Synthesis and biological evaluation of quinaldopeptin.

The second-generation total synthesis of quinaldopeptin (1) was established via a Staudinger/aza-Wittig/diastereoselective Ugi three-component reaction sequence and a racemization-free [5 + 5] coupling and macrolactamization. A single-crystal X-ray structure of the chromophore analogue 26 confirmed the structural and stereochemical assignments of the macrocycle. Synthetic 1 successfully unwound supercoiled DNA to form a relaxed DNA in a dose-dependent manner, the binding affinity of 1 to four dsODNs was within a similar range (Kb = 1.45–2.53 × 107 M–1), and the sequence selectivity was subtle. It was suggested that 1 possesses biological behaviors similar to those of sandramycin (2) in terms of cytotoxic activity against human cancer cell lines (IC50 = 3.2–12 nM) and HIF-1 inhibitory activity.