Formation of Aromatic Amidoximes with Hydroxylamine using Microreactor Technology

Repurposing 1,2,4-oxadiazoles as SARS-CoV-2 PLpro inhibitors and investigation of their possible viral entry blockade potential

Although vaccines are obviously mitigating the COVID-19 pandemic diffusion, efficient complementary antiviral agents are urgently needed to combat SARS-CoV-2. The viral papain-like protease (PLpro) is a promising therapeutic target being one of only two essential proteases crucial for viral replication. Nevertheless, it dysregulates the host immune sensing response. Here we report repositioning of the privileged 1,2,4-oxadiazole scaffold as promising SARS-CoV-2 PLpro inhibitor with potential viral entry inhibition profile. The design strategy relied on mimicking the general structural features of the lead benzamide PLpro inhibitor GRL0617 with isosteric replacement of its pharmacophoric amide backbone by 1,2,4-oxadiazole core. Inspired by the multitarget antiviral agents, the substitution pattern was rationalized to tune the scaffold's potency against other additional viral targets, especially the spike receptor binding domain (RBD) that is responsible for the viral invasion. The Adopted facial synthetic protocol allowed easy access to various rationally substituted derivatives. Among the evaluated series, the 2-[5-(pyridin-4-yl)-1,2,4-oxadiazol-3-yl]aniline (5) displayed the most balanced dual inhibitory potential against SARS-CoV-2 PLpro (IC50=7.197 μM) and spike protein RBD (IC50 = 8.673 μM), with acceptable ligand efficiency metrics, practical LogP (3.8) and safety profile on Wi-38 (CC50 = 51.78 μM) and LT-A549 (CC50 = 45.77 μM) lung cells. Docking simulations declared the possible structural determinants of activities and enriched the SAR data for further optimization studies.

Beyond direct Nrf2 activation; reinvestigating 1,2,4-oxadiazole scaffold as a master key unlocking the antioxidant cellular machinery for cancer therapy

Harnessing the antioxidant cellular machinery has sparked considerable interest as an efficient anticancer strategy. Activating Nrf2, the master switch of the cellular redox system, suppresses ROS, alleviates oxidative stress, and halts cancer progression. 1,2,4-oxadiazoles are iconic direct Nrf2 activators that disrupt Nrf2 interaction with its endogenous repressor Keap1. This study introduces rationally designed 1,2,4-oxadiazole derivatives that inhibit other Nrf2 suppressors (TrxR1, IKKα, and NF-kB) thus enhancing Nrf2 activation for preventing oxidative stress and carcinogenesis. Preliminary screening showed that the phenolic oxadiazoles 11, 15, and 19 were comparable to ascorbic acid (ROS scavenging) and EDTA (iron chelation), and superior to doxorubicin against HepG-2, MDA-MB231, and Caco-2 cells. They suppressed ROS by 3 folds and activated Nrf2 by 2 folds in HepG-2 cells. Mechanistically, they inhibited TrxR1 (IC₅₀; 13.19, 17.89, and 9.21 nM) and IKKα (IC₅₀; 11.0, 15.94, and 19.58 nM), and downregulated NF-κB (7.6, 1.4 and 1.9 folds in HepG-2), respectively. They inhibited NADPH oxidase (IC₅₀; 16.4, 21.94, and 10.71 nM, respectively) that potentiates their antioxidant activities. Docking studies predicted their important structural features. Finally, they recorded drug-like in silico physicochemical properties, ADMET, and ligand efficiency metrics.

Compact reaction-module on a pad for scalable flow-production of organophosphates as drug scaffolds

Continuous pharmaceutical manufacturing receives intense attention as an alternative way to meet flexible market needs with the assurance of higher safety and quality control. Here, we report a compact reaction-module on a pad (CRP, 170 × 170 × 1.2 mm) for scale-up production of drug precursors in a continuous-flow. The CRP system was devised by stacking 9 films of the patterned polyimide to integrate micro-flow circuits, combining the functions of the even distribution of feeds, being completely mixed in less than a few milliseconds. A methodology of using a highly reactive species for the single-step synthesis of α-phosphonyloxy ketone, a drug scaffold, required the synthesis time of a few seconds in microfluidics. The fast reaction in the single CRP was capable of producing 19.2 g h-1 drug precursor, which indicates a solid step toward kilogram-scale pharmaceutical manufacturing in small footage.

Postsynthetic functionalization of covalent organic frameworks

Covalent organic frameworks (COFs) have been at the forefront of porous-material research in recent years. With predictable structural compositions and controllable functionalities, the structures and properties of COFs could be controlled to achieve targeted materials. On the other hand, the predesigned structure of COFs allows fruitful postsynthetic modifications to introduce new properties and functions. In this review, the postsynthetic functionalizations of COFs are discussed and their impacts towards structural qualities and performances are comparatively elaborated on. The functionalization involves the formation of specific interactions (covalent or coordination/ionic bonds) and chemical reactions (oxidation/reduction reaction) with pendant groups, skeleton and reactive linkages of COFs. The chemical stability and performance of COFs including catalytic activity, storage, sorption and opto-electronic properties might be enhanced by specific postsynthetic functionalization. The generality of these strategies in terms of chemical reactions and the range of suitable COFs places them as a pivotal role for the development of COF-based smart materials.

Continued exploration of 1,2,4-oxadiazole periphery for carbonic anhydrase-targeting primary arene sulfonamides: Discovery of subnanomolar inhibitors of membrane-bound hCA IX isoform that selectively kill cancer cells in hypoxic environment

An expanded set of diversely substituted 1,2,4-oxadiazole-containing primary aromatic sulfonamides was synthesized and tested for inhibition of human carbonic anhydrase I, II, IX and XII isoforms. The initial biochemical profiling revealed a significantly more potent inhibition of cancer-related, membrane-bound isoform hCA IX (reaching into submicromolar range), on top of potent inhibition of hCA XII that is another cancer target. The observed structure-activity relationships have been rationalized by molecular modeling. Comparative single-concentration profiling of the carbonic anhydrase inhibitors synthesized for antiproliferative effects against normal (ARPE-19) and cancer (PANC-1) cell lines under chemically induced hypoxia conditions revealed several candidate compounds selectively targeting cancer cells. More in-depth characterization of these leads revealed two structurally related compounds that showed promising selective cytotoxicity against pancreatic cancer (PANC-1) and melanoma (SK-MEL-2) cell lines.

“One-pot” synthesis of amidoxime via Pd-catalyzed cyanation and amidoximation

“One-pot” synthesis of amidoxime was developed for studies on the interactions between amidoxime and uranyl.