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(R)- And (S)-11-hydroxy-10-methylaporphine 1 and 2 are, respectively, a potent, highly specific serotonergic (5-HT1A) agonist and antagonist. In an ongoing structure-activity study, racemates of the positional isomers 8-hydroxy-9-methyl- and 8-methyl-9-hydroxyaporphine were prepared by modifications of literature methods and were resolved. The methyl ethers of the target compounds were also evaluated pharmacologically. All of the free phenolic derivatives [(+)- and (-)-8 and 10] were inert in an assay for 5-HT1A receptor activity. All of the methyl ethers [(+)- and (-)-9 and 11] demonstrated quantitatively similar low potency stimulant effect at 5-HT1A receptors. The agonist or antagonist activity exhibited by 1 and 2 reflects the high degree of structural specificity required of aporphine derivatives for action at 5-HT1A receptors.

p-Dimethoxyaryl analogs of certain potent catechol-derived dopaminergic agonists show dopaminergic properties for which no structure-activity relationship has yet been defined. (S)-3-(3-Hydroxyphenyl)-N-n-propylpiperidine (1, S-"3-PPP") is a dopaminergic autoreceptor agonist, and at high doses it also exhibits postsynaptic antagonism. (R)-1 is a postsynaptic agonist. In a continuation of studies of effects of the p-dimethoxy moiety at dopamine receptors, synthesis and resolution of the 2,5-dimethoxy analog 3 of 3-PPP was undertaken. The two enantiomers and the racemic modification showed cardiovascular effects consistent with actions at DA-2 receptors. The potency of all three compounds was much lower than that of 3-PPP, although they displayed approximately the same duration of action. Absolute configuration does not seem to be a major determinant of these compounds' ability to interact with DA-2 receptors.

The subject compounds were prepared as a part of a continuing structure-activity study of the contrasting actions (agonism-antagonism) of (+)- and (-)-11-hydroxy-10-methylaporphine at serotonin (5-HT1A) receptors. None of the targeted nonoxygenated aporphine derivatives demonstrated significant activity in assays for any effects at serotonin 5-HT1A receptors. It is concluded that, in the aporphine series, serotonergic agonist or antagonism requires an alkyl group ortho to a phenolic OH group in the A ring.

Molecular modifications have been made on a highly potent, active antagonist to organophosphate-induced toxicity, 4,4'-bis[1,3-dioxan-2-ylmethyl)methylamino]acetyl]biphenyl dimethobromide (1). Stepwise removal of the oxygen atoms from the dioxane rings, as well as changing the position of attachment of substituents on the 1,3-dioxane rings and decreasing the ring size from six-membered to five-membered caused drastic or complete loss of pharmacological effect. Partial structures of 1 were all inactive. Thus, the structure of 1 seems to be remarkably specific. Additional pharmacological data are reported for 1.

The isomeric monomethyl ether derivatives of (RS)-9,10-dihydroxyaporphine ("isoapomorphine") were synthesized unequivocally as possible metabolites in catechol-O-methyltransferase (COMT) mediated O-methylation reactions. In vitro incubation studies revealed that isoapomorphine is not a substrate for the COMT using experimental conditions under which apomorphine (10,11-dihydroxyaporphine) is converted in high yield into its 10-methyl ether, apocodeine. The in vivo dopaminergic inactivity of isoapomorphine (as compared with that of apomorphine) seems to be due to factors other than metabolic inactivation by COMT.

In order to facilitate identification of possible metabolites arising from in vitro action of catechol-O-methyltransferase upon 7,8-dihydroxy- and 8,9-dihydroxy-4-n-propyl-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinolines (11, 12), all four possible monomethyl ether derivatives have been synthesized. Incubation of 11 and 12 with the enzyme revealed that the 8,9-dihydroxy positional isomer 12 (which contains the dopamine moiety held in the beta conformation) but not the 7,8-dihydroxy isomer 11 (which holds the dopamine moiety in the alpha conformation) was a substrate for the enzyme. The sole detectable product of 12 was 8-hydroxy-9-methoxy derivative 15 in which the "meta" hydroxy group of the dopamine moiety is etherified.

A series of congeners of hemicholinium-3, in which the 1,4-oxazinium rings of hemicholinium are replaced by pyrrolidine, piperidine, 1,3-dioxane, or 1,4-oxazine rings, is described. Several of the target compounds produced blockade of neuromuscular transmission in the rabbit, and three heterocyclic derivatives, 10, 11, and 13, significantly antagonized paraoxon-induced lethality in mice. 1,3-Dioxane derivative 11 was an extremely potent antagonist of paraoxon-induced toxicity in mice, compared with prototypical protective agents physostigmine and pyridostigmine. Compound 11 exhibited a much more favorable therapeutic ratio than the reference drugs. The mechanism of action of 11 has not been elucidated, although it is concluded that it differs from that of hemicholinium-3 (inhibition of high-affinity, sodium-dependent uptake of choline into nerve terminals).

A series of N-alkylated alpha-methyldopamine derivatives has been prepared for comparison of their biological effects with those of semirigid dopamine congeners derived from 2-aminotetralin systems. All of the alpha-methyldopamine derivatives were inert as dopaminergic agonists in a variety of animal assays, both centrally and peripherally, although certain compounds produced powerful and prolonged locomotor hyperactivity on intra-accumbens injection in mice, by indirect mechanism(s). A rationalization, based upon conformational analysis, is presented for the lack of direct dopaminergic agonist activity of alpha-methyldopamine derivatives.

The title compound was prepared to complete a series of small ring (cyclopropane, cyclobutane) cis/trans 1,2-disubstituted semirigid congeners of acetylcholine. A multistep synthetic sequence, beginning with cis-cyclobutane-1,2-dicarboxylic anhydride, permitted unequivocal preparation of the (+/-)-cis target compound 4. The geometry of 4 was confirmed by comparison with an authentic sample of the (+/-)-trans isomer. The cis and trans isomers were equipotent as muscarinic agonists, but they were much weaker than acetyl-beta-methylcholine.

The (+/-) title compound was prepared to evaluate prior observations that certain acetylcholine congeners derived from cyclobutane are devoid of muscarinic effects. It was prepared by a multistep sequence from trans-2-carbomethoxycyclobutyl methyl ketone. In a guinea pig ileum assay, it was 0.02 times as active as AcCh, and in a dog blood pressure assay, it was 0.09 times as active. In these assays, its (+/-)-cyclopropane congener and AcCh were equally active. This is the first cyclobutane-derived AcCh congener possessing significant muscarinic effect.

Series of N-alkylated derivatives of trans-octahydrobenzo[g]quinoline and of cis- and trans-octahydrobenzo[f]quinoline were prepared for pharmacological testing as congeners of 2-amino-5,7-dihydroxytetralin, which elicits dopaminergic effects in a variety of assays. Trans-fused compounds bearing N-ethyl or N-n-propyl displayed high potency/activity in inhibition of effect of stimulation of the cat cardioaccelerator nerve. Certain N-alkyl homologues in the octahydrobenzo[f]quinoline series showed high potency in binding studies in rat caudate homogenate.

Prompted by previous findings that a p-dimethoxy substitution pattern on an aromatic ring permits retention of dopaminergic agonist effects in certain ring systems, catechol derivatives of which are potent dopaminergic agonists, an 8,11-dimethoxy substitution pattern was introduced into the aporphine ring in place of the 10,11-dihydroxy moiety in apomorphine. Acid-catalyzed rearrangement of an appropriate morphine derivative provided the aporphine ring system with retention of the stereochemical integrity of the 6a asymmetric center. The hydroxyl group at position 10 was removed by catalytic hydrogenolysis of its phenyltetrazoyl ether. The methyl ether of the resulting 11-hydroxyaporphine was iodinated in high yield at position 8 with trifluoroacetyl hypiodite. This is the first account of synthesis of an iodinated aporphine derivative. The 8-iodo substituent was replaced with methoxyl by reaction with sodium methoxide and cuprous iodide. Neither the N-methyl target compound 7 nor the N-n-propyl derivative 8 demonstrated dopaminergic nor serotonergic agonism. However, 7 exhibited receptor-binding characteristics and other pharmacological properties suggesting that it may be a 5-HT1A receptor antagonist.

Secondary and tertiary amino homologs of the title compounds have been prepared, bearing an N-isopropyl group. In peripheral evaluation, certain members of the series exhibited beta-adrenergic agonist effects of lower activity than isoproterenol. N-Methyl-N-isopropyl-5,6-dihydroxytetralin exhibited marked properties consistent with its being an alpha agonist, and it is concluded that introduction of considerable bulk about the nitrogen of a catecholamine does not a priori destroy alpha-agonist effects. The compounds qualitatively paralleled the effects of dopamine in assays based upon direct intrastriatal administration in rats, although they were less potent than dopamine.

Three series of bicyclic, semirigid congeners of beta-phenethylamine have been prepared for evaluation of the effect of ring size (and of concomitant conformational variation) on biological activity in a variety of assays for adrenergic and dopaminergic actions. Pharmacologic activity was associated with 2-aminotetralin and 2-aminoindan derivateves, but was not found with 6-aminobenzocycloheptene derivatives. Noteworthy is the ability of several aminotetralins and aminoindans to increase the hot-plate reaction time without eliciting dopaminergic effects. This action was not blocked by pretreatment with naloxone.

Two series of N-substituted 2-aminoindan systems have been prepared: 4,5-dihydroxy-2-aminoindan (1) has a hydroxylation pattern analogous to the alpha conformer of dopamine, and 5,6-dihydroxy-2-aminoindan (2) has a hydroxylation pattern of the beta conformer of dopamine. All members of both series demonstrated only extremely weak binding to calf caudate homogenate. Certain N-alkylated 4,5-dihydroxyindans were violent emetics in the dog and were potent in blockade of the effect of stimulation of the cardioaccelerator nerve of the cat. In contrast, the 5,6-dihydroxy series displayed low or no activity/potency in these assays. Conformational analysis of the 2-aminoindan system is described and discussed.

The title compounds have been synthesized and evaluated for emetic effects in the dog, actions on the cardioaccelerator nerve in the cat, pecking in pigeons, and for behavioral effects following both peripheral and direct intracerebral injection into the nucleus accumbens and caudate-putamen of the rat. Generally, in the series studied, the N,N-diethyl and N,N-di-n-propyl congeners of dopamine displayed notably high degrees of activity. However, the test compounds exerted differing effects on peripheral and central dopamine receptors and in the area postrema. Differentiations of the activities of the different homologues within the brain were also shown.

The title compounds were prepared as congeners of the dopaminergically potent 2-amino-5,6-dihydroxytetralin series ("A-5,6-DTN"). None of the variously nitrogen-substituted benzocycloheptenes demonstrated any dopamine-like effects in a variety of assays. The primary amine had alpha 1-adrenoceptor stimulant effects. This lack of dopaminergic effect parallels the inactivity found in 6-aminobenzocycloheptenes bearing no oxygen substitutents, those bearing a single phenolic group, and those bearing a resorcinol 1,3-diphenolic substitution pattern.

Replacement of the catechol 3,4-dihydroxylation pattern of certain adrenergic beta-phenethylamines by a resorcinol 3,5-dihydroxylation pattern has led to a greater selectivity of adrenergic agonist effects in certain molecules. This strategy has been applied to a series of dopaminergic agents derived from 2-aminotetralin, leading to a 5,7-dihydroxylation pattern. Traditional literature approaches to formation of a tetralin ring with this oxygenation pattern failed. A method was used which involved cyclization of 3,5-dimethoxybenzylsuccinic acid derivatives with pyridinium poly(HF) and subsequent modification of the tetralin ring. The resorcinol-derived 2-aminotetralins were less potent and less active dopaminergic agents than their catechol-derived isomers (5,6-dihydroxy and/or 6,7-dihydroxy). Certain of the subject compounds demonstrated alpha- and beta 1-adrenoceptor activating properties.

On the basis of the premise that the dopaminergic agonist profile of 2-(di-n-propylamino)-5-hydroxy-6-methyltetralin (1a) is due to in vivo oxidation of the 6-methyl moiety and that 1a may represent a novel prodrug strategy, the vicinal methyl-hydroxyl substitution pattern was incorporated into the 6- and 7-positions of 2-(di-n-propylamino)tetralin to give the 6-methyl-7-hydroxy and 6-hydroxy-7-methyl isomers 8 and 9, respectively. A multistep synthetic approach was devised which permitted preparation of target molecules 8 and 9. Pharmacological data revealed that both target compounds exhibit modest dopamine-like effects in the cardioaccelerator nerve assay in the cat, but neither appeared to be metabolically activated as was the case with 1a. The effects of 9 (but not of 8) were antagonized by pretreatment with haloperidol. Thus, the 5-hydroxy-6-methyl substitution pattern in the 2-aminotetralins remains unique as a dopaminergic agonist prodrug structure.

The title compound was proposed to be a biologically active metabolite of a dopaminergic agent, 4-[2-(di-n-propylamino)ethyl]indole. This proposed metabolite was synthesized by a multistep sequence beginning with methyl 3,5-dinitro o-toluate, and involving the Batcho-Leimgruber modification of the Reissert indole synthesis. The target compound exhibited high potency/activity in vivo in a cat cardioaccelerator nerve assay and in vitro in an isolated cat atrium assay. It manifested maximal pharmacological effect less than 5 min after intravenous administration in cats, as compared with a 20-min lag time following intravenous administration of the nonoxygenated congener. These pharmacological data are consistent with the proposal that the target compound is a metabolite of 4-[2-(di-n-propylamino)ethyl]indole.

The N-n-propyl homologues of the title compounds were prepared for further assessment of the ability of the "p-dimethoxy" moiety to confer dopaminergic agonism upon a variety of ring systems. Both the angularly and the linearly annulated trans-benzoquinoline ring derivatives displayed prominent DA2 dopaminergic effects on the peripheral sympathetic nerve terminal and displayed postjunctional dopamine receptor agonist properties in the striatum. It is speculated that the angular octahydrobenzo[f]quinoline derivative (but not the linear octahydrobenzo[g]quinoline derivative) may owe its dopamine-like effects to metabolic activation phenomena. In contrast, the cis-fused isomer of the angularly annulated benzoquinoline was inactive, as was the simple benzene derivative N,N-di-n-propyl-beta-(2,6-dimethoxyphenyl)ethylamine.

In a study of conformational requirements for certain dopaminergic agonist molecules, a series of conformationally predictable dopamine congeners related to cis- and trans-octahydrobenzo[f]quinoline was prepared. The complexity and equivocal character of the reduction of variously substituted 4-methyl-1,2,3,4,5,6-hexahydrobenzo[f]quinolines were demonstrated and studied. It was shown that several literature methods for reduction of these systems were in error regarding the stereochemical nature of the product(s). It has been concluded that geometrically specific and predictable reductions of these hexahydrobenzo[f]quinolines seem unlikely to attain, and a plausible rationalization for this conclusion has been proposed. Pharmacologic data on the compounds prepared are consistent with our earlier proposals of a biologically significant conformation of dopamine for emesis, the pecking syndrome in pigeons, and other physiological effects.

Two synthetic paths have been investigated for the preparation of cis and trans 8,9-dioxygenated octahydrobenz[h]isoquinoline ring systems. A sequence involving intramolecular Diels--Alder cyclization of a ring-opened intermediate product of a benzocyclobutene derivative was more satisfactory. The trans-fused isomers of the title compounds are frozen congeners of the alpha conformer of dopamine, isomeric with certain other tricyclic heterocycles which elicit a high degree of dopamine agonist activity. However, the present series of compounds exhibited a very low potency in an assay for dopamine-like actions. A possible reason for this inactivity has been suggested.

The vinyl ethers of choline and of its alpha- and beta-methyl homologues were prepared to determine their cholinergic effects and to determine whether a separation of the dual physiologic activity (nicotinic and muscarinic) reported for the vinyl ether of choline could be achieved by this modification. A literature method of vinyl transetherification of amino alcohols has been studied and modified. The ethyl ethers of choline and of alpha- and beta-methylcholine were prepared for comparison with the vinyl ethers. Two independent, unequivocal syntheses of the ethyl ether of beta-methylcholine have been accomplished. This study showed that the two literature methods for synthesis of this compound are equivocal, and, hence, the biological data reported for this compound in the older literature may not be valid. Certain of the ethers showed marked nicotinic or muscarinic activities.

Prior work in these laboratories identified (+/-)-5-hydroxy-6-methyl-2- (di-n-propylamino)tetralin as a dopaminergic agonist prodrug. The ortho methyl hydroxy aromatic substitution pattern in this molecule has now been incorporated into the aporphine ring system to give a congener of the dopaminergic agonist apomorphine in which the position 10 OH group has been replaced by methyl. Preparation of the target compound involved acid-catalyzed rearrangement of the 3-(1-phenyltetrazolyl) ether of morphine and subsequent molecular modification of the product, the 10-(1-phenyltetrazolyl) ether of (R)-(-)-apomorphine. Surprisingly, the target compound elicited no responses in any assays for effects at dopamine receptors, but rather it displayed pharmacological properties consistent with its being a serotonergic agonist with a high degree of selectivity for 5-HT1A receptors similar to the serotonergic agonist 8-hydroxy-2-(di-n-propylamino)tetralin.

A series of cis- and trans-dihydroxycotahydrobenzo[f]quinoline congeners of dopamine has been prepared, in which the N substitutent is H, ethyl, or n-propyl. The trans isomers include the dopamine moiety held rigidly in an antiperiplanar diposition which is believed to be necessary for certian central and peripheral dopaminergic effects. The cis isomers are flexible molecules; the dopamine moiety lacks conformational integrity and it can exist in a conformation which is believed not to favor dopaminergic activity. The trans series of compounds was shown to possess a high level of central and peripheral dopaminergic effects, whereas the cis series was of low activity or was inert. These data further support previous proposals concerning stereochemical requirements for certain dopaminergic agonist activity.

The so-called beta conformer of dopamine has been proposed to be involved in agonist--receptor interactions at several sites in the dopaminergic nervous system. Further to evaluate this proposal, rigid congeners of the beta conformer derived from linearly and angularly annelated octahydrobenzoquinolines have been synthesized. Certain N-alkylated trans-angularly annelated systems exhibited unusually potent and highly selective dopamine-like effects in an assay on a cardioaccelerator nerve preparation in the cat, but these compounds were inactive in a variety of assays for CNS effects. These compounds present a clear separation of CNS effects from some potent peripheral effects.

A series of variously N-substituted 2-aminotetralins having OH groups at 5 and 6 and at 6 and 7 positions, as well as nonoxygenated systems, has been evaluated for central dopaminergic effects. Stereotypical behavioral effects (sniffing, compulsive gnawing, and hyperactivity) produced by direct intracerebral administration of some of the agents were shown to differ strikingly from responses resulting from peripheral administration. The centrally mediated responses of hyperactivity and sterotypical gnawing-biting head and limb movements were shown to be separable in some test compounds. An improved route to 2-aminotetralin systems has been utilized for some of the compounds, which involves Pummerer rearrangement and cyclization of beta-keto sulfoxides and reductive amination of beta-tetralones with a NaBH4-carboxylic acid complex.

The title compounds were designed to provide semirigid congeners of m-tyramine in which the ring position ortho to the phenolic OH is blocked to metabolic hydroxylation. A sequence leading to a key synthetic intermediate, 5-methoxy-6-methyl-2-tetralone, has been developed. In animal test models for dopamine-like effects, the title compounds demonstrated qualitative and quantitative differences from the isomeric 5-methyl-6-hydroxy-2-aminotetralins and from 5,6-dihydroxy-2-aminotetralins. Two of the compounds were potent in a cat cardioaccelerator nerve assay, which involves dopamine receptors.

The physiological and pharmacological roles of pre- and postsynaptic dopamine receptors in modification of neuronal transmission centrally and peripherally will be subjects for intense research during the next decade. As enumerated by Langer, dopamine-sensitive receptors have been described that may inhibit or facilitate release of neurotransmitter substances. It is likely that dopaminergic agents that are highly selective for specific transmitters will be discovered. Likewise, dopaminergic agents that are nonselective (i.e., that modify the function of two or more neurotransmitters) may offer many opportunities for modification of behavior.

A synthetic precursor to a potent dopaminergic agonist, (RS)-4-hydroxy-2-(di-n-propylamino)indan, has been resolved by classical recrystallization procedures, and the absolute configurations of the enantiomers have been established by X-ray crystallographic analysis. The enantiomers were converted by literature procedures into (R)- and (S)-1. (R)-1 was approximately 100 times as potent as (S)-1 in an assay for dopamine agonist effect in the isolated cat atrium.

The title compounds were designed as flexible congeners of trans-octahydrobenz[h]isoquinoline, in which the dopamine moiety can exist in the alpha conformation. Extremely low dopamine-like effects in the title series in the cat cardioaccelerator nerve assay paralleled low activity in the trans-octahydrobenz[h]isoquinoline compounds and was consistent with a prior proposal of the presence of a bulky region on the dopamine receptor(s).

The ortho hydroxy/methyl, hydroxy/hydroxymethyl, hydroxy/formyl, and hydroxy/carboxy substitution patterns, some of which confer dopaminergic agonist effects upon 2-aminotetralin ring systems, have been incorporated into beta-phenethylamine, 2-aminoindan, and trans-octahydrobenzo[f]quinoline rings. Certain of the 2-aminoindan derivatives displayed pharmacologic properties consistent with their being dopaminergic agonists. The beta-phenethylamine derivative did not show any significant dopamine-like activity. The 7-hydroxy-8-methyloctahydrobenzo[f]quinoline derivative 4a was a moderately potent, short-acting DA2 receptor antagonist. All of the carboxylic acid derivatives were inert. Of the ortho hydroxy/methyl derivatives, only the 5-hydroxy-6-methyl-2-aminotetralin derivative displayed pharmacological properties consistent with its being a dopaminergic prodrug. It is concluded that 5-hydroxy-6-methyl-2-(di-n-propylamino)tetralin (1a) is structurally unique for a dopaminergic drug.

Series of N-alkylated derivatives of 2-amino-4,6-dihydroxyindan 3 and 6-amino-1,3-dihydroxybenzocycloheptene 2 were prepared for pharmacological testing as congeners of 2-amino-5,7-dihydroxytetralin, which elicits dopaminergic effects in a variety of assays. All of the subject compounds demonstrated a lower order of dopamine-like activity than the tetralin derivatives. Some of the subject compounds showed weak interactions with alpha 1- and beta 1-adrenoceptors, but the major determinant of activity seemed to be the nature of the N-alkyl substituent rather than ring size.