Synthesis of 4′/5′-Spirocyclopropanated Uridine and d-Xylouridine Derivatives and Their Activity against the Human Respiratory Syncytial Virus

Synthesis of gem-Difluorinated Oxa/Azaspiro[2.4]heptanes via Palladium-Catalyzed Spirocyclopropanation

A palladium-catalyzed spirocyclopropanation of gem-difluoroalkenes with π-allylpalladium 1,4-dipoles has been successfully developed, which gives a powerful and straightforward synthetic strategy for the construction of novel gem-difluorinated spirocyclic compounds, 6,6-difluoro-5-oxa/azaspiro[2.4]heptanes. The scope of gem-difluoroalkenes can be extended to styrenes, acrylic esters, and acrylamides to realize the installment of various functional groups and different heteroatoms on the spirocyclic skeletons, which could be converted to valuable compounds with potential biological activity. The mechanistic investigations revealed the competition between spirocyclopropanation and β-F elimination of π-allylpalladium zwitterionic intermediates.

Stereocontrolled Synthesis of Aryl C-Nucleosides under Ambient Conditions

A stereocontrolled synthesis of an aryl C-nucleoside has been developed using D-ribals and arylboronic acids catalyzed by palladium without additional ligands in common solvents under an open-air atmosphere at room temperature. This protocol features very mild conditions, simplicity in operation, exclusive β-stereoselectivity, broad substrate scopes, and good compatibility with reactive amino and hydroxyl groups. The functionalization of unsaturated C-nucleosides and the late-stage glycosylation of natural products/drugs demonstrated the high practicality of this strategy.

Nucleoside Analogs: A Review of Its Source and Separation Processes

Nucleoside analogs play a crucial role in the production of high-value antitumor and antimicrobial drugs. Currently, nucleoside analogs are mainly obtained through nucleic acid degradation, chemical synthesis, and biotransformation. However, these methods face several challenges, such as low concentration of the main product, the presence of complex matrices, and the generation of numerous by-products that significantly limit the development of new drugs and their pharmacological studies. Therefore, this work aims to summarize the universal separation methods of nucleoside analogs, including crystallization, high-performance liquid chromatography (HPLC), column chromatography, solvent extraction, and adsorption. The review also explores the application of molecular imprinting techniques (MITs) in enhancing the identification of the separation process. It compares existing studies reported on adsorbents of molecularly imprinted polymers (MIPs) for the separation of nucleoside analogs. The development of new methods for selective separation and purification of nucleosides is vital to improving the efficiency and quality of nucleoside production. It enables us to obtain nucleoside products that are essential for the development of antitumor and antiviral drugs. Additionally, these methods possess immense potential in the prevention and control of serious diseases, offering significant economic, social, and scientific benefits to the fields of environment, biomedical research, and clinical therapeutics.

Simmons-Smith Cyclopropanation: A Multifaceted Synthetic Protocol toward the Synthesis of Natural Products and Drugs: A Review

Simmons-Smith cyclopropanation is a widely used reaction in organic synthesis for stereospecific conversion of alkenes into cyclopropane. The utility of this reaction can be realized by the fact that the cyclopropane motif is a privileged synthetic intermediate and a core structural unit of many biologically active natural compounds such as terpenoids, alkaloids, nucleosides, amino acids, fatty acids, polyketides and drugs. The modified form of Simmons-Smith cyclopropanation involves the employment of Et2Zn and CH2I2 (Furukawa reagent) toward the total synthesis of a variety of structurally complex natural products that possess broad range of biological activities including anticancer, antimicrobial and antiviral activities. This review aims to provide an intriguing glimpse of the Furukawa-modified Simmons-Smith cyclopropanation, within the year range of 2005 to 2022.

Synthesis of Spirocyclic Cyclopropyl Glycosyl-1-phosphate Analogues

A general methodology allowing the preparation of phosphonylated 1-spirocyclopropyl analogues of glycosyl-1-phosphates is reported. The scope of this reaction has been assessed using various exo-glycals easily obtained from the corresponding pyranoses and furanoses. The cyclopropanation was found to be stereospecific, and the cis/trans selectivity only depends on the E/Z configuration of the starting exo-glycal. The four possible isomers of spirocyclopropyl ribose-1-phosphonate could thus be prepared in a controlled manner, protected and deprotected.

Stereodivergent Synthesis of Biologically Active Spironucleoside Scaffolds via Catalytic Cyclopropanation of 4-exo-Methylene Furanosides

Cyclopropane fusion of the only rotatable carbon-carbon bond in furanosyl nucleosides (i.e., exocyclic 4'-5') is a powerful design strategy to arrive at conformationally constrained analogues. Herein, we report a direct stereodivergent route toward the synthesis of the four possible configurations of 4-spirocyclopropane furanoses, which have been transformed into the corresponding 4'-spirocyclic adenosine analogues. The latter showed differential inhibition of the protein methyltransferase PRMT5-MEP50 complex, with one analogue inhibiting more effectively than adenosine itself, demonstrating the utility of rationally probing 4'-5' side chain orientations.

Asymmetric synthesis of pharmaceutically relevant 1-aryl-2-heteroaryl- and 1,2-diheteroarylcyclopropane-1-carboxylates

This study describes general methods for the enantioselective syntheses of pharmaceutically relevant 1-aryl-2-heteroaryl- and 1,2-diheteroarylcyclopropane-1-carboxylates through dirhodium tetracarboxylate-catalysed asymmetric cyclopropanation of vinyl heterocycles with aryl- or heteroaryldiazoacetates. The reactions are highly diastereoselective and high asymmetric induction could be achieved using either (R)-pantolactone as a chiral auxiliary or chiral dirhodium tetracarboxylate catalysts. For meta- or para-substituted aryl- or heteroaryldiazoacetates the optimum catalyst was Rh2(R-p-Ph-TPCP)4. In the case of ortho-substituted aryl- or heteroaryldiazoacetates, the optimum catalyst was Rh2(R-TPPTTL)4. For a highly enantioselective reaction with the ortho-substituted substrates, 2-chloropyridine was required as an additive in the presence of either 4 Å molecular sieves or 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Under the optimized conditions, the cyclopropanation could be conducted in the presence of a variety of heterocycles, such as pyridines, pyrazines, quinolines, indoles, oxadiazoles, thiophenes and pyrazoles.

Synthesis and Evaluation of Biological Activities of Bis(spiropyrazolone)cyclopropanes: A Potential Application against Leishmaniasis

This work focuses on the search and development of drugs that may become new alternatives to the commercial drugs currently available for treatment of leishmaniasis. We have designed and synthesized 12 derivatives of bis(spiropyrazolone)cyclopropanes. We then characterized their potential application in therapeutic use. For this, the in vitro biological activities against three eukaryotic models-S. cerevisiae, five cancer cell lines, and the parasite L. mexicana-were evaluated. In addition, cytotoxicity against non-cancerous mammalian cells has been evaluated and other properties of interest have been characterized, such as genotoxicity, antioxidant properties and, in silico predictive adsorption, distribution, metabolism, and excretion (ADME). The results that we present here represent a first screening, indicating two derivatives of bis(spiropyrazolone)cyclopropanes as good candidates for the treatment of leishmaniasis. They have good specificity against parasites with respect to mammalian cells.

Synthesis and duplex-forming ability of oligonucleotides modified with 4'-C,5'-C-methylene-bridged nucleic acid (4',5'-BNA)

We describe herein the design and synthesis of 4'-C,5'-C-methylene-bridged nucleic acid (4',5'-BNA), a novel artificial nucleic acid with the torsion angle γ in a non-canonical +ac range. The 4',5'-BNA phosphoramidite bearing a thymine nucleobase was synthesized from a commercially available thymidine analog in 11 steps and successfully incorporated into oligonucleotides. The resulting oligonucleotides were evaluated for their duplex-forming ability toward single-stranded DNA and RNA.

Stereoselective Synthesis of Ribofuranoid exo-Glycals by One-Pot Julia Olefination Using Ribofuranosyl Sulfones

One-pot Julia olefination using ribofuranosyl sulfones is described. The α-anomers of the ribofuranosyl sulfones were synthesized with complete α-selectivity via the glycosylation of heteroarylthiols using ribofuranosyl iodides as glycosyl donors and the subsequent oxidation of the resulting heteroaryl 1-thioribofuranosides with magnesium monoperphthalate (MMPP). The Julia olefination of the α-ribofuranosyl sulfones with aldehydes proceeded smoothly in one pot to afford the thermodynamically less stable (E)-exo-glycals with modest-to-excellent stereoselectivity (up to E/Z = 94:6) under the optimized conditions. The E selectivity was especially high for aromatic aldehydes. In contrast, the (Z)-exo-glycal was obtained as the main product with low stereoselectivity when the corresponding β-ribofuranosyl sulfone was used (E/Z = 41:59). The remarkable impact of the anomeric configuration of the ribofuranosyl sulfones on the stereoselectivity of the Julia olefination has been rationalized using density functional theory (DFT) calculations. The protected ribose moiety of the resulting exo-glycals induced completely α-selective cyclopropanation on the exocyclic carbon-carbon double bond via the Simmons-Smith-Furukawa reaction. The 2-cyanoethyl group was found to be useful for the protection of the exo-glycals, as it could be removed without affecting the exocyclic C═C bond.

Direct N-Glycosylation of Amides/Amines with Glycal Donors

Direct N-glycosylation between glycals and amides/amines was achieved with exclusive stereoselectivity in moderate to high yields. Various amides, amines, and 3,4-O-carbonate-glycals were tolerated, and unique β-N-glycosides were obtained. The strategy was based on palladium-catalyzed decarboxylative allylation, and the high 1,4-cis-selectivity was proposed because of the hydrogen bonding effect. Notably, all the synthesized products were subjected to preliminary bioactivity studies, revealing that three compounds were cytotoxic to tumor cells and nontoxic to normal human cells.

Protecting-Group-Mediated Diastereoselective Synthesis of C4'-Methylated Uridine Analogs and Their Activity against the Human Respiratory Syncytial Virus

Adjusting the protecting group strategy, from an alkyl ether to a bidentate ketal at the carbohydrate backbone of uridine, facilitates a switchable diastereoselective α- or β-C4'/C5'-spirocyclopropanation. Using these spirocyclopropanated nucleosides as key intermediates, we synthesized a variety of C4'-methylated d-ribose and l-lyxose-configured uridine derivatives by a base-mediated ring-opening of the spirocyclopropanol moiety. Investigations of antiviral activity against the human respiratory syncytial virus were carried out for selected derivatives, showing moderate activity.