Iodomethane

To synthesize N^1,6-methyladenosine, N⁶-methyladenosine (Selleckchem) was dissolved in dry DMF and followed with addition of iodomethane (Acros Organics; 10:1 molar ratio iodomethane:N⁶-methyladenosine). The mixture was stirred overnight at room temperature. The product was purified by flash chromatography on silica gel (EMD), eluting with methanol and dichloromethane (1:10 to 1:5; ACS or HPLC grade solvents). This resulted in a product yield of 46.3% N^1,6-methyladenosine. Product identity was confirmed by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HR-MS).
NMR spectra were recorded using a 500-MHz Bruker DMX-500 instrument at room temperature, and chemical shifts were referenced to the residual solvent peak. Shifts were as follows: ¹H NMR (500 MHz, DMSO-d₆) δ 8.11 (s, 1H), 8.04 (s, 1H), 5.76 (d, J = 5.8 Hz, 1H), 5.15 (s, 1H), 4.43 (t, J = 5.4 Hz, 1H), 4.15 (m, 2H), 3.92 (d, J = 3.7 Hz, 1H), 3.63 (dd, J = 12.0, 3.9 Hz, 1H), 3.56 (m, 2H), 3.50 (s, 3H), 3.45 (d, J = 6.5 Hz, 1H), 1.23 (s, 3H).
HR-MS data were recorded with Waters LCT-Premier XE at room temperature. For a predicted mass for N^1,6-methyladenosine, or C₁₂H₁₈N₅O₄⁺, of 296.1353, the mass found was 296.1361.

For the biological test, bacto tryptone and bacto yeast extract were provided by Fisher Scientific (Illkirch, France). Potassium phosphate monobasic, potassium phosphate dibasic, and agar were purchased from Sigma-Aldrich (Saint-Quentin, Fallavier, France).
For extraction, purification, and chemical analysis, chloroform, ethyl acetate, methanol, formic acid, and water (of ULC-MS grade) were all purchased from Biosolve BV (Valkenswaard, The Netherlands). Hydrochloric acid solution (1M) was purchased from Sigma-Aldrich (Saint-Quentin, Fallavier, France). Deuterated reagent, such as deuterated chloroform (CDCl₃), was purchased from Euriso-top (Saint-Aubin, France).
For organic synthesis, tropolone, 18-crown-6, iodomethane, N-bromosuccinimide, trifluoroacetic acid, and acetic anhydride were purchased form Thermo Scientific (Illkirch, France). Benzene and toluene were purchased from Sigma-Aldrich (Saint-Quentin, Fallavier, France).

Iodomethane (99%) was purchased from Thermo Scientific. Sodium hydride (60% in mineral oil) was purchased from Aldrich. Anhydrous DME (99.5%, water content of 23 ppm) and 1 M LiPF₆-EC-DEC (v: v = 1: 1, water content of 7 ppm) electrolyte were purchased from Sigma. Anhydrous THF (water content below 10 ppm) was obtained from a solvent drying system passed by alumina column to remove trace water. 1,2-dimethoxypropane (DMP, > 98%, water content of 6 ppm after molecular sieves drying) was purchased from Tokyo Chemical Industry (TCI). Battery grade LiFSI (99.9%, Canrd), Al foil (14 μm, 99.6%), Cu foil (9 μm, 99.99%), and NCM811 laminate (8 mg cm⁻¹ with the thickness of 32 μm and 20 mg cm⁻¹ with the thickness of 79 μm, loading is only based on the active material, cathodes contain 94.5% active material, 2.5% PVDF and 3% Super-P by weight) were purchased from Guangdong Canrd New Energy Technology Co.,Ltd. Li disc (Φ16 mm, 600 μm, 99.95%) and Li foil (20 μm, 99.95%) were purchased from China Energy Lithium Co., Ltd. All the chemicals and reagents used without further purification unless otherwise stated.