HPLC analysis of crude sample MR-409 on Agilent Zorbax 300SB C18 column (2.1 mm × 50 mm, particle size 5 μm), UV detector 220 nm, sample injection 20 μg/25 μl, Eluent A: 0.1% trifluoroacetic acid in water, Eluent B: 0.1% trifluoroacetic acid, 70% acetonitrile in water, linear gradient from 20% B to 60% B in 40 min. MR-409 peak purity: 81%.