Initial planar support derivatization. Reagents and conditions: (i) N,N′-diisopropylcarbodiimide (DIC), N-hydroxysuccinimide (HOSu), diisopropylethylamine (DIPEA), NMP, MW 95 °C, 8 min. (ii) Capping step: Ac2O, DIPEA, DMF, rt, 20 min (2×).17 (iii) 20% piperidine in DMF, rt, 10 min (2×). (iv) DIC, HOSu, DIPEA, NMP, MW 100 °C, 10 min.