General Procedure:(3R,4S,5S)-tert-butyl 4-(((benzyloxy)carbonyl)(methyl)amino)-3-methoxy-5-methylheptanoate (13.37 g, 33.98 mmol, 1 eq.) was dissolved in methanol (134 mL, 0.1 M), concentrated hydrochloric acid (3.1 mL, 37.4 mmol, 1.1 eq.) was added, and 10% palladium carbon (50% wet, 0.1 wt%, 1.34 g, 3.40 mmol). The reaction mixture was hydrogenated under 45 psi hydrogen pressure for 3 hours. Upon completion of the reaction, the hydrogen was replaced with nitrogen, the catalyst was removed by filtration through diatomaceous earth, and the filtrate was concentrated under reduced pressure to afford tert-butyl (3R,4S,5S)-3-methoxy-5-methyl-4-(methylamino)heptanoate hydrochloride (9.20 g, 92% yield) as a white solid. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 9.65 (br s, 1H), 8.97 (br s, 1H), 3.98-4.04 (m, 1H), 3.40 (s, 3H), 3.06-3.13 (br m, 1H), 2.82 (br dd, J=6,5 Hz, 3H), 2.74-2.80 (m 1H), 2.68 (dd, half of ABX mode, J=16.3,4.2 Hz, 1H), 2.00-2.10 (br m, 1H), 1.73-1.84 (m, 1H), 1.46 (s, 9H), 1.38-1.45 (m, 1H), 1.13 (d, J=7.0 Hz, 3H), 0.99 (t, J= 7.4 Hz, 3H).
