Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates as nucleotide analogues

Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Covalent Ligand Screening Uncovers a RNF4 E3 Ligase Recruiter for Targeted Protein Degradation Applications

Targeted protein degradation has arisen as a powerful strategy for drug discovery allowing the targeting of undruggable proteins for proteasomal degradation. This approach most often employs heterobifunctional degraders consisting of a protein-targeting ligand linked to an E3 ligase recruiter to ubiquitinate and mark proteins of interest for proteasomal degradation. One challenge with this approach, however, is that only a few E3 ligase recruiters currently exist for targeted protein degradation applications, despite the hundreds of known E3 ligases in the human genome. Here, we utilized activity-based protein profiling (ABPP)-based covalent ligand screening approaches to identify cysteine-reactive small-molecules that react with the E3 ubiquitin ligase RNF4 and provide chemical starting points for the design of RNF4-based degraders. The hit covalent ligand from this screen reacted with either of two zinc-coordinating cysteines in the RING domain, C132 and C135, with no effect on RNF4 activity. We further optimized the potency of this hit and incorporated this potential RNF4 recruiter into a bifunctional degrader linked to JQ1, an inhibitor of the BET family of bromodomain proteins. We demonstrate that the resulting compound CCW 28-3 is capable of degrading BRD4 in a proteasome- and RNF4-dependent manner. In this study, we have shown the feasibility of using chemoproteomics-enabled covalent ligand screening platforms to expand the scope of E3 ligase recruiters that can be exploited for targeted protein degradation applications.

Harnessing the anti-cancer natural product nimbolide for targeted protein degradation

Nimbolide, a terpenoid natural product derived from the Neem tree, impairs cancer pathogenicity; however, the direct targets and mechanisms by which nimbolide exerts its effects are poorly understood. Here, we used activity-based protein profiling (ABPP) chemoproteomic platforms to discover that nimbolide reacts with a novel functional cysteine crucial for substrate recognition in the E3 ubiquitin ligase RNF114. Nimbolide impairs breast cancer cell proliferation in-part by disrupting RNF114 substrate recognition, leading to inhibition of ubiquitination and degradation of the tumor-suppressors such as p21, resulting in their rapid stabilization. We further demonstrate that nimbolide can be harnessed to recruit RNF114 as an E3 ligase in targeted protein degradation applications and show that synthetically simpler scaffolds are also capable of accessing this unique reactive site. Our study highlights the utility of ABPP platforms in uncovering unique druggable modalities accessed by natural products for cancer therapy and targeted protein degradation applications.

Additive-free regio- and diastereoselective construction of fully-substituted isoxazolidines employing diazo compounds

An efficient additive-free three-component access to densely functionalized isoxazolidines using diazo compounds, nitrosoarene, and allenic esters has been uncovered.

Design, antiviral and cytostatic properties of isoxazolidine-containing amonafide analogues

A novel series of 5-arylcarbamoyl- and 5-arylmethyl-2-methylisoxazolidin-3-yl-3-phosphonates have been synthesized via cycloaddition of N-methyl-C-(diethoxyphosphoryl)nitrone with N-substituted naphthalimide acrylamides and N-allylnaphthalimides. All cis- and trans-isoxazolidine phosphonates obtained herein were assessed for antiviral activity against a broad range of DNA and RNA viruses. Isoxazolidines trans-9d and trans-9f exhibited the highest activity (EC₅₀ = 8.9 μM) toward cytomegalovirus. Compounds cis- and trans-9d as well as cis- and trans-9f were found potent against HSV and Vaccinia viruses (EC₅₀ in the 45–58 μM range), whereas isoxazolidines 10a and 10d suppressed replication of Coxsackie B4 and Punta Toro viruses (EC₅₀ in the 45–73 μM range). Antiproliferative evaluation of all obtained isoxazolidines revealed the promising activity of cis-9b, cis-9d, trans-9d, cis-9e, trans-9e, cis-9f and trans-9f toward tested cancer cell lines with IC₅₀ in the 1.1–19 μM range.