6-(alkylamino)-9-alkylpurines. A new class of potential antipsychotic agents.

A series of 6-(alkylamino)-9-alkylpurines was synthesized and evaluated for the property of antagonizing the behavioral effects in animals of the dopamine agonist apomorphine. This model for identifying potential antipsychotic agents is based on the hypothesis that agents that antagonize apomorphine-induced aggressive behavior in rats and apomorphine-induced climbing in mice, but that do not block stereotyped behavior, could have an antipsychotic effect in humans without producing extrapyramidal side effects. The antiaggressive-behavior activity of lead compound 1 (6-(dimethylamino)-9-(3-phenylalaninamidobenzyl)-9H-purine) was improved 48-fold with 6-(cyclopropylamino)-9-(cyclopropylmethyl)-2-(trifluoromethyl)-9H- purine (80) (po ED50 of 2 mg/kg), which was obtained through an iterative sequence of structure--activity relationship studies that encompassed evaluation of the effects of structure variations at the purine 9-, 6-, and 2-positions. Potency was enhanced with a 9-cyclopropyl group, the duration of action was improved with the 6-(cyclopropylamino) substituent, potency was further enhanced with an N-formyl prodrug, and an agent with reduced cardiovascular effect emerged with the 2-trifluoromethyl purine 80. This potential antipsychotic agent was not developed further due to undesirable effects on the stomach.

Benzodiazepine receptor binding activity of 8-substituted-9-(3-substituted-benzyl)-6-(dimethylamino)-9H-purines.

A series of 8-substituted analogues of 9-(3-aminobenzyl)-6-(dimethylamino)-9H-purine (8) were synthesized and tested for their ability to bind to the benzodiazepine receptor (BZR) in rat brain tissue. The most active compound was the 8-bromo-9-(3-formamidobenzyl) analogue 16 (IC50 = 0.011 microM), which was 1000-fold more active than the parent 9-benzyl-6-(dimethylamino)-9H-purine (1) and nearly as active as diazepam. Although substitution of a m-formamido group and an 8-bromo substituent on 1 imparted potent BZR binding activity, neither 16 nor 11 analogues exhibited significant anxiolytic activity on a modified Geller-Seifter conflict schedule.

9-Benzyl-6-(dimethylamino)-9H-purines with antirhinovirus activity.

A series of 9-benzyl-6-(dimethylamino)-9H-purines and 9-benzyl-2-chloro-6-(dimethylamino)-9H-purines were synthesized and tested in cell culture for activity against rhinovirus type 1B. The 9-benzylpurines that were unsubstituted in the 2-position had weak activity. However, introduction of a 2-chloro substituent resulted in a substantial increase in antiviral activity. One of the most active compounds, 2-chloro-6-(dimethylamino)-9-(4-methylbenzyl)-9H-purine (29), had an IC50 value of 0.08 microM against serotype 1B. Four compounds were tested against 18 other rhinovirus serotypes, but the majority tested were less sensitive than type 1B. The range of serotype sensitivity for 29 varied from 0.08 to 14 microM. These 9-benzyl-2-chloro-9H-purines represent a new class of antiviral agents with in vitro activity against rhinoviruses.

9-(2-Fluorobenzyl)-6-(alkylamino)-9H-purines. A new class of anticonvulsant agents.

Several substituted aryl and 6-alkylamino analogues of the anticonvulsant purine 9-(2-fluorobenzyl)-6-(methyl-amino)-9H-purine (1) were synthesized and tested for anticonvulsant activity against maximal electroshock-induced seizures (MES) in rats. Derivatives with a second fluoro substituent in the 5- or 6-position of the aryl moiety were very active with ip ED50's that ranged from 2 to 4 mg/kg. Congeners in which the purine 6-substituent was varied among a number of alkylamino groups possessed potent activity against MES that was comparable to or several times better than phenytoin.

6-(Alkylamino)-9-benzyl-9H-purines. A new class of anticonvulsant agents.

Several 9-alkyl-6-substituted-purines were synthesized and tested for anticonvulsant activity against maximal electroshock-induced seizures (MES) in rats. Most compounds were prepared in three steps from 5-amino-4,6-dichloropyrimidine or in two steps via alkylation of 6-chloropurine. Potent anticonvulsant activity against MES resided in compounds that contain a benzyl substituent at the 9-position of 6-(methylamino)- or 6-(dimethyl-amino)purine. Among commonly used agents for control of seizures, this type of structure represents a new class of potent anticonvulsant agents.

Purine acyclic nucleosides. Nitrogen isosteres of 9-[(2-hydroxyethoxy)methyl]guanine as candidate antivirals.

A number of nitrogen analogues of 9-[(2-hydroxyethoxy)methyl]guanine [acylovir, Zovirax] containing amine functions in the side chain were synthesized and tested for antiviral activity. These purine acyclic nucleosides were prepared by reaction of tris(trimethylsilyl)guanine or 2,6-diaminopurine sodium salt with the chloromethyl ethers prepared from N-(2-hydroxyethyl)phthalimide, N-[2-(2-hydroxyethoxy)ethyl]phthalimide, or N-(2-hydroxyethyl)oxazolidin-2-one to give the N-blocked intermediates 5-8. Deprotection with hydrazine or by alkaline hydrolysis gave 9-[(2-aminoethoxy)methyl]guanine (9), 9-[(2-aminoethoxy)methyl]-2,6-diaminopurine (10), 9-[2(2-aminoethoxy]ethoxymethyl]guanine (11), and 9-[[2-[(2-hydroxyethyl)amino]ethoxy]methyl]guanine (12). When tested against herpes simplex virus type 1, only 9 was active with an IC50 = 8 microM. Little or no activity was observed against a range of other DNA and RNA viruses.

Pyrimidine acyclic nucleosides, 1-[(2-Hydroxyethoxy)methyl]pyrimidines as candidate antivirals.

A number of pyrimidine acyclic nucleosides were synthesized and tested for activity against herpes simplex virus type 1. Synthesis of 1-[(2-hydroxyethoxy)methyl]cytosine (8) and 1-[(2-hydroxyethoxy)methyl]uracil (14) was accomplished in two or three steps from 2,4-diethoxypyrimidine and 2-(benzoyloxy)ethoxymethyl chloride. The 5-methyl (20), 5-(trifluoromethyl) (21), and 5-fluoro (22) analogues of 14 were available in two steps form the appropriate bis(trimethylsilyl)ated 5-substituted uracil and 2-(acetoxymethoxy)ethyl acetate or 2-(benzoyloxy)ethoxymethyl chloride. Bromination of 8 and 14 or iodination of 14 gave the 5-halogeno-1-[(2-hydroxyethoxy)methyl]pyrimidines 9, 23, and 24. These pyrimidine acyclic nucleosides exhibited little or no activity against herpes simplex virus type 1 or against a range of other DNA and RNA viruses. This is compatible with their lack of substrate properties toward herpes simplex virus induced thymidine kinase.

Pyrimidine acyclic nucleosides. 5-Substituted 1-[(2-aminoethoxy)methyl]uracils as candidate antivirals.

Several 5-substituted analogues of the acyclic aminonucleoside 1-[2-aminoethoxy)methyl]uracil (5) were prepared for evaluation as antivirals. The uracil and thymine analogues were prepared in two steps from N-[2-(chloromethoxy)ethyl]phthalimide (1). The 5-chloro, 5-bromo, and 5-iodo analogues were prepared by halogenation of 5. These acyclic aminonucleosides exhibited neither cell toxicity nor antiviral activity. This is compatible with their lack of substrate properties toward herpes simplex virus thymidine kinase.