Pyrimidine Nucleosides from Streptomyces sp. SSA28

Eleven new pyrimidine nucleosides (1–11) and 12 known analogues (12–23) were isolated from the marine-derived Streptomyces sp. SSA28. All of the new structures were elucidated by extensive NMR spectroscopic analysis and HRESIMS data. The absolute configurations of compound 1 were determined by X-ray diffraction. The configurations of 2–16 were investigated by ECD calculations. Compounds 11–16 showed cytotoxicity against HCT-116 human colon cancer cell lines with IC50 values from 0.39 ± 0.03 to 6.63 ± 0.47 μM.