Stereoselective Synthesis of (S)- and (N)-Cyclopropyl-Fused Carbocyclic Nucleosides Using Stereoselective Cyclopropanation

Synthesis and biological evaluation of sugar-modified truncated carbanucleosides as A2A and A3 adenosine receptor ligands to explore conformational effect to the receptors

This study investigated the impact of conformation on the binding affinity of carbanucleosides to A2A and A3 adenosine receptors (ARs). A series of nucleosides, including saturated, unsaturated, North (N)-methano, and South (S)-methanocarbanucleosides was prepared, and their binding affinities to A2AAR and A3AR were assessed. Biological evaluations revealed that all synthesized (S)-methanocarbanucleosides had negligible binding to both receptors, and most (N)-methanocarbanucleosides exhibited high binding affinities. Molecular docking analysis showed that the (N)-methanocarbanucleoside 6a exhibited favorable interactions and minimal steric clashes in both A2AAR and A3AR. Conversely, the (S)-methanocarbanucleoside 7a appears to encounter significant steric clashes, which impeded its binding to A2AAR. Furthermore, when adopting the South conformation 7a was unable to bind to A3AR. Expanding upon the (N)-methanocarba moiety, various C8-aromatic groups were introduced to convert A2AAR agonists into antagonists and these modified compounds also exhibited strong binding affinity. These results suggest that the North conformation is favored by both A2AAR and A3AR, and that (N)-methanocarbanucleosides can serve as versatile structural moieties for dual targeting of A2AAR and A3AR. These findings offer promising avenues for the development of dual ligands for therapeutic applications in obesity and immunotherapy.

Is it still worth renewing nucleoside anticancer drugs nowadays?

Nucleoside has situated the convergence point in the discovery of novel drugs for decades, and a large number of nucleoside derivatives have been constructed for screening novel pharmacological properties at various experimental platforms. Notably, nearly 20 nucleosides are approved to be used in the clinic treatment of various cancers. Nevertheless, the blossom of synthetic nucleoside analogs in comparison with the scarcity of nucleoside anticancer drugs leads to a question: Is it still worth insisting on the screening of novel anticancer drugs from nucleoside derivatives? Hence, this review attempts to emphasize the importance of nucleoside analogs in the discovery of novel anticancer drugs. Firstly, we introduce the metabolic procedures of nucleoside anticancer drug (such as 5-fluorouracil) and summarize the designing of novel nucleoside anticancer candidates based on clinically used nucleoside anticancer drugs (such as gemcitabine). Furthermore, we collect anticancer properties of some recently synthesized nucleoside analogs, aiming at emphasizing the availability of nucleoside analogs in the discovery of anticancer drugs. Finally, a variety of synthetic strategies including the linkage of sugar moiety with nucleobase scaffold, modifications on the sugar moiety, and variations on the nucleobase structure are collected to exhibit the abundant protocols in the achievement of nucleoside analogs. Taken the above discussions collectively, nucleoside still advantages for the finding of novel anticancer drugs because of the clearly metabolic procedures, successfully clinic applications, and abundantly synthetic routines.

Stereoselective Approach for the Synthesis of Diverse 1'-Modified Carbanucleosides

We describe an efficient and stereoselective synthesis of 1'-substituted-β-carbocylic nucleosides 5 via gem-dichlorooxirane intermediate 7, which directly condensed with weak nucleophiles such as pyrimidines or purines. The formation of gem-dichlorooxirane 7 and direct nucleobase condensation exclusively proceeded in protic polar solvents like MeOH. This method provides a general and modular route for the late-stage diversification of 1'-modified nucleosides.

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.

Structure–Activity Relationships of Truncated 1′-Homologated Carbaadenosine Derivatives as New PPARγ/δ Ligands: A Study on Sugar Puckering Affecting Binding to PPARs

Peroxisome proliferator-activated receptors (PPARs) are associated with the regulation of metabolic homeostasis. Based on a previous report that 1'-homologated 4'-thionucleoside acts as a dual PPARγ/δ modulator, carbocyclic nucleosides 2-5 with various sugar conformations were synthesized to determine whether sugar puckering affects binding to PPARs. (S)-conformer 2 was synthesized using Charette asymmetric cyclopropanation, whereas (N)-conformer 3 was synthesized using stereoselective Simmons-Smith cyclopropanation. All synthesized nucleosides did not exhibit binding affinity to PPARα but exhibited significant binding affinities to PPARγ/δ. The binding affinity of final nucleosides to PPARγ did not differ significantly based on their conformation, but their affinity to PPARδ depended greatly on their conformation, correlated with adiponectin production. (N)-conformer 3h was discovered to be the most potent PPARδ antagonist with good adiponectin production, which exhibited the most effective activity in inhibiting the mRNA levels of LPS-induced IL-1β expression in RAW 264.7 macrophages, implicating its anti-inflammatory activity.

Synthesis of Enantiomerically Pure Pyrimidine Ribonucleosides Locked in the South Conformation

The conformation of the central five-membered ring of a nucleoside plays an important role in enzyme recognition. Bicyclo[3.1.0]hexane, also known as the methanocarba (MC), serves as a template that can mimic the locked forms of the two distinctive conformations, namely, the north and south conformations. While modified nucleosides locked in the north conformation have been actively investigated, the south counterpart remains largely unexplored because it is difficult to synthesize. Herein, we report a concise synthetic route that can provide the key amino sugar intermediate essential for the synthesis of (S)-MC ribonucleosides in a 100% stereoselective manner. Also, through the proposed synthetic approach, we report the first synthesis of enantiomerically pure (S)-MC cytidine 1. We believe our findings would greatly contribute to the field of nucleoside chemistry and provide opportunities for novel nucleoside discovery.

Conformationally Locked Carbocyclic Nucleosides Built on a 4'-Hydroxymethyl-3'-hydroxybicyclo[4.1.0]heptane Template. Stereoselective Synthesis and Antiviral Activity

Two new families of enantiomerically pure carbocyclic nucleoside analogues based on a cyclohexane moiety with five chiral centers and a fused cyclopropyl ring have been synthesized. A highly regio- and stereoselective synthetic approach for the modular construction of the functionalized bicyclo[4.1.0]heptyl azide intermediate 6 has been established. Key steps to achieve this asymmetric synthesis involved highly diastereoselective allylic oxidation and hydroboration reactions. The first family of compounds, 1a,b and 2, presents different natural nucleobases, whereas the second one 3a-e bears functionalized 1,2,3-triazoles. These derivatives have been tested as antiviral agents, and compound 3d has shown to display moderate activity against coxsackie B4 virus.

Fluorinated Nucleosides: Synthesis, Modulation in Conformation and Therapeutic Application

Over the last twenty years, fluorination on nucleoside has established itself as the most promising tool to use to get biologically active compounds that could sustain the clinical trial by affecting the pharmacodynamics and pharmacokinetic properties. Due to fluorine's inherent unique properties and its judicious introduction into the molecule, makes the corresponding nucleoside metabolically very stable, lipophilic, and opens a new site of intermolecular binding. Fluorination on various nucleosides has been extensively studied as a result, a series of fluorinated nucleosides come up for different therapeutic uses which are either approved by the FDA or under the advanced stage of the clinical trial. Here in this review, we are summarizing the latest development in the chemistry of fluorination on nucleoside that led to varieties of new analogs like carbocyclic, acyclic, and conformationally biased nucleoside and their biological properties, the influence of fluorine on conformation, oligonucleotide stability, and their use in therapeutics.