General synthetic scheme of the new compounds investigated here illustrated for the case of compound 6. The general coupling procedure used (a and c) was similar for all compounds. Reagents and conditions: (a) HCTU, Et3N, DMF, 0°C to RT, 24 h, 65%; (b) H2 (balloon), Pd/C, DMF-EtOH, 80°C, 80%; (c) HCTU, Et3N, DMF, 0°C to RT, 24 h, 91%. For details, see the experimental section.