To a suspension of 10a-(4-hydroxyphenyl)-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrrolo[1,2-d]pyrazin-5-one (50 mg, 0.19 mmol) and potassium carbonate (77 mg, 0.56 mmol) in DMF (1 mL) was added (2-bromoethoxy)-tert-butyldimethylsilane (120 μL, 0.56 mmol). The mixture was heated at 100° C. The outcome of the reaction was monitored by LCMS. After completion (45 minutes) the mixture was diluted with a saturated aqueous solution of NH4Cl (6 mL) and extracted with ethyl acetate (3×2.5 mL). The combined organic layers were dried (MgSO4), filtered and concentrated in vacuo to yield a pale yellow solid that was purified by flash chromatography (Biotage SP4, 12 g silica cartridge, gradient 0-10% MeOH in CH2Cl2) to give 10a-[4-(2-{[tert-butyl(dimethyl)silyl]oxy]ethoxy)phenyl}-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrrolo[1,2-d]pyrazin-5-one (86 mg, quantitative yield). ESI-MI m/z [M+H]+ 428.2.
