Field of the Invention This invention relates to compositions and methods for suppressing appetite, modifying macronut- rient preferences, and effecting weight loss in a sub¬ ject animal.

Background of the Invention

Compounds containing the benzothiophene nucleus exhibit a broad range of pharmacological activities. Triaryl ethylene derivatives exhibiting estrogenic and/or estrogen antagonist properties have shown anti-fertility properties in rodents, as have sev¬ eral 4-aminobenzo[b]thiophenes, tetrahydrodibenzothio- phene carboxylic acids, and 4-keto-4,5,6,7-tetrahydro- benzo[b]thiophenes. A number of phenyl- and thienyl- substituted benzo[b]thiophene acetic acids, 2-aryl- benzo[b]thiophen-3(2H)-one 1,1-dioxides, benzo[b]- [2,3-d]pyrimidines, and benzo[b]thiophene 2- and 3-

acetic acid derivatives exhibit antiinflammatory activity in rodents.

Useful anti-adrenergic and anti-anginal activities have been attributed to 3-(4-dialkylamino- alkoxy-3,5-disubstituted)benzoylbenzo[b]thiophenes and anti-hypertensive and/or diuretic properties to certain 2-imidazolinylaminobenzo[b]thiophenes, cyclopentafb]- benzo[b]thiophen-3-ones and sulfonamide derivatives of 2,3-dihydrobenzo[b]-thiophene 1,1-dioxides. Sulfur analogs of several thiosemicarbazone derivatives, including a series of benzo[b]thiophene-2- and 3-carbox- aldehyde thiosemicarbazones exhibit significant anti- fungal and anti-viral activities; benzo[b]thiophene analogs of 3-methoxymethyl-7-acylaminocephalosporins reportedly possess antibacterial actions.

Centrally active benzo[b] hiophene derivatives include isosteres of psilocin and 5-hydroxytryptamine (serotonin). Several lH-[l]benzo[b]thieno[2,3-c]pyran derivatives exhibit antidepressant activity, as do amides of benzo[b]thiophene-2-carboxylic acids such as 3-bromo-2-( -morpholinoethyl)benzo[b]thiophene carbox- imide, which additionally possesses anticonvulsant prop¬ erties. Central nervous system depressant activity has been claimed for a number of N-[(4-phenyl-l-piper- azinyl)alkyl]benzo[b]thiophene-2-carboxyamide and 3- substituted-2,3-dihydro-lH-cyclopenta[b]benzo[b]thio- phenes; amides of 2-(3-benzo[b]thienyl)ethyl mine and a series of 4-benzo[b]thienyloxyalkyl amidoxines report¬ edly reduce aggressive behavior in rodents (T. Bosin and E. Campaigne, Adv in Drug Res (1977), 11:191-233) .

The compounds of the present invention are 1,2,3,4-tetrahydrobenzo[b]thienopyridine derivatives, sulfur-containing analogs of tetrahydronorharman, a naturally-occurring plant and animal alkaloid. Little is known about the biological activities of these benzo- thiophene derivatives apart from the fact that they

reportedly inhibit antisocial behavior, cause central nervous system depression, and reduce spontaneous motor activity in several mammalian species (U.S. Pat. No. 3,636,218; U.S. Pat. No. 3,518,278; Miller et al, The Pharmacologist (1971) 13.207) .

Central monoamine neurotransmitter systems have long been implicated in the regulation of ingestive behavior. Virtually all anorectic agents in current clinical use act upon catecholamine and/or serotonergic mechanisms. Those acting principally upon catecholamine systems possess significant stimulant properties; those acting on serotonergic systems do not. Although stimulant agents rsduce food consumption and can lead to significant short-term weight loss, their ethical forms are more frequently abused and produce a higher inci¬ dence of adverse side effects than their non-stimulant counterparts.

1,2,3,4-tetrahydrobenzo[b]thieno[2,3-c]- pyridine and several substituted derivatives have been disclosed in U.S. patents 3,636,218 and 3,518,278 and claimed as CNS depressants and tranquilizing agents. However, there is no disclosure of anorectic activity.

Disclosure of the Invention 1,2,3,4-tetrahydrobenzo[b]thienopyridine derivatives are unique in that they exhibit pharmaco¬ logical properties consistent with those of both stimulant and non-stimulant anorectics. We have now found that these compounds are weak inhibitors of both catecholamine and 5-hydroxytryptamine uptake in crude brain synaptosomal preparations. We have discovered these compounds to be anorexigenic, and, at low doses, to selectively suppress carbohydrate cravings without necessarily influencing appetite for other macro- nutrients.

The present invention provides a pharmaco¬ logical method for suppressing appetite and altering macronutrient preferences in-mammals by administering an effective amount of a l,2,3,4-tetrahydrobenzo[b]thieno- [2,3-c]pyridine compound. If desired, one may addition¬ ally coadminister an amount of mild stimulant to counteract CNS depression, which may appear as a side effect in some instances. Administration of these com¬ pounds according to the invention produces dose-related decrements of food intake, and can selectively suppress appetite for specific macronutrients, e.g., carbo¬ hydrates. Because of their anorexigenic properties, compounds of the present invention are useful as dieting aids in both medicinal and veterinary practice. Due to their special ability to selectively inhibit carbo¬ hydrate intake at low doses, compounds of the present invention are additionally useful for treating indi¬ viduals with abnormal or excessive appetite for carbo¬ hydrate-rich foods. This activity correlates with activity against chemical dependency conditions, such as alcoholism, tobacco addiction, and opiate addiction, and also with activity against obsessive-compulsive behav¬ ior. The present invention thus further comprises a method for treating substance cravings and bulemic syn- dromes in which a subject (not necessarily obese) experiences powerful urges to consume carbohydrate-con¬ taining foods at specific times of the day or night.

Thus, one aspect of the invention is a method for suppressing feeding behavior in a mammal in need thereof, which comprises administering to said mammal an effective amount of a compound of formula 1 _^ :

wherein R. and R ₃ are each independently H, hydroxy-alkyl, alpha-cyanoalkyl, S0 ₃ H, S0 ₂ NH ₂ , or C(0)R, where R is OH, NH _2. lower alkoxy, benzyloxy, or aliphatic amino acyl; is H, lower alkyl, benzyl, succinyl, or C(0)R ₄ , where R. is H, lower alkyl, hydro¬ carboxy-lower alkylene, or lower alkoxycarboxy-lower alkylene; and R _ζ , R _g , R_, and R„ are each independently H, halo, lower alkyl, hydroxy, lower alkoxy, or two adjacent radicals form methylenedioxy or ethylenedioxy. Another aspect of the invention is a composi¬ tion useful for suppressing feeding behavior in a mam¬ mal, which composition comprises a pharmaceutically acceptable excipient and a compound of formula 1_ wherein ^l l' R ₂ , and R ₃ are not simultaneously H.

Another aspect of the invention is the method for altering macronutrient preference by administering an appetite-altering amount of a compound of formula 1 to a mammal in need thereof. Another aspect of the invention is a composition for altering macronutrient preference in a mammal which comprises a pharmaceuti¬ cally acceptable excipient and an appetite-altering amount of a compound of formula _1 wherein R., R ₂ , and R, are not simultaneously H.

Another aspect of the invention is the method for suppressing substance cravings or substance abuse by administering an appetite-altering amount of a compound of formula 1 to a mammal in need thereof. Another aspect of the invention is a composition for suppressing substance cravings or substance abuse in a mammal which comprises a pharmaceutically acceptable excipient and an appetite-altering amount of a compound of formula .1 wherein R-, R ₂ , and R, are not simultaneously H.

Another aspect of the invention is the method for suppressing obsessive-compulsive behavior by admin¬ istering a behavior-altering amount of a compound of formula 1 to a mammal in need thereof. Another aspect of the invention is a composition for suppressing obsessive-compulsive behavior in a mammal which com¬ prises a pharmaceutically acceptable excipient and a behavior-altering amount of a compound of formula 1 _, wherein R-, R ₂ , and R~ are not simultaneously H.

Modes of Carrying Out the Invention

A. Definitions

The term "compound of formula 1." refers to compounds of the formula

and its pharmaceutically acceptable acid addition salts, wherein R. and R ₃ are each independently H, hydroxy- alkyl, alpha-cyanoalkyl, SO-,H, S0 ₂ NH ₂ , or C(0)R, where R is OH, NH ₂ , lower alkoxy, benzyloxy, or aliphatic amino acyl; R~ is H, lower alkyl, benzyl, succinyl, or

C(0)R ₄ , where R. is H, lower alkyl, hydrocarboxy-lower alkylene, or lower alkoxycarboxy-lower alkylene; and R _e , R-, R ₇ , and R„ are each independently H, halo, lower alkyl, hydroxy, lower alkoxy, or two adjacent radicals form methylenedioxy or ethylenedioxy.

The term "lower alkyl" as used herein refers to saturated monovalent hydrocarbon radicals having from 1 to 6 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, butyl, hexyl, and the like. The term "lower alkoxy" refers to radicals of the form -OR, where R is lower alkyl as defined above. Suitable lower alkoxy radicals include methoxy, ethoxy, propoxy, and the like.

The term "hydroxy-alkyl" refers to a lower alkyl group wherein one hydrogen atom is replaced with a hydroxy radical, for example, hydroxymethyl, 2-hydroxy- ethyl, 1-hydroxyethyl, 3-hydroxypropyl, 2-methyl-2- hydroxypropyl, and the like.

The term "alpha-cyanoalkyl" refers to a radical of the form -CH(CN)R, where R is lower alkyl as defined above. Exemplary alpha-cyanoalkyl radicals include without limitation cyanomethyl, 1-cyanoethyl, 1- cyanopropyl, l-cyano-3-methylbutyl, 1-cyanohexyl, and the like. The term "halo" means fluoro, chloro, bromo, or iodo.

The terms "methylenedioxy" and "ethylenedioxy" refer to divalent radicals of the formula -0-CH ₂ -0- and -0-CH ₂ CH ₂ -0-, respectively. When two adjacent radicals are methylenedioxy or ethylenedioxy, a five or six _r

membered ring is formed. "Two adjacent radicals" means R _g and Rg, Rg and R_, or R_ and R„.

The term "aliphatic amino acyl" refers to radicals derived from commonly-available amino acids which are fully saturated. Specifically, aliphatic amino acyl refers to glycyl, alanyl, leucyl, isoleucyl, valyl, and norleucyl.

The term "hydrocarboxy-lower alkylene" refers to radicals of the form -(CH Δ _n )'nCOOH, where n is an inte- ger from 0 to 6. Thus, where R ₂ is C(0)R ₄ and R. is hydrocarboxy-lower alkylene, suitable radicals will include oxalyl, malonyl, succinyl, glutaryl, and adipoyl.

The term "alkoxycarboxy-lower alkylene" refers to radicals of the form -( ^v CH 1 _n ) 'nCOOR, where n is an inte- ger from 0 to 6 and R is lower alkyl as defined above. Thus, where R ₂ is C(0)R ₄ and R ₄ is alkoxycarboxy-lower alkylene, suitable radicals will include methyloxalyl, methylmalonyl, ethylmalonyl, propylsuccinyl, and the like.

The term "feeding behavior" as used herein refers to food intake and associated behavior. "Sup¬ pression" of feeding behavior refers to reduction of feeding behavior to 80% or less of control behavior. The term "effective amount" refers to the amount of a selected compound of formula 1 _^ which is nec¬ essary to cause suppression of feeding behavior. The precise amount required will vary depending upon the particular compound selected, the age and weight of the subject, route of administration, and so forth, but may easily be determined by routine experimentation. Suit¬ able experiments are described in the Examples. In gen¬ eral, however, an effective amount will range from about 0.1 g/Kg to about 100 mg/Kg, preferably about 1 mg/Kg to about 30 mg/Kg, more preferably about 1.5-12 mg/Kg.

The term "appetite-altering amount" refers to the dosage of compound required to alter the appetite for carbohydrates experienced by the subject animal, i.e., to alter the subject's macronutrient preferences. The. term "appetite-altering amount" also applies to the quantity required to effect a change in chemical depend¬ ency; in other words, a therapeutic amount in the treatment of e.g., alcohol, tobacco, narcotic or opiate addiction. The precise appetite-altering amount required will vary with the particular compounds employed, the species, age and condition of the subject to be treated. However, the amount may be determined by one of ordinary skill in the art with only routine experimentation, following methods known in the art, and disclosed below. In general, an appetite-altering amount will be roughly one half to one tenth the effec¬ tive amount described above. Thus, the appetite- altering amount will range from about 0.01 to about 10 mg/Kg body weight, preferably about 0.5-5 mg/Kg, and most preferably about 0.5 mg/Kg.

The term "drugs of abuse" refers to those com¬ pounds other than alcohol and tobacco which present the potential for addiction and chemical dependency, such as opiates (e.g., heroin, morphine, etc.), alkaloids (e.g., cocaine), marijuana, peyote, and the like.

The term "obsessive-compulsive behavior" refers to actions and/or thoughts which a mammal experi¬ ences on a frequent or repetitive basis with little or no volitional control. "Habits" are a very mild, sub- clinical form of such behavior, but are generally not considered obsessive-compulsive behavior until they become socially debilitating. Subjects exhibiting obsessive-compulsive behaviors are generally aware of their behavior and its abnormality, but are unable to consciously modify their behavior. Examples of obsessive-compulsive behavior include compulsive hand-

washing, obsessive counting, continual hand-wringing, and the like. A "behavior modifying amount" refers to the amount of a compound of formula 1 _^ which is necessary to assist a subject in regaining volitional control, so that an obsessive-compulsive behavior may be consciously suppressed. The behavior modifying amount will gener¬ ally be similar to the amount needed for appetite sup¬ pression.

The term "pharmaceutically acceptable" refers to a compound, salt, or excipient which is not unaccept- ably toxic to the subject to which it is administered. Pharmaceutically acceptable salts include inorganic anions such as chloride, bromide, iodide, sulfate, sulfite, nitrate, nitrite, phosphate, and the like, and organic anions such as acetate, malonate, pyruvate, pro ionate _r cinnamate, tosylate, and the like. Pharma¬ ceutically acceptable excipients are described at length by E.W. Martin, in "Remington's Pharmaceutical Sciences" (Mack Pub. Co.) . The term -"pharmaceutically acceptable carrier" refers to any generally acceptable excipient that is relatively inert, non-toxic, and non-irritating. As the compositions of the invention are well suited to oral administration, preferred carriers will facilitate for- m lation in tablet or capsule form. Exemplary carriers include calcium carbonate, sucrose, dextrose, mannose, albumin, starch, cellulose, silica gel, polyethylene glycol (PEG) , dried skim milk, rice flour, magnesium stearate, and the like. Carriers for parenteral admin- istration include, without limitation, aqueous solutions of dextrose, saline, pure water, ethanol, glycerol, propylene glycol, peanut oil, sesame oil, polyoxy- ethylene-polyoxypropylene block polymers, and the like. Other suitable excipients include saline. Ringer's solu- tion, dextrose solution, and solutions of ethanol, .glu¬ cose, sucrose, dextran, mannose, mannitol, sorbitol,

polyethylene glycol (PEG), phosphate, acetate, gelatin, collagen, Carbopol®, vegetable oils, and the like. One may additionally include suitable preservatives, stabi¬ lizers, antioxidants, antimicrobials, and buffering agents, for example, BHA, BHT, citric acid, ascorbic acid, tetracycline, and the like. Suitable formulations and additional carriers are described in "Remington's Pharmaceutical Sciences", (17th Ed., Mack Pub. Co., 1985).

The term "mild stimulant" as used herein refers to those pharmaceutical agents useful for counteracting mild CNS (central nervous system) depres¬ sion, such as caffeine, dyphylline, oxtryphylline, theo- phylline, deanol acetamidobenzoate, methylphenidate hydrochloride, and the like. Caffeine is presently pre¬ ferred.

B. General Method

The invention relates to 1,2,3,4-tetrahydro- benzo[b]thieno[2,3-cJpyridine and substituted derivatives and their use as appetite suppressants. The pharmaceutical compositions of the present invention contain, as active ingredients, one or several compounds of the following formula:

wherein R, and R^ are each independently H, hydroxy-alkyl, alpha-cyanoalkyl, S0-,H, S0 ₂ H ₂ , or C(0)R,

where R is OH, NH ₂ , lower alkoxy, benzyloxy, or aliphatic amino acyl;

R ₂ is H, lower alkyl, benzyl, succinyl, or C(0)R., where R ₄ is H, lower alkyl, hydrocarboxy-lower alkylene, or lower alkoxycarboxy-lower alkylene; and

R _ς , Rg, R_, and Rg are each independently H, halo, lower alkyl, hydroxy, lower alkoxy, or two adja¬ cent radicals form methylenedioxy or ethylenedioxy. These compounds may be prepared, for example, by the following methods.

Preparation;

Basic starting materials used in the prepara¬ tion of the above-mentioned compounds may include 3-(2- aminoethyl)benzo[b]thiophenes of formula 2 \

in which R ₅ _ _o are as previously defined. The ethylamines may be prepared from 3-(2-chloromethyl)- benzo[b]thiophenes and the corresponding cyano compounds by any of several conventional methods described in the literature. (S. Avakian et al, J Am Chem Soc (1948) 7Tj:3075-76; W. Herz, J Am Chem Soc, 72:4999 (1950); Campaigne and Neiss, J Heterocvclic Chem, 2 _^ :231 (1965); Campaigne and Neiss, J Heterocyclic Chem, 3^6 (1966); Campaigne et al., J Med Chem, _11:1049 (1968); Campaigne and Homfeld, J Heterocvclic Chem, 16_:1321 (1979)). • One synthetic process is illustrated in Scheme I below.

Scheme I

R 8

A convenient alternative method for preparing compounds of formula 2 _^ is that of Campaigne and Homfeld, J Heterocyclic Chem (1979) _1(5:1321. This method is presently preferred. A substituted thiophenol is con- densed with ethyl 4-chloroacetoacetate and the product then cyclized to the correspondingly substituted ethyl 3-(benzo[b]thienyl)acetate using polyphosphoric acid. This product is ammonolyzed to the corresponding substi¬ tuted acetamide which is then reduced with borane in THF to the appropriate 3-(2-aminoethyl)benzo[b]thiophene of formula 2_. The process is illustrated in Scheme II below.

Scheme II

RB

Compounds of the present invention may be pre¬ pared from the aforementioned starting materials by sev¬ eral methods described in the literature (Campaigne and Homfeld, J Heterocyclic Chem, 16.:1321 (1979); U.S. pat¬ ent No. 3,636,218). One convenient method involves con¬ densation of substituted ethylamine starting materials with formaldehyde to produce the methylene-bis compound which can be acid hydrolyzed to the 1,2,3,4-tetrahydro- benzo[b]thieno[2,3-c]pyridine derivative. The process

the 1,2,3,4-tetrahydro- benzo[b]thieno[2,3-c]pyridines may be prepared by con¬ tacting the free base with a suitable non-toxic acid. Exemplary non-toxic acids include mineral acids such as hydrochloric acid, phosphoric acid, phosphorus acid, and the like, as well as organic acids including, for example, acetic acid, citric acid, maleic acid, tartaric acid, and benzoic acid.

Administration:

The present invention comprises, in one aspect, a method of suppressing feeding behavior in animals employing l,2,3,4-tetrahydrobenzo[b]thieno- [2,3-c]pyridine derivatives of formula JL. In another aspect, the present invention comprises a method of

altering macronutrient appetite in animals by adminis¬ tering compounds of formula .1. Another aspect of the invention is the method of suppressing substance crav¬ ings or abuse by administering compound of formula .. Another aspect of the invention is the method of sup¬ pressing obsessive-compulsive behavior by administering a compound of formula -. These compounds are adminis¬ tered topically, or by parenteral means, including sub¬ cutaneous and intramuscular injection, implantation of sustained-release depots, intravenous injection, intra- nasal administration, and the like. Such compositions may be aqueous solutions, emulsions, creams, ointments, suspensions, gels, liposomal suspensions, and the like. Alternatively, one may incorporate or encapsulate the compound of formula 1 in a suitable polymer matrix or membrane, thus providing a sustained-release delivery device suitable for implantation near the site to be treated locally. Other devices include indwelling cath¬ eters and devices such as the Alzets minipump. A thor- ough discussion of pharmaceutically acceptable excipients is available in "Remington's Pharmaceutical Sciences" (Mack Pub. Co.).

In an additional aspect of the present inven¬ tion, administration of 1,2,3,4-tetrahydrobenzo[b]- thieno[2,3-c]pyridines is accompanied by administration of a mild stimulant such as caffeine. The coadministra- tion of the mild stimulant in safe and effective doses counters CNS depressive effects if present. Typical dosage formulations for inducing anorexia would contain from 5-25 mg of a compound of formula 1 as a pharmaceu¬ tically acceptable salt in combination with 25-50 mg caffeine. Typical dosage formulations for altering macronutrient appetite would contain from 0.1-5 mg of the compound as a pharmaceutically acceptable salt in combination with 5-20 mg caffeine. One or more dosage forms may be administered daily; however, the amount of

compound of formula 1 administered will not normally exceed about 100 mg/Kg.

C. Examples The following examples are presented to illustrate the present invention, and are not intended to limit the same.

Example 1 (Preparation of Compounds)

(A) 6-Methyl-l,2,3,4-tetrahydrobenzo[b]- thieno[2,3-c]pyridine hydrochloride was prepared as follows: 4-Thiocresol (10 mol, 1.24 g) was dissolved in 1.2 mL pyridine under a nitrogen atmosphere, and ethyl 4-chloroacetoacetate (11 mmol, 1.81 g) was added dropwise with stirring. The product, ethyl 4-(4-cresyl- thio)acetoacetate began to separate immediately. Stir- ring was continued for 1 hr. Diethyl ether (4 mL) and water (3 mL) were added and the mixture was shaken and centrifuged. The organic layer was washed with 1 N HCl, dried over MgS0 ₄ , and the diethyl ether removed under vacuum. In a 50 mL round-bottomed flask fitted with a reflux condensor, polyphosphoric acid (12 g) was heated to 115+5°C with vigorous stirring, and 2.6 mL crude ethyl 4-(4-cresylthio)acetoacetate in xylene (5 mL) added slowly. After continued heating and stirring for 2.5 hrs, a further 10 mL xylene and about 15 g crushed ice were added. Following centrifugation, the organic layer was dried over MgS0 ₄ and the xylene removed under vacuum. The residue was shaken with 50 mL petroleum ether (60-80°C b.p. ) :dichloromethane:acetonitrile (25:2:1, v:v:v) . Two layers separated on standing. The top layer (about 95% of the total volume) was reduced to

about 2 mL under vacuum, the solution clarified by addi¬ tion of chloroform (about 2 mL) , and the solution applied to a silica gel column (250 x 25 mm, Merck G-60, 40-63 um) . The material was eluted with petroleum ether (60-80°C b.p. ) :dichloromethane:acetonitrile (25:2:1, v:v:v), and ethyl 3-(5-methylbenzo[b]thienyl)acetate was collected from 150-500 mL eluate.

The eluate was evaporated under vacuum, and the product redissolved in 11 mL methanol, followed by addition to 44 mL anhydrous ethylene glycol saturated with ammonia. The mixture was stirred at ambient tem¬ perature overnight, regassed with ammonia for 10 min, and stirred for a further 24 hr. Water (120 mL) was added with swirling, and the off-white crystals of 3-(5- methylbenzo[b]thienyl)acetamide were filtered, washed with water, and dried over P- _j O,..

3-(5-Methylbenzo[bjthienyl)acetamide (4 mmol, 821 mg) was dissolved in 20 mL sodium-dried THF under nitrogen, and 10 mL 1 M borane-THF complex in THF added dropwise. The mixture was heated at reflux for 4 hr, and the THF then removed under vacuum. Next, 40 mL diethyl ether was added, followed by dropwise addition of 2.5 mL cone. HCl with shaking. The mixture was then basified with 1 N NaOH (40 mL) and extracted with diethyl ether (3 X 40 mL) . The pooled ether extracts were dried over MgS0 ₄ , filtered, and gassed with dry HCl until no more precipitation of 3-(2-aminoethyl)-5- methylbenzo[b]thiophene hydrochloride was observed. 3-(2-Aminoethyl)-5-methylbenzo[b]thiophene hydrochloride (2 mmol, 402 mg) was dissolved in 50% aqueous acetic acid (3.6 mL) , and 37% aqueous formalde¬ hyde (1.8 mL) was added. The mixture was heated at reflux for 1 hr, then added to 44 mL 1 N NaOH. The resulting creamy precipitate of N,N'-methylene-bis-(6- methyl-1,2,3,4-tetrahydrobenzo[b]thieno[2,3-c]pyridine was filtered, washed with water, and dissolved in 71 mL

1 N HCl. This solution was distilled to 35 mL, fil¬ tered, basified with 10 N NaOH, and extracted with diethyl ether (3 X 60 mL) . The combined ether extracts were dried over MgS0 ₄ , filtered, and gassed with dry HCl to afford a creamy precipitate of 6-methyl-l,2,3,4- tetrahydrobenzo[b]thieno[2,3-c]pyridine hydrochloride (R, ₅ = R ₇ _g - H, Rg = CH ₃ ), which was recrystallized from isopropanol.

Calculated for C ₁₂ H ₁₄ NSC1 (%): C-60.11; H- 5.89; N-5.84; S-13.37; Cl-14.79. Found: C-60.36; H-5.75; N-5.68; S-13.53; Cl-14.65.

(B) 1,2,3,4-Tetrahydrobenzo[b]thieno[2,3-c]- pyridine-3-carboxylic acid is prepared as follows:

A vigorously-stirred mixture of benzothiophene (100 mmol, 13.4 g) and 37% aqueous formaldehyde (15 mL) is gassed with dry HCl over an ice bath. After 6 hr, ice water (75 mL) is added, and the mixture extracted with diethyl ether (3 X 100 mL) . The combined ether extracts are washed with saturated NaHC0 ₃ , and dried over MgS0 ₄ . The ether is removed under vacuum, and the product 3-chloromethylbenzo[b] hiophene distilled under vacuum and crystallized from petroleum ether (b.p. 30- 60°C).

A mixture of 3-chloromethylbenzo[b]thiophene (50 mmol, 9.2 g) , diethylformamidomalonate (50 mmol,

10.2 g) , and sodium ethoxide (50 mmol, 3.4 g) in ethanol (100 mL) is heated at reflux for 3 hr. Water (1 L) is added, and the mixture extracted with diethyl ether (3 X 1 L) . The combined ether extracts are dried over MgSO., filtered, and the ether removed under vacuum. The product, diethyl (3-benzo[b]thienyl)formamido malonate, is crystallized from benzene-petroleum ether (b.p. 60- 80°C) . A mixture of diethyl (3-benzo[b]thienyl)form- amido malonate (23 mmol, 8 g) and cone. HCl (80 mL) is heated at reflux for 10 hr, and the resulting solution

evaporated to dryness to provide alpha-amino-beta-(3- benzo[b]thienyl)propionic acid hydrochloride.

A solution of alpha-amino-beta-(3-benzo[b]- thienyl)propionic acid hydrochloride (15.5 mmol, 4 g) in 50% aqueous acetic acid (80 mL) is stirred with 37% aqueous formaldehyde (12 mL) at ambient temperature overnight. The precipitated product, 1,2,3,4-tetra- hydrobenzo[b]thieno[2,3-c]pyridine-3-carboxylic acid (R._ ₂ = R _ ₈ = H, R ₃ = COOH) was filtered, washed with water, and dried over P ₂ O _g . Thin layer chromatography on silica gel (Whatman LHP-K) with methyl acetate:methanol:cone, ammonia (5:5:1 v:v:v) as mobile phase yielded a single spot (visualized with iodine vapor) at R _f 0.5, which did not respond to ninhydrin. (C) Methyl l,2,3,4-tetrahydrobenzo[b]thieno-

[2,3-c]pyridine-3-carboxylate hydrochloride was prepared as follows:

A suspension of l,2,3,4-tetrahydrobenzo[b]- thieno[2,3-c]pyridine-3-carboxylic acid (6.4 mmol, 1.5 g) in dry methanol (125 mL) was semi-saturated with dry HCl, and then heated at reflux for 24 hrs, cooled, and filtered. The filtrate was dried under a stream of nitrogen, and the residue crystallized from methanol/ ethyl acetate to yield methyl 1,2,3,4-tetrahydrobenzo- [b]thieno[2,3-c]pyridine-3-carboxylate hydrochloride

(R ₁ _ ₂ = Rc o ^{= H} ' ^R 3 ⁼ COOMe). Thin layer chromatogra¬ phy on silica gel (Whatman LHP-K) with chloroform ethanol:cone, ammonia (9:1:1 v:v:v) gave a single spot (R _f 0.8) when visualized with iodine vapor, which did not react with ninhydrin. Mass spectrometry in chemical ionization (using ammonia and electron impact modes) produced the expected parent ion at m/z 247.

(D) l,2,3,4-Tetrahydrobenzo[b]thieno[2,3-c]- pyridine hydrochloride is produced as follows:

A solution of 3-chloromethylbenzo[b]thiophene (50 mmol, 9.2 g) in 50 mL EtOH is added dropwise with

stirring to hot aqueous sodium cyanide (2.1 g in 10 mL) . After heating for 4 hr with stirring, the ethanol is boiled off while the solution volume is maintained by adding water. The solution is then cooled and extracted with diethyl ether (3 X 100 mL), and the combined extracts dried under vacuum. The residue is distilled under vacuum, and the product 3-cyanomethylbenzo[b]thio¬ phene recrystallized from benzene/petroleum ether (b.p. 60-80°C) . 3-Cyanomethylbenzo[b]thiophene (25 mmol, 4.3 g) is added to 20 mL cone. HCl at 40-45°C with stirring. Water (25 mL) is then added, and the white slurry which forms is cooled and filtered. The solid crude product is stirred with 10% NaHCO-., filtered, and the remaining solid recrystallized from water to provide benzo[b]thio- phene-3-acetamide.

A separatory funnel with a pressure-equalizing side arm is fitted with a condensor and drying tube, and attached to a 1 L flask fitted with a stopper. Benzo- [b]thiophene-3-acetamide (3 g) is placed in the separa¬ tory funnel, and 200 mL sodium-dried diethyl ether and LiAlH ₄ (2 g) placed in the flask. The ether is stirred and heated at reflux so that the benzo[b]thiophene-3- acetamide is leached into the flask. The process is continued for 8 hr. Excess LiAlH. is decomposed by dropwise addition of ethyl acetate (60 mL) followed by dropwise addition of 2.5 N NaOH. The ether layer is collected, and the remaining mixture washed with more diethyl ether. The combined ether extract is washed with brine and dried over MgS0 ₄ . After removal of the ether under vacuum, the residue is distilled under vacuum to give 3-(2-aminoethyl)benzo[b]thiophene. The hydrochloride salt is prepared by gassing a solution of 3-(2-aminoethyl)benzo[b]thiophene in diethyl ether with

dry HCl, and collecting the precipitated salt by filtra¬ tion.

The resulting 3-(2-aminoethyl)benzo[b]thio¬ phene hydrochloride is converted to 1,2,3,4-tetrahydro- benzo[b]thieno[2,3-c]pyridine following the procedure described in part A above, substituting 3-(2-amino- ethyl)benzo[b]thiophene for 5-methyl-3-(2-aminoethyl)- benzo[b]thiophene. 1,2,3,4-tetrahydrobenzo[b]thieno- [2,3-cJpyridine hydrochloride was synthesized as described in Campaigne and Homfeld, J Heterocyclic Chem (1979) 3^:1321, and exhibited a melting point of 262- 264°C.

(E) Other compounds of the invention are prepared as described above, substituting appropriate starting materials for those materials described in this example. See also S. Avakian et al, J Am Chem Soc (1948) 7):3075-76; N.B. Chapman et al, J Chem Soc (C) (1969) 1855.

Example 2

(Inhibition of Feeding Behavior) Forty-eight 70-to-80-day-old male rats (Bantin & Kingman, Fremont, California) were housed singly in suspended cages, and were acclimated to the laboratory setting for a period of 12 days prior to testing. Dur¬ ing this time, they were allowed ad libitum access to food (Ralston-Purina #5001M) and water. The room was kept at 24-27°C and maintained on a 12:12-hr light:dark schedule (0700-1900 h) . Animals matched by body weight and mean daily food intake were assigned to 4 groups (n = 12/group) . Food jars were removed at 0900 h. Twenty-four hours later, rats were injected with either sterile 0.9% saline or saline containing l,2,3,4-tetrahydrobenzo[b]- thieno[2,3-c]pyridine HCl (5, 10, or 25 mg/kg, ip) ..

Pre-weighed food jars containing meal (Ralston-Purina #5001M) were presented immediately post-injection.

These were weighed at intervals over the next 24 hours, and food consumption was calculated for each interval. Animals were provided with water in quantities suf¬ ficient for ad libitum consumption throughout the experiment.

Cumulative food intake measures are presented in Table 1. As seen, l,2,3,4-tetrahydrobenzo[b]thieno- [2,3-c]pyridine produces a dose-related decrement in food consumption. At 2 hours post-injection, food intakes for all experimental groups were significantly lower than control values. Rats in the high dose (25 mg/kg) group continued to show substantially lower cumu¬ lative food intake at 24 hours post-injection than con¬ trols.

Table 1

Cumulative Food Intake (gm)

Dose lhr 2hr 6hr 8hr 24hr 0 5.3+1.3 5.9+1.2 8.4+0.9 10. +1.6 31.2+2.1

5 1.3+0.6* 2.5+0.7* 7.4+1.6 9.2+1.6 27.4+2.8

10 0.9+0.9* 2.0±1.1* 6.3+2.3 7.7+2.5 26.8+2.8*

25 0.1+0.2* 0.2+0.3* 2.2+2.4* 3.0+2.6* 20.1+2.6*

Doses in mg/Kg

Data expressed as mean + SD. * Significantly different from control (p<0.02), by two-tailed Student t-test with critical t-values cor¬ rected for multiple contrasts.

In summary, compositions containing 5 mg/kg of 1,2,3,4-tetrahydrobenzo[b]thieno[2,3-c]pyridine, which is representative of the class, significantly reduce food consumption in rats when administered intraperiton- eally. In acute toxicity studies in mice, 1,2,3,4- tetrahydrobenzo[b]thieno[2,3-cJpyridine yields LD- _Q val¬ ues in excess of 100 mg/kg when administered intra- peritoneally and 100 mg/kg when administered by the oral route.

Example 3 (Alteration of Macronutrient Preference)

This Example demonstrates alteration of macro¬ nutrient preference in rats. Sixty adult male rats (Sprague-Dawley, 225-300 g) were acclimated to laboratory conditions for a period of 10 days, during which they were allowed unrestricted access to food (Ralston-Purina #5001M) and water. All subjects were housed in individual cages, and the animal facility was maintained on a 12:12 hour light:dark cycle at 24-27°C.

Animals were assigned to 6 groups (10 per group) , then allowed to consume, ad libitum, one of two iso-nitrogenous test diets containing either 75% or 25% carbohydrate. After 3 days, food jars were removed. After an additional 24 hours, rats were administered either saline or 1,2,3,4-tetrahydrobenzo[b]thieno- [2,3-c]pyridine (1.5 or 3.0 mg/Kg body weight), then given immediate access to the test diets. Data listed in Table 3 indicate the cumulative amount in grams (mean + SEM) of each diet consumed by the experimental and control groups during the subsequent 2-hour period.

Table 3

75% Carbohydrate 25% Carbohydrate Treatment 1 hr 2 hr 1 hr 2 hr

saline 6.6+0.5 8.4+1.6 6.4+0.5 7.5+1.7

Compound JL

(1.5 mg/Kg) 4.4+0.2* 5.8+0.8* 5.6+0.3 7.6+1.0

Compound 1 _^

(3.0 mg/Kg) 4.5+0.2* 6.0+1.3* 5.4+0.3 7.0+1.1

* indicates significantly different from control, p<0.01 by two-tailed Student's t-test.

The results indicate that animals receiving l,2,3,4-tetrahydrobenzo[b]thieno[2,3-cjpyridine consumed significantly less of the high carbohydrate diet than did controls, but consumed equivalent quantities of the low carbohydrate diet. Thus, compounds of the invention selectively suppress carbohydrate cravings when adminis¬ tered at doses lower than the dosage effective for glo¬ bal reduction in appetite. This demonstrates the util¬ ity of the present invention as a method for reducing substance cravings per se, insofar as food cravings model clinical syndromes in which there is excessive preoccupation with, or urges for, specific habituating substances (Glassman et al.. Science (1984) 226:864) . Accordingly, this Example may be taken as evidencing efficacy in the treatment of alcohol, tobacco, or drug (particularly opiate) addiction.

Example 4 (Reduction of Food Intake) Dose ranging studies showed that compounds of formula I significantly reduced food intake when admin¬ istered parenterally to rats in. amounts appreciably lower than 25 mg/Kg.

Adult male rats weighing between 250 and 300 g were acclimated to laboratory conditions for a period of 4-5 days, during which they were allowed unrestricted access to food (Ralston-Purina #5001M) and water. All animals were housed in individual cages. The animal facility was maintained on a 12:12 hr light-dark sched- ule at 22°C.

Fasted animals were sorted into groups of 10- 12 each by weight and baseline food intake. Each was then given saline containing 0-32 mg/Kg of a compound of the invention by intraperitoneal injection. After 20 minutes, animals were allowed access to food and water. Cumulative food intake was measured at 1 hour post-

injection. Doses as low as 1.5 mg/Kg significantly reduced food consumption (Table 4).

In the examples herein, compounds were admin¬ istered parenterally. In clinical usage as an anorectic agent in mammals, particularly humans, the oral, intra- nasal, or transdermal routes of administration would be preferred. In the case of intraperitoneal administra¬ tion in rodents, amounts as low as about 1.5 mg/Kg of body weight have been shown to achieve effective sig- nificant appetite suppression.

Table 4 (Reduction of Food Intake)

BZTP 1.5 3.96 + 0.47 <0.048

< ^R l-8 = H) 3.0 3.55 + 0.21 <0.0011 (HCl) 6.0 2.01 + 0.24 <6.7 x 10 -7 12.0 0.19 + 0.03 <1.1 x 10-7

0 4.19 + 0.40 NA

R ₆ = Me 3.0 2.95 + 0.31 <0.013

(HCl) 6.0 4.03 + 0.52 <0.4

12.0 2.34 + 0.22 <0.00061 24.0 0.84 + 0.23 <5.0 x 10 ^"7

0 6.02 + 0.55 NA

R ₃ = COOMe 1.0 5.77 + 0.52 <0.37

3.2 4.18 + 0.48 <0.01

10.0 3.32 + 0.20 <0.00036 32.0 2.16 + 0.31 <4.3 x 10 ^"6

0 4.30 + 0.50 NA

R ₃ = COOH 3.2 1.79 + 0.32 <0.00025 10.0 ' 1.07 + 0.16 <3.8 x 10 ^"5

32.0 1.86 + 0.29 <0.00026

56.0 1.65 + 0.10 <0.00021

R. g = H unless otherwise specified. Me = methyl p values computed by two-tailed Students t-test.

Example 5 (Subacute Administration) Compounds of the present invention retain anorectic potency when administered chronically to warm-

blooded animals. The following example illustrates this finding.

Thirty male rats (Sprague-Dawley) were used. Animals, housed under laboratory conditions described above, were adapted to a 6 hr (900-1500 h) daily feeding schedule, then given intraperitoneal injections of either normal saline (N = 15 rats/group) or 1,2,3,4- tetrahydrobenzo[b]thieno[2,3-c]pyridine (N - 15 rats/ group, 8 mg/Kg) each morning for 30 consecutive days. Injections were given immediately preceding food

(Ralston-Purina #5001) presentation. Cumulative food intake was measured at 1 (1000 h) and 6 hours (1500 h) post-injection. Findings are summarized in Table 5 below. As shown, food intake for the Compound group was significantly less than that of the Saline group at all time points. During the 30 day regimen there was no observed tolerance, nor did rebound occur following drug withdrawal. Both daily food intake and the rate of nor¬ mal weight gain were significantly reduced in the compound-treated group.

Table 5

(Food intake)

1 Hour 6 Hours

Day Saline Compound Saline Compound

1-5 9.0+0.3 4.4+0.2* 21.2+0.4 18.0+0.5*

6-10 9.4+0.4 6.5+0.2* 21.0+0.5 19.9+0.4**

11-15 8.9+0.3 6.3+0.3* 20.9+0.4 19.7+0.4*

16-20 9.1+0.3 6.6+0.2 21.0+0.4 20.1+0.4**

21-25 9.9+0.3 6.5+0.2* 21.3+0.4 20.0+0.4*

26-30 9.2+0.3 6.5+0.3* 20.7+0.3 19.6+0.4*

Values are mean + SEM. * Saline vs. Compound p < 0.05 by two-tailed Student's t-test

** Saline vs. Compound p < 0.1 by two-tailed Student's t-test

Example 6 (Formulations) (A) A representative capsule formulation is prepared as follows:

Compound 50.0 mg starch 3.0 mg magnesium stearate 3.0 mg lactose 110.0 mg polyvinylpyrro1idone 3.0 mg

The compound of formula 3., starch, magnesium stearate, lactose, and polyvinylpyrrolidone are granula¬ ted in methanol, dried, and loaded into capsules. Alternatively, the mixture may be tableted by standard methods.

(B) An oral suspension is prepared as follows:

Compound 60.0 mg fumaric acid 0.5 g

NaCl 2.0 g methyl paraben 0.1 g granulated sugar 25.5 g sorbitol (70% aq) 12.85 g

Veegum K 1.0 g flavorings 0.035 mL colorings 0.5 mg distilled water qs 100.0 mL

The components are mixed together and stored in a sealed vessel.

(D) A formulation suitable for parenteral administration is prepared as follows:

Compound 40.0 mg

KH2PO4 buffer (0.4M) 2.0 mL

KOH (IN) qs pH 7.0 water qs 20.0 mL

The components are mixed together and stored under sterile conditions.