To a solution of Compound 4 (1.9 g), prepared in the same manner as Compound 5 in Example 11, in a 1:1 mixture of DMF and CH2Cl2 (60 mL) is slowly added a solution of Compound 3 (2.32 g) in a 1:1 mixture of DMF and CH2Cl2 (30 mL), under N2. N,N-Diisopropylethylamine (0.98 mL) is added dropwise and the reaction is allowed to stir at ambient temperature until complete. Upon completion, methanol (15 mL) is added and the mixture is stirred for 15 minutes. The volatiles are removed in vacuo until a small mount of DMF remains whereupon methanol (150 mL) is added. The mixture is stirred for 5 minutes and filtered to obtain Compound 5.
