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 mu M.