Cangumycins A–F, six new angucyclinone analogues with immunosuppressive activity from Streptomyces

Abstract Cangumycins A–F (1–6), six new angucyclinone analogues, together with two known ones (7 and 8), were isolated from the fermentation broth of a soil-derived Streptomyces sp. KIB-M10. Structures of these compounds were elucidated via a joint use of spectroscopic analyses and single-crystal X-ray diffractions. Among them, cangumycins E (5) and F (6) share a C-ring cleaved backbone, and cangumycins B (2) and E (5) exhibit potent immunosuppressive activity (IC50 8.1 and 2.7 μmol·L−1, respectively) against human T cell proliferation at a non-cytotoxic concentration.