To a stirred mixture of (2S*,3R*)-2-amino-3-hydroxy-4,4-dimethyl-pentanoic acid (0.36 g, 2.24 mmol) and NaHCO3 (0.188 g, 2.24 mmol) in H2O (15 mL), at rt, the isomeric mixture containing 5-phenyl-pentyl-2-pyridyl-carbonate and 5-phenyl-pentyl-2-oxopyridine-1-carboxylate (1.95 g, 6.84 mmol) [prepared as for example 32, step 1] in THF (15 mL) was added. After 15 h at rt, the crude mixture was rotary evaporated to remove the organics and subsequently extracted with Et2O (3×40 mL). The aqueous phase was acidified with 2.0 M HCl solution to pH 2-3 and subsequently extracted with AcOEt (3×40 mL). The organic fraction was dried over Na2SO4, filtered and concentrated to dryness to afford the title compound (0.346 g, 44%), as an off-white solid, which was used in the next step without further purification. MS (ESI) m/z: 352 [M−H]+; (ESI) m/z: 350 [M−H]−. 1H NMR (DMSO-d6) δ 0.86 (s, 9H), 1.33 (tt, J=5.95, 9.00 Hz, 2H), 1.57 (ddt, J=3.93, 6.59, 10.94 Hz, 4H), 2.57 (t, J=7.70 Hz, 2H), 3.59 (s, 1H), 3.87-4.03 (m, 2H), 4.12-4.21 (m, 1H), 6.25 (d, J=9.37 Hz, 1H), 7.10-7.32 (m, 5H), 11.55 (s, 1H).
