The first phytochemical study of Simira eliezeriana Peixoto (Rubiaceae) allowed the isolation and structural determination of two new diterpenes named simirane A [(5R,6R,8R,9R,10S,11S,13S)-6β,11β-dihydroxy-2,4(18),15-erythroxylatrien-1-one] (1) and simirane B [(5S,8R,9R,10S,11S,13S)-11β-hydroxy-2,4(18),15-erythroxylatrien-1-one] (2), together with seven known compounds: sitosterol (3), stigmasterol (4), campesterol (5), coniferaldehyde (6), vanillin (7), pinoresinol (8) and harman (9) from the bark of the plant. The structures of the compounds were established on the basis of spectroscopic methods, including 1-D and 2-D NMR, HRESI-MS and CD analysis and comparisons with available literature data of known compounds.