Sodium Chloride → (2S,3S)-2-Hydroxy-3-methylpentanoic acid

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Reaction Steps

To a solution of L-isoleucine(+) [1] (11.73 g, 89.4 mmol, [α]D20 =+40° (5% in 6M HCl)) in 300 ml of 1N aq. H2SO4 at 2° was slowly added (ca. 12 h) a solution of NaNO2 (19.5 g, 0.28 mol) in 300 ml of demineralised water. After stirring overnight at room temperature, 7.7 g of powdered NaHCO3 were added to bring the pH above 2. The solution was saturated with NaCl and extracted 6 times with ethyl acetate, maintaining the pH between 2 and 3 (1N aq. H2SO4, pH meter). After drying (Na2SO4), the organic layer was concentrated and the crude product (10.73 g, 91%) was recrystallised from hexane/ethyl acetate 9/1 at -30° to give pure (+)-(2S, 3S)-2-hydroxy-3-methylpentanoic acid [2].

Provenance & Evidence