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 —(CH
2
)
l
—N(R
1
) (R
2
) groups represent a same substituent; R
1
and R
2
each represents a hydrogen atom, or a same or different alkyl group; or alternatively, R
1
and R
2
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; R
3
, R
4
and R
5
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.)