General procedure for the synthesis of tert-butyl 4-hydroxybutyrate from mono-tert-butyl succinate: BH3-Me2S (2.0 M solution in THF, 6.6 mL, 13.1 mmol) was slowly added dropwise to a solution of mono-tert-butyl succinate (2.12 g, 12.2 mmol) in anhydrous THF (20 mL) that was cooled to 0 °C. The reaction mixture was gradually warmed to room temperature and stirred continuously for 24 hours. Upon completion of the reaction, EtOAc (100 mL) was added for dilution and the organic layer was separated. The organic layer was washed sequentially with water (70 mL) and saturated saline (70 mL) and dried with anhydrous MgSO4. After filtration, the solvent was removed by concentration under reduced pressure to afford tert-butyl 4-hydroxybutyrate (1.92 g, 12.2 mmol, quantitative yield), the product was a light yellow oil, which could be used in the subsequent reaction without further purification.
[1] Tetrahedron, 2014, vol. 70, # 44, p. 8343 - 8347
[2] Bioconjugate Chemistry, 2010, vol. 21, # 5, p. 979 - 987
[3] Beilstein Journal of Organic Chemistry, 2017, vol. 13, p. 2428 - 2441
[4] Journal of Organic Chemistry, 2003, vol. 68, # 17, p. 6679 - 6684
[5] Bioorganic and Medicinal Chemistry Letters, 2005, vol. 15, # 18, p. 4004 - 4009