To a solution of hemiaminal 10 (1.89 g, 3.55 mmol) and allylamine 23 (1.24 g, 2.96 mmol) in ethanol (50 ml) were added NaCNBH4 (372.0 mg, 5.92 mmol) and acetic acid (0.169 ml, 2.96 mmol) at room temperature. The reaction mixture was stirred at 80 ºC for 4 hours. Then the reaction mixture was concentrated in vacuo. The residue was diluted with AcOEt, and the resulting solution was filtered through a pad of Celite. Concentration of the filtrate afforded crude products, which was used for next step without further purification. To a solution of the crude products in CH2Cl2 (50 ml) and saturated aq. NaHCO3 (50 ml) was added Boc2O (1.29 g, 5.92 mmol) at room temperature. After stirring for 8 hours, the resulting mixture was partitioned. The aqueous layer was extracted with CH2Cl2, and the combined organic layer was washed with brine, dried over MgSO4, filtered. The filtrate was concentrated in vacuo and the residue was purified with flash column chromatography (5 % AcOEt in hexane) to afford 24 (1.53 g, 60.0%) as colorless oil.

[α]D 20 +49.2º (c 1.00, CHCl3); IR (film) 2954, 2929, 2857, 1688, 1469, 1412, 1250, 1174 cm-1 ; 1 H NMR (400 MHz, CDCl3) δ 7.92 (d, J = 8.0 Hz, 1 H), 7.75 (d, J = 8.3 Hz, 2 H), 7.42 (s, 1 H), 7.35 (d, J = 8.0 Hz, 1 H), 7.24 (br s, 2 H), 7.09 (dd, J = 8.0 Hz, 8.0 Hz, 1 H), 6.09 (br s, 1 H), 5.60 (br s, 1 H), 5.11 (d, J = 5.0 Hz, 1 H), 5.08 (br s, 1 H), 4.89 (br s, 1 H), 4.76 (d, J = 16.5 Hz, 1 H), 4.46 (br s, 0.4 H), 4.36 (br s, 0.6 H), 3.24-3.45 (m, 5 H), 2.92 (dd, J = 3.7 Hz, 13.7 Hz, 1 H), 2.79 (br s, 1 H), 2.58 (br s, 1 H), 2.35 (s, 3 H), 11.52 (s, 6 H), 1.40 (s, 3 H), 0.90 (s, 9 H), 0.76 (s, 9 H), 0.00 (s, 6 H), −0.10 (s, 3 H), −0.42 (s, 3 H); 13C NMR (100 MHz, CDCl3) δ 155.3, 145.0, 139.0, 138.3, 136.3, 135.6, 135.0, 129.9, 128.9, 127.7, 127.0, 126.4, 125.1, 119.6, 118.7, 115.1, 115.1, 114.2, 112.8, 79.6, 74.1, 74.1, 65.8, 64.9, 62.4, 61.2, 52.5, 51.3, 46.9, 46.6, 28.5, 27.8, 26.0, 25.8, 21.5, 18.3, 17.9, −4.3, −5.4, −5.4; HRMS (ESI) calcd for C42H65BrN2O6SSi2Na (M+Na)+ : 883.3183, found 883.3205.