Two new dipimprinine alkaloids dipimprinine E (1) and dipimprinine F (2) were isolated from Streptomyces sp. 44414B. The structure was elucidated by extensive spectroscopic analysis, including ESI-MS, HR-MS, and 1D and 2D NMR experiments. Dipimprinines F (2) showed cytotoxic activities against three tumor cell lines, including A-875, Hep G2, and H-460, with IC(50) values of 26.4, 0.5, and 9.0 mug ml(-1), respectively.