Extended Data Fig. 1: Synthesis of NHC-phosphoramidite 3 (M-PA).
From: Mechanism of molnupiravir-induced SARS-CoV-2 mutagenesis
5’-O-DMT-2’-O-TOM-O4-chlorophenyluridine (A) was synthesized from uridine as previously reported (L. Buttner, J. Seikowski, K. Wawrzyniak, A. Ochmann, C. Hobartner, Synthesis of spin-labeled riboswitch RNAs using convertible nucleosides and DNA-catalyzed RNA ligation. Bioorg Med Chem 21, 6171-6180 (2013)). The chlorophenol group was displaced by hydroxylamine to give new compound 1. After selective benzoyl protection at N4 with benzoic anhydride, compound 2 was converted to the phosphoramidite M-PA (3) using 2-cyanoethyl-N,N,N’,N’-tetraisopropylphosphorodiamidite and 4,5-dicyano-imidazol (DCI) in analogy to a previous report (J. Lu, L. Nan-Sheng, J. A. Piccirilli, Efficient Synthesis of N 4-Methyl- and N 4-Hydroxycytidine Phosphoramidites. Synthesis 16, 2708-2712 (2010)). DMT-Cl = 4,4’-dimethoxy-trityl chloride, TOM-Cl = triisopropylsilyloxymethyl chloride, DBU = 1,8-diazabicyclo [5.4.0]undec-7-ene, DMAP = 4-(N,N-dimethylamino)- pyridine.
