Synthesis
A suspension was prepared from 5-aminolevulinic acid hydrochloride (2) (5.00 g, 29.8 mmol), NaHCO3 (15.04 g, 179.0 mmol) and di-tert-butyl dicarbonate (6.51 g, 29.8 mmol) in anhydrous methanol and the reaction was stirred at room temperature overnight. Upon completion of the reaction, the insoluble solids were removed by filtration followed by evaporation to remove the solvent. The oily residue obtained was dissolved in water and the pH of the aqueous phase was adjusted with 10% aqueous KHSO4 to 2. The mixture was extracted with ethyl acetate (EtOAc), the organic phase was washed with saturated saline, dried over anhydrous Na2SO4, filtered and concentrated. The oily residue was purified by silica gel column chromatography (eluent ratio CH2Cl2/MeOH = 10/1) to afford the target product 5-((tert-butoxycarbonyl)amino)-4-oxopentanoic acid (3) (6.24 g, 90% yield) as a white solid with a melting point of 72-74°C (literature value 74-77°C). The spectral data of product 3 were in agreement with literature reports.
References
[1] Arkivoc, 2014, vol. 2014, # 3, p. 228 - 238
[2] Journal of Medicinal Chemistry, 2008, vol. 51, # 23, p. 7356 - 7369
[3] Photochemistry and Photobiology, 2003, vol. 78, # 5, p. 481 - 486
