Trimethylsilylated diazomethane (2 M solution in hexane, 14 mL) was slowly added dropwise to a mixture of (R)-N-Boc-2-piperazinecarboxylic acid (5 g) dissolved in methanol (100 mL) and dichloromethane (115 mL). The reaction mixture was stirred at room temperature for 16 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure and the residue obtained was purified by column chromatography, first using ethyl acetate as eluent and subsequently using a solution of ethyl acetate containing 5% methanol and 7N ammonia as eluent to afford methyl (R)-1-Boc-2-piperazinecarboxylate as an oil (2.55 g, 48% yield). NMR hydrogen spectrum (DMSO-d6) δ 1.40 (s, 9H), 2.10 (bs, 1H), 2.52 (m, 1H), 2.72 (dd, 1H), 2.82 (d, 1H), 2.97 (m, 1H), 3.29 (d, 1H), 3.61 (d, 1H), 3.67 (s, 3H), 4.43 (m, 1H); mass spectrum showed the molecular ion peak MH+ 245.
