Syntheses and ring-closures of difunctional tetrahydroisoquinolines

Starting from homoveratrylamine and N-protected amino acids 1,2,3,4-tetrahydroisoquinoline diamines were prepared by a convenient four-step process. This synthetic method was successfully extended to substituted beta-alanine and homoveratrylamine derivatives. In the case of the 1'-methyl-substituted derivatives, the reducing agent applied and the sequence of the reduction and deprotection steps proved to have marked effects on the formation of the possible diamine diastereomers. By N-amination of the corresponding amino alcohols, tetrahydroisoquinoline hydrazino alcohol regioisomers were prepared. Condensation products of the prepared tetrahydroisoquinoline 1,2- and 1,3-diamines containing a primary amino group with aromatic aldehydes proved to participate in three-component ring-chain tautomeric equilibria. The tautomeric equilibrium was sensitive to the electronic effects of the aromatic substituents, the ring size and the methyl substituents of the skeleton. By N-substitution reactions of 1-(Cbz-aminomethyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline with isocyanates and isothiocyanates, the corresponding urea or thiourea derivatives were obtained some derivatives of which showed a remarkable MDR modulating activity. By ring-closures of tetrahydroisoquinoline diamines and hydrazino alcohols with phosphorus-containing reagents, saturated 1,3,2-diazaphosphino[6,1-a]isoquinolines, and 1,3,4,2-oxadiazaphosphino[5,4-a]- and [4,5-b]isoquinolines as the first representatives of these ring systems were prepared. The conformational behaviour of these compounds was studied by NMR and X-ray diffractional analyses.     

Specific dopamine D-1 and DA1 properties of 4-(mono- and -dihydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline and its tetrahydrothieno[2,3-c]pyridine analogue

The title compounds were prepared and examined to elucidate further the structure-activity relationships of dopamine agonists related to nomifensine. Two of the compounds, 4-(3,4-dihydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline and 4-(3,4-dihydroxyphenyl)-1,2,3,4-tetrahydrothieno[2,3-c]pyridine, have been reported in the patent literature. In stimulation of rat retinal adenylate cyclase, a measure of dopamine D-1 agonist activity, the tetrahydroisoquinoline was about equipotent to dopamine. The thienyl isostere had nearly twice the potency. Both compounds were potent vasodilators in the canine renal artery, producing dilation through stimulation of DA1 type peripheral dopamine receptors. A monohydroxy analogue, 4-(3-hydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline, had only slight activity in the cyclase assay and was inactive in the canine renal artery. These results, combined with those from an earlier study, demonstrate that N-alkylation decreases both dopamine D-1 and DA-1 agonist potency, with activity ordered as H greater than methyl greater than ethyl greater than propyl. The results also demonstrate the necessity for the catechol function in this series.     

(R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl]amino-4-oxo-2,3,4,5- tetrahydro-1,5-benzothiazepine-5-acetic acid (CV-5975): a new potent and long-lasting inhibitor of angiotensin converting enzyme

The synthetic design and the biological activities of structurally new angiotensin converting enzyme (ACE) inhibitors, (R)-3-amino-4-oxo-2,3,4,5-tetrahydro-1,5-benzothiazepine-5-acetic acid derivatives, are described. A number of compounds in this series showed potent ACE inhibitory activity in vitro and in vivo. Structure-activity studies indicated that a piperidyl moiety on the amino group at the 3-position in this series conferred long-lasting ACE inhibitory activity and that the duration of activity depended on the length of the carbon chain in the 1-carboxy-omega-(4-piperidyl)alkyl group. (R)-3-[(S)-1-carboxy-5-(4-piperidyl)-pentyl]amino-4-oxo-2,3,4,5-tetrahydro- 1,5-benzothiazepine-5-acetic acid (CV-5975) was selected as the most promising ACE inhibitor for further studies because of its marked inhibitory activity.     

Hyperactivity induced by tetrahydroisoquinoline derivatives injected into the nucleus accumbens.

Several derivatives of tetrahydroisoquinoline were injected bilaterally into the nucleus accumbens of rat 2 h after a nialamide pretreatment and activity recorded in cages fitted with photocells. 1,2,3,4-Tetrahydroisoquinoline, 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline, 1,2,3,4-tetrahydro-6,7-dihydroxy-1-(3,4-dihydroxybenzyl)-isoquinoline (tetrahydropapaveroline) and 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline caused virtually no change in locomotor activity and 2-methyl-1,2,3,4-tetrahydroisoquinoline and 2-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline caused only modest hyperactivity responses. However, 3-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline and 3-methyl-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline were both shown to markedly increase activity in a dose-dependent manner. Of these two compounds, the 3-methyl-6,7-methylenedioxyderivatives was most active and equalled the effectiveness of dopamine. The responses to dopamine and to 3-methyl-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline were both threshold at 3.125 mug and maximum at 50 mug. Both effects developed within 1-2 h and persisted for at least 6 h. The hyperactivity induced by dopamine was antagonised in a dose-dependent manner by haloperidol: propranolol and aceperone were without effect. Similar results were obtained for these blocking agents against the responses to 3-methyl-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline and 2-methyl-1,2,3,4-tetrahydroisoquinoline but aceperone and propranolol, in addition to haloperidol, were shown to inhibit the hyperactivity induced by 3-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline.     

Synthesis and pharmacological evaluation of some new tetrahydroisoquinoline derivatives inhibiting dopamine uptake and/or possessing a dopaminomimetic property

As shown by structure-activity relationship studies in 8-(substituted-amino)-4-aryl-2-methyl-1,2,3,4-tetrahydroisoquinolines, the most important structural requirement for a marked antidepressant action is the presence of an ureido, (alkoxycarbonyl)amino, or [(alkylamino)acyl]amino group attached to the isoquinoline skeleton in position 8. In one of the biological tests a significant difference was found between 8-amino-4-phenyl-2-methyl-1,2,3,4-tetrahydroisoquinoline (nomifensine) and the new compounds synthesized. Nearly all compounds substituted in the amino group either decrease the spontaneous motility in mice or exert no effect on it. Two syntheses have been elaborated for the preparation of the compounds represented by the general formulas II-V where R1 = hydrogen, halogen, or methyl; Y = CONHR, OCOR, or CO(CH2)nNHR, in which R = alkyl or aralkyl or NHR = cyclic amine and n = 1-2. The syntheses start either from the corresponding 8-amino-4-aryl-2-methyl-1,2,3,4-tetrahydroisoquinolines or from the corresponding noncyclized amino alcohols. Of the compounds, 4-(p-chlorophenyl)-8-[(ethoxy-carbonyl)amino]-2-methyl-1,2,3,4- tetrahydroisoquinoline was found to possess the highest activity.     

Synthesis of 1-substituted analogues of trimetoquinol possessing differential and selective beta-adrenergic properties.

The synthesis of the 1,1-disubstituted tetrahydroisoquinoline analogues, 1-methyl-1-(3,4,5-trimethoxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline hydrochloride (2) and 1-benzyl-1-(3,4,5-trimethoxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline hydrochloride (3), is described. The profile of beta-adrenergic activity for these analogues was determined and compared to that of trimetoquinol (1) in isolated guinea pig atrial, tracheal, and rat adipocyte preparations. Unexpected selective beta1-blocking activity in guinea pig trachea was noted with analogue 3. With the exception of 2 in guinea pig atria, 2 and 3 did not possess any beta-stimulant activity. Substitution at the 1 position of trimetoquinol (1) has revealed qualitative differences in beta-adrenergic activity.     

1-［1-(6-甲氧基-2-萘基)乙基］-2-(4-硝基苄基)-6,7-二甲氧基-1,2,3,4-四氢异喹啉氢溴酸盐的光降解产物研究

研究1-［1-(6-甲氧基-2-萘基)乙基］-2-(4-硝基苄基)-6,7-二甲氧基-1,2,3,4-四氢异喹啉氢溴酸盐(编号P91024)遇光后颜色变暗的光降解产物。采用HPLC-MS及波谱分析鉴定光降解产物的化学结构，并经有机反应合成对照验证。P91024光降解的3个主要产物分别为溴化N-(4-硝基苄基)-6,7-二甲氧基-3,4-二氢异喹啉、1-［1-(6-甲氧基-2-萘基)乙基］-6,7-二甲氧基-1,2,3,4-四氢异喹啉和2-异丙基-6-甲氧基萘。     

Identification of (3R)-7-hydroxy-N-((1S)-1-[[(3R,4R)-4-(3-hydroxyphenyl)- 3,4-dimethyl-1-piperidinyl]methyl]-2-methylpropyl)-1,2,3,4-tetrahydro- 3-isoquinolinecarboxamide as a novel potent and selective opioid kappa receptor antagonist

(3R)-7-Hydroxy-N-((1S)-1-[[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl]-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic) was identified as a potent and selective kappa opioid receptor antagonist. Structure-activity relationship (SAR) studies on JDTic analogues revealed that the 3R,4R stereochemistry of the 3,4-dimethyl-4-(3-hydroxyphenyl)piperidine core structure, the 3R attachment of the 7-hydroxy-1,2,3,4-tetrahydroisoquinoline group, and the 1S configuration of the 2-methylpropyl (isopropyl) group were all important to its kappa potency and selectivity. The results suggest that, like other kappa opioid antagonists such as nor-BNI and GNTI, JDTic requires a second basic amino group to express potent and selective kappa antagonist activity in the [(35)S]GTPgammaS functional assay. However, unlike previously reported kappa antagonists, JDTic also requires a second phenol group in rigid proximity to this second basic amino group. The potent and selective kappa antagonist properties of JDTic can be rationalized using the "message-address" concept wherein the (3R,4R)-3,4-dimethyl-4-(hydroxyphenyl)piperidinyl group represents the message, and the basic amino and phenol group in the N substituent constitutes the address. It is interesting to note the structural commonality (an amino and phenol groups) in both the message and address components of JDTic. The unique structural features of JDTic will make this compound highly useful in further characterization of the kappa receptor.     

Synthese des 6,7-Dimethoxy-3-(3,4-dimethoxy-α-hydroxybenzyl)-2-methyl-1,2,3,4-tetrahydroisochinolins

Synthesis of 6,7-Dimethoxy-3-(3,4-dimethoxy-α-hydroxybenzyl)-2-methyl-1,2,3,4-tetrahydroisoquinoline The synthesis and chemical reactivity of 6,7-dimethoxy-3(3,4-dimethoxy-α-hydroxybenzyl)-2-methyl-1,2,3,4-tetrahydroisoquinoline (I) are described.     

Inhibition of phenylethanolamine N-methyltransferase (PNMT) by aromatic hydroxy-substituted 1,2,3,4,-tetrahydroisoquinolines: further studies on the hydrophilic pocket of the aromatic ring binding region of the active site

In a continuation of studies directed toward characterizing the hydrophilic pocket within the aromatic ring binding region of the active site of phenylethanolamine N-methyltransferase (PNMT), 5-, 6-, 7-, and 8-hydroxy-1,2,3,4-tetrahydroisoquinoline were prepared and evaluated as substrates and inhibitors of PNMT. In order to discern the necessity of an acidic hydrogen for interaction at this pocket the corresponding methyl ethers were also evaluated. The enhanced affinity of 7-hydroxy-1,2,3,4-tetrahydroisoquinoline (16) versus tetrahydroisoquinoline (13) itself indicates that a hydrophilic pocket exists off of carbon C7 in bound tetrahydroisoquinolines. The diminished affinity of the corresponding methyl ether is consistent with a requirement for the acidic hydrogen of 16 for interaction of the aromatic hydroxyl at this site. From the relative activities of the other regioisomeric aromatic hydroxyl-substituted tetrahydroisoquinolines, their corresponding methyl ethers, and 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, it appears that the hydrophilic pocket is spatially compact with respect to bound tetrahydroisoquinolines and is surrounded by larger areas of lipophilic character. To allow a comparison of the results of this study with previous data on bound beta-phenylethylamines, the methyl ethers of 5-, 6-, 7-, and 8-hydroxy-exo-2-aminobenzonorbornene and of 5- and 6-hydroxy-anti-9-aminobenzonorbornene were also evaluated for their activity as substrates and inhibitors for PNMT. The results of this study are in agreement with previous findings for bound beta-phenylethylamines and support the conclusion that the natural substrate for PNMT, norepinephrine, has a different active site binding orientation than most known substrates and competitive inhibitors of the enzyme.     

Antihypertensive action of a new angiotensin converting enzyme inhibitor, (R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl]amino-4-oxo-2,3,4,5-tetr ahy dro-1,5-benzothiazepine-5-acetic acid (CV-5975), in various hypertensive models

The antihypertensive activity of a new angiotensin converting enzyme (ACE) inhibitor, CV-5975, (R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl] amino-4-oxo-2,3,4,5-tetrahydro-1,5-benzothiazepine-5-acetic acid, was examined in normotensive rats and various hypertensive animal models. In spontaneously hypertensive rats, CV-5975 (1 to 10 mg/kg, p.o.) had a dose-related, sustained antihypertensive action, which was more potent and longer than that of enalapril. The potency and duration of action of CV-5975 was intensified when it was administered repeatedly or combined with hydrochlorothiazide. CV-5975 (1 mg/kg, p.o.) inhibited the ACE activity of plasma and tissues; inhibition on the ACE activity of the aorta, kidney, and brain was marked when CV-5975 was administered repeatedly. In 2-kidney, 1 clip hypertensive rats (1 to 10 mg/kg, p.o.) and dogs (0.3 and 1 mg/kg, p.o.), CV-5975 had a marked, sustained antihypertensive action, which was more marked than that of enalapril. In normotensive rats (10 mg/kg), 1-kidney, 1 clip hypertensive rats (3 and 10 mg/kg), and hyporeninemic DOCA/salt hypertensive rats (1 to 10 mg/kg/day), CV-5975 administered orally once or repeatedly reduced blood pressure, whereas enalapril did not. These results indicate that CV-5975 is a potent and long-lasting antihypertensive agent, the action of which is mediated primarily by inhibiting ACE activity and partly by some unknown mechanisms.     

Synthesis and evaluation of the biological activities of some 3-{[5-(6-methyl-4-aryl-2-oxo-1,2,3,4-tetrahydropyrimidin-5-yl)-1,3,4-oxadiazol-2-yl]-imino}-1,3-dihydro-2H-indol-2-one derivatives

Reaction of ethyl-6-methyl-2-oxo-4-aryl-1,2,3,4-tetrahydropyrimidin-5-carboxylates (1a-i) with hydrazine hydrate yielded 6-methyl-2-oxo-4-aryl-1,2,3,4-tetrahydropyrimidin-5-carbohydrazides (2a-i). These products, on reaction with cyanogen bromide, gave 5-(5-amino-1,3,4-oxadiazol-2-yl)-6-methyl-4-aryl-3,4-dihydropyrimidin-2 (1H)-ones (3a-i). The resultant aminooxadiazolylpyrimidinones were condensed with isatin to obtain various 3-{[5-(6-methyl-4-aryl-2-oxo-1,2,3,4-tetrahydropyrimidin-5-yl)-1,3,4-oxadiazol-2-yl]-imino}-1,3-dihydro-2H-indol-2-ones (4a-i). These products were characterized by IR, 1H NMR, mass spectra and elemental analysis. Products (4a-i) revealed promising antibacterial, antifungal and antioxidant activity.     

Synthesis and properties of the derivatives of 2-alkylthio-4-oxo-3,4- (and -1,4)-dihydropyrido-[2,3-d]pyrimidine-5- and -6-carboxylic acids

Condensation of diethyl 2-amino-6-methylpyridine-3,4-dicarboxylate (I) with the corresponding isothiocyanates afforded derivatives of ethyl 4-oxo-2-thioxo-1,2,3,4-tetrahydropyrido [2,3-d]pyrimidine-5-carboxylate (V-VII). Alkylation of (V), (VI) and (XI) gave the corresponding derivatives of ethyl 2-alkylthio-4-oxo-3,4-(and 1,4)-dihydropyrido[2,3-d]pyrimidine-5- and -6- carboxylate [(XII-XVI), (XX-XXII)]. Some of the obtained compounds were active pharmacologically.     

Inhibition of angiotensin converting enzyme by (R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl]amino-4-oxo-2,3,4,5-tetra- hydro-1,5-benzothiazepine-6-acetic acid (CV-5975), a non-sulfhydryl compound

CV-5975, (R)-3-[(S)-1-carboxy-5-(4-piperidyl)pentyl]amino-4-oxo- 2,3,4,5-tetrahydro-1,5-benzothiazepine-5-acetic acid, was found to inhibit rabbit lung angiotensin converting enzyme (ACE) activity with an IC50 of 3.1 x 10(-9) M and a Ki of 2.6 x 10(-9) M, inhibit the angiotensin I (A-I)-induced contraction of the guinea pig ileum with an IC50 of 1.3 x 10(-8) M, and augment the bradykinin (BK)-induced contraction of the ileum with an AC50 of 9.2 x 10(-10) M. The activity of CV-5975 was comparable to or slightly more potent than that of enalaprilat. The overall inhibition constant (Ki*), calculated from a steady-state analysis of enzyme reactions, was 4.4 x 10(-12) M for CV-5975; this indicates that the inhibition was about 5 times more potent than that of enalaprilat (2.0 x 10(-11) M). In rats, CV-5975 (0.03 and 0.3 mg/kg, i.v. and 3 and 10 mg/kg, p.o.) inhibited the A-I-induced pressor action more potently and for a longer period than did the corresponding doses of enalaprilat and enalapril. CV-5975 and enalapril (3 mg/kg, p.o.) augmented the BK-induced depressor action to a similar extent. In dogs, CV-5975 (0.3 and 1 mg/kg, p.o.) markedly inhibited the A-I-induced pressor action in a dose related manner, and the duration of this inhibitory activity was longer than with the corresponding doses of enalapril. These data provide evidence for the proposal that CV-5975 is a highly potent and long lasting ACE inhibitor.     

Analogues of the dioxolanes dexoxadrol and etoxadrol as potential phencyclidine-like agents. Synthesis and structure-activity relationships.

A series of dioxolane analogues based on dexoxadrol ((4S,6S)-2,2-diphenyl-4-(2-piperidyl)-1,3-dioxolane) and etoxadrol ((2S,4S,6S)-2-ethyl-2-phenyl-4-(2-piperidyl)-1,3-dioxolane) were prepared and tested for their ability to displace [3H]TCP (1-[1-(2-thienyl)cyclohexyl]piperidine) from PCP (1-(1-phenylcyclohexyl)piperidine) binding sites in rat brain tissue homogenates. Qualitative structure-activity relationships within this series were explored through modifications of the three major structural units of dexoxadrol, the piperidine, 1,3-dioxolane, and aromatic rings of the molecule. N-Alkyl derivatives of dexoxadrol were found to be inactive, as were those analogues where the dioxolane ring was modified. Phenyl-substituted etoxadrol analogues were compared to similarly substituted PCP analogues and distinct differences were found in their structure-activity relationships suggesting that the aromatic rings in these two drug classes interact differently with the PCP binding sites. The replacement of the phenyl ring in etoxadrol by either a 2- or 3-thienyl ring led to compounds with affinity comparable to etoxadrol, and the replacement of the ethyl moiety on etoxadrol's dioxolane ring with propyl (7) or isopropyl (8) led to compounds which were more potent than etoxadrol or PCP. The most potent compound was (2S,4S,6S)-2-ethyl- 2-(1-chlorophenyl)-4-(2-piperidyl)-1,3-dioxolane (11), where a chlorine moiety was placed in the ortho position in the aromatic ring of etoxadrol. Its potency was comparable with TCP in vitro.     

LC-MS/MS法研究1-[1-(6-甲氧基-2-萘基)乙基]-2-(4-硝基苄基)-6,7-二甲氧基-1,2,3,4-四氢异喹啉氢溴酸盐在大鼠体内的代谢产物

采用液相色谱-串联质谱法对大鼠灌胃1-［1-(6-甲氧基-2-萘基)乙基］-2-(4-硝基苄基)-6,7-二甲氧基-1,2,3,4-四氢异喹啉氢溴酸盐(编号P91024)后粪便、尿液、胆汁和血浆中的主要代谢产物进行研究。通过比较给药样品和空白样品的全扫描总离子流色谱和选择离子扫描色谱图差别寻找I相代谢产物；根据其一级和二级质谱图，确定I相代谢产物的分子结构。完全提取I相代谢产物后的样品溶液，再用葡糖醛酸酶酶解，得II相结合物的苷元部分，采用与I相代谢产物鉴定同样方法寻找和鉴定II相代谢产物苷元的结构，进而确证II相代谢产物的分子结构。从大鼠粪便中鉴定出P91024的2个I相代谢物，从胆汁中鉴定出1个I相和5个II相代谢产物，从尿液中鉴定出1个I相和3个II相代谢产物，从血浆中鉴定出4个I相和1个II相代谢产物；并分别分析推测出它们的结构。P91024在大鼠体内被代谢转化为多种产物，利用LC-MS/MS可以快速寻找和鉴定。     

Synthesis and beta-adrenergic antagonism of 2-(aryloxy)-1-(2-piperidyl)ethanols

A series of erythro- and threo-2-(aryloxy)-1-(2-piperidyl)ethanol derivatives (3) was synthesized from 2-(2-oxiranyl)pyridine for evaluation as beta-antagonists. Most compounds displayed high competitive beta-blocking potency, but they lacked significant beta 1/beta 2 selectivity. The 1-naphthoxy derivative erythro-3b was 17 (beta 1) and 33 (beta 2) times more potent than its open-chain analogue, propranolol. Within the whole series, erythro-3 diastereomers were more potent beta-blockers than the threo-3 isomers, and the potency of the latter seems to be rather insensitive to structural modification. The effect of N-methylation and of interposition of an alkyl chain between the aromatic ring and the side chain, while being detrimental to beta-blocking activity, was less marked than in the classic (aryloxy)propanolamine blockers.     

Evaluation of isomeric 4-(chlorohydroxyphenyl)-1,2,3,4-tetrahydroisoquinolines as dopamine D-1 antagonists

The isomeric 4-(3-chloro-4-hydroxyphenyl)- and 4-(4-chloro-3-hydroxyphenyl)-1,2,3,4-tetrahydroisoquinolines, the N-methyl derivative of the 4-(4-chloro-3-hydroxyphenyl) isomer, and 4-(3-hydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline were synthesized and evaluated for dopamine D-1 antagonist activity. The 4-(3-chloro-4-hydroxyphenyl) and the 4-(3-hydroxyphenyl) isomer possessed similar potencies as D-1 antagonists. Introduction of the N-methyl group enhanced potency about twofold. The "pharmacophore" for selective dopamine D-1 antagonist activity appears to be a tertiary 2-(3-hydroxyphenyl)-2-phenethylamine.     

Cholinergic effects of molecular segments of apomorphine and dopaminergic effects of N,N-dialkylated dopamines.

The hydrochlorides of molecular segments of apomorphine [2-(3',4'-dihydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline, 2-(3'4'-dihydroxybenzyl)piperidine, and 1,2,3,4-tetrahydroisoquinoline with their respective N-methyl and N-n-propyl homologs] and N,N-dialkylated dopamine compounds were synthesized and studied for (1) LD50 in intact mice; (2) stereotypy in intact mice; (3) curving of the body in unilaterally caudectomized mice; (4) rotation in 6-hydroxydopamine-lesioned rats, and (5) activation of adenylate cyclase in homogenates of mouse caudate nuclei. Instead of dopaminergic effects 1-(3',4'-dihydroxybenzyl)-2-methyl-1,2,3,4-tetrahydroisoquinoline and 2-methyl-1,2,3,4-tetrahydroisoquinoline showed cholinergic ones. These effects were blocked in atropine-pretreated animals. Of the N,N-dialkylated dopamine compounds synthesized, the N-n-propyl-N-n-butyldopamine ranked in all tests as the strongest dopamine-receptor agonist and N-methyl-N-n-propyldopamine as the weakest. In contrast, N,N-dimethyldopamine and 1-(3,4-dihydroxyphenylethyl)piperidine showed no dopaminergic effects. The effectiveness of the dopaminergic agonists depended on the length of the N-alkyl substituents suggesting interactions with hydrophobic regions of the receptor site.     

Synthesis and neuroleptic activity of 3-(1-substituted-4-piperidinyl)-1,2-benzisoxazoles

The synthesis of a series of 3-(1-substituted-4-piperidinyl)-1,2-benzisoxazoles is described. The neuroleptic activity of the series was evaluated by utilizing the climbing mice assay and inhibition of [3H]spiroperidol binding. Structure-activity relationships were studied by variation of the substituent on the benzisoxazole ring with concomitant variation of four different 1-piperidinyl substituents. Maximum neuroleptic activity was realized when there was a 6-fluoro substituent on the benzisoxazole ring. The 1-piperidinyl substituent appeared less significant, although in most cases, the (1,3-dihydro-2-oxo-2H-benzimidazol-1-yl)propyl group imparted maximum potency. The most potent compound in both assays was 6-fluoro-3-[1-[3-(1,3-dihydro-2-oxo-2H-benzimidazol-1-yl) propyl]-4-piperidinyl]-1,2-benzisoxazole (11b).