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.

8-Amino-3-benzyl-1,2,4-triazolo[4,3-a]pyrazines. Synthesis and anticonvulsant activity.

Eleven substituted 8-amino-3-benzyl-1,2,4-triazolo[4,3-a] pyrazines were synthesized and tested for anticonvulsant activity against maximal electroshock-induced seizures (MES) in rats. The compounds were prepared in four stages from the phenylacetonitriles. I. The intermediate (2,2,2-triethoxyethyl)benzenes III were condensed with 2-chloro-3-hydrazinopyrazine (IV) to provide the 3-benzyl-8-chloro-1,2,4-triazolo[4,3-a]pyrazines V. The latter were converted to the 8-amine targets VI with methylamine or ammonia. Several compounds exhibited potent activity against MES; the 3-(2-fluorobenzyl)-8-(methylamino) and 3-(2,6-difluorobenzyl)-8-(methylamino)congeners (4 and 12) exhibited the best anticonvulsant activity with oral ED50S of 3 mg/kg. The 1,2,4-triazolo[4,3-a]pyrazine ring system serves as a bioisostere of the purine ring for anticonvulsant activity; however, these agents exhibit less propensity to cause emesis.

9-[(Phosphonoalkyl)benzyl]guanines. Multisubstrate analogue inhibitors of human erythrocyte purine nucleoside phosphorylase.

A series of 9-[(phosphonoalkyl)benzyl]guanines was synthesized and tested for inhibition of human erythrocyte purine nucleoside phosphorylase (PNPase). Inhibitors of PNPase should be T-cell selective, immunosuppressive agents with potential clinical utility in the treatment of a wide variety of disorders in which T-lymphocytes are pathogenic. An initial set of six analogues of the weak PNPase inhibitor 9-benzylguanine (2) contained a phosphonic acid group linked to the ortho, meta, or para position of the aryl moiety via two- or three-atom spacers. These compounds allowed us to probe for a favorable interaction with the phosphate-binding domain. Several additional meta phosphonoalkyl substituents were examined in an effort to optimize the spacer. The two most potent compounds, [[3-[(2-amino-1,6-dihydro-6-oxo-9H-purin-9-yl)methyl] benzyl]oxy]-methylphosphonic acid (3f) and [[3-[(2-amino-1,6-dihydro-6-oxo-9H-purin-9-methyl)methyl] benzyl]-thio]methylphosphonic acid (3j), were inhibitors of PNPase with Ki's of 5.8 and 1.1 nM, respectively. These inhibitors displayed competitive kinetics with respect to inosine and inorganic phosphate, which showed that these compounds possess binding determinants for both the purine- and phosphate-binding domains of the enzyme, characteristics that are consistent with 3f and 3j being multisubstrate analogue inhibitors of PNPase. The potency of 9-benzylguanine (2) was enhanced more than 6000-fold by linking a phosphonic acid residue with a (methylthio)methyl spacer to the meta position of 2 to give 3j, which illustrates the potent enzyme inhibitory properties available to multisubstrate analogue inhibitors.

Synthesis and antirhinovirus activity of 8-substituted analogues of 6-(dimethylamino)-9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine.

Several 8-substituted analogues of 6-(dimethylamino) -9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine (1) were synthesized and tested for activity against rhinovirus type 1B. Among 16 8-substituted analogues, the 8-amino (3) and 8-bromo (2) analogues were most active with IC50s of 0.36 and 1.4 microM, respectively, under conditions where 1 had an IC50 of 0.03 microM.

Antirhinovirus activity of 6-anilino-9-benzyl-2-chloro-9H-purines.

A series of 6-anilino-9-benzyl-2-chloropurines was synthesized and tested for antirhinovirus activity. Most of the compounds were prepared by reaction of the appropriate aniline with 9-benzyl-2,6-dichloro-9H-purine. Structure-activity relationship studies revealed that compounds with small, lipophilic para substituents were good inhibitors of serotype 1B. Several compounds had good activity against four representative serotypes.

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.

Synthesis and antirhinovirus activity of 6-(dimethylamino)-2-(trifluoromethyl)-9-(substituted benzyl)-9H-purines.

A series of 6-(dimethylamino)-2-(trifluoromethyl)-9-(substituted benzyl)purines was synthesized and tested for antirhinovirus activity. Most of the compounds were synthesized by alkylation of 6-chloro-2-(trifluoromethyl)-9H-purine with the appropriate benzyl halide followed by displacement of the chloro group with dimethylamine. Alternatively, 6-(dimethylamino)-2-(trifluoromethyl)purine was alkylated with the appropriate benzyl halide. Although several different aryl substituents provided compounds with IC50's = 0.03 microM against rhinovirus serotype 1B, no congener was significantly more active than the parent 2. Twenty-three compounds were tested against 18 other serotypes, but none exhibited a uniform profile of activity.

Synthesis and structure-activity relationships of 2-substituted-6-(dimethylamino)-9-(4-methylbenzyl)-9H-purines with antirhinovirus activity.

A series of 2-substituted-6-(dimethylamino)-9-(4-methylbenzyl)-9H-purines where the 2-substituent was H, F, Cl, CF3, CH3, CH2CH3, NH2, NHCH3, N(CH3)2, SCH3, or SO2CH3 was synthesized and tested for antirhinovirus activity to evaluate the effect of 2-substituents on antiviral activity. Intuitive and quantitative structure-activity relationship (QSAR) analysis showed that optimum antirhinovirus serotype 1B activity was associated with 9-benzylpurines that contained a C-2 lipophilic, electron-withdrawing substituent. The most active compound, 6-(dimethylamino)-9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine (14), had an IC50 = 0.03 microM against serotype 1B, but its activity against 18 other serotypes was not uniform; the IC50s ranged over 260-fold.

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.

A study of bovine T-cell subsets in the blood and mammary gland secretions during the dry period.

Blood and mammary secretions were obtained from cows throughout the dry period. Quantitative and qualitative assays were performed to determine the cell types and cell distributions at weekly intervals from day of dry off until parturition. The total cell counts in secretions increased during involution and remained at high levels until a few weeks prepartum. The macrophages were the predominant cell type in mammary secretions whereas the numbers of lymphocytes were always less than neutrophils or macrophages. Enriched mononuclear cell populations derived from blood and mammary secretions were also evaluated using "T-cell rosette" assays. Changes observed in the relative distribution of three T-cell subsets in secretions did not reflect the dynamics of the cells in the peripheral blood. T-cell subsets that predominated in mammary secretions were the EN+ EAET+ and EN-EAET+ phenotypes. Distinct patterns of migration or differentiation of T-cell subsets were suggested by the changes of subsets observed in mammary secretions collected throughout the dry period.