Water → rac-Methyl N-[(benzyloxy)carbonyl]-5,5,6,6,6-pentafluoronorleucinate

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Reaction Steps

141.5 g (520.99 mmol) of rac-methyl 5,5,6,6,6-pentafluoronorleucinate hydrochloride from Example 25A were taken up in 850 ml of THF and 850 ml of water under argon, and 223.2 g (1.62 mol) of potassium carbonate were added cautiously at RT. Subsequently, 82 ml (573.09 mmol) of benzyl chloroformate were added dropwise and the suspension was stirred at RT overnight. The reaction mixture was extracted twice with 500 ml of ethyl acetate, and the organic phase was dried with magnesium sulphate, filtered and concentrated. The residue was diluted in 50 ml of dichloromethane and purified by means of silica gel chromatography (eluent:cyclohexane/ethyl acetate 9/1 to 4/1). The isolated product fractions were purified once more by means of preparative HPLC [column: Daiso C18 10 μm Bio 300×100 mm, neutral; eluent:acetonitrile/water gradient; flow rate: 250 ml/min; temperature: RT; wavelength: 210 nm). This gave 27.4 g (14% of theory) of the target compound.

Provenance & Evidence