Single-Step Microwave-Mediated Synthesis of Oxazoles and Thiazoles from 3-Oxetanone: A Synthetic and Computational Study

Novel styryl-thiazole hybrids as potential anti-Alzheimer's agents

In this study, combining the thiazole and cinnamoyl groups into the styryl-thiazole scaffold, a series of novel styryl-thiazole hybrids (6a-p) was rationally designed, synthesized, and evaluated by the multi-target-directed ligands strategy as potential candidates for the treatment of Alzheimer's disease (AD). Hybrids 6e and 6i are the most promising among the synthesized hybrids since they are able to significantly increase cell viabilities in Aβ1-42-exposed-human neuroblastoma cell line (6i at the concentration of 50 μg mL-1 and 6e at the concentration of 25 μg mL-1 resulted in ∼34% and ∼30% increase in cell viabilities, respectively). Compounds 6e and 6i exhibit highly AChE inhibitory properties in the experimental AD model at 375.6 ± 18.425 mU mL-1 and 397.6 ± 32.152 mU mL-1, respectively. Moreover, these data were also confirmed by docking studies and in vitro enzyme inhibition assays. Compared to hybrid 6e and according to the results, 6i also has the highest potential against Aβ1-42 aggregation with over 80% preventive activity. The in silico prediction of the physicochemical properties confirms that 6i possesses a better profile compared to 6e. Therefore, compound 6i presents a promising multi-targeted active molecular profile for treating AD considering the multifactorial nature of AD, and it is reasonable to deepen its mechanisms of action in an in vivo experimental model of AD.

Elaborating the excited-state double proton transfer mechanism and multiple fluorescent characteristics of 3,5-bis(2-hydroxypheny)-1H-1,2,4-triazole

Recently, Krishnamoorthy and coworkers reported a new type of proton transfer, which was labeled as 'proton transfer triggered proton transfer', in 3,5-bis(2-hydroxypheny)-1H-1,2,4-triazole (bis-HPTA). In this work, the excited-state double proton transfer (ESDPT) mechanism and multiple fluorescent characteristics of bis-HPTA were investigated. Upon photo-excitation, the intramolecular hydrogen bonding strength changed and the electron density of bis-HPTA redistributed. These changes will affect the proton transfer process. In S₀ state, the proton transfer processes of bis-HPTA were prohibited on the stepwise and concerted pathways. After vertical excitation to the S₁ state, the ESIPT-II process was more likely to occur than the ESIPT-I process, which was contrary to the conclusion that the ESIPT-II process is blocked and the ESIPT-II process takes place after the ESIPT-I process proposed by Krishnamoorthy and coworkers. When the K2 tautomer was formed through the ESIPT-II process, the second proton transfer process on the stepwise pathway was prohibited. On another stepwise pathway, after the ESIPT-I process (form the K1 tautomer), the second proton transfer process should overcome a higher potential barrier than the ESIPT-I process to form ESDPT tautomer. On the concerted pathway, the bis-HPTA can synchronous transfer double protons to form the ESDPT tautomer. The ESDPT tautomer was unstable and immediately converted to the K2 tautomer via a barrierless reverse proton transfer process. Thus, the fluorescent maximum at 465 nm from the ESDPT tautomer reported by Krishnamoorthy and coworkers was ascribed to the K2 tautomer. Most of the fluorophores show dual fluorescent properties, while the bis-HPTA undergoing ESDPT process exhibited three well-separated fluorescent peaks, corresponding to its normal form (438 nm), K1 tautomer (462 nm) and K2 tautomer (450 nm), respectively.

Discovery of Nonpungent Transient Receptor Potential Vanilloid 1 (TRPV1) Agonist as Strong Topical Analgesic

Paradoxically, some TRPV1 agonists are, at the organismal level, both nonpungent and clinically useful as topical analgesics. Here, we describe the scaled-up synthesis and characterization in mouse models of a novel, nonpungent vanilloid. Potent analgesic activity was observed in models of neuropathic pain, and the compound blocked capsaicin induced allodynia, showing dermal accumulation with little transdermal absorption. Finally, it displayed much weaker systemic toxicity compared to capsaicin and was negative in assays of genotoxicity.

Palladium-Metalated Porous Organic Polymers as Recyclable Catalysts for the Chemioselective Synthesis of Thiazoles from Thiobenzamides and Isonitriles

Two types of thiazole derivatives are synthesized through a multistep cascade sequence with Pd-metalated phosphorus-doped porous organic polymers (POPs) as heterogeneous catalysts. The POPs could be used as both ligands and catalyst supports. No obvious aggregation and loss of any catalytic activity of the catalysts were observed after 10 runs of the reaction. More importantly, imidazo[4,5- d]thiazoles, which are a new class of thiazole derivatives, could be obtained through K₂CO₃-promoted intramolecular cyclization of the synthesized polysubstituted thiazoles. Furthermore, the in vitro anticancer activity of these new compounds were tested with MTT assay, and compound 4b exhibited good antitumor activity toward T-24 and A549 cells with IC₅₀ values of 10.3 ± 0.8 and 11.8 ± 0.5 μM, respectively. In addition, the action mechanism of 4b on tumor cells was determined.

A Direct Synthesis of Highly Substituted π-Rich Aromatic Heterocycles from Oxetanes

The ubiquitous use of π-rich five-membered heterocycles has driven the development of new methods for their synthesis for more than a century. Here, we disclose a general and reliable reaction manifold for the construction of highly substituted heterocycles through a facile Lewis-acid-catalyzed oxetane rearrangement. Notably, this methodology employs a keto-oxetane motif as a 1,4-dicarbonyl surrogate, which can be synthesized using robust alkylation or alkenylation reactions, and thus obviates the need to access 1,4-dicarbonyl compounds via umpoled starting materials. We harnessed this reactivity to generate a broad range of substituted furans and pyrroles, and extended this methodology to produce benzo-fused versions thereof.