Synthesis and evaluation of novel azetidine analogs as potent inhibitors of vesicular [3H]dopamine uptake

Lobelane analogs that incorporate a central piperidine or pyrrolidine moiety have previously been reported by our group as potent inhibitors of VMAT2 function. Further central ring size reduction of the piperidine moiety in lobelane to a four-membered heterocyclic ring has been carried out in the current study to afford novel cis-and trans-azetidine analogs. These azetidine analogs (15a–15c and 22a–22c) potently inhibited [³H]dopamine (DA) uptake into isolated synaptic vesicles (K_i ? 66 nM). The cis-4-methoxy analog 22b was the most potent inhibitor (K_i = 24 nM), and was twofold more potent that either lobelane (2a, K_i = 45 nM) or norlobelane (2b, K_i = 43 nM). The trans-methylenedioxy analog, 15c (K_i = 31 nM), was equipotent with the cis-analog, 22b, in this assay. Thus, cis- and trans-azetidine analogs 22b and 15c represent potential leads in the discovery of new clinical candidates for the treatment of methamphetamine abuse.     

Coordination and derivatization of 3, 4, and 6-membered nitrogen heterocycles at a chiral tungsten(II) center

Reaction of [Tp′W(CO)₂(PhCCPh)][OTf] (1b) (Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate) with excess aziridine or 2-methylaziridine followed by protonation with produces chiral tungsten(II) amine complexes (3, 4; R = Me, Ph). An azetidine amido complex, Tp′W(CO)(PhCCMe)(H₂) (5) is synthesized by reaction of [Tp′W(CO)₂(PhCCMe)][OTf] (1a) with excess azetidine. Oxidation of amido complex 5 with I₂ in the presence of a weak base provides the corresponding 1-azetine complex, (6). Addition of methylmagnesium bromide to complex 6 results in formation of predominantly one diastereomer (S_WR_C/R_WS_C) (96:4 dr) of the 2-methylazetidine complex, Tp′W(CO)(PhCCMe)(H₂) (7). Reaction of complex 5 with results in formation of a cationic azetidine complex, (8). Reaction of 1b with excess piperidine followed by oxidation affords 2,3,4,5-tetrahydropyridine complex 9b, . Formation of an enamido complex, Tp′W(CO)(PhCCPh)(H₂) (10), is observed upon addition of base to 9b. Subsequent addition of [D⁺] to the enamido β-carbon results in the formation of the deuterated product, 9b-d₁, as determined by ²H NMR. Seven X-ray crystal structures have been determined, and these encompass complexes with 3, 4, and 6-membered heterocyclic ligands. Crystal structures are reported for two aziridine adducts (2, 4) two neutral amido complexes (5, 7), one cationic imine complex (6), and one cationic amine (8) complex derived from azetidine, and the imine complex formed from piperidine (9).     

Synthesis and preliminary biological evaluation of potent and selective 2-(3-alkoxy-1-azetidinyl) quinolines as novel PDE10A inhibitors with improved solubility

We report the discovery of a novel series of 2-(3-alkoxy-1-azetidinyl) quinolines as potent and selective PDE10A inhibitors. Structure–activity studies improved the solubility (pH 7.4) and maintained high PDE10A activity compared to initial lead compound 3, with select compounds demonstrating good oral bioavailability. X-ray crystallographic studies revealed two distinct binding modes to the catalytic site of the PDE10A enzyme. An ex vivo receptor occupancy assay in rats demonstrated that this series of compounds covered the target within the striatum.     

Fasciola hepatica: Azetidine inhibition of bile duct hyperplasia in the infected rat

In controlled experiments the luminal bile duct perimeters were compared between rats infused with l-azetidine-2-carboxylic acid (AZC) (120 μmole/rat/day) and rats infused with saline after both groups had been implanted with adult Fasciola. The average bile duct lumen in the group receiving AZC did not enlarge relative to controls, and was about one-half the average perimeter of ducts from rats infused with saline that had worm implants. These results indicate that azetidine can inhibit bile duct hyperplasia induced by Fasciola which inhabit the duct. The results also support the hypothesis that the hyperplasia of fascioliasis is mediated through the release of free proline from the worms where it is present in high concentrations.     

3-(Naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride attenuates NLRP3 inflammasome-mediated signaling pathway in lipopolysaccharide-stimulated BV2 microglial cells

The nucleotide-binding and oligomerization domain-like receptor containing a pyrin domain 3 (NLRP3) inflammasome is a multiprotein complex with a role in innate immune responses. NLRP3 inflammasome dysfunction is a common feature of chronic inflammatory diseases. Microglia activation is also associated with neuroinflammatory pathologies. We previously reported that 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride (KHG26792) reduced hypoxia-induced toxicity by modulating inflammation. However, no studies have elucidated the precise mechanisms for the anti-inflammatory action of KHG26792, in particular via inflammasome mediation. This study investigated the effects of KHG26792 on the inflammasome-mediated signaling pathway in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. KHG26792 significantly attenuated several inflammatory responses including tumor necrosis factor-α, interleukin-1β, interleukin-6, reactive oxygen species, and mitochondrial potential in these cells. KHG26792 also suppressed LPS-induced increase NLRP3, activated caspase-1, and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) levels. Furthermore, KHG26792 successfully blocked LPS-activated adenosine triphosphate (ATP) level, likely through the purinergic receptor P2X ligand-gated ion channel 7 (P2X7) receptor. Our results suggest that the anti-inflammatory functions of KHG26792 may be, at least in part, due to regulation of the P2X7R/NLRP3-mediated signaling pathway during microglial activation.     

Discovery of a novel azetidine scaffold for colony stimulating factor-1 receptor (CSF-1R) Type II inhibitors by the use of docking models

We report the discovery of a novel azetidine scaffold for colony stimulating factor-1 receptor (CSF-1R) Type II inhibitors by using a structure-based drug design (SBDD) based on a docking model. The work leads to the representative compound 4a with high CSF-1R inhibitory activity (IC₅₀?=?9.1?nM). The obtained crystal structure of an azetidine compound with CSF-1R, which matched our predicted docking model, demonstrates that the azetidine compounds bind to the DFG-out conformation of the protein as a Type II inhibitor.     

Overcoming hERG activity in the discovery of a series of 4-azetidinyl-1-aryl-cyclohexanes as CCR2 antagonists

A series of 4-azetidinyl-1-aryl-cyclohexanes as potent CCR2 antagonists with high selectivity over activity for the hERG potassium channel is discovered through divergent SARs of CCR2 and hERG.     

(3R,4S,5R,6R,7S)-3,4,5,7-Tetrahydroxyconidine,an azetidine analogue of 6,7-diepicastanospermine and a conformationally constrained d-deoxyaltronojirimycin,from l-arabinose

The synthesis from l-arabinose of an azetidine analogue of 6,7-diepicastanospermine and its glycosidase inhibition profile are described.     

Optimization of an azetidine series as inhibitors of colony stimulating factor-1 receptor (CSF-1R) Type II to lead to the clinical candidate JTE-952

Optimization of novel azetidine compounds, which we had found as colony stimulating factor-1 receptor (CSF-1R) Type II inhibitors, provided JTE-952 as a clinical candidate with high cellular activity (IC₅₀?=?20?nM) and good pharmacokinetics profile. JTE-952 was also effective against a mouse collagen-induced model of arthritis (mouse CIA-model). Additionally, the X-ray co-crystal structure of JTE-952 with CSF-1R protein was shown to be a Type II inhibitor, and the kinase panel assay indicated that JTE-952 had high kinase selectivity.     

Challenges in the development of an M4 PAM preclinical candidate: The discovery,SAR, and in vivo characterization of a series of 3-aminoazetidine-derived amides

This letter details the continued chemical optimization of a novel series of M₄ positive allosteric modulators (PAMs) based on a 5-amino-thieno[2,3-c]pyridazine core by incorporating a 3-amino azetidine amide moiety. The analogs described within this work represent the most potent M₄ PAMs reported for this series to date. The SAR to address potency, clearance, subtype selectivity, CNS exposure, and P-gp efflux are described. This work culminated in the discovery of VU6000918, which demonstrated robust efficacy in a rat amphetamine-induced hyperlocomotion reversal model at a minimum efficacious dose of 0.3 mg/kg.