[Cl:1][C:2]1[N:10]=[C:9]2[C:5]([NH:6][C:7]([S:11]([CH3:14])(=[O:13])=[O:12])=[N:8]2)=[CH:4][N:3]=1.C(N(CC)C(C)C)(C)C.[CH3:24][Si:25]([CH3:32])([CH3:31])[CH2:26][CH2:27][O:28][CH2:29]Cl.CCOC(C)=O>CN(C=O)C>[Cl:1][C:2]1[N:10]=[C:9]2[C:5]([N:6]([CH2:29][O:28][CH2:27][CH2:26][Si:25]([CH3:32])([CH3:31])[CH3:24])[C:7]([S:11]([CH3:14])(=[O:13])=[O:12])=[N:8]2)=[CH:4][N:3]=1
To a stirring solution of 2-chloro-8-(methylsulfonyl)-7H-purine (570 mg, 2.45 mmol) and N,N-diisopropylethylamine (3.42 mL, 19.60 mmol) in anhydrous DMF (16.7 mL) was added 2-(trimethylsilyl)ethoxymethyl chloride (2.17 mL, 12.25 mmol). The reaction was stirred under N2 at RT for 20 h, then added to EtOAc (1.0 L) and washed with saturated NH4Cl (0.2 L). The aqueous layer was separated and back-extracted with EtOAc (0.2 L). The organic layers combined and evaporated under reduced pressure. Flash chromatography of the resulting residue utilizing a 24 g silica RediSep Rf® Gold column and employing a 0-40% EtOAc/hexane gradient afforded the title compound. LC-MS: calculated for C12H19ClN4O3SSi 362.06 observed m/e: 385.30 (M+23)′ (Rt 1.33/2.0 min)
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