37169-36-1

24424-99-5

1421-65-4

37169-36-1

The general procedure for the synthesis of (S)-(2-((tert-butoxycarbonyl)amino)-3-(3,4-dihydroxyphenyl)propanoic acid methyl ester from di-tert-butyl dicarbonate and (S)-2-amino-3-(3,4-dihydroxyphenyl)propanoic acid methyl ester hydrochloride was carried out as follows: under ice-bath conditions, a mixture of (S)-2-amino-3-(3,4-dihydroxyphenyl)propanoic acid methyl ester hydrochloride (0.9 g 3.6 mmol) solution of THF (6.5 mL), saturated aqueous NaHCO3 solution (6.5 mL) and di-tert-butyl dicarbonate (0.87 g, 4.0 mmol) were added sequentially to the reaction flask. Subsequently, additional THF (4.0 mL) was added slowly. The reaction mixture was stirred at room temperature for 1 h, after which the organic solvent was removed by rotary evaporation. The aqueous phase was extracted three times with CH2Cl2 and the combined organic layers were washed with brine, dried over anhydrous Na2SO4 and concentrated to dryness. The residue was ground with Et2O and allowed to stand at low temperature. Finally, the target product (S)-(2-((tert-butoxycarbonyl)amino)-3-(3,4-dihydroxyphenyl)propanoic acid methyl ester was obtained by vacuum filtration.