(S)-(-)-2-(Boc-Amino)-1,4-butanediol

• Thiourea-based organocatalysts for asymmetric Michael addition reactions of nitroalkenes to α-nitrocyclohexanone.
• Bis-copper (II) complex based catalysts for enantioselective Michael reactions.

130622-08-1

128427-10-1

B. Add lithium aluminum hydride (0.870 g, 22.9 mmol) to a pre-oven-dried round-bottomed flask under a dry nitrogen atmosphere. The flask was cooled to 0°C in an ice bath, followed by the addition of 100 mL of anhydrous ether. In another dry round-bottomed flask, compound 2 (2.021 g, 7.735 mmol) was dissolved in 50 mL of anhydrous ether, sonicated if necessary to ensure complete dissolution. This ester solution was slowly added dropwise to the reaction mixture. After the dropwise addition was completed, the reaction mixture was continued to be stirred at 0°C for 30 minutes, then warmed to room temperature and reacted for 2 hours. Upon completion of the reaction, 0.87 mL of water, 0.87 mL of 15% w/w NaOH solution and 2.6 mL of water were added slowly and sequentially at 0°C to quench the reaction. The mixture was stirred at room temperature for 1 hour. The aluminum salt was collected by vacuum filtration and subjected to sequential solid-liquid extraction with dichloromethane using a Soxhlet extractor. The organic extract was combined with the original organic filtrate and concentrated under reduced pressure. Purification by fast chromatography (eluent: ethyl acetate) afforded (S)-tert-butyl-1,4-dihydroxybutan-2-ylcarbamate (3) (1.310 g, 82% yield) in white solid form. Compound 3 was prepared from L-aspartic acid by a different route. [00161] 1H NMR (400 MHz, DMSO-d6) δ = 6.46 (d, J = 8.8 Hz, 1H), 4.56 (t, J = 5.7 Hz, 1H), 4.34 (t, J = 5.1 Hz, 1H), 3.46-3.37 (m, 3H), 3.32 (dt, J = 10.6, 5.4 Hz, 1H) 3.23 (dt, J = 10.6, 5.9 Hz, 1H), 1.69-1.61 (m, 1H), 1.45-1.37 (m, 1H), 1.37 (s, 9H); 13C NMR (75 MHz, CDCl3) δ = 157.2, 80.1, 65.4, 58.9, 49.5, 35.0, 28.5; HRMS ( ESI) calculated value [C9H19NO4Na]+ (M + Na+) m/z = 228.1207, measured value 228.1201.