Three new trichostatin analogues, ulleunganilines A-C (1-3), and seven known trichostatins (4-10) were isolated from cultures of Streptomyces sp. 13F051. NMR, UV, and MS data indicated that the planar structures of 1-3 consisted of modified side chains in the trichostatic acid moiety. The absolute configuration of the 2,4-dimethyl-branched carbon chains in 1 and 2 was determined by the PGME method, while the amino acid group in 3 was identified by advanced Marfey's method. Based on the structure of the modified side chains, the origin of 1-3 is proposed. Further experiments indicated that 1 and 3 displayed moderate histone deacetylase inhibitory activity, suggesting that not only the hydroxamate group but also the N,N-dimethyl group were essential for the inhibitory activity.