A solution of the title B compound in Example 9, 2-(2,4-dimethoxybenzyl)-1,1-dioxo-1,2,5-thiadiazolidin-3-one (742 mg, 2.59 mmol) and (4-hydroxymethyl-benzyl)-carbamic acid t-butyl ester (738 mg, 3.11 mmol) in THF (15 mL) is treated with triphenylphosphine (1.36 g, 5.18 mmol). The mixture is stirred for 10 min and diethyl azodicarboxylate (902 mg, 5.18 mmol) is added dropwise over 1 min. The mixture is stirred for 72 h. The solvent is evaporated and the residue is chromatographed on silica gel using 1% MeOH/CH2Cl2 as the eluent to afford {4-[5-(2,4-dimethoxy-benzyl)-1,1,4-trioxo-1,2,5-thiadiazolidin-2-ylmethyl]-benzyl}-carbamic acid t-butyl ester as a white solid: [M+NH4]+=523.
