, respectively.

The resuspended sample-was loaded onto a 1. 6 X 200 cm column (25 mL) of Sigma Cibacron Blue Agarose-type 300 equilibrated in Buffer A. The sample was cycled through the column 4 to 6 times over the course of 12 hours. The column was washed in succession with 125 to 250 mL of Buffer A, 125 to 250 mL of Buffer A containing 1. 5 M NaCl, and 25 to 50 mL of Buffer A. The enzyme was eluted with 50 to 75 mL of Buffer E (50 mM Tris HCl pH 8, 2 mM EDTA, 2 mM EGTA, 1 mM DTT, 2 mM benzamidine HCl, and 20 mM cAMP) and 50 to 75 mL of Buffer E containing 1 M NaCl. The PDE activity peak was pooled, and precip- itated with ammonium sulfate (0. 4 g/mL. enzyme pool) to remove excess cyclic nucleotide. The precipi- tated proteins were resuspended in Buffer X (25 mM MOPS pH 7. 5, 5 pM ZnSO4, 50 mM NaCl, 1 mM DTT, and 1 mM benzamidine HCl) and desalted via gel filtration 3 on a Pharmacia PD-10 column per manufacturer's instructions. The enzyme pool was dialyzed over- night against Buffer X containing 50% glycerol.

This enzyme was quick-frozen in a dry ice/ethanol bath and stored at-70°C.

The resultant preparations were about >90% pure by SDS-PAGE. These preparations had specific activities of about 10 to 50 mol cAMP hydrolyzed per minute per milligram protein.

Preparation of PDE4C from S. cerevisiae Yeast cells (150 g of yeast strain YI30 harboring HDUN3. 48) were thawed by mixing with 100 mL glass beads (0. 5 mM, acid washed) and 150 mL Lysis Buffer (50 mM MOPS pH 7. 2, 2 mM EDTA, 2 mM EGTA, 1 mM DTT, 2 mM benzamidine HCl, 5. zg/mL each of pepstatin,-leupeptin, aprotinin, calpain inhibi- tors I and II) at room temperature. The mixture was @ cooled to 4°C, transferred to a BEAD-BEATER, and the cells lysed by rapid mixing for 6 cycles of 30 sec each. The homogenate was centrifuged for 22 minutes in a Beckman J2-21M centrifuge using a JA-10 rotor at 9, 000 rpm and 4°C. The supernatant was recovered and centrifuged in a Beckman XL-80 ultra- centrifuge using a TI45 rotor at36, 000 rpm for 45 minutes at 4°C.

The supernatant was recovered. and PDE4C was precipitated by the addition of solid ammonium sulfate (0. 26 g/mL supernatant) while stirring in an ice bath and maintaining the pH. between 7. 0 and 7. 5.

Thirty minutes later, this mixture was centrifuged for 22 minutes in a Beckman J2 centrifuge using a JA-10 rotor at 9, 000 rpm (12, 000 X g). The super- natant was discarded and the pellet was dissolved in 200 mL of Buffer A (50 mM MOPS pH 7. 5, 5 mM MgCl2, 1 mM DTT, 2 mM benzamidine HC1, and 5 SglmL each of leupeptin, pepstatin, and aprotinin). The pH and conductivity were corrected to 7. 5 and 15-20 mS, respectively.

The resuspended sample was loaded onto a 1. 6 X 20 cm column (25 mL) of Sigma Cibacron Blue Agarose-type 300 equilibrated in Buffer A. The

sample was cycled through the column 4 to 6 times over the course of 12 hours. The column was washed in succession with 125 to 250 mL of Buffer A, 125 to 250 mL of Buffer A containing 1. 5 M NaCl, and then 25 to 50 mL of Buffer A. The enzyme was eluted with 50 to 75 mL of Buffer E (50 mM Tris HCl pH 8, 2 mM EDTA, 2 mM EGTA, 1 mM DTT, 2 mM benzamidine HCl, and 20 mM cAMP) and 50 to 75 mL of Buffer E containing 1 M NaCl. The PDE4C activity peak was pooled, and. precipitated with ammonium sulfate (0. 4 g/mL enzyme pool) to remove excess cyclic nucleotide ; The pre- cipitated proteins were resuspended in Buffer X (25 mM MOPS pH 7. 2, 5, uM ZnSO4, 50 mM NaCl, 1 mM DTT, and 1 mM benzamidine HCl) and desalted via gel fil- @ tration on a Pharmacia PD-10 column per manufac- turer's instructions. The enzyme pool was dialyzed overnight against Buffer X containing 50% glycerol.

This enzyme was quick-frozen in a dry ice/ethanol bath and stored at-70°C.

The resultant preparations were about >80% pure by SDS-PAGE. These preparations had specific activities of about 10 to 20 limol cAMP hydrolyzed per minute per milligram protein.

Preparation of PDE4D from S. cerevisiae Yeast cells (100 g of yeast strain YI29 harboring HDUN4. 11) were thawed by mixing with 150 mL glass beads (0. 5 mM, acid washed) and 150 mL Lysis Buffer (50 mM MOPS pH 7. 2, 10 SM ZnS04, 2 mM MgCl2, 14. 2 mM 2-mercaptoethanol, 2 mM benzamidine HCl, 5 Sg/mL each of pepstatin, leupeptin, aprotin- in, calpain inhibitors I and II) at room tempera-

ture. The mixture was cooled to 4°C, transferred to @ a Bead-Beater, and the cells lysed by rapid mixing for 6 cycles of 30 sec each. The homogenate was centrifuged for 22 minutes in a Beckman J2-21M cen- trifuge using a JA-10 rotor at 9, 000 rpm and 4°C.

The supernatant was recovered and centrifuged in a Beckman XL-80 ultracentrifuge using a TI45 rotor at 36, 000 rpm for 45 minutes at 4°C. The supernatant was recovered and PDE4D was precipitated by the addition of solid ammonium sulfate (0. 33 g/mL super- natant) while stirring in. an ice bath and maintain- ing the pH between 7. 0 and 7. 5. Thirty-minutes later, this mixture was centrifuged for 22 minutes in a Beckman J2 centrifuge usina a JA-10 rotor at 9, 000 rpm (12, 000 X g). The supernatant was. dis- carded and the pellet was dissolved in. 100 mL of Buffer A (50 mM MOPS pH 7. 5, 10 LzM ZnS34, 5 mM MgCl2, 14. 2 mM 2-mercaptoethanol, 100 mM benzamidine HCl, and 5, ug/mL each of leupeptin, pepstatin, aprotinin, calpain inhibitor I and II). The. pH and conductiv- ity were corrected to 7. 5 and 15-20 mS, respec- tively.

At a flow rate of 0. 67 mL/min, the resus- pended sample was loaded onto a 1. 6 X 20 cm column (10 mL) of Sigma Cibacron Blue Agarose-type 300 equilibrated in Buffer A.'The column was washed in succession with 50 to 100 mL of Buffer A, 20 to 30 mL of Buffer A containing 20 mM 5'-AMP, 50 to 100 mL of Buffer A containing 1. 5 M NaCl, and then 10 to 20 mL of Buffer C (50 mM Tris HCl pH 8, 10 uM ZnS04, 14. 2 mM 2-mercaptoethanol, 2 mM benzamidine HCl).

The enzyme was eluted with 20 to 30 mL of Buffer C containing 20 mM cAMP.

The PDE4D activity peak was pooled and precipitated with ammonium sulfate (0. 4 g/mL enzyme pool) to remove excess cyclic nucleotide. The pre- cipitated proteins were resuspended in Buffer X (25 mM MOPS pH 7. 2, 5 M ZnSO, 50 mM NaCl, 1 mM DTT, and 1 mM benzamidine HCl) and desalted via gel fil- @ tration on a Pharmacia PD-10 column per manufac- turer's instructions. The enzyme pool was dialyzed overnight against Buffer X containing 50W glycerol.

This enzyme preparation was quick-frozen in a dry ice/ethanol bath and stored at-70°C.

The resultant preparations were about >80% pure by SDS-PAGE. These preparations had specific activities of about 20 to. 50 Smol cAMP hydrolyzed per minute per milligram protein.

Lipopolysaccharide-Stimulated TNF Release from Human Peripheral Blood Lymphocytes To assess the ability. of a compound to reduce TNFa secretion in human peripheral blood lymphocytes (PBL), the following tests were per- formed. Previous studies have demonstrated that incubation of human PBL with cAMP-elevating agents, such as prostaglandin E21, fbrskolin, 8-bromo-cAMP, or dibutryl-cAMP, inhibits the secretion of TNFa by the cells when stimulated by lipopolysaccharide (LPS ; endotoxin). Accordingly, preliminary experi- ments have been performed to demonstrate that selec- tive PDE4 inhibitors, such as rolipram, inhibit LPS- induced TNFa secretion from human lymphocytes in a dose-dependent fashion. Hence, TNFa secretion from human PBL was used as a standard for the ability of

a compound to elevate intracellular cAMP concentra- tions and/or to inhibit PDE4 activity within the cell.

Heparinized blood (approximately 30 mL) drawn from human volunteers was mixed 1 : 1 with Dulbecco's modified phosphate-buffered saline. This @ mixture was mixed 1. : 1 with HISTOPAQUE and cer. tri- fuged at 1, 500 rpm at room temperature without brak- ing in the swinging bucket of a Beckman model TJ6 centrifuge. Erythrocytes were centrifuged to the bottom of the tubes, and serum remained at the sur- face of the tubes. A layer containing lymphocytes @ sedimented between the serum and HISTOPAQUE layers, and was removed by aspiration to a fresh tube. The cells were quantified and adjusted to 3 X 106 cells/mL and a 100 gL aliquot is placed into the wells of a 96 well plate. Test compounds and. RPMI media (Gibco/BRL Life Sciences) are added to each of the wells 15 minutes prior to addition of bacterial LPS (25 mg/mL). The mixture was allowed to incubate' for 20 hours at 37°C in a humidified chamber. The cells then were separated by centrifuging at 800 rpm for 5 minutes at room temperature. An aliquot of 180 pL of supernatant was transferred to a new plate for determination of TNFa concentration. TNFa pro- tein in the cell supernatant fluids was measured using a commercially available enzyme-linked immuno- @ sorbent assay (ELISA) (CYTOSCREEN Immunoassay Kit from Biosource International).

The cell-based assay provided the follow- ing results for various pyrrolidine compounds of the present invention. The EC51 values (i. e., effective concentration of the compound capable of inhibiting

50% of the total TNFa) illustrate the ability of the present compounds to inhibit LPS-stimulated TNFa release from human PBL.

The table below illustrates the ability of compounds of formuia (II) to inhibit PDE4 activity and TNFa release in vitro. In the following table, the ICso values were determined against human recom- binant PDE4..

Example PDE4 ICso PBL/TNFA ECso Numberl' (M x 10-9) (M x lO-9) 1 1400. 0 775. 5 2 28. 5 142. 0 3 3134. 1 4 3091. 7 5 2513. 9 6 506. 5 730. 0 7 57. 0 52. 5 8 673. 2 1562. 3 9 57. 5 608. 7 10 2951. 1 11 27,050. 7 12 14,695. 9 13 2436. 0 14 529. 2 598. 2 15 8967. 0 16 9075. 7 17 8663. 4 18 7392. 7 19 51. 7 59. 0 20 22. 0 198. 3 21 2204. 7 22 5888. 2 23 7549. 3 24 22. 9 76. 5 25 53. 0 85. 5 26 235. 1 450. 0 27 479. 3 816. 0 28 590. 9 1392. 0

The data presented above shows that the present compounds are potent inhibitors of PDE4, e. g., the compounds have an ICso vs. human recombi- nant PDE4 of about 700 pM to about 15 uM. Preferred compounds have an ICo of about 100 nM or less, and especially preferred compounds have an IC50 of about 50 nM or less.

Similarly, preferred compounds have a PBL/TNFa ECso about 500 nM or less, and preferably about 200 nM or less. More preferred compounds have a PBL/TNFa of about 100 nM or less.

To achieve the full advantage of the pres- ent invention, the compound has an ICso vs. human recombinant PDE4 of about 100 Su or less and PBL/TNFa ECso of about 500 liM or less. More prefera- bly, : the compound has an ICso of about 50 nM or less and a PBL/TNFa ECso of about 100 nM or less.

Animal Models Combined Mouse endotoxin-stimulated TNFa Release and Locomotor Activity Assay The purpose of this study was to determine the efficacy of PDE4 inhibitors in vivo in an LPS mouse model together with a determination with re- spect to central nervous system (CNS) side-effects manifested by a decrease. in spontaneous mobility.

The test animals were female Balb/c mice, having an average weight of about 20 g. The PDE4 @ inhibitors, formulated in 30% Cremophor EL, were administered via intraperitoneal (i. p.) injections at doses of 0. 1, 1. 0, 10. 0, and 100 mg/kg. Individ- ual dose volumes (about 150 SL) were adjusted based

on the body weights measured. One hour later, 5 mg/kg LPS in a final volume of 200 L was injected via the tail vein to each animal. Ninety minutes following the LPS treatment, the animals were bled and serum samples were collected before being stored at-70°C until assayed.

For efficacy determination, the serum samples were diluted two-fold and TNFa levels were @ determined using the CYTOSCREEN Immunoassay Kit (Biosource International). The data were averaged between triplicate sample subjects for each of the tested compounds.

Movement of the X-Y plane, or rearing up on the hind legs, was quantified by counting the number of"lìght-beam"crosses per unit of time. A decrease in the number of activity events is di- rectly proportional to the mobility or immobiliza- tion of the animal. The quantitative scoring corre- lated well with the subjective measurements de- scribed above.

The following table summarizes the mouse locomotor activity assay as mobility (% activity) obtained by the above-described method : Mobility (% activity Example Number') at 50 mg/kg dose) 7 16% 9 55% 19 145% 20 93% It also was determined that compounds of formula (II) have fewer central nervous system side

effects compared to rolipram and to compounds dis- closed in Feldman et al. U. S. Patent No. 5, 665, 754.

It also was found that central nervous system activ- ity is related to the absolute stereochemistry of the present compounds.

The results summarized above show that the compounds of the present invention are useful for selectively inhibiting PDE4 activity in a mammal, without exhibiting the adverse CNS and emetic ef- fects associated with prior PDE4 inhibitors.

Obviously, many modifications and varia- tions of the invention as hereinbefore set forth can be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated by the appended claims.