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The general procedure for the synthesis of ethyl [6-[(tert-butoxycarbonyl)amino]-2-pyridinyl]acetate from tert-butyl (6-methylpyridin-2-yl)carbamate and diethyl carbonate was as follows: to an anhydrous THF solution of tert-butyl (6-methylpyridin-2-yl)carbamate (0.97 g, 4.66 mmol) was slowly added, at -78 °C, LDA (1.8 M heptane solution, 4 equiv, 18.6 mmol) and the reaction mixture was stirred for 30 min. Subsequently, diethyl carbonate (2 eq., 9.32 mmol) was added and stirring was continued at -78 °C for 10 min. The reaction mixture was slowly warmed to 0 °C and stirring was continued at this temperature for 2 hours. Upon completion of the reaction, the reaction was quenched with saturated NH4Cl solution followed by extraction of the reaction mixture with ethyl acetate. The organic phases were combined, dried with anhydrous MgSO4 and concentrated under reduced pressure to remove the solvent. The crude product was purified by column chromatography with heptane/ethyl acetate as eluent (gradient from 98:2 to 95:5) to afford the target product [6-[(tert-butoxycarbonyl)amino]-2-pyridinyl]ethyl acetate (1.36 g in >100% yield, probably due to incomplete removal of trace solvent).

[1] Patent: WO2006/50908, 2006, A1. Location in patent: Page/Page column 32; 39-40
[2] Patent: WO2014/182829, 2014, A1. Location in patent: Page/Page column 62; 63
[3] Bioorganic and Medicinal Chemistry Letters, 2005, vol. 15, # 11, p. 2771 - 2775