Diethylamine → (3S)-3-amino-4-oxobutyric acid tert-butyl ester semicarbazone

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Reaction Steps

(3S)-3-(1-Fluorenylmethyloxycarbonylamino)-4-oxobutyric acid tert-butyl ester semicarbazone (210 mg, 0.45 mol, Prepared in a similar manner to the benzyloxycarbonyl analog in Graybill et al., Int. J. Protein Res., 44, pp. 173-82 (1994).) was dissolved in 10 ml of DMF and 2 ml of diethylamine and stirred for 2 h. The reaction was concentrated in vacuo to give (3S)-3-amino-4-oxobutyric acid tert-butyl ester semicarbazone. The 0° C. solution of the above residue and 603a (200 mg, 0.42 mmol) in 5 ml of DMF and 5 ml of CH2Cl2 was treated with 1-hydroxybenzotriazole (57 mg, 0.42 mmol) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (98 mg, 0.51 mmol). The reaction was stirred at RT for 18 h, poured onto EtOAc (75 ml) and washed with aq. 0.3 N KHSO4, sat. aq. NaHCO3 and sat. aq. NaCl, dried over NaSO4 and concentrated in vacuo. Chromatography (flash, SiO2, 0% to 4% MeOH/0.1% NH4OH/CH2Cl2) to give 240 mg (83%) of 604a.

Provenance & Evidence