Methyl iodide → Ethyl 8-(benzyloxy)-2-methyl-1-oxo-6-propionyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate

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Reaction Conditions

Reaction Steps

To a cold (−78° C.) solution of ethyl 6-acetyl-8-(benzyloxy)-2-methyl-1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate (0.60 g, 1.62 mmol; Example 7, step 7) in anhydrous DMF (17 mL), a solution of lithium bis(trimethylsilyl)amide (1.94 mL, 1.94 mmol) in MTBE was added. The mixture was stirred at −78° C. for 15 minutes, treated with iodomethane (0.12 mL, 1.94 mmol), allowed to slowly warm up to room temperature, and stirred at the temperature overnight. The product mixture was concentrated under vacuum. The residue was partitioned between chloroform and dilute hydrochloric acid. The organic extract was washed with brine, dried over anhydrous magnesium sulfate, filtered, and concentrated under vacuum. The residue was subjected to preparation HPLC on C-18 stationary phase eluting with a gradient of methanol in water in the presence of ammonium acetate (1 g/L). Collection and concentration of appropriate fractions provided the title compound. The corresponding bis-methylated ketone was also isolated and was used for the preparation of Examples 60 & 61.

Provenance & Evidence