3-pyridyloxymethyl heterocyclic ether compounds useful in controlling chemical synaptic transmission

Novel 3-pyridyloxymethyl heterocyclic ether compounds of the formula: or the pharmaceutically-acceptable salts or prodrugs thereof are selective and potent ligands at neuronal nicotinic cholinergic channel receptors, and are effective in controlling synaptic transmission. Key intermediates and processes using this key intermediates to produce compounds of formula I with the variables defined in the specification are also described.

TECHNICAL FIELD

This invention relates to 3-pyridyloxymethyl heterocyclic ether compounds which control chemical synaptic transmission; to therapeutically-effective pharmaceutical compositions of these compounds; and to the use of said compositions to selectively control synaptic transmission.

BACKGROUND OF THE INVENTION

Compounds that selectively control chemical synaptic transmission offer therapeutic utility in treating disorders that are associated with dysfunctions in synaptic transmission. This utility may arise from controlling either pre-synaptic or post-synaptic chemical transmission. The control of synaptic chemical transmission is, in turn, a direct result of a modulation of the excitability of the synaptic membrane. Presynaptic control of membrane excitability results from the direct effect an active compound has upon the organelles and enzymes present in the nerve terminal for synthesizing, storing, and releasing the neurotransmitter, as well as the process for active re-uptake. Postsynaptic control of membrane excitability results from the influence an active compound has upon the cytoplasmic organelles that respond to neurotransmitter action.

An explanation of the processes involved in chemical synaptic transmission will help to illustrate more fully the potential applications of the invention. (For a fuller explanation of chemical synaptic transmission refer to Hoffman et al., Neurotransmission: The autonomic and somatic motor nervous systems. In: Goodman and Gilman's, The Pharmacological Basis of Therapeutics , 9th ed., J. G. Hardman, L. E. Limbird, P. B. Molinoff, R. W. Ruddon, and A. Goodman Gilman, eds., Pergamon Press, New York, 1996, pp. 105-139).

Typically, chemical synaptic transmission begins with a stimulus that depolarizes the transmembrane potential of the synaptic junction above the threshold that elicits an all-or-none action potential in a nerve axon. The action potential propagates to the nerve terminal where ion fluxes activate a mobilization process leading to neurotransmitter secretion and transmission to the postsynaptic cell. Those cells which receive communication from the central and peripheral nervous systems in the form of neurotransmitters are referred to as excitable cells. Excitable cells are cells such as nerves, smooth muscle cells, cardiac cells and glands. The effect of a neurotransmitter upon an excitable cell may be to cause either an excitatory or an inhibitory postsynaptic potential (EPSP or IPSP, respectively) depending upon the nature of the postsynaptic receptor for the particular neurotransmitter and the extent to which other neurotransmitters are present. Whether a particular neurotransmitter causes excitation or inhibition depends principally on the ionic channels that are opened in the postsynaptic membrane (i.e., in the excitable cell).

EPSPs typically result from a local depolarization of the membrane due to a generalized increased permeability to cations (notably Na and K ), whereas IPSPs are the result of stabilization or hyperpolarization of the membrane excitability due to a increase in permeability to primarily smaller ions (including K and Cl ). For example, the neurotransmitter acetylcholine excites at skeletal muscle junctions by opening permeability channels for Na and K . At other synapses, such as cardiac cells, acetylcholine can be inhibitory, primarily resulting from an increase in K conductance.

The biological effects of the compounds of the present invention result from modulation of a particular subtype of acetylcholine receptor. It is, therefore, important to understand the differences between two receptor subtypes. The two distinct subfamilies of acetylcholine receptors are defined as nicotinic acetylcholine receptors and muscarinic acetylcholine receptors. (See Goodman and Gilman's, The Pharmacological Basis of Therapeutics , op. Cit.).

The responses of these receptor subtypes are mediated by two entirely different classes of second messenger systems. When the nicotinic acetylcholine receptor is activated, the response is an increased flux of specific extracellular ions (e.g. Na , K and Ca ) through the neuronal membrane. In contrast, muscarinic acetylcholine receptor activation leads to changes in intracellular systems that contain complex molecules such as G-proteins and inositol phosphates. Thus, the biological consequences of nicotinic acetylcholine receptor-activation are distinct from those of muscarinic receptor activation. In an analogous manner, inhibition of nicotinic acetylcholine receptors results in still other biological effects, which are distinct and different from those arising from muscarinic receptor inhibition.

As indicated above, the two principal sites to which drug compounds that affect chemical synaptic transmission may be directed are the presynaptic nerve terminal and the postsynaptic membrane. Actions of drugs directed to the presynaptic site may be mediated through presynaptic receptors that respond to the neurotransmitter which the same secreting structure has released (i.e., an autoreceptor), or through a presynaptic receptor that responds to another neurotransmitter (i.e., a heteroreceptor). Actions of drugs directed to the postsynaptic membrane mimic the action of the endogenous neurotransmitter or inhibit the interaction of the endogenous neurotransmitter with a postsynaptic receptor.

Classic examples of drugs that modulate postsynaptic membrane excitability are the neuromuscular blocking agents which interact with nicotinic acetylcholine-gated channel receptors on skeletal muscle, for example, competitive (stabilizing) agents, such as curare, or depolarizing agents, such as succinylcholine.

In the central nervous system, postsynaptic cells can have many neurotransmitters impinging upon them. This makes it difficult to know the precise net balance of chemical synaptic transmission required to control a given cell. Nonetheless, by designing compounds that selectively affect only one pre- or postsynaptic receptor, it is possible to modulate the net balance of all the other inputs. Obviously, the more that is understood about chemical synaptic transmission in CNS disorders, the easier it would be to design drugs to treat such disorders.

Knowing how specific neurotransmitters act in the CNS allows one to speculate about the disorders that may be treatable with certain CNS-active drugs. For example, dopamine is widely recognized as an important neurotransmitter in the central nervous systems in humans and animals. Many aspects of the phannacology of dopamine have been reviewed by Roth and Elsworth, Biochemical Pharmacology of Midbrain Dopamine Neurons , In: Psychopharmacology: The Fourth Generation of Progress , F. E. Bloom and D. J. Kupfer, Eds., Raven Press, N.Y., 1995, pp 227-243). Patients with Parkinson's disease have a primary loss of dopamine containing neurons of the nigrostriatal pathway, which results in profound loss of motor control. Therapeutic strategies to replace the dopamine deficiency with dopamine mimetics, as well as administering pharmacologic agents that modify dopamine release and other neurotransmitters have been found to have therapeutic benefit ( Parkinson's Disease , In: Psychopharmacology: The Fourth Generation of Procress , op. cit, pp 1479-1484).

New and selective neurotransmitter controlling agents are still being sought, in the hope that one or more will be useful in important, but as yet poorly controlled, disease states or behavior models. For example, dementia, such as is seen with Alzheimer's disease or Parkinsonism, remains largely untreatable. Symptoms of chronic alcoholism and nicotine withdrawal involve aspects of the central nervous system, as does the behavioral disorder Attention-Deficit Disorder (ADD). Specific agents for treatment of these and related disorders are few in number or non-existent.

A more complete discussion of the possible utility as CNS-active agents of compounds with activity as cholinergic ligands selective for neuronal nicotinic receptors, (i.e., for controlling chemical synaptic transmission) may be found in U.S. Pat. No. 5,472,958, to Gunn et al., issued Dec. 5, 1995, which is incorporated herein by reference.

Certain other 2-pyridyloxy-substituted compounds are disclosed inter alia by Engel et al. in U.S. Pat. No. 4,946,836 as having analgesic activity.

Certain nicotine-related compounds having utility in enhancing cognitive function have been reported by Lin in U.S. Pat. No. 5,278,176, issued Jan. 11, 1994. Also, 2-(nitro)phenoxy compounds with similar fintion have been reported by Gunn et al., U.S. Pat. No. 5,472,958, issued Dec. 5, 1995.

In the PCT Patent Application W094 08992 of Abreo et al., published Apr. 28, 1994, are disclosed, inter alia, various 3-pyridyloxy-heterocyclic compounds that are either unsubstituted or mono-substituted on the pyridine ring with groups such as Br, Cl, F, hydroxyl, C 1 -C 3 -alkyl or C 1 -C 3 -alkoxy, such compounds also described as having utility in enhancing cognitive function.

SUMMARY OF THE INVENTION

In accordance with the principal embodiment of the present invention, there is provided a class of 5-substituted 3-pyridyloxymethyl heterocyclic ether compounds which are selective and potent neuronal nicotinic cholinergic compounds useful in controlling synaptic transmission.

The compounds of the present invention are represented by formula (I):

or a pharmaceutically acceptable salt thereof wherein n is selected from 1, 2 or 3.

The substituents R 1 is selected from the group consisting of hydrogen, allyl, and alkyl of one to six carbon atoms.

R 2 is selected from the group consisting of hydrogen, C 1 -C 3 alkyl, fluorine, chlorine, ethenyl, and phenyl.

The linking group, L, is absent or is selected from the group consisting of alkylene of one to six carbon atoms, C C (C 0 -C 6 -alkyl)-, CH CH p (C 0 -C 6 -alkyl)- where p is one or two

where M is selected from CH 2 , and NH .

The substituent R 3 is selected from the group consisting of a) hydrogen, b) alkyl of one to eight carbon atoms, c) alkeynl of 2-6 carbon atoms d) haloalkyl of one to six carbon atoms, e) hydroxyalkyl of one to six carbon atoms, f) alkoxy of one to six carbon atoms, g) amino, h) alkylamino of one to six carbon atoms, h ) azacycle attached to L through a nitrogen atom, i) dialkylamino in which the two alkyl groups are independently of one to six carbon atoms, j) phenyl, k) naphthyl, 1) biphenyl, m) furyl, n) thienyl, o) pyridinyl, p) pyrazinyl, q) pyridazinyl, r) pyrimidinyl, s) pyrrolyl, t) pyrazolyl, u) imidazolyl, v) indolyl, w) thiazolyl, x) oxazolyl, y) isoxazolyl, z) thiadiazolyl, aa) oxadiazolyl, bb) quinolinyl, cc) isoquinolinyl, and cc) any of b) or j) through cc) above substituted with one or two substituents independently selected from the group consisting of alkyl of one to six carbon atoms, haloalkyl of one to six carbon atoms, alkoxy of one to six carbon atoms, alkoxyalkyl in which the alkoxy and alkyl portions are independently of one to six carbon atoms, alkoxyalkoxyl in which the alkoxy portions are independently of one to six carbon atoms, halogen, cyano, hydroxy, amino, alkylamino of one to six carbon atoms, carboxyl, and alkoxycarbonyl of two to six carbon atoms.

Alternatively, L R 3 is O CH 2 R 4 , wherein R 4 is selected from CH 3 OCH 2 , or from substituents i) through bb) above, which may be substituted with one or two substituents independently selected from the group consisting of alkyl of one to six carbon atoms, haloalkyl of one to six carbon atoms, alkoxy of one to six carbon atoms, alkoxyalkyl in which the alkoxy and alkyl portions are independently of one to six carbon atoms, alkoxyalkoxyl in which the alkoxy portions are independently of one to six carbon atoms, halogen, cyano, hydroxy, amino, alkylamino of one to six carbon atoms, carboxyl, and alkoxycarbonyl of two to six carbon atoms.

The above definitions of the various linking and substituent groups in the compounds of the present invention are limited by the provisos that i) when L is absent, R 3 may not be hydrogen, alkyl of one to eight carbon atoms, alkoxy of 1-6 carbons, amino, alkylamino or dialkylamino; ii) when L is absent and R 3 is hydrogen, R 2 is selected from ethenyl, unsubstituted phenyl, and phenyl substituted as defined in bb) above; iii) when L is alkylene, R 3 may not be hydrogen or alkyl;

iv) when L is

then R 3 is selected from alkyl of one to eight carbon atoms, a carbocyclic aryl erocyclic aryl ring selected from h ) i), j), k), l), m), n), o), p), q), bb), and cc) as defined above, and any of i), j), k), 1), m), n),o), p), bb) and cc) as substituted as defined in dd) above; v) when L is

and M is CH 2 , then R 3 may not be hydrogen; and

vi) f) through y) above maya substituted as defined in z) above by no more than one alkylamino, carboxyl, or alkoxycarbonyl substituent.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the invention there are provided a class of substituted azetidine compounds of Formula (I) above wherein n is 1.

In another embodiment of the invention there are provided a class of substituted pyrrolidine compounds of Formula (I) above wherein n is 2.

In yet another embodiment of the present invention, there are provided a class of substituted piperidine compounds of Formula (I) above wherein n is 3.

Representative substituted azetidine compounds of the invention include, but are not limited to:

5-(2-hydroxy-1-naphthyl)-3-(2-(R)-azetidinylmethoxy)pyridine; and

Representative substituted pyrrolidine compounds of the present invention include, but are not limited to:

5-(4 -methyl-4-biphenyl)-3-(2-(S)-pyrrolidinylmethoxy)pyridine; or a pharmaceutically acceptable salt thereof.

Representative substituted piperidine compounds of the present invention include, but are not limited to:

5-(2-chloro-3-thienyl)-3-(2-(R)-piperidinylmethoxy)pyridine; and

The present invention also includes compounds selected from:

5-Allyl-3-(1-methyl-2-(S)-pyrrolidinylmethoxyl)pyridine; and pharmaceutically acceptable salts or pro-drugs thereof.

The present invention also relates to:

an intermediate compound selected from the group consisting of:

5-bromo-6-methyl-3-(1-methyl-2-(S)-pyrrolidinemethoxy)pyridine and to an intermediate compound selected from the group consisting of,

The present invention also relates to a method of using a compound of formula (I) wherein R 1 is hydrogen, alkyl of one to six carbons, or a nitrogen protecting group, n is 1, 2, or 3, R 2 is hydrogen, fluoro, chloro, or C 1 -C 3 -alkyl, L is absent and R 3 is bromo or iodo for preparation of a compound of formula (1) according to claim 1 .

The present invention further relates to a process for producing a compound of formula (I) according to claim 1 comprising,

(a) Preparing a compound of formula (I) wherein R 1 is hydrogen, alkyl of one to six carbons, or a nitrogen protecting group, n is 1, 2, or 3, R 2 is hydrogen, fluoro, chloro, or C 1 -C 3 -alkyl, L is absent and R 3 is bromo or iodo

(b) Reacting the compound of formula (I) wherein R 1 is hydrogen, alkyl of one to six carbons, or a nitrogen protecting group, n is 1, 2, or 3, R 2 is hydrogen, fluoro, chloro, or C 1 -C 3 -alkyl, L is absent and R 3 is bromo or iodo with

(iv) A metal cyanide; to form in the case of step (i), a compound of formula (I) wherein

LR 3 is an alkene, diene, alkyne, or alkoxycarbonyl; or

in the case of step (ii), a compound of formula (1) wherein LR 3 is an aryl group; or

in the case of step (iii), a compound of formula (I) wherein LR 3 is an alkenyl or alkyl group; or,

in the case of step (iv), a compound of formula (I) wherein LR 3 is a cyano group, which is utilized as an intermediate to form a compound of formula (I) wherein L is carbonyl and R 3 is selected from alkyl of one to eight carbon atoms, h ), i), j), k), l), m), n), o), p), q), bb), and cc) as defined above, or any of i), j), k), l), m), n),o), p), q), bb) and cc) optionally substituted as defined in dd) above, or to form a compound of formula (I) wherein L is CH 2 NHC( O) (C 0 -C 6 -alkyl)- and R 3 is selected from (a) through (dd) in claim 1 above.

The invention also relates to a process wherein the intermediate compound of formula (I) wherein R 1 is hydrogen, alkyl of one to six carbons, or a nitrogen protecting group, n is 1, 2, or 3, R 2 is hydrogen, fluoro, chloro, or C 1 -C 3 -alkyl, L is absent and R 3 is bromo or iodo is selected from those intermediate compounds identified above.

Definitions

The terms C 1 -C 3 -alkyl and alkyl of one to three carbon atoms as used herein refer to a univalent radical derived by removal of a single hydrogen atom from a saturated, straight- or branched-chain hydrocarbon containing between one and three carbon atoms. Examples of C 1 -C 3 -alkyl radicals include methyl, ethyl, propyl, and isopropyl,

The terms C 1 -C 6 -alkyl and alkyl of one to six carbon atoms as used herein refers to a univalent radical derived by removal of a single hydrogen atom from a saturated, straight- or branched-chain hydrocarbon containing between one and six carbon atoms. Examples of C 1 -C 6 -alkyl radicals include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, neopentyl, n-hexyl.

The terms C 1 -C 8 -alkyl and alkyl of one to eight carbon atoms as used herein refers to a univalent radical derived by removal of a single hydrogen atom from a saturated, straight- or branched-chain hydrocarbon containing between one and six carbon atoms. Examples of C 1 -C 8 -alkyl radicals include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, neopentyl, n-hexyl, n-octyl, 2-octyl and the like.

The term C 2 -C 6 -alkenyl as used herein refers to a univalent radical derived by removal of a single hydrogen atom from a straight- or branched-chain hydrocarbon containing between one and six carbon atoms and one double bond. Examples of C 2 -C 6 -alkenyl radicals include ethenyl, 3-propenyl, 2-propenyl, 1-propenyl, hex-2-en-1-yl, and the like.

The term haloalkyl refers to an alkyl group, as defined above, substituted by one or more halogen atoms and includes, for example, trifluoromethyl, chloroethyl, bromobutyl, and the like.

The term C 1 -C 6 -alkoxy and alkoxy of one to six carbon atoms as used herein refer to an alkyl group, as previously defined, attached to the parent molecular moiety through an oxygen atom. Examples of C 1 -C 6 -alkoxy, but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, tert-butoxy, neopentoxy and n-hexoxy.

One or more asymmetric centers may exist in the compounds of the present invention. Except where otherwise noted, the present invention contemplates the various stereoisomers and mixtures thereof.

The term prodrug refers to compounds that are rapidly transformed in vivo to yield the parent compounds of Formula (I), as for example, by hydrolysis in blood. T. Higuchi and V. Stella provide a thorough discussion of the prodrug concept in Prodrugs as Novel Delivery Systems , Vol. 14 of the A.C.S. Symposium Series, American Chemical Society (1975). Examples of esters useful as prodrugs for compounds containing carboxyl groups may be found on pages 14-21 of Bioreversible Carriers in Drug Design: Theory and Application , edited by E. B. Roche, Pergamon Press (1987).

The term prodrug ester group refers to any of several ester-forming groups that are hydrolyzed under physiological conditions. Examples of prodrug ester groups include pivoyloxymethyl, acetoxymethyl, phthalidyl, indanyl and methoxymethyl, as well as other such groups known in the art.

Solid compositions of a similar type may also be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugar as well as high molecular weight polethylene glycols and the like.

According to the methods of treatment of the present invention, disorders in synaptic transmission are treated or prevented in a patient such as a human or lower mammal by administering to the patient a therapeutically effective amount of a compound of the invention, in such amounts and for such time as is necessary to achieve the desired result. By a therapeutically effective amount of a compound of the invention is meant a sufficient amount of the compound to treat disorders in synaptic transmission, at a reasonable benefit/risk ratio applicable to any medical treatment. It will be understood, however, that the total daily usage of the compounds and compositions of the present invention will be decided by the attending physician within the scope of sound medical judgement. The specific therapeutically effective dose level for any particular patient will depend upon a variety of factors including the disorder being treated and the severity of the disorder; the activity of the specific compound employed; the specific composition employed; the age, body weight, general health, sex and diet of the patient; the time of administration, route of administration, and rate of excretion of the specific compound employed; the duration of the treatment; drugs used in combination or coincidental with the specific compound employed; and like factors well known in the medical arts.

The total daily dose of the compounds of this invention administered to a human or other mammal in single or in divided doses can be in amounts, for example, from 0.001 to 50 mg/kg body weight or more usually from 0.01 to 25 mg/kg body weight. Single dose compositions may contain such amounts or submultiples thereof to make up the daily dose. In general, treatment regimens according to the present invention comprise administration to a patient in need of such treatment from about 1 mg to about 1000 mg of the compound(s) of this invention per day in single or multiple doses.

Abbreviations

Abbreviations which have been used in the descriptions of the scheme and the examples that follow are: BOC for t-butyloxycarbonyl; CBZ for benzyloxycarbonyl; DEAD for diethylazodicarboxylate; DMF for dimethyl formamide; DPPA for diphenylphosphoryl azide; EDC for 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide HCl; Et 2 O for diethyl ether; EtOAc for ethyl acetate; MeOH for methanol; NaN(TMS) 2 for sodium bis(trimethylsilyl)amide; NMMO for N-methylmorpholine N-oxide; (Ph) 3 for triphenyl; TEA for triethylamine; THF for tetrahydrofuran; TFA for trifluoroacetic acid, TPP for triphenylphosphine; other abbreviations are found in J. Org. Chem . 1996, 62.22A.

Synthetic Methods

The compounds and processes of the present invention will be better understood in connection with the following synthetic schemes which illustrate the methods by which the compounds of the invention may be prepared. The groups n, R 1 R 2 , R 3 and R 4 are as defined above unless otherwise noted.

In accordance with Scheme 1 intermediate compounds are prepared by reaction of an alcohol compound (1), wherein n is 1 to 3 and R 1 is allyl or C 1 -C 6 -alkyl or a protecting group such as BOC or CBZ, for example, with a 3-hydroxypyridine compound (2), wherein R 2 is H, F or Cl, for compounds of Formula (I) above, in the presence of triphenylphosphine and DEAD under Mitsunobu reaction conditions (cf., Synthesis , 1981: 1) to form the 5-bromopyridyl ether compound (3).

Alternately, in accordance with Scheme 2 selected intermediate pyrrolidine compounds (3), wherein R 1 is allyl or C 1 -C 6 -alkyl or a protecting group such as t-BOC or CBZ, for example, may be prepared by reaction of an pyrrolidinemethanol compound (1) with a 3,5-dibromopyridine compound (4), wherein R 2 is H or phenyl, in the presence of a strong base, such as an alkyl lithium compound, an alkali metal such as Na or Li, or an alkali metal hydride, such as NaH or KH, for example, in an aprotic solvent such as THF, DMSO or DMF under anydrous conditions and inert atmospheres, at temperatures from room temperature to 120 C., for example.

In accordance with Scheme 3 an intermediate compound (3), wherein R 1 is allyl or C 1 -C 6 -alkyl or a protecting group such as t-BOC or CBZ, for example, is reacted with an unsaturated compound (5), (7) or (9), to give compounds (6), (8) or (10), respectively, which are specific or protected compounds of Formula (I), by treatment with a palladium (II) catalyst under weakly basic conditions at reflux temperature in an organic or aqueous solvent. Compound (5) may be prepared by reacting a compound R 3 CHO, wherein R 3 is as described above, with (phenyl) 3 P CH 2 in refluxing toluene. Compound (7) may be prepared by reacting a compound R 3 CHO, wherein R 3 is as described above, with (Ph) 3 P CH CHO in refluxing toluene to give R 3 CH CH CHO, then reacting R 3 CH CH CHO with (Ph) 3 P CH 2 in refluxing toluene. Compound (9) may be prepared by reacting R 3 CHO, wherein R 3 is as described above, with CBr 4 and P(Ph) 3 to give R 3 CH CBr 2 , then reacting R 3 CH CBr 2 with 2 equivalents of n-butyllithium followed by treatment with H . Alternatively, a compound of formula (I) wherein L is carbonyl and R 3 is C 1 -C 3 -alkoxy is prepared by reaction of a compound of formula (3) with carbon monoxide and a C 1 -C 3 -alcohol in the presence of a palladium (II) catalyst in the presence of a weak base such as triethylamine. The resulting ester may then be treated with a cyclic secondary amine, for example, azetidine, pyrrolidine piperidine, or piperazine, to afford a compound of formula (I) wherein L is carbonyl and R 3 is an azacyclic group attached to the carbonyl through a nitrogen. In the cases wherein R 1 is a protecting group such as t-BOC or CBZ it must be removed under well-known standard conditions for removing those groups in order to give the desired compound of Formula (I). In some cases wherein R 1 is allyl or C 1 -C 6 -alkyl, it may be desirable to place this grouping in the compound after the protecting R 1 group has been removed. When R 1 is allyl, this may be accomplished by reacting the unprotected nitrogen atom with allyl chloride in the presence of a weak base such as triethylamine. When R 1 is C 1 -C 6 -alkyl, this may be accomplished by reacting the unprotected nitrogen atom with the appropriate aldehyde in the presence of NaCNBH 3 , for example.

In accordance with Scheme 4 an intermediate compound (3), wherein R 1 is allyl or C 1 -C 6 -alkyl or a protecting group such as t-BOC or CBZ, for example, is reacted with a suitable boronic acid compound (11) wherein R 3 is as described in options (a)-(l) for Formula (1) above, in the presence of Pd(0) under the conditions of the Suzuki reaction, for example in the presence of a weak base such as NaHCO 3 and in an aprotic solvent, such as toluene, benzene or CH 2 Cl 2 at reflux temperatures to give a compound (12), wherein R 3 is as described above, to produce specific compounds of Formula (I). In an alternate method, compound (11) may be replaced by R 3 Sn(n-Bu) 3 or compound (11) and the palladium catalyst may be replaced by a R 3 MgX compound and Ni(dppp) 2 Cl 2 catalyst to give compound (12). In the cases wherein R 1 is a protecting group such as t-BOC or CBZ it must be removed under well-known standard conditions for removing those groups in order to give the desired compound of Formula (I). In some cases wherein R 1 is allyl or C 1 -C 6 -alkyl, it may be desirable to place this grouping in the compound after the protecting R 1 group has been removed. When R 1 is allyl, this may be accomplished by reacting the unprotected nitrogen atom with allyl chloride in the presence of a weak base such as triethylamine. When R 1 is C 1 -C 6 -alkyl, this may be accomplished by reacting the unprotected nitrogen atom with the appropriate aldehyde in the presence of NaCNBH 3 , for example.

In accordance with Scheme 5 are prepared compounds of Formula (I) wherein R 2 is ethenyl, phenyl or substituted phenyl. Reaction of a starting material compound (12) wherein R 2 is chloro with phenylboronic acid (13) in the presence of Pd(0) under the conditions of the Suzuki reaction, for example in the presence of a weak base such as NaHCO 3 and in an aprotic solvent, such as toluene, benzene or CH 2 Cl 2 at reflux temperatures to give the compound 14. Reaction of a starting material compound (12) wherein R 2 is chloro with vinyl-Sn(n-butyl) 3 (15) in the presence of Pd(0) under Stille reaction conditions to give the compound (16). In the cases wherein R 1 is a protecting group such as t-BOC or CBZ it must be removed under well-known standard conditions for removing those groups in order to give the desired compound of Formula (I). In some cases wherein R 1 is allyl or C 1 -C 6 -alkyl, it may be desirable to place this grouping in the compound after the protecting R 1 group has been removed. When R 1 is allyl, this may be accomplished by reacting the unprotected nitrogen atom with allyl chloride in the presence of a weak base such as triethylamine. When R 1 is C 1 -C 6 -alkyl, this may be accomplished by reacting the unprotected nitrogen atom with the appropriate aldehyde in the presence of NaCNBH 3 , for example.

In Scheme 6 is shown an alternate process for preparing desired compounds of the invention. Whereas in Schemes 1 and 3, the heterocyclic and the pyridine moieties are first joined, and the R 3 grouping is added according to Schemes 4 and 5, Scheme 6 allows for the placement of the R 3 group before joining. Accordingly compound (2) is treated with the appropriate reagent, such as a trialkylsilyl or benzyl chloride, to protect the hydroxyl group with a protecting group PG, such as trialkylsilyl or benzyl, respectively, for example to give compound (17). Compound (17) may then be reacted with an appropriate reagent, as described in Schemes 4 and 5, to give the compound (18) having the desired substitution at R 2 and R 3 . Subsequent deprotection of (18) by standard methods gives (19), which is then coupled with compound (1) according to the method of Scheme 1 to give the desired compound of Formula (I).

In accordance with Scheme 7 are prepared additional compounds of Formula (I). Compund (3) is first reacted with Zn(CN) 2 and tetrakis(triphenylphosphine)palladium(0) under anhydrous conditons in DMF or a similar solvent at room temperature to 120 C. for 12-24 hours, to give the cyano intermediate compound (20). Compound (20) may then be reacted with a reagent R 5 M, wherein R 5 is as described for Formula (I) above and M is lithium or a magnesium halide moiety, under the appropriate anhydrous conditions, with cooling if necessary, for 2-8 hours or until the reaction is complete to give, followed by treatment with aqueous acid to dissociate the metal complexes and give compound (21). Alternately, the cyano group of compound (20) may be reduced by treatment with 1 atm of H 2 in the presence of Raney nickel at room temperature for 1-8 hours to give an intermediate amino compound. The intermediate amino compound may then be treated with a suitable acylating reagent, for example ethyl formate, an acyl chloride R 6 Cl, wherein R 6 is, for example, C 1 -C 8 -alkyl, substituted-C 1 -C 8 -alkyl, phenyl, substituted-phenyl, heteroaryl, substituted-heteroaryl, aryl-C 1 -C 6 -alkyl-, substituted-aryl-C 1 -C 6 -alkyl-, heteroaryl-C 1 -C 6 -alkyl-, or substituted-heteroaryl-C 1 -C 6 -alkyl-, a di-C 1 -C 8 -alkyl dicarbonate, or an appropriate carbamylating reagent, Cl CO N R 7 R 8 , for example, wherein R 7 may be H or C 1 -C 3 -alkyl-, and R 8 may be H, C 1 -C 3 -alkyl-, phenyl or substituted-phenyl.

In accordance with Scheme 8 are prepared additional compounds of Formula (I). Compound (23) is reacted with the anion of benzyl alcohol under anhydrous conditions in DMF to give the benzyloxy entermediate (24), which is treated with ammonia in the presence of a copper catalyst and heat and pressure to afford amino compound (25). Compound (25) is treated under diazotizing conditions followed by heating with aqueous acid (or altemtively by acetic anhydride and heat followed by saponification) to afford pyridinol (26). When the diazo intermediate is heated in the presence of 1,2-dimethoxyethane and a Lewis acid, intermediate (27) is obtained, which can be debenzylated by catalytic hydrogenolysis to afford pyridinol (28). The foregoing procedures are most applicable when R 2 is H, alkyl or phenyl. For R 2 is F or Cl, pyridinols (26) and (28) can be further substituted at the position para to the hydroxyl group by electrophilic aromatic substitution to provide directly R 2 F or Cl, or alternatively by a diazo coupling/hydrogenolysis sequence to install an amino substituent, which is readily converted to chloro or fluoro by well-known methods. If necessary or desired, selectively removable blocking groups, e.g. iodo, may be used at postions ortho to the hydroxyl group to achieve the desired regioselectivity for installation of R 2 . Pyridinols are then coupled with alcohols (1) according to procedures described under Scheme 1 to afford intermediates (29), which can be elaborated (e.g. N-deprotection, optionally followed by N-alkylation) to compounds of Formula (I). Alternatively, (29) is debenzylated under acidic or hydrogenolytic or electrolytic conditions to (30), which is O-alkylated with alkylating agents R 4 CH 2 -X, where X is a leaving group,to provide (31), which can be elaborated to compounds of Formula (I). Coupling of (1) to (28) provides an intermediate compound which can be similarly elaborated to compounds of Formula (I).

In Vitro Determination of Neuronal Nicotinic Receptor Binding Potencies Selectivity and Functionality

For the purpose of identifying compounds as cholinergic agents which are capable of interacting with cholinergic channel receptors in the brain, a ligand-receptor binding assay was carried out as the initial screen. Compounds of the present invention were effective at interacting with neuronal nicotinic cholinergic receptors as assayed in vitro for their ability to displace radioligand from neuronal nicotinic cholinergic channel receptors labeled with 3 H -cytisine ( 3 H -CYT) (Protocol A below).

For the purpose of directly evaluating the ability of test compounds to functionally activate or inhibit certain subtypes of neuronal nicotinic cholinergic channels, an assay to determine 86 Rb Efflux in IMR-32 cells was employed (Protocol B below).

A. Protocol For Determination of Nicotinic Cholinergic Channel Receptor Binding Potencies of Ligands

Binding of 3 H -cytisine ( 3 H -CYT) to nicotinic receptors was accomplished using crude synaptic membrane preparations from whole rat brain (Pabreza et al., Molecular Pharmacol , 1990, 39:9). Washed membranes were stored at 80 C. prior to use. Frozen aliquots were slowly thawed and resuspended in 20 volumes of buffer (containing: 120 mM NaCl, 5 mM KCl, 2 mM MgCl 2 , 2 mM CaCl 2 and 50 mM Tris-Cl, pH 7.4 4 C.). After centrifuging at 20,000 g for 15 minutes, the pellets were resuspended in 30 volumes of buffer. Homogenate (containing 125-150 g protein) was added to triplicate tubes containing concentrations of test compound and 3 H -CYT (1.25 nM) in a final volume of 500 L. Samples were incubated for 60 minutes at 4 C., then rapidly filtered through Whatman GF/B filters presoaked in 0.5% polyethyleneimine using 3 4 mL of ice-cold buffer. The filters are counted in 4 mL of Ecolume (ICN). Nonspecific binding was determined in the presence of 10 M ( )-nicotine and values were expressed as a percentage of total binding. IC 50 values were determined with the RS-1 (BBN) nonlinear least squares curve-fitting program and IC 50 values were converted to Ki values using the Cheng and Prusoff correction (Ki IC 50 /(I ligand /Kd of ligand). Alternately, data were expressed as a percentage of the total specific binding. The binding data (shown in Table 1) suggest that the compounds of the present invention have high affinity for the neuronal nicotinic cholinergic channel receptor.

B. Protocols for the Determination of Functional Effects of Cholinerzic Channel Receptor Ligands on Synaptic Transmission

Cells of the IMR-32 human neuroblastoma clonal cell line (ATCC, Rockville, Md.) were maintained in a log phase of growth according to established procedures (Lukas, 1993). Experimental cells were seeded at a density of 500,000 cells/ml into a 24-well tissue culture dish. Plated cells were allowed to proliferate for at least 48 hours before loading with 2 Ci/ml of 86 Rb (35 Ci/mmol) overnight at 37 C. The 86 Rb efflux assays were performed according to previously published protocols (Lukas, R. J., J. Pharmacol. Exp. Ther ., 265: 294-302, 1993) except serum-free Dulbecco's Modified Eagle's Medium was used during the 86 Rb loading, rinsing, and agonist-induced efflux steps.

EC 50 data and maximal responses (reported as percent relative to the response elicited by 100 M (S)-nicotine) are shown for selected compounds of the invention. The inhibition data (given for a larger number of compounds) reflect inhibition of the efflux elicited by 100 M (S)-nicotine for either a single dose (% inhibition at 1 M or at 10 M) or over a range of doses (IC 50 of inhibition). The results (also shown in Table 1) suggest that selected compounds of the present invention either activate or inhibit the initial ion flux aspects of synaptic transmission mediated by neuronal nicotinic acetylcholine receptors. This finding is in agreement with the results of others who have linked dopamine release, which is dependent upon the ion flux in synaptic transmission, to binding at nicotinic receptors (cf., for example, Lippiello and Caldwell, U.S. Pat. No. 5,242,935, issued Sep. 7, 1993; Caldwell and Lippiello, U.S. Pat. No. 5,248,690, issued Sep. 28, 1993; and Wonnacott et al., Prog. Brain Res., 79: 157-163 (1989)).

The present invention will be better understood in connection with the wing examples, which are intended as an illustration of, and not a limitation the scope of the invention.

Preparations of Starting Materials

Several starting materials are used repeatedly throughout the examples that follow. 1-Methyl-2-(S)-pyrrolidinemethanol was obtained from Aldrich Chemical Co. 1-Methyl-2-(R)-pyrrolidinemethanol was obtained from Fluka.

In the PCT Patent Application WO94 08992 of Abreo et al., published Apr. 28, 1994, are disclosed, inter alia, the (R) and (S) 1-BOC-2-(S)-pyrrolidinemethanol compounds and the (R) and (S) 1-BOC-2-(S)-azetidinemethanol compounds

The following procedures were also used to prepare starting materials.

N-BOC-(S)-proline (Sigma Chemical Co., 12.97 g, 60.02 mmol) was dissolved in anhydrous THF and brought to 0 C. with stirring. Borane/THF complex was added dropwise via syringe over a 10 minute period. The reaction mixture was stirred at room temperature for 1 hour, then the reaction was quenched slowly with saturated NaHCO 3 and stirred for an additional hour. The solvent was removed in vacuo, and the residue was diluted with H 2 O. The desired compound was extracted from the aqueous phase with Et 2 O (3 ). The organic layer was then washed with brine (2 ) dried (MgSO 4 ) and evaporated.

N-BOC-(R)-proline was converted to the desired product by procedures similar to those for the preparation of the 1-BOC-2-(S)-pyrrolidinemethanol described above.

Intermediate Compound

Intermediate Compound

To a solution of 5-bromo-6-chloro-3-(1-BOC-2-(S)-pyrrolidinylmethoxy)pyridine (500 mg, 1.28 mmol) in acetonitrile (4.0 mL) was added 4-vinylpyridine (156 mg, 1.5 mmol), palladium acetate (29.0 mg, 0.12 mmol), tri-o-tolylphosphine (156 mg, 0.12 mmol) and triethylamine (3.2 mL). The reaction mixture was heated in a sealed tube at 100 C. overnight, then cooled to room temperature. Minimum amount of saturated sodium bicarbonate was added to free the amine hydrochloride salt, and the mixture was extracted with EtOAc, dried (MgSO 4 ), and concentrated. The residue was chromatographed on a silica gel column, eluting with 4 to 50% Et 2 O in hexane) to give the title compound (282 mg). MS (CI/NH 3 ) m/z 416 (M H) .

3-Bromoquinoline (0.4 mL, 3 mmol) was dissolved in THF, and the solution was cooled to 78 C. To this solution was added t-butyllithium (4.1 mL, 7 mmol), and the reaction mixture was stirred for 20 minutes. Trimethyl borate (0.81 mL, 7.1 mmol) was added at 78 C., and the mixture was stirred and allowed to warm to room temperature. The reaction was quenched with water, and the solvents were removed under vacuum. The residue 180 mg was taken directly to the next step.

1-Methylindole (0.38 mL, 3 mmol) was dissolved in THF (10 mL), and the solution was cooled to 78 C. To this solution was added sec-butyllithium (1.9 mL, 2.5 mmol), and the reaction mixture was stirred for 20 minutes. Trimethyl borate (0.34 mL, 3 mmol) was added at 78 C., and the mixture was stirred and allowed to warm to room temperature. The reaction was quenched with water, and the solvents were removed under vacuum. The residue was taken directly to the next step.

To a suspension of 3,5-dibromopyridine (1.5 g, 6.05 mmol) and 60% NaH (307 mg, 7.7 mmol) in DMF (6 mL) was added 1-tosyl-2-(S)-pyrrolidinemethanol (1.4 g, 5.5 mmol), and the reaction mixture was stirred for 4 hours at room temperature and 1 hour at 60 C. The DMF was removed under reduced pressure, and the residue was chromatographed on a silica gel column, eluting with EtOAc/hexane 6:1 to afford the title compound (1.2 g).

5-bromo-3-(1-tosyl-2-(S)-pyrrolidinylmethoxy)pyridine from step 51b (300 mg, 10.73 mmol), boric acid (107 mg, 10.88 mmol) and Pd(0) (26 mg) were mixed together in benzene (2 mrL), and the mixture was heated at reflux for 16 hours. NaHCO 3 solution (2%, lmL) was added, and the mixture was extracted with CHCl 3 . The CHCl 3 was removed under reduced pressure, and the residue was chromatographed on a silica gel column, eluting with EtOAc/hexane 1:1 to afford the title compound (300 mg).

Intermediate Compound

(S)-Azeditinecarboxylic acid (Aldrich) was treated with di-t-butyl dicarbonate to give the 1-BOC-(S)-azeditinecarboxylic acid. This compound in turn was was dissolved in anhydrous THF and brought to 0 C. with stirring. Borane/THF complex was added dropwise via syringe over a 10 minute period. The reaction mixture was stirred at room temperature for 1 hour, then the reaction was quenched slowly with saturated NaHCO 3 and stirred for an additional hour. The solvent was removed in vacuo, and the residue was diluted with H 2 O. The desired compound was extracted from the aqueous phase with Et 2 O (3 ). The organic layer was then washed with brine (2 ) dried (MgSO 4 ) and evaporated to afford the title compound.

5-(5,5-Dimethyl-1,3-hexadienyl)-6-chloro-3-(2-(R)-pyrrolidinylmethoxy)pyridine Citric Acid Salt

Intermediate Compound

To a solution of diethyl azodicarboxylate (1.52 mL, 9.6 mmol) in THF (56 mL) was added triphenylphosphine (2.52 g, 9.6 mmol) at 0 C., and the reaction mixture was stirred for half an hour. 1-BOC-2-(S)-azetidinemethanol (1.44 g, 7.7 mmol) and 5-bromo-6-chloropyridine-3-ol (1.4 g, 6.4 mmol; prepared according to V. Koch and S. Schnatterer, Synthesis 1990, 499-501)) were then added. The reaction mixture was slowly warmed up to room temperature overnight. Solvent was removed, and the residue was chromatographed on a silica gel column, eluting with CHCl 3 :MeOH 100:1 to afford the title compound. MS (CI/NH 3 ) m/z 377/379 (M H) .

Intermediate Compound

Intermediate Compound

Following the procedure of Example 69b, except substituting 5-bromo-6-chloro-3-(1-BOC-2-(S)-pyrrolidinylmethoxy)pyridine from Example 23a for the 5-bromo-6-chloro-3-(1-BOC-2-(R)-pyrrolidinylmethoxy)pyridine of step 69b, the title compound was prepared. MS (CI/NH 3 ) lI/z 390 (M H) .

5-(2-(4-Pyridinyl)ethenyl)-6-chloro-3-(2-(S)-azetidnylmethoxy)pyridine Citric Acid Salt

3-(1-BOC-2-(S)-azetidinylmethoxy)-6-chloro-5-cyanopyridine (0.26 g, 0.80 mmol) from step 92a was stirred in the presence of Raney nickel (0.047 g, 0.80 mmol) under 1 atm of hydrogen at room temperature for 2 hours. The mixture was filtered, and the solvent was removed to give the title compound.

Following the procedure of Example 91b, substituting 5-((N-benzoylamino)methyl)-6-chloro-3-(2-(S)-azetidinylmethoxy)pyridine for the compound of 91a thereof, and carrying the reactions forward as described in Example 91b, the title compound is prepared.

Following the procedure of Example 92, replacing the 5-bromo-6-chloro-3-(1-BOC-2-(S)-azetidinylmethoxy)pyridine starting material thereof with the starting materials shown in Table xxxxx below, and replacing the benzoyl chloride of step 92c with the acylating reagent shown in Table 2, the desired compounds 94-99 having R 2 and R 6 as described in Table 2 are prepared.

Following the procedure of Example 92, replacing the 5-bromo-6-chloro-3-(1-methyl-2-(S)-pyridinylmethoxy)pyridine starting material thereof with the starting materials shown in Table xxxxx below, and replacing the benzoyl chloride of step 92c with the acylating reagent shown in Table 3, the desired compounds 100-105 having R 2 and R 6 as described in Table 3 are prepared.

The compound from step 106b above (3.0 g 15.9 mmol) was dissolved in 50 ml of HF pyridine (Aldrich) and cooled to 0 C. under nitrogen and sodium nitrite (1.09 g 15.8 mmol) was added in portions over 20 min. The reaction was heated to 50 C. for one hour, cooled to 0 C. and then basified with 20% sodium hydroxide. The aqueous phase was washed with CH 2 Cl 2 (5 100 ml), neutralized with HCl (pH 7), and extracted with EtOAc (5 100 ml). These extracts were dried (MgSO 4 ), filtered, and concentrated in vacuo yielding the title compound as a tan solid. MS (CI/NH 3 ) m/e 192/194 (M H) . 1 H NMR (DMSO-d6, 300 MHz) : 9.38 (d, J 2.6 Hz, 1H), 9.20-9.19 (d, J 2.6 Hz, 1H).

A sample of 1-BOC-2-(S)-pyrrolidinemethanol, prepared as described above, and of 3-bromo-2-fluoro-5-hydroxypyridine, prepared as in step b above, are reacted with triphenylphosphine and DEAD in THF at room temperature for 16 hours, to give the title compound.

The BOC group is removed from the compound of step 106d by treatment with TFA in CH 2 Cl 2 to give the free base of the title compound. The base is converted to the salt by treatment with hydrogen chloride saturated EtOH. The solvents are removed under vacuum to give the title compound.

The 5-cyano-6-chloro-3-(1-BOC-2-(S)-azetidinylmethoxy)pyridine of example 92a in anhydrous Et 2 O at 0 C. is treated with 1.5 equivalents of phenylmagnesium bromide in Et 2 O and stirring is maintained at 0 to 35 C. until the nitrile is largely consumed. The solvent is evaporated and the residue is treated with 2M aqueous potassium hydrogen sulfate to hydrolyze the intermediate imine. The solution is made basic with potassium carbonate and extracted with EtOAc. The combined extracts are dried (Na 2 SO 4 ) and concentrated to a residue which is chromatographed (silica gel) to afford the title compound.

5-benzoyl-6-chloro-3-(1-BOC-2-(S)-azetidinylmethoxy)pyridine from step 107a is dissolved in CH 2 Cl 2 (10 mL). The mixture is cooled to 0 C., TFA (10 mL) is added and the reaction is stirred for 45 minutes as it warms to room temperature. The mixture is concentrated in vacuo and taken up in a minimum amount of H 2 O. The aqueous mixture is basified with 15% NaOH and extracted with CH 2 Cl 2 (200 mL), which is dried (MgSO 4 ) and concentrated. The residue is chromatographed (silica gel) to afford the free amine. The isolated free amine is taken up in a minimum amount of Et 2 O, cooled to 0 C., and treated with HCl in EtOH to afford the hydrochloride salt.

Following the procedure of Example 107, replacing the 5-cyano-6-chloro-3-(1-BOC-2-(S)-azetidinylmethoxy)pyridine with the starting material compounds shown in Table 3 and replacing the phenylmagnesium bromide reagent thereof with a R 3 -Mg-Br Grignard reagent or a R 5 -Li reagent shown in Table 4 below, the desired compounds 108-111 having R 2 and R 5 as described in Table 4 are prepared.

Following the procedure of Example 107, replacing the 5-cyano-6-chloro-3-(1-BOC-2-(S)-azetidinylmethoxy)pyridine with the starting material compounds shown in Table 3 and replacing the phenylmagnesium bromide reagent thereof with a R 3 -Mg-Br Grignard reagent shown in Table 5 below, the desired compounds 112-117 having R 2 and R 5 as described in Table 5 are prepared.

Following the procedure of Example 18, replacing the styrene starting material thereof with the starting material compounds shown in Table 7, then hidrogenating the product thereof with palladium on charcoal according to the procedure of Example 21 the desired compounds 118-121 having R 2 and R 3 as described in Table 6 are prepared.

Following the procedure of Example 7, replacing the 5-bromo-3-(1-methyl-2-pyrrolidinylmethoxy)-pyridine thereof with the starting material compound in Table 7 and replacing the 3-pyridinyltributyltin reagent thereof with the shown in Table 7, the desired compounds 122-130 having R 2 and R 3 as ed in Table 7 are prepared.

Following the procedure of Example 18, replacing the styrene starting material thereof with the starting material compounds shown in Table 8, then hidrogenating the product thereof with palladium on charcoal according to the procedure of Example 21 the desired compounds 131-133 having R 2 and R 3 as described in Table 8 are prepared.

Following the procedure of Example 3, replacing the 5-bromo-3-(1-methyl-2-(S)-pyrrolidinylmethoxy)-pyridine thereof with the starting material compound shown in Table 7 and replacing the 3-methoxyphenylboronic acid reagent thereof with the reagent shown in Table 9, the desired compounds 134-137 having R 2 and R 3 as described in Table 9 are prepared.

The product from step a above (760 mg, 1.93 mmol) in MeOH (20 mL) was added potassium carbonate (293 mg, 2.12 mmol). It was allowed to stir at room temperature for 6 h. EtOAc was added. The reaction mixture was washed with H 2 O (3 ). The organic layers were dried (MgSO 4 ) and concentrated to afford the crude product (610 mg, 98%).

The compound of 196a (17.1 g, 78.8 mmol) was dissolved in HOAc (50 mL) and water (150 mL) and treated with iron powder (13.3 g, 236 mmol) added in portions over 2 h. The reaction was filtered and the filtrate was extracted with EtOAc. The filter cake was also washed with EtOAc and all EtOAc washings were combined and extracted with 1 M bicarbonate followed by water and dried (MgSO 4 ) to provide 12.65 g (67.6 mmol, 86%) of amine product: TLC R f 0.25 (2:1 hexanes/EtOAc); MS (CI/NH 3 ) m/z 187 (M H) , 204 (M NH 4 ) .

Triphenylphosphine (6.3 g, 24 mmol) was dissolved in THF (100 mL), cooled to 0 C. and treated with diethylazodicarboxylate (3.8 mL, 24 mmol) for 15 min. Then the compound of 196d (3 g, 16 mmol) followed by 1-BOC-2-(S)-azetidinemethanol (3.4 g, 18 mmol) was added and the reaction was allowed to warm slowly to ambient temperature. After 3 days, the solvent was evaporated and the crude residue was chromatographed (silica gel; hexanes/ EtOAc, 4:1) to provide an oil. The product was contaminated with a byproduct related to the DEAD reagent and was taken forward as is; the subsequent allowed isolation of the byproduct and revealed 35 wt % contamination therefor the calculated yield was 70% (4.0 g, 11.2 mmol): TLC R f 0.6 (1:1 hexanes/EtOAc); MS (CI/NH 3 ) m/z 357 (M H) .

NaH (60% in mineral oil) (40.9 g, 1.03 mol) in 800 mL of DMF was cooled to 0 C. and benzyl alcohol (105 mL, 1.02 mol) was added slowly. The reaction mixture was stirred for 1 h at 20 C., then 3,5-dibromopyridine (200.4 g, 846 mmol) was added and the mixture was stirred for 16 h. The mixture was quenched with saturated NH 4 Cl (500 mL), diluted with 400 mL of water and extracted with Et 2 O (5 300 mL). The combined Et 2 O extracts were washed with 50% brine (6 300 mL) and dried (MgSO 4 ). The solvent was evaporated in vacuo and the crude product was recrystallized from Et 2 O to afford 161 g (72 %) of the title product: mp 63-68 C.; 1 H NMR (CDCl 3 , 300 MHz) 5.1 (s, 1H), 7.35-7.50 (m, 6H), 8.27-8.37 (m, 2H); MS (CI/NH 3 ) m/z 264,266 (M H) .

1-BOC-(S)-azetidinemethanol (36.5 g, 0.195 mol) was dissolved in CH 2 Cl 2 (195 mL) followed by addition of NEt 3 (35.6 ml, 0.255 mol) and then toluenesulfonyl chloride (48.5 g, 0.254 mol). The resulting mixture was stirred at room temperature for 16 h. A 10% solution of NaOH was added rapidly and the mixture stirred for 1 h. After phase separation, the aqueous phase was extracted with additional CH 2 Cl 2 , combined with the organic phase, and then washed with NaHCO 3 solution and brine. The resulting solution was dried (MgSO 4 ), filtered, and concentrated in vacuo to give 1-BOC-2-(S)-azetidinemethyl-p-toluenesulfonate (63.1 g, 94.8%).

To a stirred solution of the 5-acetoxy-2-fluoro-3-ethenylpyridine from b above (1.40 g, 7.70 mmol) in MeOH (50 mL) was added K 2 CO 3 (0.53 g, 3.90 mmol). The reaction mixture was allowed to stir at room temperature 24 h. The solvent was evaporated and the residue was diluted with Et 2 O (100 mL) and water (100 mL). The phases were separated and the aqueous phase was neutralized (pH 7) by the addition of 1 N aqueous HCl, and extracted with Et 2 O (2 100 mL). The combined ethereal extracts were washed with brine (50 mL), dried (MgSO 4 ), and the solvent was evaporated. The crude product was purified by column chromatography (silica gel; EtOAc/hexane, 4:6) to afford the desired material as an off-white solid (0.81 g, 76%): 1 H NMR (CDCl 3 , 300 MHz) 5.50 (d, J 11.0 Hz, 1H), 5.87 (d, J 17.5 Hz, 1H), 6.75 (m, 1H), 7.72 (dd, J 3.0, 5.0 Hz, 1H), 7.69 (m, 1H); MS (CI/NH 3 ) m/z 140 (M H) , 157 (M NH 4 ) .