Synthesis, corticotropin-releasing factor receptor binding affinity, and pharmacokinetic properties of triazolo-, imidazo-, and pyrrolopyrimidines and -pyridines

Selectfluor-Induced Oxidative Amination of N-Heteroaromatics with Purine

An oxidative coupling reaction between purines and aromatic N-heterocycles was developed to synthesize a series of N-heteroaryl purine derivatives using Selectfluor as an oxidant at room temperature. This process uses a commercial oxidant, uses no base, metal, or other additives, is simple to carry out, and has a broad range of substrates.

Purinyl N(3)-Directed Palladium-Catalyzed C-H Alkoxylation of N(9)-Arylpurines: A Late-Stage Strategy to Synthesize N(9)-(ortho-Alkoxyl)arylpurines

A palladium-catalyzed alkoxylation of N(9)-arylpurines with primary or secondary alcohols has been developed successfully, which is a rare C-H activation reaction of polynitrogenated purines and offers a late-stage strategy to synthesize N(9)-(ortho-alkoxyl)arylpurines. Although there are more than four nitrogen atoms present in the purine moiety, the reaction can be effectively conducted by sterically blocking the N(1) site for catalyst coordination and first employing the purinyl N(3) atom as a directing group.

Discovery of 1-[9-(4-chlorophenyl)-8-(2-chlorophenyl)-9H-purin-6-yl]-4-ethylaminopiperidine-4-carboxylic acid amide hydrochloride (CP-945,598), a novel, potent, and selective cannabinoid type 1 receptor antagonist

We report the structure-activity relationships, design, and synthesis of the novel cannabinoid type 1 (CB1) receptor antagonist 3a (CP-945,598). Compound 3a showed subnanomolar potency at human CB1 receptors in binding (Ki = 0.7 nM) and functional assays (Ki = 0.12 nM). In vivo, compound 3a reversed cannabinoid agonist-mediated responses, reduced food intake, and increased energy expenditure and fat oxidation in rodents.

Antalarmin

In the mol­ecule of the title compund [systematic name: N-butyl-N-ethyl-2,5,6-trimethyl-7-(2,4,6-trimethyl­phen­yl)-7H-pyrrolo[2,3-d]pyrimidin-4-amine], C₂₄H₃₄N₄, the pyrrolopy­rimidine ring system is nearly planar, its five- and six-membered rings forming a dihedral angle of 5.3 (2)°. The benzene ring is nearly orthogonal to the central ring system. The N atom carrying the ethyl and n-butyl groups is flattened pyramidal.

Kv7/KCNQ/M-channels in rat glutamatergic hippocampal axons and their role in regulation of excitability and transmitter release

M-current (I(M)) plays a key role in regulating neuronal excitability. Mutations in Kv7/KCNQ subunits, the molecular correlates of I(M), are associated with a familial human epilepsy syndrome. Kv7/KCNQ subunits are widely expressed, and I(M) has been recorded in somata of several types of neurons, but the subcellular distribution of M-channels remains elusive. By combining field-potential, whole-cell and intracellular recordings from area CA1 in rat hippocampal slices, and computational modelling, we provide evidence for functional M-channels in unmyelinated axons in the brain. Our data indicate that presynaptic M-channels can regulate axonal excitability and synaptic transmission, provided the axons are depolarized into the I(M) activation range (beyond approximately -65 mV). Here, such depolarization was achieved by increasing the extracellular K(+) concentration ([K(+)](o)). Extracellular recordings in the presence of moderately elevated [K(+)](o) (7-11 mm), showed that the specific M-channel blocker XE991 reduced the amplitude of the presynaptic fibre volley and the field EPSP in a [K(+)](o)-dependent manner, both in stratum radiatum and in stratum lacknosum moleculare. The M-channel opener, retigabine, had opposite effects. The higher the [K(+)](o), the greater the effects of XE991 and retigabine. Similar pharmacological modulation of EPSPs recorded intracellularly from CA1 pyramidal neurons, while blocking postsynaptic K(+) channels with intracellular Cs(+), confirmed that active M-channels are located presynaptically. Computational analysis with an axon model showed that presynaptic I(M) can control Na(+) channel inactivation and thereby affect the presynaptic action potential amplitude and Ca(2+) influx, provided the axonal membrane potential is sufficiently depolarized. Finally, we compared the effects of blocking I(M) on the spike after-depolarization and bursting in CA3 pyramidal neuron somata versus their axons. In standard [K(+)](o) (2.5 mm), XE991 increased the ADP and promoted burst firing at the soma, but not in the axons. However, I(M) contributed to the refractory period in the axons when spikes were broadened by a low dose 4-aminopyridine (200 microm). Our results indicate that functional Kv7/KCNQ/M-channels are present in unmyelinated axons in the brain, and that these channels may have contrasting effects on excitability depending on their subcellular localization.

Microwave-assisted N-nitroarylation of some pyrimidine and purine nucleobases

An efficient procedure for the synthesis of some N-nitroaryl derivatives of nucleobases via microwave-assisted N-nitroarylation of nucleobases in the presence of SiO2 and Cs2CO3 in DMSO, as the homogenizing solvent, is described. In this method, some pyrimidine and purine nucleobases are nitroarylated regioselectively in moderate to high yields and short reaction times.Key words: microwave, N-nitroarylation, pyrimidine, purine, SNAr.

First dual M3 antagonists-PDE4 inhibitors: synthesis and SAR of 4,6-diaminopyrimidine derivatives

SAR around 4,6-diaminopyrimidine derivatives allowed the discovery of the first potent dual M(3) antagonists and PDE4 inhibitors. Various chemical modulations around that scaffold led to the discovery of ucb-101333-3 which is characterized by the most interesting profile on both targets.

2-n-Butyl-9-methyl-8-[1,2,3]triazol-2-yl-9H-purin-6-ylamine and analogues as A2A adenosine receptor antagonists. Design, synthesis, and pharmacological characterization

Two types of adenosine receptor ligands were designed, i.e., 9H-purine and 1H-imidazo[4,5-c]pyridines, to obtain selective A(2A) antagonists, and we report here their synthesis and binding affinities for the four adenosine receptor subtypes A(1), A(2A), A(2B) and A(3). The design was carried out on the basis of the molecular modeling of a number of potent adenosine receptor antagonists described in the literature. Three compounds (25b-d) showed an interesting affinity and selectivity for the A(2A) subtype. One of them, i.e., ST1535 (2-n-butyl-9-methyl-8-[1,2,3]triazol-2-yl-9H-purin-6-ylamine, 25b) (K(i) A(2A) = 6.6 nM, K(i) A(1)/A(2A) = 12; K(i) A(2B)/A(2A) = 58; K(i) A(3)/A(2A) > 160), was selected for in vivo study and shown to induce a dose-related increase in locomotor activity, suggestive of an A(2A) antagonist type of activity.

Synthesis of Tricyclic 4-Chloro-pyrimido[4,5-b][1,4]benzodiazepines

[reaction: see text] A novel methodology was developed for the efficient synthesis of 4-chloro-pyrimido[4,5-b][1,4]benzodiazepines. The key is the intramolecular Friedel-Crafts cyclization of 5-amino-4-(N-substituted)anilino-6-chloropyrimidine with either a carboxylic acid or its derivatives to construct the 4-chloro-pyrimido[4,5-b][1,4]benzodiazepine core. Subsequent nucleophilic substitution allows the introduction of one more diversity point in the target molecules. This strategy provides an efficient method to access a library of compounds based on privileged substructures that are of great interest in drug discovery.

Preparation of a Fully Substituted Purine Library

A library of tetra-substituted purine analogues was readily prepared via parallel synthesis. This strategy relies on a key cyclization of a 4,5-diaminopyrimidine with either a carboxylic acid or its derivative to construct the 2,8,9-trisubstituted 6-chloropurine core. Further elaborations of this core allow the introduction of other diversity points. This methodology is demonstrated through the preparation of a 135-membered library of tetra-substituted purines in good yields and high purity.

Structure-activity studies on the corticotropin releasing factor antagonist astressin, leading to a minimal sequence necessary for antagonistic activity

Corticotropin Releasing Factor (CRF) antagonists are considered promising for treatment of stress-related illnesses such as major depression and anxiety-related disorders. We report here the design, synthesis and biological evaluation of 91 truncated astressin analogues in order to deduce the pharmacophoric amino acid residues. Such truncated peptides may serve as valuable lead structures for the development of new small, non-peptide-based CRF antagonists. N-Terminal truncation of astressin led to active CRF antagonists that are substantially reduced in size and are selectively active at the human CRF receptor type 1 in vitro and in vivo. Subsequently, an alanine scan in combination with further truncated derivatives led to the proposal of a new pharmacophoric model of peptide-based CRF antagonists. It was found that the astressin(27-41)C sequence is the shortest active CRF antagonist. The first eight N-terminal amino acid residues were found to be an important structural determinant and were replaceable by alanine residues, thus enhancing the alpha-helical propensity. A covalent structural constraint is of utmost importance for the preorganization of the C-terminal amino acid residues. The C-terminal heptapeptide sequence, however, was found to be crucial for the antagonistic activity, since substitution or deletion of any residue led to inactive compounds.

Synthesis and SAR of 8-arylquinolines as potent corticotropin-releasing factor1 (CRF1) receptor antagonists

A series of 4-substituted 8-aryl-2-methylquinolines 4 was designed and synthesized as highly potent antagonists for the human CRF(1) receptor. This series of compounds displayed parallel SAR to other bicyclic systems such as pyrazolo[1,5-a]pyrimidines, with several compounds possessing low nanomolar binding affinity. In addition to the high potency, the basicity of this 4-aminoquinoline core may offer CRF(1) antagonists with lower lipophilicity.

Pyrazolo-[1,5-a]-1,3,5-triazine corticotropin-releasing factor (CRF) receptor ligands

The syntheses and rat CRF receptor binding affinities of 'retro-pyrazolotriazine' corticotropin-releasing factor (CRF) ligands 4 are reported. Some have high affinity for rat CRF receptors (K(i)< or =10 nM). The data provide additional support for the hypothesis that it is possible to interchange isosteric cores with similar electronic properties in the design of high-affinity CRF receptor ligands, provided the peripheral pharmacophore elements are maintained in the same three-dimensional array.

Effects of antalarmin, a CRF type 1 receptor antagonist, on anxiety-like behavior and motor activation in the rat

Molecular studies point to a role for the type 1 corticotropin-releasing factor receptor (CRF(1)) in anxiogenic-like and activating effects of CRF and stress. However, CP-154,526, a selective CRF(1) antagonist, has yielded mixed results in such tests. Few studies have examined the behavioral effects of other CRF(1) antagonists. Therefore, we examined the effects of antalarmin, a structurally related analog of CP-154,526, on anxiety-like behavior and motor activation. Antalarmin blocked the anxiogenic-like effect of CRF in the elevated plus maze, without affecting anxiety-like behavior in vehicle-treated animals. Antalarmin decreased spontaneous defensive withdrawal behavior in a novel, brightly illuminated open field. Finally, antalarmin blocked the activating effects of CRF, but not D-amphetamine, without producing motor sedation. These findings indicate that the CRF(1) receptor mediates anxiogenic-like effects of novelty stress and the anxiogenic-like and activating effects of CRF and support the hypothesis that CRF(1) antagonists may be useful for the pharmacotherapy of pathological anxiety.

3-Aryl pyrazolo[4,3-d]pyrimidine derivatives: Nonpeptide CRF-1 antagonists

The synthesis of a series of 3-aryl pyrazolo[4,3-d]pyrimidines as potential corticotropin-releasing factor (CRF-1) antagonists is described. The effects of substitution on the aromatic ring, the amino group and the pyrazolo ring on CRF-1 receptor binding were investigated.

Antimicrobial and antitumor activity of N-heteroimmine-1,2,3-dithiazoles and their transformation in triazolo-, imidazo-, and pyrazolopirimidines

The reaction of Appel's salt with o-amino nitrile heterocycles 10-19 gave the corresponding 4-chloro-5-heteroimmine-1,2,3-dithiazoles 20-29 which were evaluated for their antibacterial, antifungal and antitumor activity. Although all these N-heteroimines were devoid of significant antibacterial activity, they showed significant antifungal activity. Moreover, the same derivatives represent highly versatile intermediates in heterocyclic synthesis, in fact the pyrazoleimino dithiazoles 20-26 can be converted in one step into 2-cyano derivatives of the corresponding 4-methoxy-pyrazolo[3,4-d]pyrimidines 30-35 by sodium methoxide in refluxing methanol. This provides a general and attractive route to 4-methoxy-6-cyano pyrazolo[3,4-d]pyrimidines from 1-substituted 5-amino pyrazoles 10-19 in two simple steps. Finally, the isosteric replacement of the pyrazole ring atoms to give the imidazole[3,4-d]pyrimidine and triazole [4,5-d] pyrimidine ring systems was examined.

CRHR1 Receptor binding and lipophilicity of pyrrolopyrimidines, potential nonpeptide corticotropin-releasing hormone type 1 receptor antagonists

A series of compounds related to N-butyl-N-ethyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amine (1, antalarmin) have been prepared and evaluated for their CRHR1 binding affinity as the initial step in the development of selective high affinity hydrophilic nonpeptide corticotropin-releasing hormone type 1 receptor (CRHR1) antagonists. Calculated log P (Clog P) values were used to evaluate the rank order of hydrophilicity for these analogues. Introducing oxygenated functionalities (delta-hydroxy or bis-beta-ethereal) into 1 gave more hydrophilic compounds, which had good affinity for the receptor. Introducing an amino group or shortening the alkyl side chain was detrimental to CRHR1 affinity. The alcohol 4-[ethyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amino]butan-1-ol (3), bearing a terminal hydroxyl group on an N-alkyl side-chain, showed the highest CRHR1 binding affinity among these compounds (K(i)=0.68 nM), and is one of the highest affinity CRHR1 ligands known. Compounds 3-5, and 8, which are likely to be less lipophilic than 1, have high CRHR1 affinity and may be valuable probes to further study the CRH system.

Synthesis and characterization of fluorinated and iodinated pyrrolopyrimidines as PET/SPECT ligands for the CRF1 receptor

Fluorine-18 labeled fluorobutyl[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo [2,3-d] pyrimidin-4-yl]ethylamine (FBPPA) and iodine-123 labeled butyl[2,5-dimethyl-7-(4-iodo-2,6-dimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl]ethyl-amine (IBPPA) were synthesized in the development of a CRF receptor ligand. The methods of synthesis, in vitro binding assays, radiolabeling and in vivo tissue distribution in rats are described. Fluorine-18 labeled FBPPA was prepared with high specific activity (3 x 10(4) Ci/mmol) by nucleophilic displacement with an average radiochemical yield of 6% (EOB). Iodine-123 labeled IBPPA was prepared by electrophilic iododestannylation with good yield (60%) and high specific activity (3.3 x 10(3) Ci/mmol). The retention of FBPPA and IBPPA in the pituitary was good (1.16% i.d./g and 2.35% i.d./g respectively at 60 min). However, the accumulation of radioactivity in the brain for both radiotracers was very low at all time points of the study, which demonstrated the difficulties for these radiopharmaceuticals to penetrate the blood brain barrier (BBB).

Corticotropin releasing hormone: therapeutic implications and medicinal chemistry developments

Corticotropin releasing hormone (CRH, sometimes known as CRF) is an endogenous 41 amino acid peptide that has been implicated in the onset of pregnancy, the 'fight or flight' response, in addition to a large number of physiological disorders. Recently, medicinal chemists have developed a number of potent and selective compounds that show promise in a vast array of therapeutic uses. Herein we review the current status of research.

Design, synthesis and structure-affinity relationships of 4-methylidenepiperidine and 4-aryl-1,2,3,6-tetrahydropyridine derivatives as corticotropin-releasing factor1 receptor antagonists

Recently, various non-peptide corticotropin-releasing factor1 (CRF1) receptor antagonists have been reported. Structure-affinity relationships (SARs) of non-peptide CRF antagonists suggest that such antagonists can be constructed of three units: a hydrophobic unit (Up-Area), a proton accepting unit (Central-Area), and an aromatic unit (Down-Area). Our interest focused on the Up-Area in deriving the novel methylidenepiperidine derivatives 8-10 and 4-aryl-1,2,3,6-tetrahydropyridine derivatives 11-13 as non-peptide CRF1 receptor antagonists. Compounds 8a and 11a had moderate affinity for CRF1 receptor, but compounds 9, 10, 12 and 13 did not exhibit CRF1 receptor affinity. Modification of derivatives 11 afforded compounds 11i (CRA1001) and 11x (CRA1000), which had high affinity and selectivity for CRF1 receptors with potent anxiolytic-like and antidepressant-like properties in some experimental animal models. These findings suggest that the hydrophonic unit (Up-Area) may be useful for design of CRF1 antagonists. We report here the design, synthesis and SARs of the derivatives 8 and 11 and isosteres 9, 10, 12 and 13.

Synthesis and biological activity of fluoro-substituted pyrrolo[2,3-d]pyrimidines: the development of potential positron emission tomography imaging agents for the corticotropin-releasing hormone type 1 receptor

A series of fluoro-substituted 4-(dialkylamino)pyrrolo[2,3-d]pyrimidines was synthesized and their binding affinity for corticotropin-releasing hormone type 1 receptor (CRHR1) was investigated. Compounds 11a and 11b possessed very high CRHR1 affinity (Ki=3.5, 0.91 nM, respectively). They are promising candidates for the development of 18F-containing nonpeptide PET radioligands for CRHR1.

4-(1,3-Dimethoxyprop-2-ylamino)-2,7-dimethyl-8-(2, 4-dichlorophenyl)pyrazolo[1,5-a]-1,3,5-triazine: a potent, orally bioavailable CRF(1) receptor antagonist

Structure-activity studies in the pyrazolo[1,5-a]-1,3,5-triazine series led to the discovery that compound 11i (DMP696) is a potent hCRF(1) receptor antagonist (K(i) = 1.7 nM vs 7.5 nM for alpha-hel-CRF(9-41), hCRF(1) adenylate cyclase IC(50) = 82 nM vs 286 nM for alpha-hel-CRF(9-41)). Compound 11i has excellent oral pharmacokinetic profiles in rats and dogs (37% and 50% oral bioavailabilities, respectively). This compound displays good activity in the rat situational anxiety model (MED = 3 mg/kg (po)), whereas a literature standard 1 (CP154526-1) was inactive (MED > 30 mg/kg (po)). Analogue 11i reduced stereotypical mouth movements in rhesus monkeys by 50% at 21 mg/kg (po) using the human intruder paradigm. Overall, the profile of pyrazolotriazine 11i indicates that hCRF(1) receptor antagonists may be anxiolytic agents, which have reduced motor side effect profiles.

The discovery of 4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)-pyrazolo-[1 ,5-a]-pyrimidine: a corticotropin-releasing factor (hCRF1) antagonist

Structure activity relationship studies led to the discovery of 4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)-pyrazo lo-[1,5-a]-pyrimidine 11-31 (DMP904), whose pharmacological profile strongly supports the hypothesis that hCRF1 antagonists may be potent anxiolytic drugs. Compound 11-31 (hCRF1 Ki = 1.0+/-0.2 nM (n = 8)) was a potent antagonist of hCRF1-coupled adenylate cyclase activity in HEK293 cells (IC50= 10.0+/-0.01 nM versus 10 nM r/hCRF, n = 8); alpha-helical CRF(9-41) had weaker potency (IC50 = 286+/-63 nM, n = 3). Analogue 11-31 had good oral activity in the rat situational anxiety test; the minimum effective dose for 11-31 was 0.3 mg/kg (po). Maximal efficacy (approximately 57% reduction in latency time in the dark compartment) was observed at this dose. Chlordiazepoxide caused a 72% reduction in latency at 20 mg/kg (po). The literature compound 1 (CP154526-1, 30 mg/kg (po)) was inactive in this test. Compound 11-31 did not inhibit open-field locomotor activity at 10, 30, and 100 mg/kg (po) in rats. In beagle dogs, this compound (5 mg/kg, iv, po) afforded good plasma levels. The key iv pharmacokinetic parameters were t1/2, CL and Vd,ss values equal to 46.4+/-7.6 h. 0.49+/-0.08 L/kg/h and 23.0+/-4.2 L/kg, respectively. After oral dosing, the mean Cmax, Tmax t1/2 and bioavailability values were equal to 1260+/-290 nM, 0.75+/-0.25 h. 45.1+/-10.2 h and 33.1%, respectively. The overall rat behavioral profile of this compound suggests that it may be an anxiolytic drug with a low motor side effect liability.

Corticotropin-releasing factor antagonists in affective disorders

Following a search lasting nearly three decades, corticotropin-releasing factor (CRF), a 41 amino acid-containing peptide, was isolated and characterised in 1981. In the preceding 18 years, a concatenation was developed that appears to show that CRF integrates not only the endocrine, but also the autonomic, immunologic and behavioural responses of mammalian organisms to stress. Direct CNS administration of CRF to laboratory animals produces actions similar to those observed after exposure to stress. Moreover, CNS administration of peptidergic CRF antagonists blocks many of the behavioural responses to stress. Since both early untoward life events as well as recently experienced stress have been implicated in the pathophysiology of affective disorders, and because there is substantial evidence for CRF neuronal hyperactivity in patients with affective disorders, small molecule, lipophilic CRF antagonists have been hypothesised to possess antidepressant and/or anxiolytic activity. Within the last few years, a number of pharmaceutical companies have developed selective, small molecule CRF(1) receptor antagonists. These compounds block the effects of CRF both in vitro and in vivo. There is also evidence that these agents possess anxiolytic and antidepressant activity in animal behavioural models. Compounds that act upon the CRF system have been hypothesised to be of value not only for certain psychiatric disorders, but also in neurodegenerative and inflammatory disorders. Some of these CRF(1) receptor antagonists are currently undergoing clinical trials to determine their efficacy and tolerability in patients with mood and anxiety disorders.

Constrained corticotropin releasing factor antagonists (astressin analogues) with long duration of action in the rat

In an earlier report we identified specific modifications and substitutions of corticotropin releasing factor (CRF) that led to the discovery of antagonists with extended duration of action as compared to that of astressin {cyclo(30-33)[DPhe(12),Nle(21),Glu(30), Lys(33),Nle(38)]hCRF((12)(-)(41))}. These additional modifications included elongation of the peptide chain by three residues at the N-terminus, its acetylation, and the [CalphaMeLeu(27)] substitution to yield cyclo(30-33)[DPhe(12), Nle(21),CalphaMeLeu(27),Glu(30), Lys(33),Nle(38)]Ac-hCRF((9)(-)(41)), which was found to be longer acting than astressin (Rivier, J.; et al. J. Med. Chem. 1998, 41, 5012-5019). To further increase the efficiency (potency, duration of action, and bioavailability) of this family of antagonists, we introduced two or more CalphaMe-leucine residues at positions shown in earlier studies to be favorable (Hernandez, J.-F.; et al. J. Med. Chem. 1993, 36, 2860-2867). Whereas the introduction of CalphaMe-leucine residues at positions 27 and either 18 (11), 37 (17), or 40 (19) resulted in dramatic increases in duration of inhibitory action in the adrenalectomized (adx) rat after intravenous injection, the same substitution at positions 27 and either 15 (7, 8), 17 (9), 19 (12, 13), or 41 (20) led to short acting analogues. Other substitutions by CalphaMeLeu at positions 27 and either 10 (4), 13 (5), 14 (6), 21 (14), 24 (15), 36 (16), or 38 (18) yielded analogues with duration of action intermediate between those mentioned above. Cyclo(30-33)[DPhe(12), Nle(21), CalphaMeLeu(27),Glu(30),Lys(33),Nle(38), CalphaMeLeu(40)]Ac-hCRF((9)(-)(41)) (astressin B, 19) was one of the most efficacious analogues of this series (>4 h inhibition of ACTH secretion at 25 microgram/adx rat). It was found to be even longer acting via subcutaneous administration in either an aqueous (>24 h inhibition of ACTH secretion at 100 microgram/adx rat) or lipid milieu (DMSO/peanut oil, >24 h inhibition of ACTH secretion at 30 microgram/adx rat) than after intravenous administration (<12 h inhibition of ACTH secretion at 100 microgram/adx rat). We concluded that Calpha-methylation at some positions may favor a bioactive conformation while also preventing degradation and/or elimination, resulting in significant extension of duration of action.

Nonpeptidic ligands for peptide and protein receptors

The first potent nonpeptidic ligands for somatostatin, luteinizing hormone-releasing hormone, glucagon and bradykinin receptors have been reported. Nonpeptidic clinical candidates have been identified or are currently under study for substance P, bradykinin, endothelin, growth hormone secretagogue, angiotensin, vasopressin, motilin and cholecystokinin. Design, screening, combinatorial chemistry and classical medicinal chemistry all played important roles in these advances.

Thiazolo[4,5-d]pyrimidine thiones and -ones as corticotropin-releasing hormone (CRH-R1) receptor antagonists

A series of thiazolo[4,5-d]pyrimidine thiones and -ones was prepared and discovered to have good binding affinity to the CRH-R1 receptor, thus showing promise as a new class of potential anxiolytics and/or antidepressants.

4-Aryl-2-anilinopyrimidines as corticotropin-releasing hormone (CRH) antagonists

A series of 4-aryl-2-(N-ethylanilino)pyrimidines has been synthesized as corticotropin-releasing hormone (CRH) inhibitors. The effect of substitution on each aromatic ring on receptor binding was investigated.

Purin-8-ones as corticotropin-releasing hormone (CRH-R1) receptor antagonists

A series of purin-8-ones was prepared and discovered to have excellent binding affinity to the CRH-R1 receptor. Structure-activity studies focused on amine side-chain optimization, urea substitution and pyridyl isostere incorporation. Thus, the highly potent purin-8-ones show promise as a new class of potential anxiolytics and/or antidepressants.

Use of the Suzuki reaction for the synthesis of aryl-substituted heterocycles as corticotropin-releasing hormone (CRH) antagonists

The Suzuki reaction has been used to synthesize a variety of aryl-substituted heterocyclic antagonists of the CRH1 receptor. Examples with several different heterocyclic cores are potent CRH receptor ligands.