Acetic Acid → (S)-2-Amino-3-ethylpentanoic acid

温度

70 °C

A mixture of the product from Example 4 (31.7 g, 0.185 mol), 10% palladium on carbon (7.9 g), glacial acetic acid (370 mL), and water (926 mL) was placed under an atmosphere of hydrogen (40 psi) and shaken on a Parr hydrogenator. After 20 h, the reaction mixture was filtered through a pad of Celite (½″), which was rinsed well with water (200 mL). The filtrate was concentrated under reduced pressure in a bath heated to 70° C. to produce a white solid. The solid was triturated with ethyl acetate (500 mL), filtered, and washed once more with ethyl acetate (500 mL), and then air dried. This gave the title compound as a white solid (21.2 g, 79%): Opt. Rot. [α]D25=+12.01° (1% solution, H2O); 1H NMR (D2O, 500 MHz): δ4.65 (s, 3H), 3.69 (d, J=3.4 Hz, 1H), 1.69 (m, 1H), 1.44 (m, 1H), 1.03-1.10 (m, 3H), 0.83 and 0.81 (two overlapping triplets, J=7.5 Hz, 6H); MS(−ESI): [M−H]−, 144 (100%); Anal. Calc. for C7H15NO2: C, 57.90; H, 10.41; N, 9.65. Found: C, 57.75; H, 10.89; N, 9.40. Chiral HPLC (Symmetry C18 column, eluant: solvent A=50 mM triethylamine pH adjusted to 3.0 with phosphoric acid, solvent B=AcCN, gradient 80% A/20%B to 50% A/50%B over 20 min, flow rate 1.0 mL/min, detection at 340 nm, S isomer has a retention time of 12.26 min and R isomer has a retention time of 15.46 min) of the amino acid derivatized by Marfey's reagent (N-α-(2,4-dinitro-5-fluorophenyl)-L-alaninamide) gave an enantiomeric ratio of 99.5:0.5 (2S:2R).