Synthesis of Bisubstrate Analogues for RNA Methylation Studies using two Transition‐Metal‐Catalyzed Reactions

Abstract

RNA methyltransferases (RNA MTases) are a family of enzymes that catalyze the methylation of RNA using the cofactor S‐adenosyl‐L‐methionine. While RNA MTases are promising drug targets, new molecules are needed to fully understand their roles in disease and to develop effective drugs that can modulate their activity. Since RNA MTases are suitable for bisubstrate binding, we report an original strategy for the synthesis of a new family of m6A MTases bisubstrate analogues. Six compounds containing a S‐adenosyl‐L‐methionine (SAM) analogue unit covalently tethered by a triazole ring to the N‐6 position of an adenosine were synthesized. A procedure using two transition‐metal‐catalyzed reactions was used to introduce the α‐amino acid motif mimicking the methionine chain of the cofactor SAM. First, a copper(I)‐catalyzed alkyne‐azide iodo‐cycloaddition (iCuAAC) reaction afforded the 5‐iodo‐1,4‐disubstituted‐1,2,3‐triazole which was functionalized by palladium‐catalyzed cross‐coupling to connect the α‐amino acid substituent. Docking studies of our molecules in the active site of the m6A ribosomal MTase RlmJ show that the use of triazole as a linker provides additional interactions and the presence of the α‐amino acid chain stabilizes the bisubstrate. The synthetic method developed here enhances the structural diversity of bisubstrate analogues to explore the active site of RNA modification enzymes and to develop new inhibitors.

Halo‐1,2,3‐triazoles: Valuable Compounds to Access Biologically Relevant Molecules

“…Recently, our group developed a two-step metal-catalyzed procedure to access bisubstrate analogues of RNA methyltransferases (RNMTase) based on the synthesis and the modification of a 5-iodo-triazole ring. [41] The reactivity of unprotected adenosine derivatives 55 and 56 was first examined by iCuAAC. The reaction conditions were optimized and the use of Cu(ClO 4 ) 2 , a TBTA ligand, NaI and DIPEA in DMF allowed us to obtain the 5-iodo-triazole compound 57 in 38 % yield (Scheme 8A).…”

N-Arylsulfonamide-based adenosine analogues to target RNA cap N7-methyltransferase nsp14 of SARS-CoV-2

“…1B) and to investigate how modification of the initial scaffold by these new linkers would impact on N 7-MTase inhibitory activity in vitro . Previously, the N -methyltriazole linker had been used in the same way to synthesize bisubstrates interfering with the protein N-terminal MTase (NTMT1) by Huang and co-workers, 30 m 6 A and m 1 A RNA MTases by the Ethève-Quelquejeu's group, 31,32 or to prepare 5′ cap mimics with a triazole ring inside the oligophosphate chain by Jemielity's group. 33 Using click chemistry to combine two parts of a complex molecule represents an attractive approach over conventional multi-step approaches, which are often more time-consuming and tedious.…”

The catalytic mechanism of the RNA methyltransferase METTL3

“…BAs aim to mimic the transition state in which both the substrate nucleoside and the cosubstrate SAM are bound in the catalytic pocket of the enzyme while the methyl group is transferred from SAM to the adenosine N 6 -atom of the substrate RNA during catalysis ( Figure 2A ; Oerum et al, 2019 ; Atdjian et al, 2018 ; Atdjian et al, 2020 ; Meynier et al, 2022 ; Coelho et al, 2023 ). They consist of a SAM analogue (5’N-SAM) covalently linked to the N 6 position of an adenosine of a ribonucleotide(-like) fragment ( Figure 2B ; Atdjian et al, 2018 ; Schapira, 2016 ).…”