Menaquinone-4 (vitamin K_2) is a ligand for a nuclear receptor, steroid and xenobiotic receptor (SXR), that induces the gene expressions of CYP3A4. We synthesized vitamin K_2 analogues with hydroxyl or phenyl groups at the ω-terminal of the side chain. The up-regulation of SXR-mediated transcription of the target gene by the analogues was dependent on the length of the side chain and the hydrophobicity of the ω-terminal residues. A new analogue that has phenyl group introduced to menaquinone-3 showed the most potent activity among our synthesized compounds. The analogue was approximately estimated twice as active as menaquinone-4, and almost same as the known SXR ligand rifampicin.