A Synthetic Strategy for Conjugation of Paromomycin to Cell-Penetrating Tat(48-60) for Delivery and Visualization into Leishmania Parasites

Scheme 1

Synthetic approach to Tat-linked fluorescent PMM derivatives. Reagents and conditions: (i) piperidine/DMF (1 : 4), 1 + 20 min, then Bodi Fluor 488 acid (4 equiv), DIPCDI (4 equiv), CH₂Cl₂, 1 h + 1 h; (ii) TFA/H₂O/TIS (95 : 2.5 : 2.5 v/v), 90 min, HPLC purification; (iii) TFA/CH₂Cl₂ (1%), 4 × 5 min, then DIEA/CH₂Cl₂ (5%), 4 × 5 min; (iv) 6,3′,4′,6′, 2′′,5′′,3′′′,4′′′-octa-O-acetyl-paromomycin (4 equiv), HBTU (4 equiv), DIEA (8 equiv), DMF, 2 h; (v) NaOMe/MeOH 0.5 M in CH₂Cl₂ (10 : 1), 2 h, then 15-crown-5/THF 0.05 M in acetic acid 20 : 1, 4 × 5 min, then TFA/H₂O/TIS (95 : 2.5 : 2.5 v/v), 90 min, HPLC purification.