Measurement of the class III antidysrhythmic drug, UK-68,798, in plasma by radioimmunoassay

A sensitive radioimmunoassay (RIA) for the specific determination of 1-(4-methanesulphonamidophenoxy)-2-[N-(4-methanesulphonamido -phenethyl)-N- methylamino]ethane (UK-68,798), a novel class III antidysrhythmic agent, in human plasma is described. Specific antisera were raised in sheep using desmesyl-UK-68,798-succinate-ovalbumin conjugate as the antigenic hapten carrier protein. The antisera produced exhibited high specificity for UK-68,798 compared with known metabolites from animals, other antidysrhythmic agents and co-administered drugs. Good correlation was found in a comparison of the RIA method with a high-performance liquid chromatography (HPLC) method (r = 0.997) and a 10-fold lower limit of determination was observed for the RIA method compared with the HPLC method (0.05 and 0.5 ng ml-1, respectively). The RIA method was applied to the analysis of UK-68,798 in plasma obtained from human volunteers receiving the compound.

Synthesis of (R)-(-)- and (S)-(+)-4-fluorodeprenyl and (R)-(-)- and (S)-(+)-[N-11C-methyl]-4-fluorodeprenyl and positron emission tomography studies in baboon brain

(R)-(-)- and (S)-(+)-alpha-methyl-beta-4-(fluorophenyl)-N-methyl-N- propynylethylamine [R)-(-)- and (S)-(+)-4-fluorodeprenyl) were synthesized via the reaction of 4-fluorobenzaldehyde with nitroethane followed by reduction with lithium aluminum hydride to produce racemic 4-fluoroamphetamine, which was resolved by recrystallization with L- or D-N-acetylleucine to yield (R)-(-)-4-fluoroamphetamine or (S)-(+)-4-fluoroamphetamine in greater than 96% enantiomeric excesses and in yields of 42 and 39%, respectively. Alkylation with propargyl bromide gave (R)-(-)- or (S)-(+)-4-fluoronordeprenyl which was reductively methylated (Borch conditions) to produce (R)-(-)- or (S)-(+)-4-fluorodeprenyl. Alkylation of (R)-(-)- or (S)-(+)-4-fluoronordeprenyl with carbon-11 labeled methyl iodide gave (R)-(-)- or (S)-(+)-[N-11C-methyl]-4-fluorodeprenyl in a radiochemical yield of 30-40%. Comparative PET studies of the two labeled enantiomers in baboons showed a significantly lower retention of radioactivity in the striatum for the (S)-(+) enantiomer relative to the (R)-(-) enantiomer.

Selective class III antiarrhythmic agents. 1 Bis(arylalkyl)amines

A series of bis(arylalkyl)amines is described and their effects on prolonging effective refractory period in isolated cardiac tissue listed. Most compounds prolonged the cardiac action potential without significantly altering the maximum rate of depolarization and may be defined as selective class III antiarrhythmic agents. It was found that a particularly advantageous structural feature was to have a methanesulfonamido moiety on both of the aryl rings. Thus, compound 16 [1-(4-methanesulfonamidophenoxy)2-[N-(4-methanesulfonamidophene thyl)-N- methylamine]ethane] was selected for further investigations. The compound is highly potent and selective class III agent which acts by blockade of cardiac potassium channels.

Amides of beta-(4-chlorophenoxy)-alpha-phenyl-ethylamines are inhibitors of cholesterol biosynthesis in vitro

Amides of beta-(4-chlorophenoxy)-alpha-phenyl-ethylamines were prepared and tested for their inhibitory activity on cholesterol biosynthesis in vitro. Among the substances prepared, (II e), (II g), (II k) and (II m) had much greater inhibitory activity than clofibrate.

Conformational requirements of substrates for activity with phenylethanolamine N-methyltransferase

beta-Phenylethanolamines have long been known to be substrates for the enzyme that converts norepinephrine to epinephrine (phenylethanolamine N-methyltransferase, PNMT, EC 2.1.1.28). In an effort to determine which, if any, particular conformation of the aminoethyl side chain of phenylethanolamines is required for PNMT active site binding and catalysis, we have prepared and evaluated conformationally restricted phenylethanolamine analogues 8-10. The folded phenylethanolamine derivative 4-hydroxy-1,2,3,4-tetrahydroisoquinoline (8) is not a substrate and does not interact with the enzyme active site as an inhibitor as well as 1,2,3,4-tetrahydroisoquinoline (6). In the cyclic 2-aminotetralol systems, only cis-phenylethanolamine derivative 9 demonstrates activity as a PNMT substrate. The corresponding trans isomer 10 is not a substrate, in spite of enhanced active site interactions with respect to the parent analogue (2-aminotetralin, 4). Comparison of the inhibition constants for the folded (8,Ki = 175 microM) and extended (10,Ki = 9 microM) phenylethanolamine analogues strongly suggests that simultaneous binding of both the amino and hydroxyl functionalities to the PNMT active site requires an extended aminoethyl side chain conformation.

(+/-)alpha-Phenyl-beta-(3,4-dimethoxy)- and (+/-)alpha-phenyl-beta -(3,4-dihydroxy)phenethylamines: potential probes for nicotinic acetylcholine receptor-ion channel molecule from torpedo electric organ

The synthesis of some N-methyl, N-alkyl derivatives of (+/-)alpha-phenyl-beta-(3,4-dimethoxy)- and (+/-)alpha-phenyl-beta-(3,4-dihydroxy)-phenethylamines was achieved. These compounds were shown to bear certain structural features of acetylcholine (ACh), as well as phencyclidine (PCP). The latter was reported to act as a specific probe for the nicotinic ACh receptor-ion channel molecule from Torpedo electric organ. Biochemical binding studies revealed that for the nicotinic ACh receptor, the 3,4-dimethoxy derivatives behaved as blockers for the binding interaction of [3H]ACh, whereas the 3,4-dihydroxy analogues stimulated such binding. On the other hand, all of the tested phenethylamines exhibited potent blockade towards [3H]PCP binding interactions. The results indicated that the tested compounds might be applied as potential probes for the ACh receptor-ion channel molecule.

Kinetics of [11C]N,N-dimethylphenylethylamine in mice and humans: potential for measurement of brain MAO-B activity

Carbon-11-labeled N,N-dimethylphenylethylamine ([11C]DMPEA) was synthesized by the reaction of N-methylphenylethylamine with [11C]methyl iodide. This newly synthesized radiotracer was developed for the purpose of in vivo measurement of monoamine oxidase-B activity in the brain using a metabolic trapping method. Initially, biodistribution was investigated in mice. The rapid and high uptake of 11C radioactivity in the brain was observed following intravenous injection of [11C]DMPEA, the peak of which was reached at 1 min, followed by a decrease at 1-5 min and slowly thereafter. The kinetics of [11C]DMPEA in the human brain were determined using positron emission tomography (PET) and showed that 11C radioactivity increased gradually over 60 min following initial rapid uptake of 11C radioactivity, with basal ganglia and thalamus showing high accumulation.

Ascorbate depletion as a consequence of product recycling during dopamine beta-monooxygenase catalyzed selenoxidation

The competence of dopamine beta-monooxygenase (DBM) to process selenide substrates was investigated, in anticipation that the expected selenoxide products would exhibit unique reactivity and redox properties. The prototypical selenide phenyl 2-aminoethyl selenide (PAESe) was synthesized and shown to be a substrate for DBM with the characteristic e/O2 ratio of 2:1 for monooxygenation. The kinetic parameters for oxygenation of PAESe were found to be similar to those for the DBM-catalyzed sulfoxidation of the cognate sulfide phenyl 2-aminoethyl sulfide [May, S. W., & Phillips, R. S. (1980) J. Am. Chem. Soc. 102, 5981-5983], and selenoxidation was stimulated by fumarate in a manner similar to other well-characterized DBM monooxygenation reactions. Identification of phenyl 2-aminoethyl selenoxide (PAESeO) as the enzymatic product was accomplished by the demonstration of coincident elution of authentic PAESeO with the enzymatic product in three significantly different HPLC systems. PAESeO was found to oxidize ascorbic acid with the concomitant and stoichiometric reduction of PAESeO back to the selenide, PAESe. As a consequence of this nonenzymatic reaction, ascorbate-supported DBM turnover was prematurely terminated under standard assay conditions due to depletion of reduced ascorbate. The kinetics of the redox reaction between PAESeO and ascorbate were investigated with a spectrophotometric assay of ascorbate at 300 nm, and a second-order rate constant of 3.4 M-1 s-1 was determined at pH 5.0, 25 degrees C. Spectrophotometric assay of cytochrome c (cyt c) reduction at 550 nm during the oxidation of ascorbate by PAESeO demonstrated that no cyt c trappable semidehydroascorbate was produced in this nonenzymatic reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective monoamine oxidase inhibitors. 4. 4-Aminophenethylamine derivatives with neuron-selective action

Nine 4-aminophenethylamine derivatives were synthesized and tested for monoamine oxidase (MAO) inhibitory effects with particular attention to their selectivity for MAO within monoaminergic neurons in the rat brain. All compounds selectively inhibited the A form of MAO in vitro. Some of the compounds inhibited the MAO within the monoaminergic neurons at much lower doses than those required for inhibition of MAO within other cells in vivo. The most potent compounds in this respect were 4-amino-2-fluoro-alpha-methylphenethylamine (5) and 4-amino-2-chloro-alpha-methylphenethylamine (4).

Synthesis and dopaminergic binding of 2-aryldopamine analogues: phenethylamines, 3-benzazepines, and 9-(aminomethyl)fluorenes

A series of 2-aryldopamine analogues were synthesized and evaluated for their effects on D1 and D2 dopamine receptors. The 2-phenyldopamine and 6-phenylbenzazepine analogues exhibited weak binding to both D1 and D2 receptors. The 9-(aminomethyl)fluorenes also exhibited weak D2 binding; however, 2,5,6-trihydroxy-9H-fluorene-9-methanamine (4b) exhibited D1 binding comparable to apomorphine. The binding activity has been correlated with the calculated torsion angle of the biphenyl portion of these molecules. Good D1 dopamine binding occurs when the aromatic rings approach coplanarity; poor binding occurs when the aromatic rings are orthogonal.

[Phenylethylamine fluorides. II. Synthesis and neurobiochemistry in the rat]

Sixteen fluorinated phenylethylamines analogous to catecholamine were obtained by fluoration from the corresponding amino-alcohols. The biological activity of the compounds was evaluated by determining their affinity for the central adrenergic receptors of rat brain membranes and by measuring the monoamine synaptosomal uptake. These compounds significantly inhibited serotonine uptake, but they showed no affinity for amphetaminergic binding sites.

Facile synthesis of glycol metabolites of phenethylamine drugs

High yields of potential glycol metabolites of p-synephrine, epinephrine, octopamine, and normacromerine can be obtained from the readily available monosubstituted and disubstituted acetophenones. The general procedure involves alpha-bromination followed by displacement with acetate ion and reduction with lithium aluminum hydride. Yields ranged from 46 to 91%. Furthermore, the procedure minimizes some problems inherent in aromatic glycol synthesis which include dimerization and pinacol-pinacolone rearrangement.

[Benzoxazolinone phenylethanolamine antagonists of adrenergic receptors. A chemical and pharmacodynamic study]

Benzoxazolinone can be considered as a bioisosteric analogue of pyrocatechol. This concept has led to the synthesis of benzoxazolinonic phenylethanolamines. The pharmacological study shows that these compounds possess an affinity for adrenergic receptors. Compound (XXXIV), the most interesting, is a competitive alpha and beta adrenergic antagonist which has been studied for antihypertensive activity.

Preparation of 13N-beta-phenethylamine

Nitrogen-13-labelled beta-phenethylamine[( 13N]PEA) was synthesized by Hofmann rearrangement of [13N]phenylpropionamide prepared from phenylpropionyl chloride and aqueous [13N]ammonia solution. The reaction proceeded rapidly with a fairly good yield. [13N]PEA was isolated using preparative thin-layer chromatography, and organ distribution in mice was studied preliminarily. After i.v. administration of [13N]PEA, high accumulation and long-term retention of the radioactivity were observed in the brain and the heart.

Synthesis and evaluation of p-iodo-phentermine (IP) as a brain perfusion imaging agent

p-(123I and 131I)iodo alpha,alpha-dimethylphenethylamine (p-iodophentermine, IP) as the alpha-methylated analogue of iodoamphetamine has been prepared. It is hoped that this methyl substitution will increase the lipophilicity of the agent, enhance resistance to metabolism by monoamine oxidase, and will result in increased initial uptake and slower washout from the brain as compared to N-isopropyl-p-(123I)iodoamphetamine. IP was prepared by diazotization of p-aminophentermine followed by decomposition of the diazonium salt with KI. Radioiodinated IP was prepared either by the solid-phase isotopic exchange reaction or by decomposition of the piperidinotriazene derivative with a radiochemical yield of 40-60%. Biodistribution of 131I-IP in rats showed brain uptake in the range of 1.7% dose g-1 at 5, 30 and 60 min. Imaging studies with 123I-IP in dogs showed high brain extraction and slow washout of activity.

alpha-Phenyl-beta-(3,4-dimethoxy)phenethylamines: novel inhibitors of choline acetyltransferase from Torpedo electric organ

Some derivatives of alpha-phenyl-beta-(3,4-dimethoxy)phenethylamine that might bear a certain conformational resemblance to choline were prepared. The in vitro inhibition of choline acetyltransferase from Torpedo electric organ was investigated. These compounds gave variable degrees of inhibition; the most potent inhibitor was, N,N,N,-trimethyl-alpha-phenyl-beta-(3,4-dimethoxy)phenethylammonium++ + iodide, with an I50 of 1.3 X 10(-5) M. The inhibition of choline acetyltransferase from Spodoptera littoralis larval brains was also determined for comparative study. The aforementioned compound has an I50 of 9 X 10(-6) M on choline acetyltransferase from this source.

[Non-steroidal anti-inflammatory agents. III. Synthesis and analgesic-anti-inflammatory activity of 4-(pyrrol-1-yl)phenylacetamides and 4-(pyrrol-1-yl)phenethylamines]

Preparation of some 4-(pyrrol-1-yl)phenylacetamides and 4-(pyrrol-1-yl)phenylethylamines starting from 4-(pyrrol-1-yl)phenylacetic acid is reported. The new compounds were tested as analgesic-antiinflammatory agents. Data from pharmacological screening indicate 1-[4-(pyrrol-1-yl)phenylethyl]piperidine as the most active substance.

Synthesis and physicochemical and neurotoxicity studies of 1-(4-substituted-2,5-dihydroxyphenyl)-2-aminoethane analogues of 6-hydroxydopamine

In an attempt to evaluate the possible relationship between the neurotoxicity of 6-hydroxydopamine and the redox properties and electrophilic reactivity of the 6-hydroxydopamine-p-hydroquinone/p-quinone system, we have synthesized a series of 6-hydroxydopamine analogues in which the C4-hydroxy group is replaced with various electron-donating and electron-withdrawing substituents. With the aid of cyclic voltammetry, the formal oxidation potentials (E degrees ') for the p-hydroquinone/p-quinone redox couples and the rates of cyclization of the p-quinones to the corresponding p-iminoquinones were determined. As expected, electron-rich p-hydroquinones were easily oxidized to the p-quinones, which underwent cyclization slowly, whereas the oxidation of electron-poor p-hydroquinones required higher voltages and yielded p-quinones, which cyclized readily at pH 7.4. The neurotoxic potential of these compounds showed that in vivo destruction of noradrenergic terminals, as measured by inhibition of norepinephrine uptake by rat heart slices, occurred only with those analogues bearing electron-donating substituents. Potent neurotoxic properties were associated only with the 4-amino and 4-hydroxy derivatives, both of which form p-quinones, which do not cyclize readily at pH 7.4. These results support the thesis that the p-quinone derived from 6-hydroxydopamine may be an important species in the mediation of the neurodestruction caused by 6-hydrodopamine.

Phenylthioalkylamines in experimental tumor treatment in mice

Two phenylthioalkylamines, phenylthioethylamine (PTEA) and phenylthiopropylamine (PTPA), were prepared and tested for cytotoxicity in vitro and as antitumor agents in (C57BL X DBA/2)F1 (BDF1) mice. Low concentrations of PTEA (median effective concentrations of 8.0, 12.0, and 1.3 micrograms PTEA/ml) inhibited the growth of P388 murine lymphoma, L1210 leukemia, and B16 melanoma cells in culture. PTPA was more effective; concentrations of 0.80, 0.56, and 0.35 micrograms PTPA/ml inhibited the growth of P388, L1210, and B16 in vitro by 50%. PTEA and PTPA treatment increased survival times in BDF1 mice bearing the P388 lymphoma, L1210 leukemia, B16 melanoma, and Lewis lung tumors. Multiple daily administrations of the test compounds were more effective than single daily injections in increasing the life-span in mice bearing the P388 lymphoma and B16 melanoma. Both PTEA and PTPA inhibited the enzyme copper-zinc superoxide dismutase.

Importance of the aromatic ring in adrenergic amines. 6. Nonaromatic analogues of phenylethanolamine as inhibitors of phenylethanolamine N-methyltransferase: role of pi-electronic and steric interactions

To probe the importance of pi-electronic and steric interactions of nonaromatic analogues of phenylethanolamine as inhibitors of phenylethanolamine N-methyltransferase (PNMT), a series of norbornane and norbornene ethanolamines was prepared and evaluated as inhibitors of PNMT (liquid chromatographic-electrochemical detector assay). Previous studies indicated a major importance of hydrophobic interaction of the ring moiety attached to the ethanolamine side chain, but a possible importance of pi-complex formation could have been obscured by conformational differences among the analogues. In this study, norbornane and norbornene substituted with an ethanolamine side chain at positions 1,2-exo, and 2-endo were prepared from the corresponding aldehydes by addition of trimethylsilyl cyanide (Me3SiCN) and lithium aluminum hydride reduction. The saturated (norbornane) analogues were two times more potent as inhibitors of the enzyme than were the norbornene analogues, thus suggesting that pi-complex formation is not an important contribution to binding and, as previously proposed, a hydrophobic interaction is the significant binding interaction of the ring moiety. The hydrophobic binding area has a critical size that requires the hydrophobic moiety to be of sufficient length (the bridgehead-substituted norbornane and norbornene ethanolamines being too "'short" for optimal binding). The 2-exo orientation of the ethanolamine side chain was preferred to the 2-endo orientation, supporting our earlier hypothesis that the ring moiety prefers to be oriented away from the side chain.

Comparison of biological effects of N-alkylated congeners of beta-phenethylamine derived from 2-aminotetralin, 2-aminoindan, and 6-aminobenzocycloheptene

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.

New biphenyl derivatives i: 1-(4-biphenylyl)-2-phenylethylamines as potential antispasmodic and cardiovascular agents

A series of 1-(4-biphenylyl)-2-phenylethylamine derivatives was synthesized as potential antispasmodic and cardiovascular agents related to papaverine. Preliminary pharmacological tests, on isolated guinea pig ileum and anesthetized cat blood pressure, showed that the new compounds possess nonspecific inhibitory action on smooth muscles.

Selective monoamine oxidase inhibitors. 1. Compounds related to 4-aminophenethylamine

A series of derivatives of 4-aminophenethylamine was synthesized and their effect on monoamine oxidase (MAO) activity in the brain was evaluated. Several of the new compounds were potent and selective inhibitors of the A form of MAO but were poor inhibitors of the B form. The most active compounds were the 2,6-dichloro-(9) and the 2-halogeno-4-dimethylaminophenethylamines (5, 6, and 8). Some of the compounds also strongly antagonized aggressive behavior in isolated male mice. This effect was correlated to the MAO inhibition when tyramine was used as substrate. Significant correlations between MAO inhibition in vivo and potentiation of the syndromes produced by 5-hydroxytryptophan and tryptamine and antagonism of reserpine sedation were obtained.

Phenylalanyl transfer ribonucleic acid synthetase from Escherichia coli B. Potent inhibition by analogues of N-benzyl-2-phenylethylamine

A potent new class of inhibitors of phenylalanyl-tRNA synthetase from Escherichia coli B is described. N-Benzyl-2-phenylethylamine is a competitive inhibitor with respect to L-phenylalanine and appears to possess the structural features required for near-optimal binding. Hydrophobic substituents at the ortho position of either ring appear to be well tolerated, but substituents on both rings lead to large losses in binding. Poor noncompetitive inhibitors resllt from alkylation of the secondary nitrogen, further separation of the N-benzyl group from the nitrogen, or alkylation at the alpha position of the N-benzyl moiety. In contrast, placement of a methyl group at the 1 position of the 2-phenylethylamine moiety to give N-benzyl-D-amphetamine results in the most potent inhibitor yet described for this enzyme.

Selectivity of 4-methoxyphenethylamine derivatives as inhibitors of monoamine oxidase

It has been established that the oxidative deamination of tyramine by monoamine xodase is inhibited by (+/-)-4-methoxy-beta-hydroxyphenethylamine and its N-methylated derivatives. This particular series of compounds does not inhibit the action of monoamine oxidase when tryptamine is used as the substrate. In contrast, 4-methoxyphenethylamine and its N-methylated homologs inhibit the monoamine oxidase-catalyzed deamination of both tyramine and tryptamine.

Importance of the aromatic ring in adrenergic amines. 2. Synthesis and adrenergic activity of some nonaromatic six- and eight-membered ring analogs of beta-phenylethanolamine

The synthesis of beta-phenylethanolamine analogs in which the phenyl ring is replaced by cyclohexyl, cyclohexen-4-yl, cyclooctyl, cyclooctenyl, cycloocta-1,3-dien-2-yl, cycloocta-1,5-dienyl, and cyclooctatetraenyl was accompanied by conversion of the corresponding aldehydes to the cyanohydrins followed by reduction with lithium aluminum hydride. A preparatively useful synthesis of 1-formylcyclooctatetraene is described utilizing the photocycloaddition of methyl propiolate to benzene followed by reduction to the alcohol and oxidation with MnO2. All compounds, as their hydrochloride salts, exhibited indirect adrenergic activity on the rat vas deferens. On the reserpinized rat vas deferens all compounds potentiated the effects of exogenous norepinephrine. The results are in agreement with the conclusion that the more saturated the ring moiety, the greater the affinity for the amine uptake site of the vas deferens and suggest that there is no important interaction between the drug and this uptake site that involves pi-complex formation.

Affinity labeling of catechol O-methyltransferase by N-haloacetyl derivatives of 3,5-dimethoxy-4-hydroxyphenylethylamine and 3,4-dimethoxy-5-hydroxyphenylethylamine. Kinetics of inactivation

In an attempt to elucidate the relationship between the chemical structure and the catalytic function of catechol O-methyltransferase (COMT), several classes of affinity labeling reagents have been synthesized and their interaction with COMT has been studied. Earlier studies have shown that various N-haloacetyl derivatives of 3,5-dimethoxy-4-hydroxyphenylethylamine were effective affinity labeling reagents for this enzyme. In this report we have shown that N-haloacetyl derivatives of the isomeric 3,4-dimethoxy-5-hydroxyphenylethylamine also rapidly and irreversibly inactivate COMT ant they satisfy many of the criteria established for affinity labeling reagents. This latter group of agents appear to modify a nucleophilic residue at the active site of COMT different from that modified by the 3,5-dimethoxy-4-hydroxyphenylethylamine series. Evidence to support this conclusion has been obtained by comparing the kinetics of COMT inactivation and the substrate protection profiles for these two classes of affinity labeling reagents.

The action of plasma amine oxidase on beta-haloamines. Evidence for proton abstraction in the oxidative reaction

The action of plasma amine oxidase upon beta-Br-ethylamine beta-Cl-ethylamine, beta-OH-phenylethylamine, and beta-Cl-phenylethylamine was examined. Beta-Br-ethylamine is a substrate and irreversible inactivator of the enzyme. The enzyme becomes covalently labeled by the inactivator. Approximately 2 mol of inactivator are incorporated per mol of enzyme (MW 170,000). The reduced enzyme is not inactivated. The enzyme catalyzes the elimination of HCl from beta-Cl-phenylethylamine to produce phenylacetaldehyde. The rate of the elimination reaction is comparable to the normal oxidative reaction. We conclude that the occurrence of this elimination reaction establishes the ability of the enzyme to catalyze proton abstraction from C-1 of the substrate and that proton abstraction occurs during the catalytic oxidation normally catalyzed by plasma amine oxidase. Beta-Cl-ethylamine is only oxidized to corresponding aldehyde. Beta-OH-phenylethylamine is neither oxidized, nor does elimination occur. It is a competitive inhibitor in the oxidation of benzylamine and in the elimination of HCl from beta-Cl-phenylethylamine.

Monoamine oxidase inhibiting activity of a series of (+/-)-4-methoxy-beta-hydroxyphenethylamines

The synthesis and selected pharmacological testing of (+/-)-4-methoxy-beta-hydroxyphenethylamine [1-(4-methoxyphenyl)-2-aminoethanol] and its N-methylated derivatives are presented. Members of this series were found to exert partial prevention of reserpine-induced hypothermia in mice and to inhibit monoamine oxidase in Warburg studies. Activity was essentially dose dependent. The secondary amine was the most active member of the series. The tertiary amine was least active, and the primary amine exhibited intermediate activity.

Catechol O-methyltransferase. 6. Affinity labeling with N-haloacetyl-3,5-dimethoxy-4-hydroxyphenylalkylamines

Several N-acyl-3,5-dimethoxy-4-hydroxyphenylalkylamines have been synthesized and evaluated for their ability to inactive catechol 9-methyltransferase (COMT). N-iodoacetyl-3,5-dimethoxy-4-hydroxyphenylethylamine was found to rapidly and irreversibly inactivate this enzyme. The corresponding N-bromoacetyl derivative also produced inactivation of COMT but at a slower rate than the N-iodoacetyl derivative. The N-acetyl and N-fumaryl derivatives were completely inactive. The inactivation of COMT by these reagents appears to proceed by a unimolecular reaction within a dissociable complex rather than by a nonspecific bimolecular reaction. The proximity of the amino acid residue being modified relative to the site which binds the aromatic portion of these inhibitors was determined using N-iodoacetylphenylakylamines of varying chain length. The number of methylene carbons separating the aromatic ring and the iodoacetamide moiety in these inhibitors did not greatly influence the binding to COMT nor did it affect how rapidly the enzyme was inactivated. From these observations it was concluded that the amino acid moiety being modified by this class of affinity labeling reagents must be relatively close to or part of the site which binds the aromatic region of these inhibitors.

Cardioselective beta-adrenergic blocking agents. 1. 1-((3,4-Dimethoxyphenethyl)amino)-3-aryloxy-2-propanols

A series of 1-amino-3-aryloxy-2-propanols has been synthesized and examined for cardioselective beta-blockade. The introduction of the (3,4-dimethoxyphenethyl)amino group lead to the most cardioselective agents. Structure-activity relationships are discussed. Of the compounds tested 1-[(3,4-dimethoxyphenethyl)amino]-3-(m-tolyloxy)-2-propanol was selected for clinical trial because of optimal potency and selectivity.