Trifluoroacetic acid → (3r,4r,5r)-3-Amino-4,5-dimethyloctanoic acid

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Reaction Steps

To the solution of (4R,5R)-4,5-dimethyl-(R)-3-(toluene-4-sulfinylamino)-octanoic acid tert-butyl ester (1.8 g, 4.71 mmol) in dry methanol (30 mL) at 0° C. under nitrogen was added excess trifluoroacetic acid (25 mL) and stirred for 2 hours at that temperature. The solution was concentrated to dryness followed by the addition of dry dichloromethane (20 mL) and trifluoroacetic acid (20 mL). The resulting mixture was stirred for 2 hours under nitrogen and concentrated to dryness. The residue was applied to BondElute SCX ion exchange resin and eluted with water until the eluent was at constant pH of 6.5. The resin was then eluted with a 1:1 solution of methanol and with 10% ammonium hydroxide solution. The ammonium hydroxide solution was evaporated and the residue was crystallized with methanol-acetonitrile mixture to afford the titled compound (0.717 g, 81.2% yield) as a white solid: 1H NMR (400 MHz, CD3OD-D) δ ppm 0.9 (m, 11 H) 1.1 (m, 2 H) 1.3 (m, 1 H) 1.4 (m, 1 H) 1.6 (m, 1 H) 1.7 (m, 2 H) 2.3 (dd, J=16.6, 10.0 Hz, 1 H) 2.5 (dd, J=16.7, 3.5 Hz, 1 H) 3.3 (m, 1 H). MS, m/z (relative intensity): 188 [M+1H, 100%], 186 [M−1H, 100%].

Provenance & Evidence