The title compound of example 1 (3.0 g, 8.72 mmol) was added to a solution of L-cysteine (1.0 g, 8.26 mmol) and DIEA (4.4 mL, 24.7 mmol) in EtOH-H2O (1:1, 100 mL). The resulting heterogeneous mixture was stirred vigorously at room temperature (20°-22° C.) for 18 h. The mixture was rendered acidic by the addition of 1N HCl (ph=6). The solid in the reaction mixture was collected on a filter and washed with H2O and EtOH. A suspension of the solid in EtOH (70 mL) was heated with stirring then allowed to cool. The solid in the suspension was collected on a filter, washed with EtOH, Et2O and dried to give the title compound (1.2 g).
