Synthesis of 1-methyl-3-phenylpyrazolo[4,3-b]pyridines via a methylation of 4-phthalimino-3-phenylpyrazoles and optimization toward highly potent corticotropin-releasing factor type-1 antagonists

1-Methyl-3-phenylpyrazolo[4,3-b]pyridines were synthesized via a cyclization reaction of 1-methyl-4-amino-3-phenylpyrazoles 8 with ethyl acetoacetate. Optimization of this series of compounds resulted in CRF(1) antagonists with subnanomolar binding affinity. Compounds bearing a polar group such as methoxy or hydroxy were also found to be very active.     

Synthesis of 3-(alpha- and beta-D-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine

Di-O-isopropylidene- and O-methanesulfonyl-protected 1-C-(6-chloro-1,2,4-triazolo[4,3-b]pyridazin-3-yl)pentitols were prepared in three to four steps from D-galactose, D-glucose, D-mannose, and 2,3:5,6-di-O-isopropylidene-alpha-D-mannofuranose. Acid-catalysed treatment of (1S)- and (1R)-1-C-(6-chloro-1,2,4-triazolo[4,3-b]-pyridazin-3-yl)-2,3:4,5-di-O-isopropylidene-1-O-methanesulfonyl-D-arabinitols in refluxing 1,2-dimethoxyethane furnished 3-(alpha- and beta-D-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine, respectively. Several structures, including the structure of the 3-(beta-D-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine, were also determined by single-crystal X-ray diffraction analysis.     

Novel 1-(azacyclyl)-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines as 5-HT6 agonists and antagonists

1-Aminoethyl-3-arylsulfonyl-1H-indoles 1 are 5-HT(6) receptor ligands with modest activity in a 5-HT(6) cyclase assay. Introduction of an additional nitrogen in the indole ring provides 1-aminoethyl-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines 2 with both enhanced 5-HT(6) affinity and cyclase activity, many acting as 5-HT(6) agonists. We constrained the basic side chain as part of a ring to make 1-(azacyclyl)-3-arylsulfonyl-1H-pyrrolo[2,3-b]pyridines incorporating a pyrrolidinyl 3 or piperidinyl 4 ring system. Preparation of compounds 3 and 4 required synthesis of the key intermediates, 1-(pyrrolidin-3-yl)-1H-pyrrolo[2,3-b]pyridines 7 and 1-(piperidin-3-yl)-1H-pyrrolo[2,3-b]pyridines 8, respectively. Intermediates 7 were prepared through alkylation of 7-azaindole while the intermediates 8 required an alternate synthesis. The compounds of both series 3 and 4 were shown to have high binding affinities for the 5-HT(6) receptor. The in vitro functional activity at the 5-HT(6) receptor varied depending on various functionalities including the selection of the arylsulfonyl, the substitution on the arylsulfonyl group, the ring size, and the substitution on the basic amine moiety producing either 5-HT(6) receptor agonists or antagonists.     

3-(4-Piperidinyl)indoles and 3-(4-piperidinyl)pyrrolo-[2,3-b]pyridines as ligands for the ORL-1 receptor

A novel series of indoles and 1H-pyrrolo[2,3-b]pyridines having a piperidine ring at the 3-position were synthesized and found to bind with high affinity to the ORL-1 receptor. Structure-activity relationships at the piperidine nitrogen were investigated in each series. Substitution on the phenyl ring and nitrogen atom of the indole and 1H-pyrrolo[2,3-b]pyridine cores generated several selective high-affinity ligands that were agonists of the ORL-1 receptor.     

Activation of a mutagen, 3-amino-1-methyl-5H-pyrido[4,3-b]indole. Identification of 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole and its reaction with DNA

A potent mutagen, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), isolated from a tryptophan pyrolysate, was activated metabolically by rat liver microsomes and bound to DNA. An active metabolite formed by rat liver microsomes was identified as 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole (N-OH-Trp-P-2). Synthetic N-OH-Trp-P-2 reacted with DNA efficiently after O-acetylation or to a lesser extent under acidic conditions (pH 5.5), but did not react appreciably under neutral conditions. Acid hydrolysis of DNA modified by O-acetylated N-OH-Trp-P-2 (N-OAc-Trp-P-2) gave 3-(8-guanyl)amino-1-methyl-5H-pyrido[4,3-b]indole (Gua-Trp-P-2), which is the main modified base of DNA formed by Trp-P-2 in the presence of microsomes. The glycoside bond of the modified base was found to be cleaved by heating at 100° for 1 hr at pH 7.0. In this way, the modified base was liberated from DNA modified by N-OAc-Trp-P-2 in good yield. N-OAc-Trp-P-2 bound to guanyl cytidine more effectively than to guanylic acid, suggesting that covalent binding with guanyl moiety of DNA involves intercalation of the ultimate mutagen into a base pair.     

5-aryl-pyrazolo[3,4-b]pyridines: potent inhibitors of glycogen synthase kinase-3 (GSK-3)

A novel series of pyrazolo[3,4-b]pyridines has been identified that are potent inhibitors of glycogen synthase kinase-3 (GSK-3).     

6-aryl-pyrazolo[3,4-b]pyridines: potent inhibitors of glycogen synthase kinase-3 (GSK-3)

A novel series of 6-aryl-pyrazolo[3,4-b]pyridines has been identified that are potent inhibitors of glycogen synthase kinase-3 (GSK-3).     

Synthesis and biological evaluation of novel pyrazolo[4,3-b]oleanane derivatives as inhibitors of glycogen phosphorylase

Eighteen pyrazolo[4,3-b]oleanane derivatives have been synthesized and biologically evaluated as inhibitors of rabbit muscle GPa. Key compound 5 was readily obtained in four steps starting from oleanolic acid (OA; 1). Further modification based on pyrazolo triterpene 5 resulted in 17 novel pyrazolo pentacyclic triterpenes. All of the synthesized pyrazolo[4,3-b]oleanane derivatives were biologically assayed against rabbit muscle GPa. Within this series of compounds, pyrazole triterpene 19 (IC(50)=9.9 microM) exhibited more potent activity than the parent compound 1. Preliminary structure-activity relationship analysis of the pyrazolo[4,3-b]oleanane derivatives as GPa inhibitors is discussed.     

Mutagenicity of some heterocyclic amines in Salmonella typhimurium with metabolic activation by human red blood cell cytosol.

Purified human red blood cell cytosol was used to activate the heterocyclic amines 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) into mutagenic intermediate(s) in the Salmonella test. The liquid preincubation method in the presence of strain TA98 was utilized. In order to understand the mechanism involved in this metabolic activation, some modulators were incorporated in the medium. The results suggest that an oxygenated hemoprotein, probably oxyhemoglobin, is involved in the activation into genotoxic intermediate(s).     

Synthesis and structure-affinity relationships at the central benzodiazepine receptor of pyridazino[4,3-b]indoles and indeno[1,2-c]pyridazines.

A series of 2-aryl-3-chloro-2H-pyridazino[4,3-b]indoles, 2-aryl-3-methoxy-2H-pyridazino[4,3-b]indoles, and 2-aryl-2,5-dihydroindeno[1,2-c]pyridazino-3(3H)-ones has been prepared and tested for their ability to inhibit the [3H]flunitrazepam binding to the central benzodiazepine receptor. SAR are presented and discussed in comparison with existing pharmacophore models.     

Synthesis and antidiabetic activity of 2,5-disubstituted-3-imidazol-2-yl-pyrrolo[2,3-b]pyridines and thieno[2,3-b]pyridines

In the present investigation, two series of 2,5-disubstituted-3-imidazol-2-yl-pyrrolo[2,3-b]pyridines (2a-l) and thieno[2,3-b]pyridines (3a-l) were designed as analogs of BL 11282 (1). The in vitro glucose dependent insulinotropic activity of all the test compounds was evaluated using RIN5F cell based assay and all the test compounds showed glucose and concentration dependent insulin secretion. The in vivo antidiabetic activities of most potent compounds from each series (2c and 3c) were assessed in C57BL/6J mice. Compounds 2c and 3c showed dose dependent insulin secretion and significant glucose reduction in vivo. In general, compounds 2c and 3c were found to be equipotent at all the three different doses selected and with respect to BL 11282, both the test compounds were found to be more potent, at all the time points.     

Effects of various radicinin analogs on pulse amplitude and arterial blood pressure

The action of some radicinin analogues on the pulse amplitude in urethane anesthetized rats has been studied. The compounds used are:2,7-dimethyl-4H,5H-pyrano[4,3-b]pyran-4,5-dione (I); 2,3-dihydro-2,7-dimethyl-4H,5H-pyrano[4,3-b]pyran-4,5-dione (II) 7,8-dihydro-2,7-dimethyl-4H,5H-pyrano[4,3-b]pyran-4,5-dione (III) 2,3,7,8-tetrahydro-2,7-dimethyl-4H,5H-pyrano[4,3-b]pyran-4,5-dione(IV); 2,3,7,8,4',8'-hexahydro-2,7-dimethyl-4H,5H-pyrano[4, 3-b]pyran-4,5-dione (V); 3-crotonyl-4-hydroxy-6-methyl-2H-pyran-2-one (VI); 3-hexanoyl-4-hydroxy-6-methyl-2H-pyran-2-one (VII); 3-hexanoyl-5,6-dihydro-4-hydroxy-6-methyl-2H-pyran-2-one (VIII). A clear increase in the pulse has been seen with the compounds (II), (V) and (VII) especially at the lowest doses, while a decrease in the pulse is caused by the compounds (I) and (VIII). The studied substances have no effects on systolic blood pressure in normotensive unanesthetized rats.     

2-substituted-4-aryl-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,5]oxazocin-5-one as a structurally new NK1 antagonist

The structurally novel pyrimido[4,5-b][1,5]oxazocine derivative 3, a hybrid compound of pyrido[4,3-b]- and [2,3-b]-1,5-oxazocine (1 and 2, respectively), was designed and synthesized. We examined the atropisomeric property and the NK1 antagonist activity of 3. Compound 3 was found to possess both a feature of 1, free rotation about the biaryl bond, and a feature of 2, potent in vivo activity.     

CRF ligands via Suzuki and Negishi couplings of 3-pyridyl boronic acids or halides with 2-benzyloxy-4-chloro-3-nitropyridine

A series of imidazo[4,5-b]pyridines with a 7-(3-pyridyl) substituent is described as high affinity CRF receptor ligands. Individual analogues were synthesized from key intermediates obtained via palladium-catalyzed coupling of 3-pyridyl zinc or boronic acid organometallic intermediates with 2-benzyloxy-4-chloro-3-nitropyridine 12.     

Carcinogenic tryptophan pyrolysis products in airborne particles and rain water

This is the first report that carcinogenic tryptophan pyrolysis products are present in airborne particles and rain water. The airborne particles were collected from August 1988 through October 1988 at 4 locations in Japan. The amounts of 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in the air were 0.23 +/- 0.17 pg/m3 air (mean +/- SD, n = 18) and 0.16 +/- 0.15 pg/m3 air (n = 18), respectively. Moreover, these carcinogens were detected in rain water. These results indicate that Trp-P-1 and Trp-P-2 are ubiquitous environmental components.     

6-heteroaryl-pyrazolo[3,4-b]pyridines: potent and selective inhibitors of glycogen synthase kinase-3 (GSK-3)

A series of 6-heteroaryl-pyrazolo[3,4-b]pyridines has been optimised to afford potent inhibitors of Glycogen Synthase Kinase-3 (GSK-3). These analogues display excellent selectivity over the closely related Cyclin Dependent Kinase-2 (CDK-2).     

Analysis of human plasma as an exposure level monitor for carcinogenic tryptophan pyrolysis products

A high-performance liquid chromatography method for detecting 3-amino-1,4- dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in human plasma was developed. Plasma samples of 10 normal subjects were examined. Trp-P-1 and Trp-P-2, carcinogenic tryptophan pyrolysis products, were detected in all specimens, and the concentrations of Trp-P-1 and Trp-P-2 in plasma were 68.31 +/- 24.03 fmoles/ml (mean +/- S.D., n = 10) and 18.79 +/- 4.99 fmoles/ml, respectively. Our results suggest that plasma levels of carcinogenic tryptophan pyrolysis products may be useful indicators for estimating the exposure levels of the dietary carcinogens.     

Inhibition of mutagenicity of food-derived heterocyclic amines by sulforaphane--a constituent of broccoli

Sulforaphane, a constituent of broccoli was investigated for its antimutagenic potential against different classes of cooked food mutagens (heterocyclic amines). These include imidazoazaarenes such as 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP); pyridoindole derivatives such as 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2); and, dipyridoimidazole derivative such as 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1). Tests were carried out by Ames Salmonella/reversion assay using Salmonella typhimurium TA98 (frame shift mutation sensitive) and TA100 (base pair mutation sensitive) bacterial strains in the presence of Aroclor 1254-induced rat liver S9. Results of these in vitro antimutagenicity studies strongly suggest that sulforaphane is a potent inhibitor of the mutagenicity induced by imidazoazaarenes such as IQ, MeIQ and MeIQx (approximately 60% inhibition) and moderately active against pyridoindole derivatives such as Trp-P-1 and Trp-P-2 (32-48% inhibition), but ineffective against dipyridoimidazole derivative (Glu-P-1) in TA 100.     

Efficient synthesis of substituted 7-methyl-2H,5H-pyrano[4,3-b]pyran-5-ones and evaluation of their in vitro antiproliferative/cytotoxic activities

Substituted 7-methyl-2H,5H-pyrano[4,3-b]pyran-5-ones and related heterocycles 3 were synthesized through an efficient domino Knoevenagel condensation/6pi-electron electrocyclization. In vitro antiproliferative/cytotoxic activity evaluation was performed with human SH-SY5Y neuroblastoma cells and revealed IC(50) values ranging from 6.7 to >200microM. The compound that was most cytotoxic to the neuroblastoma cells, that is, 2-isobutyl-3-isopropyl-7-methyl-2H,5H-pyrano[4,3-b]pyran-5-one (3a), also exhibited necrotic effects on the human IPC melanoma cells.     

Substituted furo[3,2-b]pyridines: novel bioisosteres of 5-HT 1F receptor agonists

Synthesis and evaluation of a series of 2,3,5- and 3,5-substituted furo[3,2-b]pyridines were undertaken in order to investigate their utility as bioisosteres of 5-HT(1F) receptor agonist indole analogues, 1-3. The replacement proved to be effective, providing compounds with similar 5-HT(1F) receptor affinity and improved selectivity when compared with the indole analogues. Through these studies we identified 4-fluoro-N-[3-(1-methyl-piperidin-4-yl)-furo[3,2-b]pyridin-5-yl]-benzamide (5), a potent and selective 5-HT(1F) receptor agonist with the potential to treat acute migraine.