Disclosed is a compound represented by the formula (I) below as a dihydronaphthalene compound having a chemical structure which is excellent in production efficiency when compared with lasofoxifene and nafoxidine. This compound is useful as a proteasome inhibitor and/or an antitumor agent.(In the formula, two —(CH2)l—N(R1) (R2) groups represent a same substituent R1 and R2 each represents a hydrogen atom, or a same or different alkyl group or alternatively, R1 and R2 may combine together to form a monocyclic heterocyclic ring with a nitrogen atom having them or additionally together with one or more atoms selected from an oxygen atom, a sulfur atom and a nitrogen atom R3, R4 and R5 each represents one or more substituents selected from a hydrogen atom, an alkyl group, an acyl group, an alicyclic group, an aromatic group, a halogen atom, an acyloxy group, a cyano group and a nitro group l represents an integer of 2-5 n represents an integer of 1-4 m represents an integer of 1-5 and q represents an integer of 1-3.)
