To a microwave vial containing 1-adamantanecarboxylic acid (0.05 g, 0.283 mmol) was added HATU (0.11 g, 0.283 mmol), triethylamine (0.11 mL, 0.772 mmol) and DMF (1.5 mL). The solution was allowed to stir at rt for 30 minutes before ethyl 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate Intermediate 5 (0.05 g, 0.257 mmol) was added to the solution. The solution was then allowed to stir at rt overnight and then evaporated. To the resulting residue was added DCE (3 mL) and water (1 mL). After separation, the aqueous phase was extracted with DCE (2×3 mL). The combined organic phases were concentrated to give a crude ethyl 2-(1-adamantylcarbonyl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate as a solid.
