Ammonium Chloride → 3-(S)-(4-(S)-Isopropyl-2-oxo-oxazolidine-3-carbonyl)-octanoic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

To a solution of 4 (37.082 g, 0.154 mol) in THF (300 mL) at −78° C. is added LiHMDS in THF (1.0 M, 0.162 mol, 162 mL) via cannula. The solution is stirred at −78° C. for 1 h. tert-Butylbromoacetate is added and then stirred for 30 more minutes. It is then gradually warmed to 0° C. and stirred at this temperature for 30 min. To this solution is gradually added 100 mL saturated aqueous solution of NH4Cl. The bulk of the THF is removed by rotary evaporation and the remaining mixture was extracted with CH2Cl2 (100 mL×3). The combined CH2Cl2 extracts is washed consecutively with 1N NaOH, 1 N HCl, saturated NaHCO3, and brine. It is then dried over MgSO4 and concentrated in vacuo. The residue is chromatographed in silica gel using hexane/ethyl acetate (5:1) as eluant to afford 5. 1H NMR (400 MHz, CDCl3) δ 0.85 (t, J=6.8 Hz, 3H), 0.91 (d, J=8.15 Hz, 3H), 0.93 (d, J=8.15 Hz, 3H), 1.18-1.35 (m, 6H), 1.40 (s, 9H), 1.35-1.49 (m, 1H), 1.56-1.66 (m, 1H), 2.31-2.39 (m, 1H), 2.44 (dd, J=16.6, 4.5, 1H), 2.73 (dd, J=16.6, 10.3, 1H), 4.11-4.20 (m, 1H), 4.44 (m, 1H); 13C NMR (75.45 MHz, CDCl3) δ 13.9, 14.4, 17.9, 22.4, 26.4, 27.9, 28.0, 31.4, 31.6, 31.7, 37.0, 39.2, 58.6, 62.9, 80.3, 153.5, 171.2, 175.8. HRMS calcd for C19H34NO5 (MH+): 356.2436. Found (DCI): 356.2418 (Δ=5.3 ppm).

Provenance & Evidence