). compound XZ-4b (35.28 mg, 0.0876 mmol) was dissolved in a solution of 4 M HCl in dioxane (2 mL). The reaction mixture was stirred at room temperature for 2 h, and the solvent was removed in vacuo. Diethyl ether (1 mL) was then added to obtain the hydrochloric salt in quantitative yield.