Synthesis
General procedure for the synthesis of (S)-2-hydroxy-3,3-dimethylbutanoic acid from L-tert-leucine: 3,3-dimethylbutanoic acid (1 g, 7.5 mmol) was dissolved in an aqueous solution of 1 M sulfuric acid (15 ml) and cooled to 0°C. An aqueous solution (8 ml) of sodium nitrite (1.0 g, 15 mmol) was slowly added while keeping the reaction temperature below 5°C. The reaction mixture was stirred at the same temperature overnight. After completion of the reaction, it was treated with a saturated solution of ammonium sulfate followed by extraction with ether (5 x 25 ml). The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford (S)-2-hydroxy-3,3-dimethylbutyric acid (0.27 g, 67% yield) as a colorless oil, which crystallized after standing. The product was confirmed by 1H NMR (400 MHz, CD3OD): δ 3.41 (s, 1H), 1.25 (s, 9H). LCMS analysis showed m/z 133.2 [M + H]+ with a retention time Tr = 0.39 min (using a Gemini 5u C18 150 × 4.60 mm 5 µm column at a flow rate of 3.5 ml/min with gradient elution). conditions: 5-100% acetonitrile/water with 0.1% acetic acid modifier).
References
[1] Liebigs Annalen der Chemie, 1982, vol. No. 11, p. 1952 - 1970
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[3] Patent: WO2013/185093, 2013, A1. Location in patent: Page/Page column 261
[4] Journal of Organic Chemistry, 2017, vol. 82, # 9, p. 4949 - 4957
[5] Bioorganic and Medicinal Chemistry Letters, 2005, vol. 15, # 15, p. 3540 - 3546
