1'-Cyano Intermediate Enables Rapid and Stereoretentive Access to 1'-Modified Remdesivir Nucleosides.

While biochemical, structural, and computational studies have shown the importance of remdesivir's C1'-substituent in its perturbation of SARS-CoV-2 RdRp action, we recognized the paucity of methods to stereoselectively install substituents at this position as an obstacle to rigorous explorations of SAR and mechanism. We report the utilization of an anomerically pure 1'-cyano intermediate as an entry point to a chemically diverse set of substitutions, allowing for 1'diversification while obviating the need for the tedious separation of anomeric mixtures.

Innovative Strategies for the Construction of Diverse 1'-Modified C-Nucleoside Derivatives.

Modified C-nucleosides have proven to be enormously successful as chemical probes to understand fundamental biological processes and as small-molecule drugs for cancer and infectious diseases. Historically, the modification of the glycosyl unit has focused on the 2'-, 3'-, and 4'-positions as well as the ribofuranosyl ring oxygen. By contrast, the 1'-position has rarely been studied due to the labile nature of the anomeric position. However, the improved chemical stability of C-nucleosides allows the modification of the 1'-position with substituents not found in conventional N-nucleosides. Herein, we disclose new chemistry for the installation of diverse substituents at the 1'-position of C-nucleosides, including alkyl, alkenyl, difluoromethyl, and fluoromethyl substituents, using the 4-amino-7-(1'-hydroxy-d-ribofuranosyl)pyrrolo[2,1-f][1,2,4]triazine scaffold as a representative purine nucleoside mimetic.

Cu(I)-/Base-Mediated Domino [5 + 3 + 1] Annulation for Highly π-Extended Carbazole Frameworks and DFT Mechanistic Insights.

An efficient synthesis of highly π-extended carbazoles is described via an unexpected domino [5 + 3 + 1] annulation approach. The Cu(I)-/base-promoted reactions of 2-nitrocinnamaldehydes with benzyl cyanides provide diverse benzo[ b]carbazoles. The reaction is proposed to proceed via a sequential Michael addition/intramolecular addition of an enol into a nitro group, 6π- electrocyclization, and the final oxidative aromatization as supported by density functional theory calculations. Some of the synthesized carbazoles showed significant potential in fluorescence sensing of Cu2+ ions.

One-pot construction of sterically challenging and diverse polyarylphenols via transition-metal-free benzannulation and their potent in vitro antioxidant activity.

This paper reports the novel and efficient one-pot synthesis of highly functionalized polyarylphenols from readily available 1,3-diarylpropan-2-ones and chalcones or cinnamaldehyde derivatives via benzannulation under transition-metal-free and aerobic conditions. This benzannulation proceeds through cascade Michael addition/intramolecular aldol/tautomerization/oxidation. This protocol produces various tetra- and tri-aryl substituted phenols in moderate to good yield. The synthesized compounds exhibited potent antioxidant activities compared to the standard BHT.

Transition-metal-free benzannulation for diverse and polyfunctionalized biaryl formation.

A novel and efficient synthesis of highly functionalized and diverse biaryls via mild base-promoted transition-metal-free benzannulation was achieved in good yield from readily available ß-ketoesters, ß-ketoamides, or 1,3-diketones with cinnamaldehydes or aryl aldehydes. This transformation comprises a sequence of the formation of three new bonds through multicomponent reactions as a one-pot procedure. This novel biaryl formation proceeds through domino Michael addition/intramolecular and intermolecular aldol/[1,5]-hydrogen shift/tautomerization. This protocol provides a great advantage in introducing various functional groups on the aromatic ring of biaryls.

Construction of highly functionalized carbazoles via condensation of an enolate to a nitro group.

This paper describes a novel synthesis of highly functionalized and diverse carbazoles via transition-metal-free and mild base-promoted condensations of readily available 2-nitrocinnamaldehyde or 2-nitrochalcones with various ß-ketoesters or 1,3-diaryl-2-propanones. The method selectively forms four bonds by the intramolecular conjugate addition of an enolate to the enal or chalcone bearing an o-nitro group. This group then undergoes in situ N-O bond cleavage under non-reductive conditions in a one-pot procedure. This protocol allows for the introduction of various functional groups at all positions of the newly formed aromatic ring of the carbazole moiety. The utility of this methodology is further illustrated by the concise synthesis of naturally occurring hyellazole and chlorohyellazole.

An advanced and novel one-pot synthetic method for diverse benzo[c]chromen-6-ones by transition-metal free mild base-promoted domino reactions of substituted 2-hydroxychalcones with ß-ketoesters and its application to polysubstituted terphenyls.

Novel and efficient one-pot syntheses of a variety of benzo[c]chromen-6-one derivatives were accomplished using Cs2CO3-promoted reactions between substituted 2-hydroxychalcones and ß-ketoesters. These reactions involved domino Michael addition/intramolecular aldol/oxidative aromatization/lactonization and provided a rapid synthetic route for the production of biologically interesting novel benzo[c]chromen-6-one molecules bearing several different substituents on benzene rings. As an application of this methodology, several synthesized benzo[c]chromen-6-ones were transformed into highly functionalized novel terphenyls.