An ice cold mixture of 2-(1-benzyl-6-methyl-7-oxo-4-(p-tolyl)-6,7-dihydro-1H-pyrrolo[2,3-c]pyridin-5-yl)-2-(tert-butoxy)acetic acid (64.0 mg, 0.140 mmol) in Tetrahydrofuran (THF) (2.0 mL) was treated with dropwise addition of LDA, 2M solution in heptane/THF/ethylbenzene (0.140 mL, 0.279 mmol) and then allowed to stir at 0° C. for 45 minutes. Additional LDA (70 uL) was added and then stirred an additional 10 minutes. The mixture was quenched by adding 1N HCl and acidified to pH 2. The mixture was extracted with ethyl acetate. The combined extracts were washed with brine, dried over sodium sulfate, filtered and concentrated to give the crude debenzylation product as an orange residue. An ice cold mixture of the crude debenzylation product in methanol (1.0 mL) and diethyl ether (1.0 mL) was treated with trimethylsilyl diazomethane, 2M solution in hexanes (0.140 mL, 0.279 mmol) and then stirred at ambient temperature for 10 minutes. Additional trimethylsilyl diazomethane, 2M solution in hexanes (0.140 mL, 0.279 mmol) was added, the mixture was stirred for 5 minutes, cooled to 0° C. and then quenched with AcOH. The mixture was concentrated and then purified on silica gel (0-10% DCM/MeOH) to give the slightly impure desired product as a yellow residue (39 mg, 73% yield) which was used in the subsequent step without further purification. LC/MS (m/z) ES+=383 (M+1).
