Somatostatin receptor subtype-4 agonist NNC 26-9100 decreases extracellular and intracellular Aβ₁₋₄₂ trimers

Soluble amyloid β-protein (Aβ) oligomers are primary mediators of synaptic dysfunction associated with the progression of Alzheimer's disease. Such Aβ oligomers exist dependent on their rates of aggregation and metabolism. Use of selective somatostatin receptor-subtype agonists have been identified as a potential means to mitigate Aβ accumulation in the brain, via regulation of the enzyme neprilysin. Herein, we first evaluated the impact of the somatostatin receptor subtype-4 agonist 1-[3-[N-(5-Bromopyridin-2-yl)-N-(3,4-dichlorobenzyl)amino]propyl]-3-[3-(1H-imidazol-4-yl)propyl]thiourea (NNC 26-9100) on learning and memory in 12-month SAMP8 mice (i.c.v. injection). NNC 26-9100 (0.2 μg-dose) was shown to enhance both learning (T-maze) and memory (object recognition) compared to vehicle controls. Cortical and hippocampal tissues were evaluated subsequent to NNC 26-9100 (0.2 μg) or vehicle administration for changes in neprilysin activity, along with protein expression of amyloid-precursor protein (APP), neprilysin, and Aβ₁₋₄₂ oligomers within respective cellular fractions (extracellular, intracellular and membrane). NNC 26-9100 increased neprilysin activity in cortical tissue, with an associated protein expression increase in the extracellular fraction and decreased in the intracellular fraction. A decrease in intracellular APP expression was found with treatment in both cortical and hippocampal tissues. NNC 26-9100 also significantly decreased expression of Aβ₁₋₄₂ trimers within both the extracellular and intracellular cortical fractions. No expression changes were found in membrane fractions for any protein. These finding suggest the potential use of selective SSTR4 agonists to mitigate toxic oligomeric forms of Aβ₁₋₄₂ in critical regions of the brain identified with learning and memory decline.

Chronic peripheral administration of somatostatin receptor subtype-4 agonist NNC 26-9100 enhances learning and memory in SAMP8 mice

Selective somatostatin receptor subtype agonists have been proposed as a means to mitigate learning and memory loss associated with Alzheimer's disease. The first aim of this study evaluated blood-to-brain transport and regional brain distribution of NNC 26-9100, a selective somatostatin subtype-4 (sst4) receptor agonist. The entry rate of (131)I-NNC 26-9100 was K(i)=0.25 μl/g min, with an ~93% association with the parenchymal component. The second goal of this study was to evaluate the effect of chronic NNC 26-9100 administration (i.p.) on learning and memory, brain Aβ(x-42) levels, and protein expression of sst4 receptor and amyloid precursor protein (APP) in the senescence-accelerated mouse p8 (SAMP8) model of Alzheimer's disease. Mice chronically treated with NNC 26-9100 showed improved learning (day 21) and memory (day 28) using the T-maze paradigm (20 and 200 μg). Ex vivo tissue analyses showed a decline in Aβ(x-42) levels at the 20 μg dose, while no alterations were observed in sst4 receptor or APP protein expression compared to vehicle controls. These findings indicate NNC 26-9100 is taken up into key brain regions associated with learning and memory. Furthermore, chronic administration of NNC 26-9100 improved learning and memory and decreased Aβ(x-42) brain levels. These results suggest sst4 receptor agonists may provide a viable therapy in the treatment of Alzheimer's disease and other forms of cognitive impairment.

Recent advances in the development of dopamine D(3) receptor agonists and antagonists

Advances in molecular cloning techniques have allowed the characterization of five subtypes (D(1)-D(5)) of dopamine (DA) receptors. The limbic location of the D(3) receptor has led to speculation about its possible role in schizophrenia and drug abuse. Since the D(3) receptor is localized in the limbic region rather than the striatum, antipsychotics with D(3) receptor selectivity could be devoid of extrapyramidal side effects commonly seen with D(2) receptor antagonists. Recent work in our laboratory revealed that the benz[e] indole cis-(+/-)-44b demonstrated high selectivity for the D(3) receptor. This compound exhibits a typical antipsychotic profile without the motor effects found in commonly used antipsychotic agents. This mini-review will give a brief introduction on D(3) receptors and a detailed description of selectively-acting D(3) agonists and antagonists which have recently appeared in the literature.

2-pyridylthioureas: novel nonpeptide somatostatin agonists with SST4 selectivity

Somatostatin [somatotropin release-inhibiting factor (SRIF)] is a cyclic tetradecapeptide that is a potent inhibitor of growth hormone (GH) secretion from the anterior pituitary. In addition to the inhibitory effects on GH-release, SRIF-14 and SRIF-28, a 28-amino acid form of SRIF extended from the N-terminal end, inhibit the release of a variety of other peptides including glucagon, insulin, and gastrin, and both peptides act as neurotransmitters and neuromodulators in the central nervous system and the periphery. SRIF exerts its potent inhibitory effects following binding to high affinity SRIF receptors (ssts) that have been identified on target tissues. The recent cloning of five ssts has confirmed that the effects of SRIF are mediated by a family of G protein-coupled receptors (sst1-5). Based on structural and pharmacological properties sst2, sst3, and sst5 belong to the SRIF1 receptor subclass, and the sst1 and sst4 subtypes comprise the SRIF2 subclass. The major difference between these two subclasses is that SRIF1 receptors bind octapeptide and hexapeptide SRIF-14 analogs with high affinity, while SRIF2 receptors bind these analogs with drastically reduced affinity. A screening program was initiated to identify a lead nonpeptide with affinity for sst1-5 receptors. The search focused on a scaffold with the following attachments: (1) a heteroaromatic nucleus to mimic the Trp8 residue, (2) a nonheteroaromatic nucleus to mimic Phe7, and (3) a primary amine or other basic group to mimic the Lys9 residue of SRIF-14. Using these criteria, a novel thiourea (NNC 26-9100, 17) was discovered as a structural lead. The key fragments in this compound are a heteroaromatic moiety (pyridine), an aromatic group, and a basic imidazole group connected through a thiourea scaffold. Compound 17 exhibited a Ki = 6 nM at sst4 receptors with a 100-fold sst4/sst2 selectivity and was shown to be a full agonist at this receptor subtype. This article will review the literature on the design and development of nonpeptide somatostatin receptor ligands and the therapeutic potential of these agents. Furthermore, our work on the development of 2-pyridylthioureas as sst4 receptor agonists will be described.

Nonpeptide somatostatin agonists with sst4 selectivity: synthesis and structure-activity relationships of thioureas

Utilizing NNC 26-9100 (11) as a structural lead, a variety of nonpeptide derivatives of somatostatin were synthesized and evaluated for sst2 and sst4 receptor binding affinity. A novel thiourea scaffold was utilized to attach (1) a heteroaromatic nucleus to mimic the Trp8 residue, (2) a nonheteroaromatic nucleus to mimic Phe7, and (3) a primary amine or other basic group to mimic the Lys9 residue of somatostatin. Displacement studies were carried out using membranes from cell lines expressing ssts [BHK cells (sst4) and HEK 293 cells (sst2)] utilizing [125I]Tyr11-SRIF as the radioligand. Several thioureas (11, 38, 39, 41, and 42) and the urea 66 exhibited Ki values of less than 100 nM. The thioureas 11 (Ki = 6 nM) and 41 (Ki = 16 nM) and the urea 66 (Ki = 14 nM) are believed to be the most potent nonpeptide sst4 agonists known. Since the thiourea 11 and the urea 66 exhibit high sst4 selectivity, these novel nonpeptide derivatives may be useful tools for studying the sst4 receptor. Studies are currently in progress to evaluate the therapeutic potential of NNC 26-9100 (11) in the treatment of glaucoma.

The preferential dopamine D3 receptor agonist cis-8-OH-PBZI induces limbic Fos expression in rat brain

The affinity, selectivity and agonistic properties of a constrained dopaminergic compound, the benz[e]indole cis-8-hydroxy-3-(n-propyl)1,2,3a.4,5,9b-hexahydro-1H-benz[e]indole (cis-8-OH-PBZI), for the dopamine D3 receptor were evaluated in competition binding experiments with cloned human dopamine receptor subtypes and, to further extend its profile, in in vitro radioligand binding assays. The Ki value measured for competition binding of this compound to the dopamine D3 receptor was 27.4+/-3.1 nM; this was 775-fold, 550-fold, 90-fold and 10-fold higher affinity than that measured at dopamine D1A, D5, D2s and D4 receptors, respectively. Evidence of dopamine receptor activation by cis-8-OH-PBZI was obtained by measuring dose-dependent increases in extracellular acidification rates and decreases in cAMP synthesis. In vivo, cis-8-OH-PBZI potently induced Fos protein immunoreactivity in the rat medial prefrontal cortex and shell region of the nucleus accumbens, but only marginally in the motor dorsolateral striatum, indicating a selective limbic site of action. In conclusion, the present data identify cis-8-OH-PBZI as having preference for the dopamine D3 receptor in vitro, and as having dopamine agonist activity and limbic sites of action in vivo.

Anticonvulsant activity of novel derivatives of 2- and 3-piperidinecarboxylic acid in mice and rats

The relative ability of derivatives of 2-piperidinecarboxylic acid (2-PC; pipecolic acid) and 3-piperidinecarboxylic acid (3-PC; nipecotic acid) to block maximal electroshock (MES)-induced seizures, elevate the threshold for electroshock-induced seizures and be neurotoxic in mice was investigated. Protective index (PI) values, based on the MES test and rotorod performance, ranged from 1.3 to 4.5 for 2-PC benzylamides and from < 1 to > 7.2 for 3-PC derivatives. PI values based on elevation of threshold for electroshock-induced seizures and rotorod performance ranged from > 1.6 to > 20 for both types of derivatives. Since preliminary data indicated that benzylamide derivatives of 2-PC displace [3H]1-[1-(2-thienyl)-cyclohexyl]piperidine (TCP) binding to the phencyclidine (PCP) site of the N-methyl-D-aspartate (NMDA) receptor in the micromolar range and such low affinity uncompetitive antagonists of the NMDA receptor-associated ionophore have been shown to be effective anticonvulsants with low neurological toxicity, the 2-PC derivatives were evaluated in rat brain homogenates for binding affinity to the PCP site. Although all compounds inhibited [3H]TCP binding, a clear correlation between pharmacological activity and binding affinity was not apparent. Select compounds demonstrated minimal ability to protect against pentylenetetrazol-, 4-aminopyridine- and NMDA-induced seizures in mice. Corneal and amygdala kindled rats exhibited different sensitivities to both valproic acid and the nonsubstituted 2-PC benzylamide, suggesting a difference in these two models. Enantiomers of the alpha-methyl substituted benzylamide of 2-PC showed some ability to reduce seizure severity in amygdala kindled rats.

Morpholinoalkyl ester prodrugs of diclofenac: synthesis, in vitro and in vivo evaluation

Morpholinoalkyl esters (HCl salts) of diclofenac (1) were synthesized and evaluated in vitro and in vivo for their potential use as prodrugs for oral delivery. Prodrugs were freely soluble in simulated gastric fluid (SGF) and pH 7.4 phosphate buffer and showed a minimum of a 2000-fold increase in solubility over the parent drug. All prodrugs were more lipophilic than 1 as indicated by n-octanol/pH 7.4 buffer partition coefficients, but less lipophilic than 1 in terms of n-octanol/SGF partition coefficients. Potentiometrically determined ionization constants (pKas) were in the range of 7.52 to 8.40 at 25 degrees C. The chemical and enzymatic hydrolyses of prodrugs were evaluated in SGF/pH 7.4 phosphate buffer and rat plasma, respectively, at 37 degrees C. All prodrugs were quantitatively hydrolyzed to 1 by either chemical and/or enzymatic means. An increase in carbon chain length rendered the prodrugs more stable at pH 7.4, but less stable in SGF. In general, the esters were hydrolyzed rapidly in rat plasma at 37 degrees C, the half-lives of hydrolysis being in the range of 4.85 to 23.49 min. Based on in vitro results, prodrug 2 was chosen to evaluate solid-state stability, bioavailability, and in vivo ulcerogenicity. At elevated temperatures, the solid-state decomposition of 2 followed biphasic kinetics, with rapid decomposition occurring initially. The extent, but not the rate, of absorption was significantly greater in rats for prodrug 2 than 1 following single dose oral administration. Prodrug 2 was significantly less irritating to gastric mucosa than 1 following single and chronic oral administration in rats.

Synthesis and evaluation of morpholinoalkyl ester prodrugs of indomethacin and naproxen

Morpholinoalkyl esters (HCl salts) of naproxen 1 and indomethacin 3 were synthesized and evaluated in vitro and in vivo for their potential use as prodrugs for oral delivery. Prodrugs were freely soluble in simulated gastric fluid (SGF) and pH 7.4 phosphate buffer and showed a minimum of a 2000-fold increase in solubility over the parent drugs. All prodrugs were more lipophilic than parent drugs as indicated by n-octanol/pH 7.4 buffer partition coefficients but less lipophilic in terms of n-octanol/SGF partition coefficients. Potentiometrically determined pKa's for prodrugs were in the range of 6.89 to 8.62 at 25 degrees C. All prodrugs were quantitatively hydrolyzed to their respective parent drugs by enzymatic and/or by chemical means. An increase in carbon chain length rendered the prodrugs more stable at pH 7.4 but less stable in SGF. The esters were generally found to be hydrolyzed rapidly in rat plasma at 37 degrees C, the half-lives being in the range of 1.2-31.0 min. Based on in vitro results, prodrugs 2c and 4c were chosen to evaluate solid-state stability, in vivo bioavailability, and ulcerogenicity. At elevated temperatures, the solid-state decomposition of 2c and 4c followed biphasic kinetics, with rapid decomposition occurring initially. The prodrugs were 30-36% more bioavailable orally than the parent drugs following a single equimolar solution dose in rats. Prodrugs 2c and 4c were significantly less irritating to gastric mucosa than parent drugs following single-dose and chronic oral administration in rats.

cis-1,2,3a,4,5,9b-hexahydro-3H-benz[e]indoles: synthesis and in vitro binding affinity at dopamine D1 and D2 receptors

cis-1,2,3a,4,5,9b-Hexahydro-3H-benz[e]indoles were synthesized and evaluated for in vitro dopamine D1 and D2 receptor binding affinity. The target compounds 21-25 were readily prepared by reduction of the air-sensitive tricyclic enamines 10-14. Reduction of 10-14 with sodium borohydride, sodium cyanoborohydride, palladium on carbon in ethanol, and platinum oxide in ethanol or acetic acid gave only the cis (3a,9b) 1,2,3a,4,5,9b-hexahydro-3H-benz[e]indoles. The stereochemistry was confirmed by single-crystal X-ray analysis. In the 6-hydroxy series, the binding affinity at D1 and D2 receptors was of the order 22 (N-n-butyl) > 21 (N-n-propyl) > 23 (N-H). The compounds demonstrated greater binding affinity at D2 receptors than at D1 binding sites. In contrast, 8-OH derivatives exhibited affinity only for D2 receptors, with 25 (N-n-butyl) having slightly greater affinity than 24 (N-n-propyl).

Determination of m-nitrophenol and nipecotic acid in mouse tissues by high-performance liquid chromatography after administration of the anticonvulsant m-nitrophenyl-3-piperidinecarboxylate hydrochloride

The nipecotic acid ester m-nitrophenyl-3-piperidinecarboxylate (MNPC) possesses anticonvulsant activity. In the present study, the metabolites m-nitrophenol and nipecotic acid were determined in mouse blood and brain tissue after administration of MNPC. This determination was used as an indication of the distribution of the parent compound MNPC and to provide information regarding the differences in distribution between the enantiomers of MNPC, the times of onset, and effectiveness when (+/-) MNPC was administered by subcutaneous (sc) and intraperitoneal (ip) routes. m-Nitrophenol was determined by a previously reported high-performance liquid chromatography (HPLC) method. There was no significant difference in m-nitrophenol distribution after sc administration of (+)MNPC and (-)MNPC (400 mg/kg each). This similar pattern of distribution is in agreement with the earlier reported equi-effectiveness of the enantiomers of anticonvulsants. Peak m-nitrophenol levels in blood, which occurred at 15 min, were three times greater when (+/-) MNPC was administered by ip injection as compared with sc injection. This significant difference is most likely due to enhanced absorption and the peripheral metabolism of MNPC by the liver when the ip route is employed. A novel HPLC assay for the determination of nipecotic acid in mouse brain was developed, based on a modification of a reported amino acid analysis procedure. The results of the brain distribution studies showed that nipecotic acid brain levels peaked at 30 min after sc administration of (-)MNPC.(ABSTRACT TRUNCATED AT 250 WORDS)

Ester and amide prodrugs of ibuprofen and naproxen: synthesis, anti-inflammatory activity, and gastrointestinal toxicity

Ester and amide prodrugs of ibuprofen (1) and naproxen (16) were synthesized and evaluated for anti-inflammatory activity and gastrointestinal toxicity. The chemical structure of the prodrugs was varied in terms of lipophilicity and reactivity toward hydrolysis. Inhibition of acetic acid-induced writhing in mice indicated that prodrugs 7, 15, 19, and 20 exhibited significantly better activity (p less than 0.01) than the parent compounds. The average number of ulcers formed in the gastric mucosa following oral administration of 1 and 16 and prodrugs 5, 18, 21, and 22 was determined in rats. All prodrugs, except the glycine amide 21, were significantly less irritating to the gastric mucosa than either 1 or 16.

Hydrolysis of nipecotic acid phenyl esters

The synthesis and anticonvulsant activity of nipecotic acid esters (1a-1f) have been previously reported. It was thought that these prodrug esters underwent hydrolytic conversion to 1 which inhibited GABA uptake, and that both 1 and an intact ester may have caused inhibition of GABA uptake which resulted in the anticonvulsant activity. There is, however, no stability data available to help evaluate these effects. We have determined degradation half-lives (t 1/2) of these phenyl esters dissolved in 10% serum solution or in pH 7.4 buffer (ionic strength = 0.25 adjusted with KCl) at 37 degrees C by monitoring the appearance of a phenolic compound for a period of 12 h with an HPLC method. Utilizing a published method, in vitro [14C]GABA uptake was measured. Results show that the hydrolysis rate in 10% serum solution was faster than that in buffer solution and that half-lives varied between 0.20 and 3.84 h. The uptake inhibition varied between 8.2 and 41.7% at 0.02 mM concentration, and percent GABA uptake inhibition correlated with log t 1/2 (r = -0.9827, p = 0.00045, based on a t test). Our data suggest that at concentrations ranging from 0.02 to 1 mM, inhibition of GABA uptake is mainly due to 1 formed after hydrolysis of 1a-1f.

A comparison of prodrug esters of nipecotic acid

The relative ability of the enantiomers of the ethyl and m-nitrophenyl esters of nipecotic acid to block convulsions induced by bicuculline and pentylenetetrazol, as well as to block the uptake of GABA into whole brain mini-slices, was studied in mice. Neither (+)ethyl nipecotate hydrogen tartrate [(+)E.Tartrate], which is hydrolyzed to (-)nipecotic acid, nor (-)ethyl nipecotate hydrogen tartrate [(-)E.Tartrate], which is hydrolyzed to (+)nipecotic acid, provided protection against challenge with bicuculline. Both (+)E.Tartrate and (-)ethyl nipecotate hydrochloride [(-)E.HCl], which are hydrolyzed to (-)nipecotic acid, blocked seizures induced by pentylenetetrazol. However, neither (-)E.Tartrate nor (+)ethyl nipecotate hydrochloride [(+)E.HCl], which are hydrolyzed to (+)nipecotic acid, provided significant protection against challenge with pentylenetetrazol. These results agree with the relative ability of these compounds to inhibit the uptake of GABA, where (-)nipecotic acid was more potent than (+)nipecotic acid and (+)E.Tartrate was more potent than (-)E.Tartrate. The enantiomers of m-nitrophenyl-3-piperidinecarboxylate hydrochloride, (+)MNPC.HCl and (-)MNPC.HCl, were almost equi-effective in preventing seizures induced by bicuculline. This lack of significant difference in anticonvulsant activity is in contrast with the ability to inhibit the uptake of GABA, where (-)MNPC.HCl was significantly more potent than (+)MNPC.HCl. Changing the route of administration from subcutaneous to intraperitoneal injection reduced the onset of time of the peak effect and the anticonvulsant potency of (+/-)MNPC.HCl. Cholinergic effects were observed with the administration of (+)E.Tartrate and (-)E.HCl, but not with (-)E.Tartrate, (+)E.HCl, (+)MNPC.HCl or (-)MNPC.HCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Anticonvulsant activity of the nipecotic acid ester, (+/-)-m-nitrophenyl-3-piperidinecarboxylate

The nipecotic acid ester, (+/-)-m-nitrophenyl-3-piperidinecarboxylate hydrochloride (MNPC) is a potent inhibitor of uptake of GABA in vitro and should be able to penetrate into the brain much more readily than the parent compound nipecotic acid. A study of the effects of MNPC on convulsions induced by chemicals which interfere with GABA-mediated neurotransmission was carried out in the mouse, with MNPC being administered by subcutaneous injection 30, 60 or 90 min prior to challenge with bicuculline. It was found that MNPC protected against convulsions induced by bicuculline with ED50 values for clonic and tonic convulsions of 157.8 and 138.8 mg/kg, respectively, at the time of peak effect of 60 min and MNPC abolished both the clonic and tonic components of isoniazid convulsions with respective ED50 values of 255.3 and 76.7 mg/kg at 1 hr. Picrotoxin and pentylenetrazol-induced seizures were also blocked with corresponding ED50 values for clonic convulsions of 224.9 and 235.9 mg/kg at 1 hr. No serious side effects were observed during the 90 min period after the administration of MNPC in doses up to 600 mg/kg.

gamma-Aminobutyric acid uptake inhibition and anticonvulsant activity of nipecotic acid esters

n-Alkyl esters of nipecotic acid were prepared by Fischer esterification, and the esters were evaluated against bicuculline-induced seizures in mice. Evaluation of the alkyl esters for inhibition of gamma-aminobutyric acid uptake into mouse whole brain mini-slices revealed that the order of potency was proportional to chain length. The octyl ester inhibited gamma-aminobutyric acid and beta-alanine uptakes by apparently nonspecific mechanisms. A variety of phenyl esters of nipecotic acid were also synthesized utilizing either dicyclohexylcarbodiimide or 1,1'-carbonyldiimidazole as the condensing agent. Most of the phenyl esters were potent inhibitors of gamma-aminobutyric acid uptake. The uptake inhibition appeared to involve specific and nonspecific (detergent-like) mechanisms. The m-nitrophenyl and p-nitrophenyl esters were particularly potent against bicuculline-induced seizures in mice.

Synthesis and Dopaminergic Activity of 3-(3,4-Dihydroxyphenyl)-1-n-propylpyrrolidine Hydrobromide

3-(3,4-Dihydroxyphenyl)-1-n-propylpyrrolidine hydrobromide was synthesized by a six-step reaction sequence and was evaluated, and compared with apomorphine, for central dopaminergic agonist activity. The compound produced behavioral and biochemical changes characteristic of central dopaminergic stimulation. Administration of 3-(3,4-dihydroxyphenyl)-1-n-propylpyrrolidine hydrobromide to rats resulted in the reversal of the reserpine syndrome, stereotypic behavior, contralateral turning following 6-hydroxydopamine lesion of the substantia nigra, a decrease in dopamine turnover, and inhibition of prolactin release. These results indicate that 3-(3,4-dihydroxyphenyl)-1-n-propylpyrrolidine hydrobromide is a dopaminergic agonist. However, the compound exhibited a lower potency but a slightly longer duration of action than apomorphine.

Esters of nipecotic and isonipecotic acids as potential anticonvulsants

A variety of esters of nipecotic and isonipecotic acids were synthesized and evaluated for anticonvulsant activity. The ester group was varied in terms of lipophilicity and reactivity toward hydrolysis. The esters were screened against seizures induced by electroshock, pentylenetetrazol, and the putative gamma-aminobutyric acid antagonist, bicuculline. The most significant activity was demonstrated by the p-nitrophenyl esters of nipecotic and isonipecotic acids against bicuculline-induced seizures. Esters of nipecotic acid were tested for in vitro inhibition of gamma-aminobutyric acid and L-proline uptakes into mouse whole brain minislices. The p-nitrophenyl, n-octyl, and succinimidyl esters were the most potent inhibitors of gamma-aminobutyric acid uptake. The uptake of gamma-aminobutyric acid by the ester derivatives appeared to involve specific and nonspecific mechanisms.

Convenient synthesis of 6-nor-9,10-dihydrolysergic acid methyl ester

6-Nor-9,10-dihydrolysergic acid methyl ester (IV) was prepared by demethylation of 9,10-dihydrolysergic acid methyl ester (II) with 2,2,2-trichloroethyl chloroformate, followed by reduction of the intermediate carbamate (III) with zinc in acetic acid. The 6-ethyl-V and 6-n-propyl-VI derivatives were prepared by alkylation of IV with the appropriate halide. All of the ergoline derivatives were evaluated for stereotyped behavior in rats, with 6-nor-6-ethyl-9,10-dihydrolysergic acid methyl ester (V) being active but much less potent than apomorphine. Compound VI was evaluated for its effect on blood pressure; at a dose of 30 mg/kg ip, it significantly lowered, diastolic pressure in normotensive rats.

Synthesis and anticonvulsant activity of racemic 2-amino-N-substituted succinimide derivatives

Several derivatives of (R,S)-2-amino-N-substituted succinimides were synthetized and evaluated in mice against seizures produced by electroshock and pentylenetetrazol. The most active compound against both electroshock- and pentylenetetrazol-induced seizures was (R,S)-N-benzyl-2-(methanesulfamido)succinimide.

Synthesis of nitrosourea derivatives of pyridine and piperidine as potential anticancer agents

Nitrosourea derivatives 18-22 which utilize either a piperidine or pyridine ring as a carrier group were synthesized and evaluated for anticancer activity. N'-(1-Benzyl-4-piperidinyl)-N-(2-chloroethyl)-N-nitosourea hydrogen maleate (19) exhibited good activity against intracranial L1210 leukemia as well as the mouse ependymoblastoma brain tumor system. Compound 19 exhibited comparable activity in the Lewis lung carcinoma system to N,N'-bis(2-chloroethyl)-N-nitrosourea. Replacement of the N-benzyl group in both the 3-piperidinyl- and 4-piperidinylnitrosoureas resulted in less active compounds in all tumor systems tested. The 3-pyridylnitrosourea 22 was inactive in the L-1210 leukemia system.

Synthesis and anticancer activity of nitrosourea derivatives of phensuximide

Nitrosourea derivatives 9--13 which utilize phensuximide (1) as the carrier were synthesized as potential central nervous system antitumor agents. The N-(2-chloroethyl)-N-nitrosourea 13 was active in the mouse ependymoblastoma brain-tumor system, as well as the intraperitoneal L1210 leukemia system.

Ergot alkaloids. Synthesis of nitrosourea derivatives of ergolines as potential anticancer agents

Nitrosourea derivatives of ergolines have been synthesized for the purpose of obtaining agents with both prolactin-and tumor-inhibitory activity. Two derivatives of 8-amino-6-methylergoline (3), 8-[3-(2-chloroethyl)-3-nitrosoureido]-1-nitroso-6-methylergoline (5c) and 8-[3-2-chloroethyl)-3-nitrosoureido]-6-methylergoline (5a), have been prepared. In addition, nitroso (7) and chloroethylcarbamyl (8) derivatives of elymoclavine (6) are reported. Compounds 5a and 5c have activity against L1210 leukemia in mice but only moderate prolactin-inhibiting activity. The chloroethylcarbamyl derivative 8 of elymoclavine is a potent prolacting inhibitor.

Ergot alkaloids. Synthesis of 6-alkyl-8-ergolenes and 6-methyl-8-aminoergolines as potential prolactin inhibitors

The synthesis of several N-6 derivatives of elymoclavine (3) and potential alkylating derivatives of 6-methyl-8-aminoergolines (12) is described. These compounds were screened for prolactin-inhibiting ability and 6-propyl-8-hydroxymethyl-8-ergolene (9) was found to be as active as the most potent prolactin inhibitors reported to date. The total synthesis of racemic methyl dihydrolysergate I (23), having a trans C, D ring fusion, from the tricyclic ketone 18 is also described.

Potential long-acting anticonvulsants. 2. Synthesis and activity of succinimides containing an alkylating group on nitrogen or at the 3 position

The synthesis of succinimide derivatives in which alkylating groups have been attached to the imide nitrogen or to the 3 position of the ring is described. The synthesis of one bis-alkylating derivative 19 is also described. The alkylating groups used were (a) alpha-haloacetyl, (b) alpha-haloacetamido, (c) maleamyl, and (d) maleimido. These compounds were prepared as potential long-acting anticonvulsants. None of the compounds showed activity against maximal electroshock or metrazole-induced seizures.

Potential long-acting anticonvulsants. 1; Synthesis and activity of succinimides containing an alkylating group at the 2 position

The synthesis of succinimide derivatives in which alkylating groups have been attached to the 2 positions of the ring or to the para position of the 2-phenyl substituent is described. The alkylating groups used were (a) alpha-haloacetyl, (b) alpha-haloacetamido, (c) maleimido, and (d) maleamyl. These compounds were prepared as potential long-acting anticonvulsants. Several of these derivatives exhibited activity against metrazole-induced seizures comparable to phensuximde, The maleimide 16 and the bromoacetamido derivative 23 exhibited a duration of action of at least 3.5 h.