Synthesis of Novel Fluoro Analogues of MKC442 as Microbicides

Recent Advancements in the Synthesis of α-fluoroalkylated Azine-derived Heterocycles through Direct Fluorination

The review highlights recent advancements in the synthesis of α-fluoro and α,α- difluoroalkylated azines, focusing on two main approaches. The first approach involves nucleophilic deoxofluorination, wherein α-hydroxy- or α-oxoalkylated azines are treated with diethylaminosulfur trifluoride or other S-F reagents to introduce fluorine atoms. The second approach employs direct electrophilic benzylic fluorination, whereby alkylazines undergo fluorination using N-F reagents. Both methods provide flexibility in designing and synthesizing fluoroalkylated heterocycles.

Structure-directed linker optimization of novel HEPTs as non-nucleoside inhibitors of HIV-1 reverse transcriptase

1-[(2-Hydroxyethoxy)methyl]-6-(phenylthio)thymines (HEPTs) have been previously described as an important class of HIV-1 nonnucleoside reverse transcriptase inhibitors (NNRTIs). In our continuously pursuing HEPT optimization efforts, a series of novel HEPTs, featuring -C(OH)CH₂R, -CC, or -CHCH₂R linker at the benzylic α-methylene unit, were developed as NNRTIs. Among these new HEPTs, the compound C20 with -CHCH₃ group at the benzylic α-methylene unit conferred the highest potency toward WT HIV-1 and selectivity (EC₅₀ = 0.23 μM, SI = 150.20), which was better than the lead compound HEPT (EC₅₀ = 7 μM, SI = 106). Also, C20 was endowed with high efficacy against clinically relevant mutant strains (EC_50(L100I) = 1.07 μM; EC_50(K103N) = 4.33 μM; EC_50(Y181C) = 5.57 μM; EC_50(E138K) = 1.06 μM; EC_{50(F227L+V106A)} = 5.45 μM) and wild-type HIV-1 reverse transcriptase (RT) with an IC₅₀ value of 0.55 μM. Molecular docking and molecular dynamics simulations, as well as preliminary structure-activity relationship (SAR) analysis of these new compounds, provided a deeper insight into the key structural features of the interactions between HEPT analogs and HIV-1 RT and laid the foundation for further modification on HEPT scaffold.

NHC-CDI Betaine Adducts and Their Cationic Derivatives as Catalyst Precursors for Dichloromethane Valorization

Zwitterionic adducts of N-heterocyclic carbene and carbodiimide (NHC-CDI) are an emerging class of organic compounds with promising properties for applications in various fields. Herein, we report the use of the ICyCDI(p-Tol) betaine adduct (1a) and its cationic derivatives 2a and 3a as catalyst precursors for the dichloromethane valorization via transformation into high added value products CH₂Z₂ (Z = OR, SR or NR₂). This process implies selective chloride substitution of dichloromethane by a range of nucleophiles Na⁺Z^– (preformed or generated in situ from HZ and an inorganic base) to yield formaldehyde-derived acetals, dithioacetals, or aminals with full selectivity. The reactions are conducted in a multigram-scale under very mild conditions, using dichloromethane both as a reagent and solvent, and very low catalyst loading (0.01 mol %). The CH₂Z₂ derivatives were isolated in quantitative yields after filtration and evaporation, which facilitates recycling the dichloromethane excess. Mechanistic studies for the synthesis of methylal CH₂(OMe)₂ rule out organocatalysis as being responsible for the CH₂ transfer, and a phase-transfer catalysis mechanism is proposed instead. Furthermore, we observed that 1a and 2a react with NaOMe to form unusual isoureate ethers, which are the actual phase-transfer catalysts, with a strong preference for sodium over other alkali metal nucleophiles.

Synthesis of Formate Esters and Formamides Using an Au/TiO₂-Catalyzed Aerobic Oxidative Coupling of Paraformaldehyde

A simple method for the synthesis of formate esters and formamides is presented based on the Au/TiO₂-catalyzed aerobic oxidative coupling between alcohols or amines and formaldehyde. The suitable form of formaldehyde is paraformaldehyde, as cyclic trimeric 1,3,5-trioxane is inactive. The reaction proceeds via the formation of an intermediate hemiacetal or hemiaminal, respectively, followed by the Au nanoparticle-catalyzed aerobic oxidation of the intermediate. Typically, the oxidative coupling between formaldehyde (2 equiv) and amines occurs quantitatively at room temperature within 4 h, and there is no need to add a base as in analogous coupling reactions. The oxidative coupling between formaldehyde (typically 3 equiv) and alcohols is unprecedented and occurs more slowly, yet in good to excellent yields and selectivity. Minor side-products (2-12%) from the acetalization of formaldehyde by the alcohol are also formed. The catalyst is recyclable and can be reused after a simple filtration in five consecutive runs with a small loss of activity.

Facile synthesis of the NNRTI microbicide MC-1220 and synthesis of its phosphoramidate prodrugs

A facile and novel synthetic route to MC-1220 was achieved by condensation of 4,6-dichloro-N,N-5-trimethylpyrimidin-2-amine (1) with the sodium salt of 2,6-difluorophenylacetonitrile, followed by methylation and strong acidic hydrolysis. The prodrugs of MC-1220 were synthesized by reaction of chlorophosphoramidate derivatives (7a-e) or α-acetobromoglucose with the sodium salt of MC-1220. The stability and anti-HIV-1 activity of phosphoramidate prodrugs turned out to be comparable to those of the parent drug MC-1220.

Anti-HIV Drug Discovery and Development: Current Innovations and Future Trends

The early effectiveness of combinatorial antiretroviral therapy (cART) in the treatment of HIV infection has been compromised to some extent by rapid development of multidrug-resistant HIV strains, poor bioavailability, and cumulative toxicities, and so there is a need for alternative strategies of antiretroviral drug discovery and additional therapeutic agents with novel action modes or targets. From this perspective, we first review current strategies of antiretroviral drug discovery and optimization, with the aid of selected examples from the recent literature. We highlight the development of phosphate ester-based prodrugs as a means to improve the aqueous solubility of HIV inhibitors, and the introduction of the substrate envelope hypothesis as a new approach for overcoming HIV drug resistance. Finally, we discuss future directions for research, including opportunities for exploitation of novel antiretroviral targets, and the strategy of activation of latent HIV reservoirs as a means to eradicate the virus.