Reaction Steps
To a round bottom flask was added (R)-(9H-fluoren-9-yl)methyl 3-methyl-1-oxo-1-(5-oxopentylamino)-3-(tritylthio)butan-2-ylcarbamate (35 mg, 0.050 mmol), DCM (1 mL) and TFA (0.077 mL, 1.0 mmol). The reaction mixture was stirred at rt for 15 min. The reaction mixture was diluted with EtOAc (20 mL) and washed with saturated aqueous NaHCO3 (10 mL), water (10 mL) and saturated aqueous NaCl (10 mL). The organic layer was separated, dried over MgSO4, filtered and concentrated. The residue was purified using silica gel chromatography (ISCO system) eluting with a gradient of 0-100% EtOAc/Hex to give (9H-fluoren-9-yl)methyl (3R,9aS)-2,2-dimethyl-4-oxooctahydropyrido[2,1-b][1,3]thiazin-3-ylcarbamate (12 mg, 0.027 mmol, 55% yield) as a white solid. Anal. Calcd. for C25H28N2O3S m/z 436.3. found: 437.2 (M+H)+; 1H NMR (500 MHz, CDCl3) δ ppm 7.78 (d, J=7.15 Hz, 2H), 7.63 (t, J=6.60 Hz, 2H), 7.41 (td, J=7.42, 3.30 Hz, 2H), 7.33 (t, J=7.42 Hz, 2H), 5.84 (d, J=8.80 Hz, 1H), 4.90 (dd, J=8.80, 3.85 Hz, 1H), 4.63 (d, J=8.80 Hz, 1H), 4.54-4.35 (m, 2H), 4.26 (t, J=7.15 Hz, 1H), 4.16-3.99 (m, 1H), 3.22 (ddd, J=13.06, 8.39, 4.40 Hz, 1H), 2.00 (dt, J=8.80, 4.40 Hz, 1H), 1.93-1.81 (m, 1H), 1.80-1.67 (m, 3H), 1.62-1.52 (m, 1H), 1.39-1.24 (m, 3H), 1.19 (s, 3H).
