N-Boc-N-methyl glycine methyl ester

Light yellow or colorless transparent liquid

To a suspension of sarcosine (35.64 g, 0.40 mol) in 350 mL MeOH was added thionyl chloride (29.02 mL, 0.40 mol) dropwise at 0 °C. After complete addition the cooling bath was removed and the reaction mixture was stirred for 30 min at r.t. and refluxed for further 6 h. The resulting solution was concentrated in vacuum and the residue was dried in high vacuum over night at r.t. to afford sarcosine methyl ester.HCl as a white powder which was used in the next step without further purification; yield: 56.14 g (quant.); mp. 102 °C. 1H-NMR (300 MHz, CDCl3): δ = 9.76 (s, 2 H, NH2), 3.88 (t, J = 5.6 Hz, 2 H, H-2), 3.82 (s, 3 H, H-4)), 2.83 (t, J = 5.2 Hz, 3 H, H-3). 13C-NMR(75 MHz, CDCl3): δ = 166.7 (C-1), 53.3 (C-2), 48.9 (C-3), 33.4 (C-4).1 To a suspension of sarcosine methylester.HCl (59.80 g, 0.43 mol) and (Boc)2O (138.01 mL, 0.65 mol) in 1.0 L CH2Cl2 TEA (119.09 mL, 0.86 mol) was added dropwise at 0 °C. After complete addition the cooling bath was removed and the reaction mixture was stirred for two days at r.t. Aq. HCl (1 M) was added until the aqueous layer showed pH = 6. The resulting two layers were separated and the organic layer was washed with dist. H2O, dried (Na2SO4), concentrated in vacuum and volatile impurities were removed in high vacuum over night at r.t. to afford a clear oil; yield: 78.65 g (90 percent)Boc-N-sarcosine methyl ester (18) was prepared by treating a solution of Boc-Sar- OH (1.0 g, 5.3 mmol) in 1 : 1 DCM/MeOH (25 mL) cooled to 0° C portionwise with diazomethane (2M solution, excess) until the reaction mixture turned slight yellow. The reaction was kept at 0° C for 30 min and then HOAc (2 drops) was added. The organic solvents were removed to afford 1.0 g (90percent) of 18.Glycine methyl ester hydrochloride (50.0 g, 0.398 mol, 1 eq.) was added to a 1 L flask containing water (300 mL) and THF (200 mL). Sodium bicarbonate (37.8 g, 0.438 mol) was added portionwise, followed by di-tert-butyl dicarbonate (83.4 g, 0.382 mol). The reaction was stirred for 18 h, and then the separated organic phase was concentrated. The mixture was redissolved in EtOAC, washed with brine, dried over NaTo a suspension of sarcosine (35.64 g, 0.40 mol) in 350 mL MeOH was added thionyl chloride (29.02 mL, 0.40 mol) dropwise at 0 °C. After complete addition the cooling bath was removed and the reaction mixture was stirred for 30 min at r.t. and refluxed for further 6 h. The resulting solution was concentrated in vacuum and the residue was dried in high vacuum over night at r.t. to afford sarcosine methyl ester.HCl as a white powder which was used in the next step without further purification; yield: 56.14 g (quant.); mp. 102 °C. 1H-NMR (300 MHz, CDCl3): δ = 9.76 (s, 2 H, NH2), 3.88 (t, J = 5.6 Hz, 2 H, H-2), 3.82 (s, 3 H, H-4)), 2.83 (t, J = 5.2 Hz, 3 H, H-3). 13C-NMR(75 MHz, CDCl3): δ = 166.7 (C-1), 53.3 (C-2), 48.9 (C-3), 33.4 (C-4).1 To a suspension of sarcosine methylester.HCl (59.80 g, 0.43 mol) and (Boc)2O (138.01 mL, 0.65 mol) in 1.0 L CH2Cl2 TEA (119.09 mL, 0.86 mol) was added dropwise at 0 °C. After complete addition the cooling bath was removed and the reaction mixture was stirred for two days at r.t. Aq. HCl (1 M) was added until the aqueous layer showed pH = 6. The resulting two layers were separated and the organic layer was washed with dist. H2O, dried (Na2SO4), concentrated in vacuum and volatile impurities were removed in high vacuum over night at r.t. to afford a clear oil; yield: 78.65 g (90 percent)Boc-N-sarcosine methyl ester (18) was prepared by treating a solution of Boc-Sar- OH (1.0 g, 5.3 mmol) in 1 : 1 DCM/MeOH (25 mL) cooled to 0° C portionwise with diazomethane (2M solution, excess) until the reaction mixture turned slight yellow. The reaction was kept at 0° C for 30 min and then HOAc (2 drops) was added. The organic solvents were removed to afford 1.0 g (90percent) of 18.Glycine methyl ester hydrochloride (50.0 g, 0.398 mol, 1 eq.) was added to a 1 L flask containing water (300 mL) and THF (200 mL). Sodium bicarbonate (37.8 g, 0.438 mol) was added portionwise, followed by di-tert-butyl dicarbonate (83.4 g, 0.382 mol). The reaction was stirred for 18 h, and then the separated organic phase was concentrated. The mixture was redissolved in EtOAC, washed with brine, dried over Na