Step 2 To a flame-dried 100-mL round-bottomed flask equipped with a magnetic stir bar was added crude alcohol 5-3 (60.0 mmol, 1.0 equiv) and CH2Cl2 (60 mL, 1.0 M). The reaction vessel was placed in a 0 °C ice-water bath. To the stirred reaction mixture was added acetic anhydride (11.4 mL, 120 mmol, 2.0 equiv) dropwise over 2 minutes. Following this, 4-(dimethylamino)pyridine (733 mg, 6.0 mmol, 0.1 equiv) was added in one portion. After stirring for 5 minutes at 0 °C, pyridine (14.6 mL, 180 mmol, 3.0 equiv) was added dropwise over 5 minutes. The reaction vessel was then transferred to an ambient temperature water bath.