To a solution of 19.0 mg (54.8 μmol) of 2b in 1 mL of CH2Cl2 was added 165 μL (165 μmol, 1.0 M in hexanes) of DIBAL-H at 78° C. The reaction mixture was stirred at −78° C. for 1 h and then 2 mL of sat aq sodium potassium tartrate was added slowly. The reaction mixture was slowly warmed to room temperature over a period of 30 min. The solution was extracted with three 5-mL portions of ethyl acetate. The combined organic layer was washed with brine, dried (MgSO4) and concentrated under diminished pressure to give the crude product as a yellow oil: silica gel TLC Rf 0.16 (1:9 MeOH/CH2Cl2). The residue was then dissolved in 1 mL of CH3CN and 1% aq TFA, frozen and lyophilized. The crude product was purified on a Prepex C8 reversed phase semi-preparative (250 mm×10 mm) HPLC column using a gradient of methanol and water. Linear gradients were employed using 1:4 methanol/water→4:1 methanol/water over a period of 20 min, and then 4:1 methanol/water→methanol over a period of 40 min, at a flow rate of 3.5 mL/min (monitoring at 260 nm). Fractions containing the desired product eluted at 28.2 min, and were collected, frozen, and lyophilized to give 1b as a light yellow solid: yield 13.0 mg (76%); 1H NMR (CD3CN) δ 0.89 (t, 3H, J=6.8 Hz), 1.27-1.31 (m, 16H), 1.54 (quint, 2H, J=7.6 Hz), 2.13 (s, 3H), 2.70 (t, 2H, J=8.0 Hz), 2.99 (t, 2H, J=8.4 Hz), 3.06 (s, 3H) and 3.72 (t, 2H, J=8.4 Hz); 13C NMR (CDCl3) δ 13.0, 13.4, 22.4, 24.41, 27.3, 28.6, 28.9, 29.00, 29.04, 29.3, 29.3, 31.6, 32.4, 53.1, 117.3, 126.1, 132.1, 140.3, 141.5 and 152.1; mass spectrum, m/z 304.3 (M)+ (theoretical 304.3); mass spectrum (APCI), m/z 305.2590 (M+H)+ (C19H33N2O requires 305.2593).
