Trimethylsilylated diazomethane (14.18 ml, 2.0 M, 28.35 mmol) was added slowly and dropwise to a 20% methanol/toluene (100 ml) solution of 1-BOC-piperidine-3-carboxylic acid (5.00 g, 21.81 mmol) at room temperature. The reaction was monitored by thin layer chromatography (TLC) until the reaction was completed. After completion of the reaction, the reaction mixture was concentrated under reduced pressure to afford methyl N-Boc-3-piperidinecarboxylate (Intermediate 53) 4.44 g in 83.7% yield. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δppm 1.4 (s, 9H), 1.6 (d, J = 3.4 Hz, 1H), 1.6 (m, 1H), 1.7 (m, 1H), 2.0 (m, 1H), 2.4 (m, 1H), 2.8 (m, 1H), 3.0 (s, 1H), 3.7 (s, 3H) , 3.9 (d, J13.2 Hz, 1H), 4.1 (s, 1H).
