Efficient Synthesis of Methyl 3,5-Di-O-benzyl-α-d-ribofuranoside and Application to the Synthesis of 2‘-C-β-Alkoxymethyluridines

Design, synthesis, and biological evaluation of novel 2'-deoxy-2'-spirooxetane-7-deazapurine nucleoside analogs as anti-SARS-CoV-2 agents

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused an unprecedented global public health crisis and continues to pose grave threats to human health. The efficacy of current vaccines and therapeutics is likely limited for future emerging strains due to the highly mutative nature of the virus, underscoring an urgent need for the development of new, potent antiviral agents. In this study, we report the design and synthesis of a series of novel 2'-deoxy-2'-spirooxetane-7-deazapurine nucleoside analogs as potential inhibitors of SARS-CoV-2 replication. Some of these compounds demonstrate potent antiviral activity, offering a potential new weapon for therapeutic intervention against the ever-evolving SARS-CoV-2 virus. Among the tested compounds, nucleoside analog 11q exhibited the most potent antiviral activity against SARS-CoV-2 in Vero E6 cells, with IC50 values of 0.14 μM for the wild-type strain and 0.36 μM for the BA.5 strain. Notably, compound 11q exhibits up to nine times greater inhibitory activity against wild-type SARS-CoV-2 compared to Remdesivir and also possesses a superior selectivity index. These findings suggest that compound 11q is a highly promising lead candidate for future drug development aimed at combating SARS-CoV-2.

Design, synthesis and evaluation of 2'-acetylene-7-deaza-adenosine phosphoamidate derivatives as anti-EV71 and anti-EV-D68 agents

A series of phosphoamidate derivatives of nucleoside 2'-acetylene-7-deaza-adenosine (NITD008) were synthesized and evaluated for their in vitro antiviral activities against the enteroviruses EV71 and EV-D68. The phosphoamidate (15f) containing a hexyl ester of l-alanine exhibited the most promising activity against EV71 (IC₅₀ = 0.13 ± 0.08 μM) and was 4-times more potent than NITD008. Meanwhile, the derivative containing a cyclohexyl ester of l-alanine (15l) exhibited the most potent activity with high selectivity index against both EV71 (IC₅₀ = 0.19 ± 0.27 μM, SI = 117.00) and EV-D68 (IC₅₀ = 0.17 ± 0.16 μM, SI = 130.76), which were both higher than that of NITD008. The results indicated that the phosphoamidate 15l was the most promising candidate for further development as antiviral agents for the treatment of both EV71 and EV-D68 infection.

Chemical synthesis of linear ADP-ribose oligomers up to pentamer and their binding to the oncogenic helicase ALC1

ADP-ribosylation is a pivotal post-translational modification that mediates various important cellular processes producing negatively charged biopolymer, poly (ADP-ribose), the functions of which need further elucidation. Toward this end, the availability of well-defined ADP-ribose (ADPr) oligomers in sufficient quantities is a necessity. In this work, we demonstrate the chemical synthesis of linear ADPr oligomers of defined, increasing length using a modified solid phase synthesis method. An advanced phosphoramidite building block temporarily protected with the base sensitive Fm-group was designed and implemented in the repeating pyrophosphate formation via a P(v)-P(iii) coupling procedure on Tentagel solid support. Linear ADPr oligomers up to a pentamer were successfully synthesized and their affinity for the poly-(ADP-ribose)-binding macrodomain of the human oncogenic helicase and chromatin remodeling enzyme ALC1 was determined. Our data reveal a length-dependent binding manner of the nucleic acid, with larger ADPr oligomers exhibiting higher binding enthalpies for ALC1, illustrating how the activity of this molecular machine is gated by PAR.

Anti-norovirus activity of C7-modified 4-amino-pyrrolo[2,1-f][1,2,4]triazine C-nucleosides

Synthetic nucleoside analogues characterized by a C-C anomeric linkage form a family of promising therapeutics against infectious and malignant diseases. Herein, C-nucleosides comprising structural variations at the sugar and nucleobase moieties were examined for their ability to inhibit both murine and human norovirus RNA-dependent RNA polymerase (RdRp). We have found that the combination of 4-amino-pyrrolo[2,1-f][1,2,4]triazine and its 7-halogenated congeners with either a d-ribose or 2'-C-methyl-d-ribose unit resulted in analogues with good antiviral activity against murine norovirus (MNV), albeit coupled with a significant cytotoxicity. Among this series, 4-aza-7,9-dideazaadenosine notably retained a strong antiviral effect in a human norovirus (HuNoV) replicon assay with an EC₅₀ = 0.015 μM. This study demonstrates that C-nucleosides can be used as viable starting scaffolds for further optimization towards the development of nucleoside-based inhibitors of norovirus replication.

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin-Anh and Chelation-Control Models

This review describes the additions of allylmagnesium reagents to carbonyl compounds and to imines, focusing on the differences in reactivity between allylmagnesium halides and other Grignard reagents. In many cases, allylmagnesium reagents either react with low stereoselectivity when other Grignard reagents react with high selectivity, or allylmagnesium reagents react with the opposite stereoselectivity. This review collects hundreds of examples, discusses the origins of stereoselectivities or the lack of stereoselectivity, and evaluates why selectivity may not occur and when it will likely occur.

A Click-Chemistry Linked 2'3'-cGAMP Analogue

2'3'-cGAMP is an uncanonical cyclic dinucleotide where one A and one G base are connected via a 3'-5' and a unique 2'-5' linkage. The molecule is produced by the cyclase cGAS in response to cytosolic DNA binding. cGAMP activates STING and hence one of the most powerful pathways of innate immunity. cGAMP analogues with uncharged linkages that feature better cellular penetrability are currently highly desired. Here, the synthesis of a cGAMP analogue with one amide and one triazole linkage is reported. The molecule is best prepared via a first Cu^I -catalyzed click reaction, which establishes the triazole, while the cyclization is achieved by macrolactamization.

A novel and environmental friendly synthetic route for hydroxypyrrolidines using zeolites

A critical step in the synthesis of the hydroxypyrrolidines, 1,4-dideoxy-1,4-imino-l-lyxitol and 1,4-dideoxy-1,4-imino-d-lyxitol, from the corresponding d-sugars is the synthesis of O-methyl 2,3-O-isopropylidenepentofuranoses. Instead of applying homogeneous catalysis process with conventional inorganic acid catalysts like HCl and HClO₄, it was found that heterogeneous catalysis using zeolites could be used for the one-pot synthesis of O-methyl 2,3-O-isopropylidenepentofuranoses directly from d-sugars, MeOH and acetone at mild condition. The best catalyst was H-beta zeolite containing a Si/Al molar ratio of 150, where a yield of >83% was obtained. The overall yields of the five-step procedure to 1,4-dideoxy-1,4-imino-l-lyxitol and 1,4-dideoxy-1,4-imino-d-lyxitol were 57% and 50%, respectively. This synthetic procedure has several advantages such as competitive overall yield, reduced number of steps, and mild reaction conditions. Furthermore, the zeolite catalyst can be easily recovered from the reaction mixture and reused with no loss of activity.

New fluorinated fructose analogs as selective probes of the hexose transporter protein GLUT5

Two fluorinated fructose analogs are taken up by tumor cells in culture. Their high affinity for the transporter protein GLUT5 provides information on the structural demands of its binding site, and suggests approaches towards new molecular imaging probes.

A new route for the synthesis of 4-amino-5-fluoro-7-(2'-deoxy-2'-fluoro-2'-C-methyl-β-D-ribofuranosyl)-1H-pyrrolo[2,3-d]pyrimidine

A new route for the synthesis of 4-amino-5-fluoro-7-(2'-deoxy-2'-fluoro-2'-C-methyl-β-D-ribofuranosyl)-1H-pyrrolo[2,3-d]pyrimidine 1, was developed.

Synthesis and properties of triplex-forming oligonucleotides containing 2'-O-(2-methoxyethyl)-5-(3-aminoprop-1-ynyl)-uridine

2'-O-(2-Methoxyethyl)-5-(3-aminoprop-1-ynyl)-uridine phosphoramidite (MEPU) has been synthesized from d-ribose and 5-iodouracil and incorporated into triplex-forming oligonucleotides (TFOs) by automated solid-phase oligonucleotide synthesis. The TFOs gave very high triplex stability with their target duplexes as measured by ultraviolet/fluorescence melting and DNase I footprinting. The incorporation of MEPU into TFOs renders them resistant to degradation by serum nucleases.