11-Deoxylandomycinone and landomycins X-Z, new cytotoxic angucyclin(on)es from a Streptomyces cyanogenus K62 mutant strain

Four new angucyclin(on)es, 11-deoxylandomycinone (1) and landomycins X-Z (2–4) were isolated from the crude extract of Streptomyces cyanogenus K62 mutant strain, along with the recently reported landomycins S, T and V (5–7) and five other known compounds. The structures of the new compounds 1–4 were elucidated by 1D and 2D NMR studies along with HRMS analyses. Unique about the structures is that the fourth sugar moiety (sugar D) in landomycins X-Z (2–4) was β-D-amicetose instead of β-D-olivose usually found in this position. The new angucyclin(on)es were biologically evaluated in comparison with previously known congeners against a small panel of MCF-7 (estrogen responsive) and MDA 231 (estrogen refractory) breast cancer cell lines. 11-deoxylandomycinone (IC(50) 2.1 and 1.2 μM) and landomycin Y (IC(50) 1.0 and 2.0 μM) showed the highest cytotoxic potencies against both cell lines.