To a stirred solution of (S)-2-(hydroxymethyl)-6,8-dihydrospiro[cyclopenta[g]quinoline-7,3′-pyrrolo[2,3-b]pyridin]-2′(1′H)-one (1.67 g, 5.26 mmol, described in Intermediate 7) in DMF (10 mL) at 0° C. was added sodium hydride (60% dispersion in mineral oil; 210 mg, 5.26 mmol) and the mixture was stirred for 30 min. 2-(Trimethylsilyl)ethoxymethyl chloride (0.93 mL, 5.26 mmol) was then added dropwise. After 90 min, the reaction was quenched with saturated aqueous NaHCO3 (50 mL) and the mixture was extracted with CH2Cl2 (3×100 mL). The combined organic layers were washed with brine, dried over Na2SO4, filtered, concentrated in vacuo. The crude product was purified by silica gel chromatography, eluting with a gradient of CH2Cl2:MeOH:NH4OH—100:0:0 to 90:9:1, to give the title compound. MS: m/z=448 (M+1).
