Six new pimprinine alkaloids (1-6), including four dimers, dipimprinines A-D (1-4), and two monomers, (+/-)-Pimprinol D (5), and pimprinone A (6), along with six known congeners (7-12), were isolated from a soil-derived actinomycete Streptomyces sp. NEAU-C99. Structures of the new compounds were elucidated by extensive spectroscopic analyses, single-crystal X-ray diffractions, and ECD calculations. Dipimprinines A-D (1-4) showed weak cytotoxic activities against five tumor cell lines, including HL-60, SMMC-7721, A-549, MCF-7, and SW-480, with IC(50) values ranging from 12.7 to 30.7 muM. CI - Copyright (c) 2020 Yu, Jiang, Wang, Yang, Huang, Liu, Guo, Xiang and Huang.