Synthesis and Characterization of Bleomycin-Derived Compounds

Bleomycin A5 (Bleocin) was purchased from EMD Millipore and used without further purification. Hoechst carboxylic acid, 4-(3-(6-(4-methylpiperazin-1-yl)-1H,3′H-[2,5′-bibenzo[d]imidazol]-2′-yl)phenoxy)butanoic acid (6) (Ht-CO₂H), intermediate (10) and 2H-K4NMeS were synthesized as reported previously.^{14 (link)} Peptide synthesis reactions were monitored by a chloranil test. Preparative HPLC was performed using a Waters 1525 Binary HPLC pump equipped with a Waters 2487 dual absorbance detector system and a Waters Sunfire C18 OBD 5 μm 19 × 150 mm column. Absorbance was monitored at 345 and 220 nm or 254 nm. A gradient of methanol in water with 0.1% TFA varied in each purification. Purity was assessed by analytical HPLC using a Waters Symmetry C18 5 μm 4.6 × 150 mm column, and a linear gradient of 0–100% methanol in water with 0.1% TFA over 60 min. Absorbance was monitored at 345 and 254 nm or 220 nm. All compounds evaluated had ≥95% purity (see Characterization of Small Molecules). Mass spectrometry was performed with an Applied Biosystems MALDI ToF/ToF Analyzer 4800 Plus using an α-cyano-4-hydroxycinnamic acid matrix or an Agilent 1260 Infinity LC system coupled to an Agilent 6230 TOF (HR-ESI) with a Poroshell 120 EC-C18 column (Agilent, 50 mm × 4.6 mm, 2.7 μm).