SR 46559 A and related aminopyridazines are potent muscarinic agonists with no cholinergic syndrome

Synthesis and biological evaluation of 3-amino-, 3-alkoxy- and 3-aryloxy-6-(hetero)arylpyridazines as potent antitumor agents

Various 3-amino-, 3-aryloxy- and alkoxy-6-arylpyridazines have been synthesized by an electrochemical reductive cross-coupling between 3-amino-, 3-aryloxy- or 3-alkoxy-6-chloropyridazines and aryl or heteroaryl halides. In vitro antiproliferative activity of these products was evaluated against a representative panel of cancer cell lines (HuH7, CaCo-2, MDA-MB-231, HCT116, PC3, NCI-H727, HaCaT) and oncogenicity prevention of the more efficient derivatives was highlighted on human breast cancer cell line MDA-MB 468-Luc prior establishing their interaction with p44/42 and Akt-dependent signaling pathways.

Access to 4-alkylaminopyridazine derivatives via nitrogen-assisted regioselective Pd-catalyzed reactions

3-Substituted, 6-substituted, and unsymmetrical 3,6-disubstituted 4-alkylaminopyridazines were prepared from a sequence of three chemo- and regioselective reactions combining amination and palladium-catalyzed cross-coupling reactions, such as reductive dehalogenation and Suzuki-Miyaura reactions. Extension of the methodology to Sonogashira reaction yielded a novel class of 3-substituted pyrrolopyridazines.

Synthesis and in-vitro cytotoxic evaluation of novel pyridazin-4-one derivatives

A new series of N-aryl-4-oxo-1,4-dihydro-pyridazine-3-carboxylic acids has been synthesized by condensation of aryldiazonium with 4-hydroxy-6-methyl-2-pyrone. Some of these compounds exhibited in-vitro cytotoxic activity with moderate to excellent growth inhibition against the murine P815 mastocytoma cell line. Compound 5b showed an important cytotoxic activity against cell line P815 (IC(50 )= 0.40 microg/mL).

Synthesis and antibacterial activity of some glucosyl- and ribosyl-pyridazin-3-ones

Reaction of 5,6-diphenylpyridazin-3(2H)-one 1a,b with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl bromide 2 in K(2)CO(3)/acetone gave 5,6-diphenyl-N(2)-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl)pyridazin-3-one 5a,b. The same nucleosides 5a,b were obtained by reaction of 1a,b with peracetylated glucose 3 under MW irradiation. Mercuration of 1a,b followed by reaction with glucosyl bromide 2 gave the same nucleosides 5a,b. The riboside 4-cyano-5,6-diphenyl-N(2)-(2',3',5'-tri-O-acetyl-beta-D-ribofuranosyl)-pyridazin-3-one 8 was obtained by reaction of 4-cyanopyridazinone 1b with peracetylated ribose 7 under MW irradiation. The deprotected nucleosides 6a,b and 9 were obtained by stirring of 5a,b and 8 in methanol and TEA/H(2)O. The structure was confirmed using (1)H and (13)C-NMR spectra. Selected members of these compounds were screened for antibacterial activity.

Use of 4-bromo pyridazine 3,6-dione for building 3-amino pyridazine libraries

An efficient method for preparation of 4,6 or 5,6 disubstituted 3-aminopyridazines was easily carried out starting from easily available 4-bromo-pyridazine-3,6-dione, and using combination of both amination and Pd(0) cross-coupling reactions under microwave irradiation.

Selective optimization of side activities: the SOSA approach

Selective optimization of side activities of drug molecules (the SOSA approach) is an intelligent and potentially more efficient strategy than HTS for the generation of new biological activities. Only a limited number of highly diverse drug molecules are screened, for which bioavailability and toxicity studies have already been performed and efficacy in humans has been confirmed. Once the screening has generated a hit it will be used as the starting point for a drug discovery program. Using traditional medicinal chemistry as well as parallel synthesis, the initial 'side activity' is transformed into the 'main activity' and, conversely, the initial 'main activity' is significantly reduced or abolished. This strategy has a high probability of yielding safe, bioavailable, original and patentable analogues.

Aminopyridazines as acetylcholinesterase inhibitors

Following the discovery of the weak, competitive and reversible acetylcholinesterase (AChE)-inhibiting activity of minaprine (3c) (IC50 = 85 microM on homogenized rat striatum AChE), a series of 3-amino-6-phenylpyridazines was synthesized and tested for inhibition of AChE. A classical structure-activity relationship exploration suggested that, in comparison to minaprine, the critical elements for high AChE inhibition are as follows: (i) presence of a central pyridazine ring, (ii) necessity of a lipophilic cationic head, (iii) change from a 2- to a 4-5-carbon units distance between the pyridazine ring and the cationic head. Among all the derivatives investigated, 3-[2-(1-benzylpiperidin-4-yl)ethylamino]-6-phenylpyridazine (3y), which shows an IC50 of 0.12 microM on purified AChE (electric eel), was found to be one of the most potent anti-AChE inhibitors, representing a 5000-fold increase in potency compared to minaprine.1

5-HT3 antagonists derived from aminopyridazine-type muscarinic M1 agonists

A conformational analysis, performed on muscarinic M1 agonists, identified four structural features characteristic of the muscarinic M1 pharmacophore: (i) a protonable basic or quaternary nitrogen acting as a cationic head; (ii) an electronegative dipole usually part of a planar mesomeric ester, amide, or amidine function which can be replaced by an ether (muscarine) or a dioxolane (AF 30); (iii) an intercharge distance of 5 +/- 0.5 A between the cationic head and the electronegative atom of the dipole; (iv) an elevation of 0.5 +/- 0.03 A of the cationic head over the plane containing the electronegative dipole. During a reinvestigation of the conformational behavior of published structures of 5-HT3 antagonists, similar features were observed for the 5-HT3 pharmacophore. However many 5-HT3 antagonists possess additional aromatic planes not present in the muscarinic M1 agonists. These observations brought us to predict the chemical modifications that would change muscarinic M1 agonists into 5-HT3 antagonists. Four of the predicted aminopyridazines were actually synthesized and submitted to testing. The observed IC50 values for 5-HT3 receptor binding ([3H] BRL 43694) ranged from 10 to 425 nM, whereas the affinities for the muscarinic receptor preparations ([3H] pirenzepine) layed over 10,000 nM. In electrophysiological studies the two most active compounds 10 and 13 produced antagonist-like effects on the 5-HT receptor channel complexes responsible for the generation of the rapidly desensitizing ionic currents, and agonist-like effects on those responsible for the slowly desensitizing components.