In an oven dried flask was added 5-(2-trimethylsilanyl-ethoxymethyl)-5H pyrrolo[2,3-b]pyrazin-2-ylamine (0.118 g, 0.45 mmol), DIPEA (0.275 mL, 1.58 mmol) and 5 mL DCM and the flask cooled under N2 in a dry ice acetone bath. A 20% solution of phosgene in toluene was added (0.284 mL, 0.54 mmol) and the purplish red solution was stirred for 20 minutes then warmed to −20° C. A solution of trans 2-(3-amino-cyclopentyl)-5,6-dichloro-isoindole-1,3-dione (0.143 g, est 0.5 mmol, mixture with monochloro derivative) in 8 mL DMF was added and stirred for 60 minutes, quench with MeOH and concentrated in vacuo. The residue was mixed with MeOH, filtered and the solid rinsed with MeOH and dried in vacuo to give trans 1-[3-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-cyclopentyl]-3-[5-(2-trimethylsilanyl-ethoxymethyl)-5H-pyrrolo[2,3-b]pyrazin-2-yl]-urea (0.196 g, 75% yield).
