Figure 5.
Synthesis of monomer (1). Reagents and conditions: (i) NaN3, DMF, 50 °C, 16 h; (ii) 1,3-Bis(tert-butoxycarbonyl)-2-methyl-2-thiopseudourea, DIPEA, CH3CN/CH3OH, 40 °C, 16 h; (iii) CsOH·H2O, molecular sieves, 6, dry DMF, r.t., 24 h; (iv) H2, Pd/C, i-PrOH, r.t., 4 h; (v) N,N′-Di-Boc-N-methylcyclopropyl-pyrazole-1-carboxamidine, DIPEA, THF, 16 h, r.t.; (vi) TFA 10%, dry DCM, r.t., 7 h.