Figure 4 | Scientific Reports

Figure 4

From: Enhanced anti-tumor activity of the Multi-Leu peptide PACE4 inhibitor transformed into an albumin-bound tumor-targeting prodrug

Figure 4

Synthetic procedure to prepare an albumin binding NOTA conjugate probe of prodrug 2. (1) Fmoc-SPPS, TentaGelS RAM resin, couplings with the protected amino acid or Fmoc-(4-Apaa)-OH (3 equiv), HATU (3 equiv) or PyBOP (3 equiv), HOBt (3 equiv) and DIPEA (9 equiv) in the mixture of DMF/DCM, 3 h in room temp.; (2) Selective deprotection of the ivDde group with 2%hydrazine in DMF (5×) for 5 min. (3) Coupling of NOTA(tBu)2 with HATU (3 equiv), HOBt (3 equiv) and DIPEA (9 equiv) in anhydrous DMF, o/n in room temp.; (4) Deprotection of the N-terminal Fmoc group with 20% piperidine in DMF (2×) for 10 min; (5) Coupling of 6-maleimidohexanoic acid (EMC) with HATU (3 equiv), HOBt (3 equiv) and DIPEA (9 equiv) in the mixture of DMF/DCM, 3 h in room temp; (6) Cleavage from the resin and removal of the protecting groups with TFA/TIS/H2O (95:2.5:2.5, v/v/v), 3 h, precipitation in cold diethyl ether, purification by semipreparative HPLC.

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