Scheme 2.

Synthetic outline for the preparation of title compounds 2, 3 and 5. Reagents and conditions: (a) HN(OMe)Me, EDC·HCl, HOBT, Et₃N/DMF; (b) n-BuLi, THF, −78 °C (if R² = thiazole, 4,5-dimethylthiazole or benzothiazole) or LDA, THF, −78 °C (if R² = 5-arylated thiazoles); (c) TFA/H₂O; (d) 9, HBTU, DIPEA/DMF followed by HPLC purification. Note: The substituents R(acyl), R¹ and R² are indicated in Table 1, Table 2, Table 3.